A different take on ‘vermiform’

Posted on by Allison J. Gong

If I asked you to draw a worm and designate the front and back ends, you’d most likely come up with something that looks like this:

And you would be entirely correct. A worm, or any creature described as ‘vermiform’ for that matter, has an elongated, wormlike body. Some worms have actual heads with eyes and sensory tentacles, but many don’t. The great many polychaete worms that live in tubes don’t have much of a head at all: usually all you can see sticking out of the tube is a crown of tentacles used for feeding. Although even the use of the word ‘crown’ more than suggests the presence of a head, doesn’t it? After all, where else does one wear a crown?

Polychaete worms, Phragmatopoma californica, sticking their ‘heads’ out of their tubes at Natural Bridges
26 May 2016
© Allison J. Gong

Most worms, including the worm that we imagined above, are bilaterally symmetrical, with bodies elongated along the Anterior-Posterior axis. This means the head is at the anterior end and the rear is the posterior end. For animals that don’t have a prominent head, the Anterior can also be defined by the direction of locomotion. Worms crawl with their bellies against the ground, which sets up a second axis of symmetry, the Dorsal-Ventral axis. The third axis of symmetry is the Left-Right axis. These axes should sound familiar, because they apply to our own bodies, as well of those of all other vertebrates and many invertebrates. Because of our upright stance we actually walk with our ventral surface forward, which is a little confusing, but if you don’t trust me you can see for yourself by crawling around on hands and knees for a while.

Now back to our worms, hypothetical and otherwise. Consider a worm that is elongated not along its Anterior-Posterior axis, but along its Dorsal-Ventral axis. It sounds strange, but such worms do exist. They are called phoronid worms, and are classified within their own phylum, the Phoronida. They all live in tubes, and the few times I’ve seen them they have been in pretty dense aggregations. As with most tube-dwelling worms the only part of the body that you can usually see is the crown of feeding tentacles, which in these animals (as well as in the Bryozoa and Brachiopoda) is called a lophophore.

The other day I was at the harbor looking for slugs with my friend Brenna, and spotted these pale tentacles swaying in the current.

Phoronids at the Santa Cruz Yacht Harbor
18 September 2017
© Allison J. Gong

These are the lophophores of an aggregation of phoronids! I’d never seen them at the harbor before, so I was pretty excited about it. They were on the side of a floating walkway, down almost beyond the reach of my outstretched arm. The current caused the lophophores to sway continuously and I was barely able to snap some blurry photos without falling in (I couldn’t really see what I was doing and just hoped for the best) when I accidentally caught this one shot. I wanted to have at least one clear-ish shot to submit to iNaturalist. I did manage to scrape off some bits of stuff that I hoped contained intact phoronids, so I could observe them under the dissecting scope at the lab.

And these are some lovely little worms!

The tubes that these phoronids inhabit are more like burrows of slime to which the surrounding sediments adhere. The tube itself isn’t anything particularly interesting, but the bodies of the worms are beautifully transparent. One of the coolest things you can see in a living phoronid is its circulatory system. They have red blood that, like ours, contains hemoglobin, so it’s easy to see the vessels that run along the length of the worm (which is the Dorsal-Ventral axis, remember) and the two blood rings around the base of the lophophore. If you get the lighting right you can even see the vessels that extend into each tentacle of the lophophore.

Single phoronid worm extending its lophophore
18 September 2017

I was disappointed to see that none of the video clips I took really do justice to these worms. They are so pretty when I look at them through the microscope, and I wish I could capture their beauty. You may at least be able to see blood moving through the larger vessels of the body in this short video.

Seems I need to upgrade my photomicroscopy set-up. Anybody have a few thousand bucks they want to donate to the cause?

I’m keeping the phoronids for as long as I can, although I don’t know what to feed them. I had time to take just a quick look at them this morning, and they look fine. Just for kicks I offered them a little phytoplankton to see what they’d do with it and couldn’t see if they were reacting at all. Still, they are filter feeders, and if I can adjust the lighting and get a good view of those ciliated tentacles I should be able to see if they are creating a water current that is bringing food to the mouth. Friday is the next day I have time to spend with these animals that I don’t get to see very often. Maybe then I’ll have something else to report.

Lunacies

Posted on by Allison J. Gong

For several centuries now, Earth’s only natural satellite has been associated with odd or unusual behavior. Lunatics were people we would describe today as mentally ill, who behaved in ways that couldn’t be predicted and might be dangerous. The erratic behaviors were attributed to the vague condition of lunacy. These words are derived from the Latin luna, which means ‘moon’. The cycles of the moon have long been thought to influence human behavior as well; hence such legends as the werewolf.

We do know that the moon indeed has a very strong influence on aspects of many organisms, primarily through the tides. For example, reproduction in many marine animals is timed to coincide with a particular point in the tidal cycle. Grunion (Leuresthes tenuis, small, silver, finger-shaped fishes) run themselves up onto California beaches at night to spawn following the full and new moon high tides in the early summer months. Corals in the Great Barrier Reef spawn together in the handful of nights after the full moon in November. Animals such as these, which reproduce via broadcast spawning, are the ones most likely to benefit from synchronized spawning; after all, there is no point in spawning if you’re the only one doing it. Invertebrates don’t have watches or calendars; they keep time by sensing the natural cycles of sun and moon. The moon’s strong effect on the tides is a signal that all marine creatures can sense and use to coordinate spawning, increasing the probability of successful fertilization for all.

