Skip to content

3

This week my female Kellet's whelk (Kelletia kelletii) started laying eggs. She's been doing this every summer for the past several years. She lives with one other whelk, presumably the father of her brood, as the eggs are both fertilized and viable even though I've never seen the snails copulating.

That's right, copulating. Whelks are predatory marine snails, some of which get quite large. My big female's shell is a heavily calcified 12 cm or so; she's a beefy mother! Her mate is smaller, but other than the size difference I wouldn't be able to tell them apart. Anyway, whelks copulate, with the male using a penis to transfer sperm into the female's body. Not very different from the way we humans do things, actually.

So at some point in the recent past my whelks copulated, and this week the female began depositing egg cases on the walls of their shared tub. I first noticed them on Monday, but she may have started over the weekend.

Female whelk (right) laying eggs. ©Allison J. Gong
Female whelk (right) laying eggs.
© 2013 Allison J. Gong

Those pumpkin seed-shaped objects are the egg capsules. Each is actually about the size and shape of a pumpkin seed and has a tough outer covering that contains 20-50 developing embryos. After the entire clutch is lain, which usually takes this particular female a week or so, the mom will leave the eggs to develop on their own.

I'll keep an eye on these eggs for the next week or so, and might be able to get some photos of the embryos and larvae as they begin developing. Keep your fingers crossed!

2

Over the Memorial Day weekend I took my students out on the early morning low tides at Natural Bridges State Beach.  While they were ooh-ing and ahh-ing and filling out their assignment worksheet, I was playing around with my new camera, taking pictures in the water.  Because I am not a photographer and sea anemones just sit there, they quickly became my favorite subjects.  Not to mention the fact that they are simply  beautiful and photogenic creatures.

At Natural Bridges we have four species of anemones in the genus Anthopleura:

  • A. xanthogrammica - giant green anemone
  • A. sola - sunburst anemone
  • A. elegantissima - aggregating anemone
  • A. artemisia - moonglow anemone

Of these species, the first two are notable for their large size.  At Natural Bridges they can get to be the size of a dinner plate.  They live side-by-side in tidepools, and since there are many deep-ish pools at Natural Bridges they are among the most conspicuous animals in the intertidal along the northern California coast.

Anthopleura sola (left) and A. xanthogrammica (right) in a shallow pool at Franklin Point.
Anthopleura sola (left) and A. xanthogrammica (right) in a shallow pool at Franklin Point.

It's easy to identify these animals when they're sitting right next to each other.  The difficulty comes when you see only one in a pool by itself with nothing to compare it to.  In a nutshell, here are some things you can use as clues to determine which species you have in front of you.

Let's start with Anthopleura xanthogrammica, the giant green anemone.  This animal's oral surface and tentacles are a solid color, varying from bright green to golden brown.  There are no conspicuous stripes on the central disc and the tentacles are relatively short and stubby, without any white patches.

Anthopleura xanthogrammica, photographed at Natural Bridges State Beach
Anthopleura xanthogrammica, photographed at Natural Bridges State Beach

Anthopleura sola, on the other hand, usually has distinctive radiating lines on the oral disc.  Hence the common name of Sunburst Anemone.  Its tentacles are generally longer and more slender than those of A. xanthogrammica, and often have sharp-edged white patches.  Sometimes the tips of the tentacles are tinged a pale purple.  Anthopleura sola are usually brownish-green in color, and I haven't seen any that are as bright green as the A. xanthogrammica anemones.

Anthopleura sola, photographed at Natural Bridges State Beach
Anthopleura sola, photographed at Natural Bridges State Beach

That's all well and good, but sometimes you come across an individual that doesn't completely follow the rules.  Or rather, it looks like it could belong to both species. Such as this fellow (fella?):

Hmmm...sola or xanthogrammica?
Hmmm. . . sola or xanthogrammica?

The animals obviously don't read the descriptions.  This one has xanthogrammica shape and overall color, but those lines on the disc read as sola-ish.  I would call this one a xanthogrammica.  What do you think?

1

I was making my usual feeding and checking rounds at the marine lab last Wednesday, when I saw this:

Pugettia producta, molting.  Time 10:09:12

This crab is a kelp crab, Pugettia producta. It is one of the common crab species on the California coast; you can find them in the low intertidal clinging to algae. Many of them are this golden-brown color, coincidentally(?) the same color of the kelp Macrocystis pyrifera. Juveniles are often reddish or dark brown in color, again matching or blending in with the algae where you see them. This particular crab has always been this color, at least since it has been in my care.

