Category: invertebrates

True facts about sea cucumbers (and their butts)

October 20, 2022 • 2:00 pm

Here’s one of ZeFrank’s (pronounced “zay-Frank’s”) biologically informed videos, this time about sea cucumbers—echinoderms in the class Holothuroidea.

Note the new caveat at the beginning: “True Facts is not appropriate for children nor for adults who don’t act like children.”  These would be great to show to an introductory class on biological diversity, but ZeFrank’s humor might harm people! On the other hand, as ZeFrank turns out more videos, they get better and better, with more—yes—true facts leavened with humor and accompanied by terrific videos.

Watch it! Unless you’re an invertebrate biologist or fond of authentic Chinese food, which incorporates holorthuroideans in some dishes (I can’t stomach them), you won’t know much about this group. In this video, ZeFrank’s 6-year-old side is evinced by his obsession with the butts of these creatures. (Don’t miss the bit at 11:10.)

It is a fascinating group! Does anybody know who ZeFrank is?

Readers’ wildlife photos

August 9, 2022 • 8:00 am

Today we have mollusk and cnidarian photos from Taryn Overton. Her captions and narrative are indented, and you can enlarge the photos by clicking on them.  First, the introduction:

These are a few sea creature photos from South Florida.  My hand is in the majority of these photos, as one can wait rather a long wait for conchs to venture out of their shells of their own accord.  All were briefly photographed and returned to the surf.  The camera used was an iPhone 11.  Locations were various but include Sanibel Island, Marco Island, Delnor-Wiggins Pass State Park (near Naples, FL), Lauderdale-by-the-Sea (near Fort Lauderdale, FL), and Dr. Von D. Mizel-Eula Johnson State Park (near Hollywood, FL).

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Strombus alatus (Fighting Conch).  These conchs (along with numerous others in the Strombidae family) have remarkable eyes!  The eyes are located on the ends of peduncle structures called ommatophores and are of the camera-type (simple) variety.  That is, a single lens collects and focuses light onto the retina.  Research of gastropods in the Strombidae family has shown that the eyes have a complex architecture, with tightly packed photoreceptors and at least six different cell types.  Similar to cephalopods, their lenses also reduce spherical aberrations through graded refractive indexes.  These anatomical findings, taken together with recent behavioral studies, show that they have both high contrast sensitivity and high visual acuity.

If the eye is injured or amputated, the ommatophore tip experiences a migration of cells that reassemble in correct topographic orientation.  At first the regenerating eye is small, but eventually it grows to the size of the original and is once again functional.  A Master’s thesis* where Strombus alatus eyes were amputated demonstrated restoration of rhodopsin and Gq proteins (necessary for phototransduction) within 4 weeks, suggesting return of visual function by that period.  I find it fascinating – the ability of these gastropods to regenerate an entire eye from cells that then reintegrate with the central nervous system to function!

The conch photographed here has been recently injured.  Something took part of the foot, the corneous/sickle-shaped operculum (see other photos of conchs with intact feet/opercula), and the right eye.  The eye is in the process of regenerating.  I’ve found a few other conchs over the years that have been missing their operculum and part of the foot but were healed from the previous trauma.  Based on those observation alone, it does not appear that the operculum or foot regenerate in any significant capacity – but I’m not sure.

Also of note – they have a sensory tentacle that hangs from the ommatophore and functions in scent detection (food, predators, etc).  These are more readily seen in the Aliger gigas (Queen Conch) photographs.

*Figures 1.2 and 3.1 below are from the following source: Clark, J.M (2018). Restoration of visual performance and opsin expression within the retina during eye regeneration in the Florida fighting conch (Strombus alatus).  (Master’s thesis).

Strombus alatus (Fighting Conch). I often find that Fighting Conch have numerous shell pieces adhered by a mucous substance to their foot.  Over the years I’ve wondered if it was some sort of defense mechanism, as I often can’t see the organism behind the shells.  Whether or not this is deliberate on the part of the conch, a secondary effect of biology/mucus produced on the foot, or a combination of both, I’m not sure.  When the ‘My Octopus Teacher’ film came out in 2020, the behavior of the common octopus (Octopus vulgaris) covering herself with shells/debris as an apparent defense mechanism reminded me of this.

Strombus alatus (Fighting Conch) at sunset.

A juvenile Strombus alatus (Fighting Conch) peeking out of its home at sunrise

Aliger gigas (Queen Conch).  The discussion regarding eyes of Strombus alatus can be applied in a similar manner to this species.

Sinistrofulgur perversum (perversum lightning whelk).  ‘Perversum’ – derived from the Latin word perversus, meaning “turned the wrong way”.  ‘Sinistro’ – Latin for left.  Their left-handed (sinistral) aperture separates them from the majority of other marine gastropods.  Being ‘lefties’ helps to protect them against typically right-dominant predators like stone crabs.  Right-handed (dextral) lightning whelks have been documented but are rare.  I mostly find small, uninhabited shells but have run across a few larger, living specimens.

Sinistrofulgur perversum (perversum lightning whelk) egg casing that washed up in the surf.  These casings are colloquially known as ‘mermaid’s necklaces’.  They spawn from March-April, and the casings can be 27-83 cm long.  Each strand has up to ~200 disc-shaped capsules containing up to ~100 eggs (numbers vary based on the source).  If you pick them up, you can hear the rattle of the tiny whelks (protoconchs) within the capsules.  Juveniles begin to hatch in May.

Velella velella (velella).  The marine life so nice they named it twice.  Also known as ’purple sail, ’little sail’, and ‘by-the-wind sailor’.  Classification and exact nature are disputed, and I don’t have specialized taxonomy knowledge to distinguish which classification is correct.  They are not jellyfish and may be either a single large hydroid polyp, or a colony of hydroid creatures.  The organism(s) also harbor symbiotic zooxanthellae (single celled dinoflagellates) that help with sustenance.

Physalia physalis (Portuguese man o’war).  This is a siphonophore, and is a colonial organism composed of smaller units called zooids.  I often walk the beaches at dawn and dusk, and occasionally there are periods where hundreds will wash ashore.  For those that find themselves in similar positions, I recommend shoes on the beach.  These guys have long tentacles bearing nematocysts (specialized stinging cells).  Even if you’re confident you’ll manage to avoid all the tentacles, you won’t!

True Facts about sea stars (and related echinoderms)

April 9, 2022 • 2:00 pm

ZeFrank, while remaining witty and funny, is getting more and more into the biological details of his presentations and documenting them using the scientific literature. The videos are remarkably accurate, and this 18-minute documentary of starfish is quite absorbing—to both me and Matthew, at least.  Although ZeFrank concentrates on morphology and function, evolution is always there lurking in the background.  And the photography, as always is stunning.

(There’s a commercial from 4:40 to 5:40.)

I liked the discussion of tube feet, walking in brittle stars, the brittle star tussle for food, the starfish nervous system, the compound eyes on their arms, how a sea star eats a clam, the “flower sea urchin” and its nefarious traps, and ejection of parts of the body into the water that chomp on and inject venom into nearby prey. Not to mention the breakable stalks of sea lilies that, like the breakable tail of some lizards, help a seized animal escape predators. Finally, don’t miss the starfish expelling tons of toxic slime at 14:22, or the display of regenerated arms soon thereafter.

It’s a great display of what Darwin called “endless forms most beautiful and wonderful”.

Readers’ wildlife photos

January 1, 2022 • 8:30 am

This is the second part of a two-part batch of photos by Matt Young (part 1 is here). His IDs and captions are indented, and you can click on the photos to enlarge them.

I was in the Galápagos Islands during the end of December 2005, and the beginning of January 2006, bearing my trusty Canon PowerShot S30, with 3 megapixels and a 3X zoom. I took one or two pictures through an 8X monocular, but other than that I was on my own.

Mammals. The only mammals I saw, other than bipedal, were Galápagos sea lions, Zalophus wollebaeki.

A little snack:

And a nap:

Some geological features. Landscapes.

Lava tunnel. You could have easily crawled inside.

Lava flow.

Impurity.

Stubborn little plant.

Invertebrates. Sally Lightfoot crabs, Grapsus grapsus.

Painted locust, Schistocerca melanocera.

Tourist. Not exactly an invertebrate, but looking kind of spineless at the end of a hot day.

And for good measure, Machu Picchu.

Readers’ wildlife photos

December 13, 2021 • 8:00 am

Today reader David Hughes sends us an unusual animal: a marine worm. Do not be grossed out at its appearance!

David’s captions are indented, and you can enlarge his photos by clicking on them.

Early last year you featured some of my Indian safari pictures on your ‘Readers’ Wildlife Photos’ section. For obvious reasons I haven’t been on any exotic trips over the past year and a half, but I thought I’d share some images of an animal I studied for several years. The photos are mostly scans of originals taken in the pre-digital era, so the quality isn’t great, but I hope they’ll be of interest. They show an animal that I’m certain none of your readers will have ever heard of, let alone seen.

This magnificent green blob has the equally magnificent scientific name of Maxmuelleria lankesteri. It belongs to a small group of marine worms called the Echiura [“spoon worms”]. Echiurans were traditionally classed as a distinct animal phylum (one of the so-called ‘minor phyla’ often lumped together in zoology textbooks). However, DNA analysis shows that they’re actually very weird annelid worms, so they’re now demoted to a subclass of the phylum Annelida. Echiurans are a pretty obscure group, not very familiar even to most marine biologists, but they’re found throughout the oceans, with different species found all the way from the intertidal zone to the deepest trenches.

The thicker section of the blob is the animal’s body. It’s basically a thin-walled bag with the consistency of a water-filled balloon. There are no internal segments, in fact nothing much at all inside apart from a long digestive tract, gonads, excretory sacs and a very simple nervous system. The thinner body section, looking like a pale green strap, is an extendible proboscis at the front end of the animal. The  mouth is at its base. There’s no head or sense organs, and no hard parts other than a tiny pair of chitinous hooks on the anterior ventral surface. The worm’s body is quite fragile and specimens are usually crushed or fragmentary when collected. I was therefore very excited when this one came up intact in a dredge sample.