Last night, Wednesday 6 September 2017, the moon was full. Yesterday at the lab, I noticed that  the large Anthopleura sola anemones living in the corner of my table had spawned.

A male Anthopleura sola anemone that had spawned
6 September 2017
© Allison J. Gong

That diffuse grayish stuff in the right-hand side of the photo is a pile of sperm. I looked at a sample under the microscope, just to be sure. By this time they had been sitting at the bottom of the table for several hours and most of them were dead. But they were definitely sperm:

Whenever I see something unusual like this my first impulse is to see if it’s happening anywhere else at the lab. So I started poking around. The aquarists at the Seymour Center told me that some of their big anemones had spawned in the past couple of days; however, since they clean and vacuum the tanks every day all evidence was long gone.

Fortunately there are several A. sola anemones in other labs that aren’t cleaned as regularly as the public viewing areas. One of the animals in the lab next door to where I have my table had also spawned. . .

Female Anthopleura sola
6 September 2017
© Allison J. Gong

. . . and this one is a female! What looks like a pile of fine dust is actually a pile of eggs.

Eggs of Anthopleura sola
6 September 2017
© Allison J. Gong

And the eggs are really cool. See those spines? They are called cytospines and apparently deter predation. Other species in the genus Anthopleura (A. elegantissima and A. xanthogrammica) are known to have spiny eggs, so it appears that this is a shared feature. Now, if only I could get my hands on eggs of the fourth congeneric species–A. artemisia, the moonglow anemone–that occurs in our area, I’d know for certain, at least for California species. I examined the eggs under higher magnification, but due to their opacity I couldn’t tell if the had been fertilized. Most appeared to be solid single undivided cells; they could, however, be multicellular embryos.

All told, of the anemones that had obviously spawned, 1 was female and 4 were male. I sucked up some of the eggs and put them in a beaker of filtered seawater. I doubt that anything will happen, but I may be in for a pleasant surprise when I check on them tomorrow.

The fluidity of sex

Posted on by Allison J. Gong

We humans are accustomed to thinking of sexual function as being both fixed and segregated into bodies that we designate as either Female or Male. And while we, as a species, generally do things this way, in the larger animal kingdom sexual function doesn’t always follow these rules. Many animals are monoecious, or hermaphroditic, having both male and female sex organs in the same body. Not only that, but lots of animals change from one sex to the other. As in so many aspects of biology, the way humans do things may be thought of by us as “normal,” but it isn’t the most interesting way.

Take, for example, the slipper shell Crepidula adunca. This is a small limpet-like creature that lives on the shell of a larger snail. Around here the usual host is a turban snail, either Tegula funebralis or T. brunnea.

Slipper shell (Crepidula adunca) on its host, the turban snail Tegula brunnea, at Pigeon Point
1 May 2017
© Allison J. Gong

There are several species in the genus Crepidula, including C. fornicata, which lives on the Atlantic coast of North America. The species epithet gives an inkling of how reproduction occurs in at least these two species of the genus.

Sometimes C. adunca is found in stacks. I’ve never seen a stack taller than three individuals, but C. fornicata occurs in stacks of about six. The animal at the bottom of the stack is always the largest, and a given turban snail can play host to more than one stack at a time.

Two stacks of Crepidula adunca on the turban snail Tegula funebralis, at Pigeon Point
28 June 2017
© Allison J. Gong

As you might guess, it isn’t mere happenstance that these stacks of C. adunca occur. It turns out that this unusual living arrangement is key to both sexual function and eventual reproduction in this species. The individual on the bottom of the stack (i.e., the oldest) is always a female; those at the top of the stack (i.e., the youngest) are males. However, every stack begins with a single individual, and the default sex in newly settled C. adunca is male. An experiment conducted at Friday Harbor in Washington State1 showed the change from male to female began when the snails reached a size of 7 mm, and all animals larger than 10 mm were female. Animals that begin life as male and transform into females are described as protandrous hermaphrodites. How common is this phenomenon? Not uncommon among fishes, actually. Clownfishes in the genus Amphiprion are protandrous. Remember how in the beginning of the moving Finding Nemo, Nemo’s mom dies? Well, in real life Nemo’s dad would have become his new mom!

In any case, all C. adunca begin adult life as males. If they live long enough to reach about 7 mm in length, they might get to become females. Crepidula adunca‘s unusual living arrangement also facilitates reproduction. Unlike most limpet-like gastropods, C. adunca isn’t a broadcast spawner. Rather, it copulates, as hinted at by the species epithet of its congener C. fornicata. A female slipper shell with a male on her back has a convenient source of sperm with which to fertilize her eggs:  the male reaches into her mantle cavity and transfers sperm to her. Given the constraint of copulation, a female cannot mate until she carries at least one male on her back, and a male cannot reproduce unless he settles atop a female. Once the eggs have been fertilized, they develop within the mother’s mantle cavity until she pushes them out as little miniatures of herself.

Crepidula adunca on the turban snail Tegula brunnea, at Davenport Landing
27 May 2017
© Allison J. Gong

Cool little animals, aren’t they? They remind us not to think of ourselves as The Way Things Are Done. We have a lot to learn from creatures that are not like us, and it’s stories like these that ensure I will never lose my appreciation and love for the marine invertebrates.

1 Collin, R. 2000. Sex Change, Reproduction, and Development of Crepidula adunca and Crepidula lingulata (Gastropoda: Calyptraeidae). The Veliger 43(l):24-33.

Update

Posted on by Allison J. Gong

Remember that gull we rescued last week? After my husband took it to Native Animal Rescue here in Santa Cruz it was transferred up to International Bird Rescue‘s San Francisco Bay Area center in Fairfield. I e-mailed and asked how the gull was doing and whether I’d be able to witness its release back to the ocean. Yesterday I received this response:

Hi Allison,

This is Cheryl Reynolds, the Volunteer Coordinator for Bird Rescue. Thank you so much for rescuing the juvenile Western Gull and getting him into care at Native Animal Rescue. Hooks and fishing line can cause severe injuries but fortunately this guy is doing okay at this time. He/she had surgery yesterday to repair some of the damage the line caused to his leg and is being treated with antibiotics. He’s not totally out of the woods yet but luckily gulls are pretty tough! I’m giving you his case number here at Bird Rescue #17-1887 but I will be happy to follow up with you on his progress. 
To answer your other questions.. We don’t have a timeline yet on release, it depends on how he progresses. We don’t usually send the birds back to Santa Cruz, we have so many young gulls we like to release as a group and in an appropriate location locally. 
If you would like to contribute to this birds care please go to our website at https://www.bird-rescue.org/. You can also sign up to receive our Photo of the Week and patient updates and also find us on Facebook. 
Thanks again for caring for this birds welfare. 
Kind regards,
Cheryl
We hadn’t realized that the fishing line wrapped around the bird’s leg had caused damage that would require surgery. This makes me doubly glad that we were able to rescue it from the surface of Monterey Bay before the injuries became more severe. It sounds like the prognosis is good for this juvenile western gull, and I hope it and several of its cohort can be returned to the skies and sea very soon.

A good deed

Posted on by Allison J. Gong

This is the time of year when whales visit Monterey Bay and often come quite close to shore. Humpbacks, in particular, are commonly seen from beaches in the fall. Earlier in the summer they are out over the Monterey Canyon feeding on krill. In the late summer and early fall they switch to feeding on anchovies, which school in shallower water over the continental shelf. Last week they were putting on a show, to the delight of whale watchers who pay for whale watching trips out of Moss Landing and Santa Cruz.

Yesterday evening my husband and I borrowed a friend’s little boat and went out looking for whales. A humpback had been seen from the beach around the cement ship at Seacliff State Beach, lunge-feeding and breaching. Even the Monterey Bay is a big body of water, and I’d rated our chance of finding a whale at about 50%. We did eventually find one swimming parallel to the shore. And I have pictures to prove it!

Humpback whale (Megaptera novaeangliae) near Aptos, CA
17 August 2017
© Allison J. Gong
Humpback whale (Megaptera novaeangliae) near Aptos, CA
17 August 2017
© Allison J. Gong

The Marine Mammal Protection Act of 1972 prohibits humans from approaching any marine mammals, so we kept our distance. The whale undoubtedly knew we were there and it did get a little closer than this, right around the time that we noticed a flock of ~25 pelicans fly overhead and start circling over an area a short distance away. It was starting to get dark and we had to turn around and head back, and on our way we ended up where the pelicans were hanging out.

As we approached we could see a bird flapping about on the surface of the water, but unable to get airborne. It didn’t take long for us to see that it was somehow tied up with a dead common murre and a piece of kelp. We were able to pull the kelp toward the boat and grab the live bird. It appeared to be a juvenile gull.

Here’s the dead murre:

Dead common murre (Uria aalge) tangled in fishing line
17 August 2017
© Alex Johnson

And here’s the gull:

Injured juvenile gull tangled in fishing line
17 August 2017
© Alex Johnson

It had a hook in its right nostril and a hook in each foot. The hook in its beak was attached to line that went around its body, making the bird unable to raise its head. Fortunately Alex was able to cut the line while I held the bird. We didn’t have the tools to try removing the hooks, so we decided to head back in. We wrapped the bird loosely in a towel to keep it from flailing around and held onto it for the long, wet ride back to the harbor.

When we back on land I called the Marine Mammal Center because: (a) I had the number programmed into my phone; and (b) I knew they’d have a live person to answer the phone, who would be able to tell me who to call about this bird. The person I talked to transferred me to Pacific Wildlife Care in Morro Bay. The recorded message told me to place the bird in a box or pet carrier on a towel and leave it in a warm, dark place until we could bring it in the morning. We weren’t about to make a 2.5-hr drive to Morro Bay, but fortunately there is an organization right here in Santa Cruz that we’ve taken animals to before: Native Animal Rescue. We got home, dug out the kitty carrier, and tucked the bird in for the night. The only warm place we could think of that the cats couldn’t get to was the pantry, so the bird spent the night there.

Injured gull
17 August 2017
© Allison J. Gong

I had a school meeting this morning, so Alex took the bird to Native Animal Rescue. The woman who met him said the bird was a juvenile western gull (Larus occidentalis)–another WEGU. She took the bird out, wrapped it in a towel, and calmed it by simulating a hood on its head.

17 August 2017
© Alex Johnson
17 August 2017
© Alex Johnson

Poor bird. Fortunately the hooks went through the webbing in the feet, so there wasn’t any damage to bones or soft tissue.

Fishing hooks in the feet of a juvenile western gull (Larus occidentalis)
17 August 2017
© Alex Johnson

The woman pulled the hook out of the nostril pretty easily. To remove the hooks from the feet she had to first cut the barbs and then pull them back out. Alex said the whole thing took about 5 minutes. The bird seems otherwise uninjured. The folks at Native Animal Rescue will keep an eye on it for a few days and then release it back to the wild. I think I’ll give them a call tomorrow and see if we can be there when the bird is released.

Update Sunday 20 August: We called Native Animal Rescue this morning and were told that the bird had been transferred to a wildlife care facility up in Fairfield. All of the seabirds that come into Native Animal Rescue get sent up there. So we won’t get to see “our” gull be released back into the wild.

More botanical weirdness

Posted on by Allison J. Gong

In biology, it is often the exceptions to the rules we teach that are the most interesting organisms. For example, every child knows that the sky is blue and the grass is green. With a few leading questions you can get a child to generalize that all plants are green. We all know this, right? Plants are green because they have chlorophyll, which allows them to perform the magic of photosynthesis. And yes, it really is magic. Harvesting the power of the sun to build complex molecules out of CO2 and H2O? Hell yeah, photoautotrophs are freakin’ amazing!

But what about the plants that aren’t green? How do they make a living?

I’ve already written about dodder, a parasitic plant that is commonly seen growing on pickleweed at Elkhorn Slough. A few weeks ago when I was at Lake Tahoe I encountered another plant that has a parasitic lifestyle: snow plant.

Snow plant (Sarcodes sanguinea) near Carson Pass in the Sierra Nevada
26 July 2017
© Alex Johnson

Snow plant (Sarcodes sanguinea) is a non-photosynthetic plant that has zero chlorophyll and thus zero green color, and is instead a rich blood-red color hinted at by its species epithet. It lives on the forest floor in close proximity to coniferous trees. The blood-red inflorescences shoot up from the ground, apparently out of nothing; the rest of the plant lives underground. If you break an angiosperm into its basic anatomical components you have: leaves, stems, roots, and flowers. Snow plant isn’t photosynthetic, so it doesn’t need or have leaves. And since stems are essentially support structures to hold leaves up to the light it doesn’t have those, either. The roots and vegetative parts (rhizomes?) of snow plant are underground and for most of the year there’s no indication that it’s there at all, until it sends up an inflorescence in the late spring as the winter snow is melting.

Snow plant (Sarcodes sanguinea) near Carson Pass in the Sierra Nevada
26 July 2017
© Alex Johnson

Since snow plant isn’t autotrophic and doesn’t fix its own carbon, it has to obtain fixed carbon from elsewhere. Snow plant lives under conifers, but is not a parasite on the trees the way that dodder is a parasite on pickleweed. The relationship is much more complex and involves a third player. And all of the action happens underground.

Enter the third player, a mycorrhizal fungus. This fungus’s mycelium spreads through the roots of the conifers with which it has a mutualistic relationship. The tree shares photosynthate (i.e., fixed carbon) to the fungus, which in turn provides minerals to and enhances water uptake for the tree. These mycorrhizal symbioses are very common in Nature, but most often go unnoticed because they occur in the soil.

Snow plant (Sarcodes sanguinea) near Carson Pass in the Sierra Nevada
26 July 2017
© Alex Johnson

Sarcodes sanguinea, the third partner in this unusual plant-plant-fungus ménage à trois, takes advantage of the intimacy between the conifer and the fungus. Instead of parasitizing the tree it targets the fungus, siphoning off part of the fungus’s share of photosynthate. I suppose this makes snow plant an indirect parasite of the tree. The tree is doing all the work, as it is the only autotrophic member of the trio. It shares photosynthate with the fungus and gets something vital in return. Snow plant, on the other hand, doesn’t contribute anything to either the fungus or the tree. Rather, it takes directly from the fungus and only secondarily from the tree.

It would be interesting to investigate the energetics of this three-way relationship. How do the fungus and tree react to parasitism by snow plant? On which of the mycorrhizal partners does snow plant have the strongest effect? The fungus, because its share of fixed carbon is being drained directly? Or the tree, which suffers because feeding the snow plant via the fungal intermediary means less photosynthate available to support its own metabolic activities? Does the tree have any way to stop the flow of fixed carbon to an area of the fungal mycelium that is being parasitized by the snow plant?

One last note. Many of the snow plants that we saw on the trail out of Carson Pass to Big Meadow had been surrounded by stones. We never saw any signs so aren’t sure why, but I think hikers want to keep the snow plants from getting trampled. The species isn’t endangered or threatened, although it is restricted to higher altitudes in California’s mountain ranges.

Distribution of Sarcodes sanguinea in California

I think the stone rings were put there both to point out and protect the S. sanguinea inflorescences, although it would be hard to miss them. Nothing else is that bloody shade of red, and it really does stand out. Even small plants are very conspicuous.

Small snow plant (Sarcodes sanguinea)
26 July 2016
© Allison J. Gong

What a bizarre plant. It challenges our preconceived notions of what plants are all about. Ain’t Nature grand, and weird?

Gulls

Posted on by Allison J. Gong

Earlier this week I accidentally came upon a baby bird. I was on my way out to the cliff at the marine lab to dispose of a corpse (a fish that died of natural causes) when I noticed a western gull perched on the fence railing and allowing me to get unusually close. It was wary, though, and very alert. When I stopped to listen and watch for a while I heard a high-pitched “cheep-cheep-cheep” coming from beyond the shrubs on the other side of the fence. To get to the point where I could throw the dead fish off the cliff I had to pass closer than I wanted to the chick, which I could then see standing among the ground cover.

Western gull (Larus occidentalis) adult and chick at Terrace Point
2 August 2017
© Allison J. Gong

The western gull (Larus occidentalis), or WEGU in birders’ parlance, is a California Current endemic species. It is a bird of the Pacific coast of North America, and is rarely found more than a few miles inland. So if you don’t live right on the coast and have problems with gulls in landfills or parks, you cannot pin the blame on a WEGU. Western gulls are present year-round, feeding on whatever they can get. Like many gulls they are quite efficient scavengers and have a varied diet that often includes human refuse. They have become quite adapted to human presence, and have taken advantage of the fact that we tend to leave our garbage all over the place.

Western gull (Larus occidentalis) adult and chick at Terrace Point
5 August 2017
© Allison J. Gong

Yesterday the chick was in the same area, only a little more visible from directly above. I’d seen as many as five adults hanging around the chick, with no idea who the actual parents are. The chick is big and feathered enough to thermoregulate on its own but is still entirely dependent on its parents (and other cooperative adults) for food.

Being a gull, it is very vocal. It doesn’t sound like a gull, though. The calls sound like they’re coming from a much smaller bird. It cheeped continuously during the 20 minutes or so I was watching it, even with its parents standing right next to it. When this chick fledges, the only direction it can go is out over the water. Unless it can steer its flight well enough to land on one of the intertidal benches to the left of its present location, it’ll end up in the water. I imagine it will be able to swim just fine, but the next thing it will have to learn is how to get up in the air from the water.

Western gulls do not migrate and, garbage notwithstanding, depend on the California Current for most of their food. And while it may seem that there are gulls all over the place with plenty to burn, the WEGU’s restricted range makes this species vulnerable to perturbations in the ecology of the coastal ocean. Not only might their food supply be interrupted as prey species’ distributions change, but their nesting sites on cliffs may be inundated as sea level rises due to climate change.

Western gull (L. occidentalis) in adult breeding plumage
5 August 2017
© Allison J. Gong

Gulls have a reputation as trash birds, but the adult WEGU really is beautiful. Their large-ish body size, pure white head and front, and pink legs/feet are pretty distinctive. WEGUs are the only gulls that I feel at all comfortable IDing in the field, and that’s only when the birds are in adult plumage. This species, and many other gull species, takes four years to attain the adult coloration. The juveniles of many species all look very similar, which makes field identification a hazardous exercise. To make things even more complicated, western gulls are known to hybridize with the glaucous-winged gull (Larus glaucescens); fortunately for California birders, the hybridization zone is further north in Washington State.

Seabirds of all types depend on their feathers for insulation. Small-bodied endotherms like birds have an unfavorable surface area:volume ratio and would be unable to maintain their body temperature in cold water if they didn’t have insulation. One of the adaptations that enables a life in cold water is a preen gland near the base of the tail. This gland secretes an oily substance that the bird spreads over its feathers as a waterproof coating, very effectively shielding the body from the cold water. Feathers themselves have water-shedding properties of their own, but augmenting this feature with oil is sheer genius. You’ve heard the phrase “like water off a duck’s back”? We can say that because ducks and other water fowl have preen glands.

Feathers must be clean and lie properly for a bird to fly and thermoregulate, and birds at rest spend a lot of time grooming. All birds preen, but for aquatic birds this activity is especially crucial. Watching a bird preen is like watching a cat take a bath: the sequence of actions appears to be haphazard, but eventually the whole body gets attention.

Snow in July

Posted on by Allison J. Gong

The Sierra snowpack is California’s largest single reservoir of fresh water, accounting for 1/3 of the state’s water supply1. A state with a mediterranean climate, such as California, receives precipitation only during the short rain/snow season. During years of drought, when the average Californian frets about how little rain is falling, state water managers are keeping a worried eye on the amount of snow falling in the Sierra. Snow surveyors use remote sensing and field measurements to estimate the water content of the snowpack. The snow water equivalent on 1 April is used to compare snowpack water content across years.

The 2016-2017 snow year was a productive one, dumping near-record amounts of ‘Sierra cement’ on the mountains. (Skiers accustomed to the powder snows of Utah and Colorado often disparage the heavy snow in the Sierra, but Sierra cement carries a lot more water than powder so is much more beneficial to the state’s water supply). Most of that snow eventually melts, births streams and rivers, and flows from the mountains to lower elevations. After a good snow year, though, snow fields remain at high altitudes even during high summer. That definitely is the case around Lake Tahoe.

A few days ago my husband and I hiked from Carson Pass to Big Meadow, a through hike about 8 miles long. The hike goes through some gorgeous alpine meadow, with an absolutely stunning display of wildflowers. Even in late July we had to cross several streams and saw lots of snow.

Round Top Mountain, viewed from meadow above Carson Pass
25 July 2017
© Allison J. Gong
Snow field in the high Sierra
25 July 2017
© Allison J. Gong

If you look closely at the bottom photo, you may notice some faint pink streaks on the face of the snow field. This pink snow is called ‘watermelon snow’ because of the color. It is a phenomenon that occurs only at high altitudes or polar regions in the summer. Here’s a closer look, taken with a 70-200 mm lens that I rented for the week.

Watermelon snow
25 July 2017
© Allison J. Gong

Given the color of those streaks, you’d think the organism producing it would be a red alga of some sort, wouldn’t you? I did, too, until I did some research and learned that it is a green alga! Chlamydomonas is a genus of unicellular green algae, most of which are indeed green in color because the only photosynthetic pigments they contain are chlorophylls. However, Chlamydomonas nivalis also contains reddish carotenoid pigments that serve to shield the cell’s photosynthetic pigments from excess radiation, which is intense at the high altitudes where the algae live. The pigments absorb heat, which increases the melting of snow in the immediate vicinity and provides liquid water that the algae require. Watermelon snow is found in alpine regions across the globe, although it isn’t known whether or not the same species of alga is responsible in all cases.

Cross-country skiers and snowshoers pass through these areas in the winter, and never report seeing watermelon snow. What happens to the cells in the winter? Do they die?

It turns out that the alga persists year-round, although in different life history stages. Given the inhospitality of their habitat, most of the life cycle involves waiting in a dormant stage, with a short burst of activity in the spring. The red form that we see in the summer is a dormant resting stage, having lost the pair of flagella possessed by swimming unicellular green algae. These spores, former zygotes resulting from fertilization, are non-motile and cannot escape to deeper snow to avoid UV radiation, so they use carotenoids to serve as sunscreens. They are not dead, though, and continue to photosynthesize all summer. They rest through the winter and germinate in the spring, stimulated into activity by increased light and nutrients, and flowing water. Germination involves the release of biflagellated cells that swim to the surface of the snow, where at least some of them function as gametes. Fertilization occurs, with the resulting zygotes soon after forming the resting spores that result in watermelon snow.

It may seem strange that this organism spends most of its time in a dormant stage, but this is not at all uncommon for things that live in hostile habitats. When conditions for life are difficult, the best strategy can be to hang out and wait until things get better. Chlamydomonas nivalis does this on a yearly basis, as do many of the marine unicellular algae. And some animals, namely tardigrades, can dry out and live for decades or perhaps even centuries in a state of suspended animation, returning to life when returned to water. As with many natural phenomena, this kind of lifestyle seems bizarre to us because it is so unlike how we do things. But if C. nivalis could observe and think about how we live, it would no doubt consider us inconceivably wasteful, expending enormous amounts of energy to remain active at times when, clearly, it would much more sensible (from C. nivalis‘s point of view) to sleep until better conditions return.

1 California Department of Water Resources

Puzzling

Posted on by Allison J. Gong

The marine macroalgae are, as a group, the most conspicuous organisms in the intertidal. Yet, most tidepool explorers dismiss them as “seaweeds” and move on to the next thing, which they hope is somehow more interesting. This is akin to visiting the jungles of Brazil and not paying attention to the lush foliage that defines that particular biome. I will admit that, as a zoologist whose primary interest is the marine invertebrates, I have been guilty of this offense. I’ve also felt guilty about the oversight and thought to myself, “I really should know the algae better.” I have no formal training in phycology beyond auditing marine botany labs after I finished graduate school, but I’ve got the basics down and really have no excuse for the continuation of this gap in my knowledge.

So a couple of years ago I decided to start filling in that gap. I dragged out my marine botany notebook and have slowly been adding to it, building up my herbarium collection at the same time.

The red algae (Rhodophyta) are the arguably the most beautiful of the seaweeds, and inarguably are the most diverse on our coast. Some of them are easy to identify because nothing else looks like them, but many share enough morphological similarity that field IDs can be tricky if not downright impossible. For example, to ID a specimen and distinguish it from a close relative you may need to examine the number, size, and arrangement of cells in a cross-section of a blade. Some species are impossible to identify beyond genus (or even family, in some cases) unless you can look at their reproductive structures, which they might not have at the time they’re collected.

One of the most ubiquitous red seaweeds, and one that is easily identified to genus, is Mazzaella. The genus name for this group of species used to be Iridea, which gives a hint as to the appearance of the thalli–many of them are iridescent, especially when wet. The species that I see most often are M. flaccida in the mid intertidal and M. splendens lower down. These species are usually not difficult to tell apart once you get used to looking at them and their respective habitats.

