Complexity in small packages

Last week I went up to Davenport to do some collecting in the intertidal. The tide was low enough to allow access to a particular area with two pools where I have had luck in the past finding hydroids and other cool stuff. These pools are great because they are shallow and surrounded by flat-ish rocks, so I can lie down on my stomach and really get close to where the action is. At this time of year the algae and surfgrasses are starting to regrow; the surface of the pools was covered by leaves of Phyllospadix torreyi, the narrow-leafed surfgrass.

Parting the curtain of Phyllospadix leaves to gaze into the first pool I was pleasantly surprised to find this. What does it look like to you?

Aglaophenia latirostris at Davenport Landing
8 March 2017
© Allison J. Gong

There are actually two very different organisms acting as main subjects in this photo. The pink stuff is a coralline alga, a type of red alga that secretes CaCO3 in its cell walls. Coralline algae come in two different forms: one is a crust that grows over surfaces and the other, like this, grows upright and branching. Because they sequester CaCO3, corallines are likely to be affected by the projected increase of the ocean’s acidity due to the continued burning of fossil fuels. Ocean acidification is one of the sexy issues in science these days, and although it is very interesting and pertinent to today’s world it is not the topic for this post. Suffice it to say that changes in ocean chemistry are making it more difficult for any organisms to precipitate CaCO3 out of seawater to build things like shells or calcified cell walls.

It’s the tannish featherlike stuff in the photo that I was particularly interested in. At first glance the tan thing looks like a clump of a very fine, fernlike plant. It is, however, an animal. To be more specific, it is a type of colonial cnidarian called a hydroid. I love hydroids for their hidden beauty, not always visible to the naked eye, and the fact that at first glance they so closely resemble plants. In fact, many hydroid colonies grow in ways very similar to those of plants, which has often made me think that in some cases the differences between plants and animals aren’t as great as you might assume. But that’s a matter for a separate essay.

I collected this piece of hydroid and brought it back to the lab. The next day I took some photos. To give you an idea of how big the colony is, the finger bowl is about 12 cm in diameter and the longest of these fronds is about 3 cm long.

Colony of the hydroid Aglaophenia latirostris
9 March 2017
© Allison J. Gong

And here’s a closer view through the dissecting scope.

The colonial hydroid Aglaophenia latirorostris
9 March 2017
© Allison J. Gong

Each of the fronds has a structure that we describe as pinnate, or featherlike–consisting of a central rachis with smaller branches on each side. This level of complexity can be seen with the naked eye. Zooming in under the scope brings into view more of the intricacy of this body plan:

Close-up view of a single frond of Aglaophenia latirostris, showing feeding polyps and two gonangia
9 March 2017
© Allison J. Gong

At this level of magnification you can see the anatomical details that cause us to describe this animal’s structure as modular. In this context the term ‘modular’ refers to a body that is constructed of potentially independent units. A colony like this is built of several different types of modules called zooids, some of which are familiarly referred to as polyps. Each zooid has a specific job and is specialized for that job; for example, gastrozooids are the feeders, while gonozooids take care of the sexual reproduction of the colony. In this colony of Aglaophenia each of these side branches consists of several stacked gastrozooids, which you can see as the very small polyps bearing typical cnidarian feeding tentacles. Aglaophenia is a thecate hydroid; this means that each gastrozooid sits inside a tiny cup, called a theca, into which it can withdraw for protection. Those larger structures with pinkish blobs inside are called gonangia. A gonangium is a modified gonozooid, found in only thecate hydroid colonies, that contains either medusa buds or other reproductive structures called gonophores.

Pretty complicated, isn’t it? Who would expect such a small animal to have this much anatomical complexity?


In the second pool I found an entirely different type of hydroid. At first glance this one looks more animal-like than Aglaophenia does, although it is still a strange kind of animal. This is Sarsia, one of the athecate hydroids whose gastrozooids do not have a protective theca. It might be easier to think of these and other athecate hydroids (such as Ectopleura, which I wrote about here and here) as naked, with the polyps not having anywhere to hide.

Colony of the athecate hydroid Sarsia sp.
9 March 2017
© Allison J. Gong

Each of these polyps is about 1 cm tall. The mouth is located on the very end of the stalk. The tentacles, not quite conforming to the general rule of cnidarian polyp morphology, do not form a ring around the mouth. Instead, they are scattered over the end of the stalk.

Here’s a closer view:

Colony of the athecate hydroid Sarsia sp.
9 March 2017
© Allison J. Gong

In the hydroid version of Sarsia, the reproductive gonozooids are reduced to small buds that contain medusae. You can see a few round pink blobs in the lower right of the colony above; those are the medusa buds.  The medusae are fairly common in the local plankton, indicating that the hydroid stage is likewise abundant. Here’s a picture of a Sarsia medusa that I found in a plankton tow in May 2015.

Medusa of the genus Sarsia
1 May 2015
© Allison J. Gong

The medusa of Sarsia is about 1 mm in diameter and has four tentacles, which usually get retracted when the animal is dragged into a plankton net. Sometimes, if the medusa isn’t too beat up, it will relax and start swimming. I recorded some swimming behavior in a little medusa that I put into a small drop of water on a depression slide. It refused to let its tentacles down but you might be able to distinguish four tentacle bulbs.

There’s a lot more that I could say about hydroids and other cnidarians. They really are among the most intriguing animals I’ve had the pleasure to observe, both in the field and in the lab. I’ve always been fascinated by their biphasic life cycle, with its implications for the animals’ evolutionary past and ecological present. Perhaps I’ll write about that some time, too.

Posted in General natural history, Marine biology, Marine invertebrates | Tagged , , , , , | Leave a comment

Just a human, being

Recently I’ve been thinking a lot about our species’ relationship to the natural world. These musings have been brought on not only by my own impairment and inability to spend as much time in the field as I would like, but also by the current political climate in the U.S. Recent Executive Branch appointments and policy announcements make me fear that we, as a country, are going to be even more removed from the natural world than we currently are. This will have dire long-term consequences for all of us. Much has been made lately of federal cuts to spending on science and environmental protection. I am not qualified to address the economic aspects of cuts, but can speak to what I feel will be their effect on quality of life.

For several generations now, humans have become increasingly separated from the natural world around them. We live in cities surrounded by concrete and steel, most of us don’t grow or kill our own food, and we tend to view the natural world as “other,” differing from us in some fundamental way. Even among people who spend much of their leisure time outdoors, many at least occasionally view nature as something to be conquered–by climbing the highest peak, hiking the longest trail, visiting the deepest part of the ocean, or surfing the biggest wave. There isn’t necessarily anything wrong with testing your skills and challenging yourself to perform at the highest level possible. I do that all the time, by trying to learn the names and biology of the organisms I encounter in the wild. But if that’s what you’re doing every time you venture outdoors then you are missing out on something.

Sometimes you need to just be.

One of my graduate advisors, Todd Newberry, used to tell students when we went into the field to “get your face down where your feet are.” It was a simple phrase to remind students that none of the interesting stuff going on in the intertidal occurs at human eye level. And even things that you can see while standing up are very different when you observe them from the level at which they experience the world. For example, can you identify this very common and conspicuous animal from the intertidal at Natural Bridges?

7 March 2017
© Allison J. Gong

The observation skills that Todd taught us were the kind that reward patience and a certain ability to lose oneself in time. “Glance-and-go” was something that he taught us to despise as both lazy and weak, a mindset to be tolerated for a short time in rookies but completely unacceptable for anyone aspiring to the Varsity team. The true rewards of observation in the field come when you spend real time with the organisms, learning enough about them to imagine what their lives are like, and appreciating them for what they are instead of disregarding them for not being more like us.

In my experience there is something transcendent about simply being in nature. And I don’t mean temporarily occupying a bit of space that happens to be out-of-doors. I mean the act of immersing yourself, mentally as well as physically, in the natural world. I mean, instead of using your time outdoors to get from point A to point B or achieving some tangible goal such as bagging your limit or adding to your life list of species seen, stopping for a while and just being. Slowing down and stepping back from the frenzy of modern human life, even for a few minutes, allows you to notice things that ordinarily don’t catch your attention. Even seeing this happen second-hand is a lot of fun. One of the best things about taking students out in the field is hearing them exclaim, “I never noticed that before!”

I have to admit, though, that it’s not always easy to do this. Not everyone gets–or even wants–to make the Varsity team. Many people don’t have time in their busy lives to spend hours in the field every so often; certainly most don’t have the luxury of a job that requires spending time outdoors like I do. And of course there are those who just aren’t interested. That’s fine, too. After all, I’m not at all interested in the stock market, soccer, or stamp-collecting.

Now, back to that picture above. I bet that from this view, as you would see them from eye-level, you’d be able to made a good guess.

Organisms of the mid-intertidal at Natural Bridges
7 March 2017
© Allison J. Gong

These are the famous owl limpets, Lottia gigantea. They are the largest limpets on our coast, and are notable not only for their size (up to 10 cm long) but also for some rather extraordinary behavior. These large individuals, which occupy suspiciously blank areas of the mid-intertidal at Natural Bridges, are all females. The limpets are very territorial: when immersed at high tide they will cruise over the area that they monopolize and push or scrape off any interlopers such as other limpets, barnacles, or newly settled larvae.

An owl limpet (L. gigantea) in her farm at Natural Bridges
7 March 2017
© Allison J. Gong

See those zig-zaggy marks no the rock in the photo above? The owl limpet is also a farmer. As she’s patrolling her territory she uses her radula to scrape off the film of algae that grows on the rock. It takes a while for the algal film to develop, so the limpet restricts her grazing to one area at a time. She is, in effect, manipulating her environment to produce food. When humans do this we call it agriculture. Why not use the same term when a snail does it?

These Lottia farms are exactly the kind of thing that people overlook, and even stand in, without noticing that they are there. In the intertidal, as in many natural places, you don’t really see what’s going on until you slow down, let yourself just be, and get your face down where your feet are. You might be surprised at how much you can see.

Posted in General natural history | Tagged , | 2 Comments

A different sort of hatching

Newborn bald sculpin (Clinocottus recalvus) hatchlings
22 February 2017
© Allison J. Gong

My bald sculpins have begun hatching! Their egg mass has been disintegrating over the past few days and I couldn’t tell if that was because they were dying or hatching. Yesterday I was able to spend some time looking at them and was surprised to see that a few little pink blobs had wiggled their way out of the egg mass while I was manipulating it. Baby fishies! Well, they’re still mostly yolk, but each yolk has a baby fish attached to it. They flit around quite a lot and are difficult to photograph. I had to put this trio in a depression slide, the macro photographer’s trick of making the universe smaller so the creature can’t swim too far away.

Bald sculpin (C. recalvus) hatchling
22 February 2017
© Allison J. Gong

This little fish was cooperating with me, so I carefully placed a coverslip on its drop of water and took some video. The first part was shot through the dissecting microscope with epi-illumination from a fiber-optic light, which shows the surface details. The second clip was taken through the compound microscope with trans-illumination; this kind of lighting doesn’t show any of the three-dimensional structure of objects but does a wonderful job with transparent objects like larval fish.

I like that the baby fish have spots on their yolk sacs as well as the top of the head. And from the second half of the video it appears that they don’t yet have a gut, at least not one that I can see. For the time being they don’t need a gut, as they’re surviving off the energy stored in the yolk sac, but once the yolk has been absorbed they will have to start feeding. At that point they’ll need to have complete guts. I imagine they will be hungry, and hope I have something they’ll be able to eat.

How big are these baby fish, you ask? The smallest ones were about 2 mm long, and the biggest one was twice the size, with a correspondingly smaller yolk.

Bald sculpin (C. recalvus) hatchling
23 February 2017
© Allison J. Gong

And yesterday I caught some time-lapse video of a baby hatching from its egg. Why have I never played with the time-lapse function on my phone before? It’s really cool.

For now I’m keeping the babies in a mesh container, separated from their father so he cannot eat them. I don’t think I’ll end up with more than a couple dozen hatched larvae, as the egg mass has begun to decompose and many of the embryos have died inside their eggs. And no doubt some of the larvae that I’ve rescued already will die. I figure I have a few days before I need to worry about feeding the survivors. After that, who knows? Your guess is as good as mine.

Posted in General natural history | Tagged , | Leave a comment

Metamorphosis

It has been a few weeks since I posted about my most recent batches of urchin larvae. Some strange things have been happening, and I’m not yet sure what to make of them. It would be great if animals cooperated and did what I expect; somehow that never seems to be the case. The upshot of all this uncertainty is that there is always something new to learn. I, for one, am not going to complain about that.

One noteworthy thing to report is that my hybrids all died, very quickly and unexpectedly. They had been racing through development and on the dreaded Day 24 they looked great.

Hybrid larvae of purple urchin (Strongylocentrotus purpuratus) eggs fertilized by red urchin (Mesocentrotus franciscanus) sperm, age 24 days.
23 January 2017
© Allison J. Gong

And the next time I changed their water, they were all dead. So much for the hybrid vigor I had written about earlier. Teach me to get cocky and think I know what’s going on.


Fast forward to Day 52, and some of the cultures are still going strong. I originally set up four matings, and at least some individuals from each are alive. One thing that seems to happen when I start multiple batches of larvae at the same time is that the batch with the fewest numbers does the best. This time my F3xM1 mating was always the least dense culture, but some of them have already begun and completed metamorphosis. And the ones that are metamorphosing are the ones being fed what I expected to be the less desirable food source. As I said, not much of this whole experience is making sense.

The good thing is that I have an opportunity to observe these larveniles in action. As long as they don’t get arrested in this neither-here-nor-there stage, they should soon join their siblings as permanent inhabitants of the benthos.

This video contains short clips of three different larveniles. I’ve arranged the clips from earlier to later stages of metamorphosis. Although these are three separate individuals, you can imagine that each one goes all of these stages.

Having both tube feet (for crawling around the benthos) and ciliated bands (for swimming in the plankton) make these animals unsuited for either habitat. They have gotten very heavy and sink to the bottom, but it doesn’t take much water movement to knock them off their five little tube feet. It always amazes me that teensy critters like this, so fragile and easily killed, manage somehow to stick in the intertidal and survive long enough to be grown-up urchins on their own. And yet some of them will. I’ve seen it happen.

Posted in Marine biology, Marine invertebrates | Tagged , , , , | Leave a comment

A few days make all the difference

Almost a week ago, my sculpin eggs were doing great. The embryos had eyes and beating hearts and were actively squirming around inside their eggs. A few of them had died but overall they seemed to be developing well. I had high hopes that they would continue to do so, and began to think of what I’d need to do once they hatched.

Today the egg mass is 19 days old, and things aren’t going so well.

Bald sculpin (Clinocottus recalvus) egg mass, age 19 days.
18 February 2017
© Allison J. Gong

Many of the embryos on the outer edges have died, and all that remains of them are the tattered remnants of their eggs. Those opaque white eggs have been dead for a while and the pale pink shredded eggs died more recently, in the last day or so. I took a quick peek at the egg mass yesterday, and it looked much healthier than it does today. I’d guess that all told about 30% of the embryos have died since development began.

Bald sculpin (Clinocottus recalvus) egg mass, age 19 days.
18 February 2017
© Allison J. Gong

The embryos that are still alive seem to be fine. Their eyes can now move around independently but I still don’t know what, if anything, they can see. Their bodies continue to grow and now they have spots on their tails as well. I can make out where the heart is because I can see it beating, but I can’t discern any of the other internal organs. If the lighting is just right I think I can see pectoral fins on some of the embryos, which are too faint and indistinct to photograph. The baby fish are still swimming around inside their eggs, too.


Question of the Day: What caused the eggs’ condition to deteriorate so rapidly? Well, I can think of a couple of explanations.

Survivorship curves
Source: Wikimedia Commons, 2017

Explanation #1: Not everybody survives long enough to hatch. Sculpins and other fishes that lay large numbers of eggs are generally described as having a Type III survivorship curve (see right). These organisms have lots of babies, few of which survive to adulthood; probability of death is highest in the youngest age classes. Individuals that do make it to adulthood experience much lower mortality and have a decent chance of surviving into old age. In an egg mass like this, each egg has a very small probability of eventual survival to adulthood. To paraphrase an old saying, if they all survived then the world would be covered in bald sculpins. Obviously that’s not the case–and that’s a good thing!–so most of these eggs are not going to make it in the long run even in the best of circumstances.

Explanation #2: Crappy water quality. A very strong storm blasted through the area yesterday, complete with wind gusts to about 50 m.p.h. and 1-2 inches of rain, depending on location. All of this rain generates a lot of surface runoff, which carries mud and debris (think bushes and trees as well as garbage) into Monterey Bay. Plus, the high winds and turbulent swell stir up the bottom in shallow areas, resulting in brown, turbid water. This is the water that we use in the lab, and it’s our only source of seawater. Today the water was visibly cloudy. At least it seems to be just sediment, though, and not another phytoplankton bloom.

Poor water quality could affect the sculpin eggs if the sediment settles out on the surface of the egg mass, impeding gas exchange between the eggs and the surrounding water. In the field these eggs would be subjected to strong turbulence from the bashing waves, which would keep them clean and the water highly oxygenated. Some species of fish guard their egg masses and blow water on them to clear them of both sediment and fouling organisms. I hadn’t seen the parents of my sculpin eggs caring for their offspring at all, but I have been rinsing off the egg mass every day. Maybe I haven’t been able to keep the eggs clean enough. It does seem to be the eggs on the outside of the mass that are dying, so cruddiness might very well be part of the problem.

I’ll look at them again tomorrow and see if anything has changed. The news could be either good or bad, and I honestly don’t know what to expect.

Posted in General natural history, Marine biology | Tagged | Leave a comment