Maxmuelleria lankesteri is found around the western and southern coasts of Britain and Ireland, and off parts of Scandinavia. It’s especially common in the fjordic sea lochs along the west coast of Scotland. Its habitat is fine, organic-rich mud, where it occupies a burrow shaped like an extended “U”. The burrow cast shown in the photo was made by divers pouring epoxy resin down the holes at each end, leaving it to harden, then dragging it out by hand – a difficult and laborious process. The glove in the photo provides a scale, but some burrows extend much deeper than this one.

Maxmuelleria feeds by extending its proboscis out of one burrow opening, skimming-off the top layer of sediment as it goes, then withdrawing back into the burrow with its collected load. The accompanying photo is a screen-grab from a video camera placed over a burrow opening, and shows an extended proboscis in the lower-left quadrant. The animal ingests some of the collected sediment, and expels the rest out the other end of its burrow, creating a mound up to 30 cm high. Where these worms are common, the muddy seabed looks like a field of miniature volcanoes (below).

Apart from their overall weirdness, these worms have two particularly interesting features. The green colour comes from a pigment called bonellin (named after Bonellia, another echiuran genus). Bonellin is photoreactive, releasing free-radical oxygen when exposed to light. Oxygen radicals are highly destructive to the body wall tissues, so that like Count Dracula, Maxmuelleria literally falls apart and dies if exposed to sunlight. The specimen in the photos was only kept out long enough to have its portrait taken, then put into preservative. This sensitivity means that the animal only extends its feeding proboscis by night (video observations were made under infra-red light, which the worms can’t detect).]

Their life history is also odd. Big Maxmuelleria like the one shown here are all females, and in late summer, genital pouches full of eggs occupy most of the body cavity. In other species of the same family, the males are tiny dwarfs just a few millimetres long, which live in the genital pouches of the female and do nothing but fertilize her eggs. I always examined my collected Maxmuelleria specimens closely for dwarf males but never found any, so the reproductive biology of these worms is still a bit of a mystery. Small juvenile worms are also very rarely found – they’re nearly all whoppers like this one.

Apologies if this is a lot of text for a few photos, but this animal is so unfamiliar to most people that I thought it needed a bit more explanation than the usual birds and mammals. If anyone’s interested in the details of research into Maxmuelleria lankesteri, typing the  name into Google Scholar will bring up quite a few papers on the subject, mostly written by me. Echiuran worms are a niche subject in marine biology, so I’m sure far more people read WEIT than have ever read my publications!

True facts about life in the deep ocean

November 20, 2021 • 2:00 pm

ZeFrank appears to have invited himself on a virtual NOAA (National Oceanic and Atmospheric Administration) “deep dive” from the Okeanos Explorer, a research ship that has a remotely operated vehicle (ROV) that can descend to 6,000 meters. A variety of videos reside on the NOAA website, and I suspect that ZeFrank took the video, with permission, from the site.

The goals of the Ocean Exploration mission are these:

With the mission to explore the ocean for national benefit, NOAA Ocean Exploration is the only U.S. federal organization dedicated to exploring the deep ocean. We are filling gaps in the basic understanding of U.S. deep waters and the seafloor and delivering the ocean information needed to strengthen the economy, health, and security of the United States.

We execute our mission by leading expeditions on NOAA Ship Okeanos Explorer and other research vessels; establishing public, private, and academic partnerships; providing funding and other support for ocean exploration expeditions and technology development, including via a competitive grants program; and guiding and supporting the Ocean Exploration Cooperative Institute.

The “conversation” you hear is the narration of the original videos combined with voiceover from ZeFrank, creating a “dialogue” between him and the Explorer personnel. Regardless, you’re here for the weird creatures that live in the depths of the ocean.

It’s rough down there, as you’ll see.

 

h/t: Ryan

Readers’ wildlife photos

September 2, 2021 • 8:00 am

Send those photos in, please! We’re running low. Before we start, can anyone identify this raptor that perched over Botany Pond yesterday? The ducks were upset, quacked, and then formed a pack in the pond and remained very still. I took a photo, but it was hard because the bird was high up in a tree above the pond. So far we’ve never had a raptor attack a duck or duckling, but the adults still get freaked out when they see one.

Today we have a melange of California photos from Joe Dickinson. Joe’s captions are indented, and you can enlarge the photos by clicking on them.

These are from a recent trip to the Tomales Bay/Point Reyes area.  

We were visited this time by a turkey vulture (Cathartes aura).  I believe the sunning of wings has to do with reducing parasite load, rather than drying the wings as cormorants do.

These photos of a fishing shack give some sense of the range of tides.

Nearby is the Point Reyes National Elk refuge with a nice population of Tule Elk (Cervus canadensis).

Mule deer (Odocoileus hemionus) also are found within the refuge as well as elsewhere on Point Reyes.

This moon jelly (probably genus Aurelia) actually is at a cabin on the other side of the bay where stayed a few years ago. 

Nearby is the Marshall Store, home of the best BBQ oysters on the planet. 

I call this the “Entropy Boat”.  We have watched it slowly decay over the years.

There is a very nice walk to Kehoe Beach with this freshwater lagoon alongside.