Mazzaella splendens at Whaler’s Cove at Pigeon Point
28 June 2017
© Allison J. Gong
Mazzaella flaccida at Natural Bridges
9 July 2017
© Allison J. Gong

Mazzaella splendens is generally a solid brown with sometimes a green or purple cast. It is soft and floppy, and the blades are long (up to 50 cm) and taper to a point. The Marine Algae of California, which we call the MAC, uses the term “lanceolate” to describe this shape. Mazzaella flaccida is green or greenish-purple, sometimes more brownish along the edges; its blades are flexible but a teensy bit crisper than those of M. splendens, and its blades are described as cordate (heart-shaped) or broadly lanceolate.

Got it. That’s not too bad, right?

But then you see something like this, and a whole other set of questions comes to mind.

Thalli of Mazzaella flaccida at Natural Bridges
9 July 2017
© Allison J. Gong

Based on habitat alone these are both M. flaccida. The greenish thallus on top looks like textbook M. flaccida, but the lower thallus looks more ambiguous. It has the right size and shape but is the wrong color, and what’s up with all those bumps? I brought these thalli back to the lab to examine them more closely. Here are the entries from my lab notebook:

Now is the time to bring up the subject of life cycles in red algae. Algae such as Mazzaella alternate through three generations: male and female gametophytes, both of which are haploid; a diploid sporophyte; and a diploid carposporophyte. Here’s a diagram that shows how this alternation of three generations works:

Life cycle of some red algae, showing alternation of three generations
© McGraw-Hill

It was easy to see that the bumpy thallus I collected was sexy, while the smooth green thallus was probably not reproductive. Having both thalli in hand, along with the MAC and phycology texts in the lab, I was able to determine that the bumpy brown thallus is actually two generations in one body. So cool! But how does this work? The bumps on the thallus are called cystocarps. In Mazzaella a cystocarp contains the diploid tissue of the carposporophyte surrounded by the haploid tissue of the female gametophyte. Et voilà! Two generations in a single thallus.

Now, what’s inside the cystocarp? What does the carposporophyte tissue actually look like? To find out I had to do some microsurgery, first to remove a carpospore (1-1.5 mm in diameter) from the female gametophyte and then to cut it open to see what’s inside. What’s inside were microscopic diploid carpospores, which grow into the macroscopic sporophyte generation. Forcibly dissected out as they were, they don’t look like much, just tiny round cells about 2 µm in diameter.

Carpospores of Mazzaella flaccida
12 July 2017
© Allison J. Gong

The next logical step would be to isolate some of the carpospores and try to grow them up. I wasn’t thinking about that at the time and pressed both thalli. However, I do have another female gametophyte with cystocarps that I can investigate further tomorrow. It’s probably a fool’s errand, as I am not going to bother with sterile media and whatnot. Oh well. Nothing ventured, nothing gained, right?

Now you see it, now you don’t

Posted on by Allison J. Gong

This morning in the intertidal I was reminded of how often I encounter animals I wasn’t looking for and almost missed seeing at all. That got me thinking about color and pattern in the intertidal, and how they can be used either to be seen or to avoid being seen. Some critters–the nudibranchs immediately come to mind–are so brightly colored that they are impossible to miss, while others are camouflaged to the point that it takes a trained eye to see them.

Truth be told, however, most of the animals in the intertidal don’t have eyes, or at least eyes that can form images the way ours do. While just about any animal might be preyed upon by birds at low tide, most of the predators a creature of the tidepools might face would not be visual predators. This in turn begs the question of just how adaptive or not a species’ crypticness is. The way I see it, there are three options, or hypotheses about the potential benefit of an animal’s coloration and patterning:

  1. Colors and patterns that make an animal conspicuous are advantageous.
  2. Colors and patterns that make an animal cryptic or camouflaged are advantageous.
  3. Colors and patterns are neither advantageous or disadvantageous.

Today I’m going to consider hypothesis #2, as it is the most interesting one. Let’s put aside for now the question of how an animal’s color comes to be and consider only its effect on visibility to Homo sapiens (specifically, me).

Example #1 (obvious): Tonicella chitons

These are the pink chitons that I find on exposed coasts. They eat encrusting coralline algae, and I suspect their color derives at least in part from their diet. Here’s one that perfectly matches its food:

The chiton Tonicella lokii at Pistachio Beach
29 May 2017
© Allison J. Gong

On the other hand, Tonicella isn’t always this entirely pink, nor is it always seen on coralline algae:

The chiton Tonicella lokii at Pistachio Beach
29 May 2017
© Allison J. Gong
The chiton Tonicella lokii at Monastery Beach
27 October 2015
© Allison J. Gong

The chiton I saw at Monastery Beach wasn’t anywhere near coralline algae. It has obviously been eating something, probably algal films of whatever sort it comes across. Correlation is not causation, but it may not be mere coincidence that this pale version of Tonicella lokii lives on rock devoid of coralline algae.

Example #2 (obvious): Decorator crabs

Tonicella doesn’t intentionally alter its appearance by eating pink food. Given the extremely rudimentary nature of a chiton’s nervous system, it likely can’t intentionally do much of anything. It doesn’t have eyes so it cannot see, although there are light-sensing organs called aesthetes in the dorsal shell plates and light-sensitive cells in the lateral girdle. Chitons make their way through the world largely by following chemical gradients, either in the water current or on the substrate.

Crabs, on the other hand, have very complex compound eyes and can, to some extent, see what’s going on around them. The compound eyes of arthropods are highly effective motion sensors, certainly much more sensitive than our eyes are, which is why it’s so hard to sneak up on a fly even if you’re extending your reach by using a fly swatter. Crabs certainly are aware of the visual aspects of their surroundings. They can see potential threats and typically respond in one of three ways: (1) scuttling away; (2) coming out fighting; and (3) remaining still and trying not to be noticed.

It takes energy to scuttle back and forth, and the little shore crabs (Pachygrapsus crassipes) are always on the move. They are quick to run for cover when approached, but will come out and resume their explorations if you sit still for about a minute. They are really fast and difficult to catch, perhaps not quite as challenging as the Sally Lightfoot crabs that so enraged the crew of the Western Flyer during Ed Ricketts’ and John Steinbeck’s excursion to the Sea of Cortez, but hard enough to be not worth my effort. Fighting is an option only for those equipped to fight. Rock crabs (for example, Romaleon antennarium) remain hidden under algae or partially buried in sand, but when exposed they come out with big claws open and ready to pinch the hell out of anything that comes close. These are the only animals that I really worry could hurt me in the intertidal.

Which leaves the hold-still-and-hope-not-to-be-seen option. This is what decorator crabs do. In terms of temperament, decorator crabs (of which there are several species) are placid and unaggressive: they will pinch when provoked and it can hurt, but they won’t do the kind of damage that a rock crab would happily inflict. Decorator crabs hide in plain sight by covering their carapace and legs with little bits of the environment, usually algae. A well-decorated crab can be sporting several species of algae on its back.

This morning I saw and collected this small crab:

A small decorator crab, Pugettia richii, on a bed of Egregia menziesii at Davenport Landing
11 July 2017
© Allison J. Gong

I actually didn’t see it at first. I was pawing through the thick algal growth and felt its little feet scratching my hand. I peeked under the algae and there was the crab. Its carapace is about 2.5 cm across, and its claws probably wouldn’t be able to pinch human skin even if the crab tried to. Which it certainly didn’t. I wanted to observe the crab more closely in and keep it for use when I teach the crustacean diversity lab this fall, so I brought it back to be examined under the dissecting scope.

A decorated Pugettia richii, observed in the lab
11 July 201
© Allison J. Gong

The crab’s own color is a dark brownish red, which helps it hide amongst the red algae. It adds to the environment-as-appearance effect by attaching at least three species of red algae to its carapace. The crab does this by grabbing a piece of algae with one of its claws, then reaching up and behind its head to put it on the carapace, which has has tiny hooks that hang onto the decoration. It’s a very nifty scheme, but there’s one big problem. Each time the crab molts it loses its decoration and has to acquire its accessories all over again.

Example #3 (not obvious at all): Lottia digitalis

We have about a gazillion species of limpets on the California coast. Well, not really but it certainly does feel like it. To make things even more difficult I can’t seem to keep the current scientific names straight. I know that many of the commonly encountered intertidal limpets have been consolidated into the genus Lottia (this includes species that I learned by another name way back when) and I’m slowly getting used to recognizing the Lottia “look”. However, aside from the owl limpet (L. gigantea), which is much bigger and more conspicuous than any others, the other species are difficult to distinguish and I can never remember if species x has the deep ridges or if that’s species y. Ugh.

Earlier this spring I was in the field with my friend Brenna, and she was showing me the differences between Lottia scabra and L. digitalis. Brenna studies molluscs so I know she knows what she’s talking about. Lottia scabra is now easy for me to recognize, but L. digitalis is both trickier and more interesting.

Limpets Lottia scabra (upper right) and L. digitalis (left and lower right) among barnacles at Natural Bridges
25 June 2017
© Allison J. Gong

See how those all look like limpets? Now look at this:

Davenport Landing
11 July 2017
© Allison J. Gong

Do you even see the limpets?

The large animals in the photo are gooseneck barnacles, Pollicipes polymerus. They live on and amongst mussels in the mid-intertidal. This spring Brenna told me that Lottia digitalis comes in a morph that lives on and looks like Pollicipes. I’d never seen it until today. Look at the photo again. Can you see the limpets now?

Here are some more photos.

Lottia digitalis (“Pollicipes morph”) at Natural Bridges
11 July 2017
© Allison J. Gong
Lottia digitalis (“Pollicipes morph”) at Natural Bridges
11 July 2017
© Allison J. Gong

Isn’t it remarkable how these limpets have exactly the colors and pattern as the plates of Pollicipes? And I didn’t even know about them six months ago. I love having new things to learn and more reasons to pay closer attention to creatures I tend to take for granted. I think it’s time for me to tackle the challenge of identifying limpets in the field. Next season, that is. Today was probably my last day in the intertidal for a few months. We won’t have decent low tides during daylight hours until November.