Crustaceans, as all arthropods, periodically molt their entire exoskeleton in one fell swoop. The exoskeleton splits along the transverse seam between the carapace and the abdomen, then the crab sort of slithers out backward. The entire exterior of the body, including legs, antennae, and mouthparts, is left behind as a larger version of the crab scuttles away to hide out for a few days until its new shell hardens.

I've kept lots of crabs and seen lots of molts show up in their tanks, but have never caught one in the act before. From when I started watching, in the photo above, to the final wiggle out of the old exoskeleton took no longer than 5 minutes.  Here's the sequence of photos documenting the molt:

Pugettia producta molting. Time 10:09:41
Pugettia producta molting. Time 10:12:18
Pugettia producta, molting. Time 10:13:57

Pretty nifty, eh?

 

As I suspected, the little Dendronotus veligers didn't last very long.  On Wednesday the very last survivors had kicked the proverbial bucket.  All that was left in the jar was some debris and scum from leftover food.  They lasted nine days post-hatching, which is about the norm for me when I've tried to raise nudibranch larvae.  Something just happens (or doesn't happen) around Day 10 and they all crash after a week or so of apparently vigorous life.  Someday I may figure out what's going on.  In the meantime, RIP, little guys.

On the more fun side of marine biology, there's a new exhibit at the Seymour Center that is extremely cool.  Someone brought in a buoy that had been out in the ocean for a long time.  It's a perfect example of a fouling community.

People who have boats or just spend time in marinas know about fouling communities.  They're all the stuff that gets scraped off the bottoms of boats.  It's also the same stuff that grows on pilings and the underside of floating docks.  In this case the term "fouling" refers to early recruiting animals and algae that grow quickly to monopolize space.  Many of the fouling species seen in harbors are invasive non-natives.

A few years ago I hung a box of slides off one of the docks at the Santa Cruz Yacht Harbor and left them there for several months to see what would grow.  Here's what recruited and grew on a single slide measuring about 5x7.5 cm:

Fouling community of invertebrates and algae on a glass slide.
© Allison J. Gong

As you can see, it's a very colorful world down there!  The brightest red curly stuff is an introduced species of bryozoan called Watersipora.  It is a fast grower and can overtake the other stuff and form large clumps.  It grows as an encrusting sheet over surfaces, but when two sheets make contact they grow up each other and form those curly upright bits.  To model how this works, hold your hands in front of you, palms down, with the fingers facing each other.  Push your hands together until your fingertips meet, then continue to move them towards each other.  What happens is that your hands flex and your finger tips get moved upwards until your palms come together in a praying position.  If your hands were encrusting sheets of bryozoan colonies, that's how you'd get those curly pieces.

Anyway, the buoy on display at the Seymour Center has a lot of large barnacles.  The barnacles have been actively feeding and molting since they arrived last week.  They are definitely the most animated critters growing on the buoy, as shown here:

 

Barnacles are crustaceans that lie on their backs entirely encased in hard shells glued to other surfaces.  They feed by extending their thoracic appendages and sweeping them through the water to capture detritus and plankton.  It's a strange way to make a living, but it does work.

 

 

 

1

What better way to start a new blog than to talk about sex?

This morning at the Seymour Center I noticed a blob of what looked like nudibranch eggs on the wall of one of the tanks. Looking around for the likely culprit I saw three big nudibranchs on the tank. Ooh, cool!

One of two slugs of this species in this tank.

This is Dendronotus iris, a large nudibranch, or sea slug. This bad boy/girl had a foot (the flat white bit that you see reflected in the aquarium glass) that was about 15 cm long. The brownish branched structures on the slug's back are its cerata, which function as gills. These animals do not have the ctenidium, or gill, that is typical of marine snails. Other nudibranchs carry their gills in a single plume that surrounds the anus.

This species is distinguished from D. iris by its coloration and some details of its anatomy.

There is one other big slug in this tank. It has a paler body color and cerata that are banded with orange and tipped with white.

Nudibranchs are among the rock stars of marine invertebrates--they are flamboyantly colored, have short adult lives with lots of sex, and leave beautiful corpses when they die. After a planktonic larval life of a few weeks, adult nudibranchs spend their time eating, copulating, and laying eggs. Each slug is a simultaneous hermaphrodite, capable of functioning as both male and female, and mating involves an exchange of sperm. In some other species of nudibranch the act of love can be followed by an act of cannibalism.

Nudibranchs lay egg masses in ribbons or strings that are characteristic of the species. It turns out that Dendronotus egg masses look like Top Ramen noodles:

Egg mass of Dendronotus.

Each of those individual little white blobs is an egg capsule that contains 10-30 developing embryos. These eggs were deposited yesterday (3 June) and the embryos have been developing but are not yet at any distinct stage. With water temperature at about 13C, I think they'll develop pretty quickly.

%d bloggers like this: