Category: invertebrates

Readers’ wildlife photos

June 9, 2026 • 8:15 am

I forgot to post part 2 of Abby Thompson‘s latest batch of California intertidal photos, so here they are (the first batch is here). Abby’s captions and IDs are indented, and, as always, you can enlarge the photos by clicking on them.

The stars of this set, improbably enough, are two flatworms.   The first two pictures are of the elegant Eurylepta californica, which I think of as the “art-deco flatworm”.  It’s rare up here; I’ve found it once before.  The next flatworm (Family Euryleptidae) is an undescribed species.   It’s been recorded several times, almost all in the Monterey Bay area.    This is its third sighting (as recorded on inaturalist) this far north.  There isn’t agreement on the genus. It’s a beauty, and it’s unusual to have such a striking animal remain undescribed.   Both worms are about ¾” long.

Eurylepta californica (striped polyclad flatworm) Art deco flatworm:

Eurylepta californica:

Family Euryleptidae (Yellow frilly flatworm):

The starfish plague of several years ago was devastating along the coast, and several species (like the incredible sunflower stars) have not recovered, but the ochre stars are back with a vengeance.     I see many more of them than of the bat stars, but the next picture is one of each buddying up on a rock above the low tide line.

Patiria miniate and Pisaster ochraceus (bat star (red) and ochre star (yes, purple)):

The next three pictures are a slightly deceptive series.    I’m not sure that the first two pictures really are otter tracks, but the alternative is probably raccoon tracks, and otter is a better match.   They did not, in fact, end on the beach right next to the where I saw the otter in the third picture.   But at least the third picture below is definitely an otter.   This almost surely is a river otter, not a sea otter, as are most seen around here.

Otter tracks:

Close-up of otter tracks:

Lontra canadensis (North American river otter):

Finally, the roof of a cave, with sea anemones (green and pink– Anthopleura xanthogrammica and Anthopleura elegantissima) and sponges (the bright red-orange, not possible to ID from a photo):

Readers’ wildlife photos

June 1, 2026 • 8:15 am

Today we have pictures from the shore of New Jersey taken by Jan Malik.  Jan’s captions and IDs are indented, and you can enlarge the photos by clicking on them.

Here are a few pictures from my walks on Cape May and Sandy Hook, taken this April.

Starting from the Atlantic Ocean (eastern) shore on Cape May, I met this pair of American Oystercatchers (Haematopus palliatus). In Cape May, a section of the beach is fenced off to protect nesting sites for them and for Piping plovers. They are feisty birds and every spring there is a competition for nesting sites; the bird on the right is calling at another Oystercatcher:

The pair took off to drive out the intruder:

The place where I found that pair was littered with the remains of Sand fleas (possibly Emerita talpoida). These fossorial crustaceans normally stay buried in the sand, exiting only when the sand is awash with the shallow tide, but Oystercatchers’ bills are well adapted to dig them out. I think the birds ate only the soft and juicy parts of their telsons, leaving the crustaceans mortally wounded and unable to move:

These Sand fleas are small and difficult to catch alive. That’s what their front end and first pair of legs look like. These crabs dig backwards, starting from their telson, and the front pair of legs is used as a sand anchor:

Another arthropod – the Horseshoe crab (Limulus polyphemus), came ashore, atypically for it, on the Atlantic Ocean side of the peninsula. These are treacherous waters for these spiderlike creatures, for they are easily flipped over by ocean waves and become stranded. They are an interesting part of the Delaware Bay ecosystem and I may share more pictures of them later:

On the Delaware Bay shore of Cape May, there were already many Laughing gulls (Leucophaeus atricilla), which mostly move south in winter but return to their breeding grounds in the spring. They are quite similar to the Eurasian Black-headed gull:

Terns also made their appearance. I think this may be a Forster’s tern (Sterna forsteri) because of the lack of black tips on its primaries and its pure white underbelly, but they are difficult to tell apart from Common terns (Sterna hirundo):

The terns landed on old quay pilings and started courting. There’s no way to tell females from males other than by their courting behavior; males can be slightly larger, but the difference is less than 5%, which is hardly discernible to the human eye:

The courting consists of the two mates trying to look “smug”, with wings drooped, necks extended, and bills pointed toward the sky:

Then there’s the courtship dance and ritual feeding. Here is a fragment of it, taken from a large distance, so I’ve compensated for the lack of pixels by cobbling together this composite. The male presents a fry to the female and then, if she accepts (which is not a given), circles around the female while stomping his feet:

On my way home, I stopped at Sandy Hook, a sand spit where shore gun batteries protecting New York Harbor were once located. It is now a prime nesting site for Ospreys (Pandion haliaetus):

The former Army garrison required many houses for the officers, and these are now excellent nesting sites for Ospreys. Standing in the center of Officers Row (as the area is called), I counted four nests on top of chimneys:

The meadow below the houses was full of American robins (Turdus migratorius) fattening up for the nesting season by preying on earthworms. I know little about annelids, but I’m going to go out on a limb and say it is the common earthworm (Lumbricus terrestris), since it is a favorite prey for robins:

Finally, moving to the class Mammalia, here are Sandy Hook’s harbor seals (Phoca vitulina), congregating on rocks exposed by low tide (the tide was rising so, one by one, the seals were forced to slip back into the water). There are eight seals in this picture, but I counted 15 in total. Their population around the New York inlet has increased in recent years, which may soon put them on a collision course with the fishing industry:

Readers’ wildlife photos

May 27, 2026 • 8:15 am

Today we have some intertidal photos taken in California by UC Davis math professor Abby Thompson. Abby’s captions and IDs are indented, and you can enlarge her photos by clicking on them.

May is a great month on the California coast, with extreme high and low tides.   Here are some photos from the most recent, excellent, set:

Pollicipes polymerus (Gooseneck barnacles). I’ve shown these, and some relatives, several times before, but they’re amazing animals. In case you think it’s too many barnacles, Darwin spent eight years looking at barnacles.   “Originally planning a brief month-long study to establish his credentials in invertebrate zoology, he became deeply immersed and cataloged every known living and fossil species.”  (Google AI).  I’m not sure what the green is doing here, presumably just growing on top of the animals.   Some relatives of the nudibranchs stay green from what they eat, and retain bits with the ability to photosynthesize, most famously the adorable leaf sheep:.

Dendronotus venustus (nudibranch):

Paciocinebrina lurida (a snail):

Tonicella lokii (flame-lined chiton):

Genus Tegula (maybe) (another snail). There was a hermit crab living in the shell- I didn’t get a good photo of him.    I’m not sure the genus is correct, but the shell was so pretty I wanted to post it:

Nucella ostrina (Northern striped dogwinkle). About the common name—well, it has stripes.   And it’s a “winkle” (a word you have to love), or “little whelk”.  The dog part, I dunno.   They’re very common, and voracious. Some species of Nucella (not sure about this one) can be used to make a deep purple dye, which used to be hard to come by.  There’s a fun account of making the dye here, although I’m afraid many snails must have been sacrificed in the process:

Paradialychone ecaudata (worm):

Limpet, probably Lottia pelta (shield limpet). The little lacy edge is tentacles: “Pallial tentacles are tiny, sensory structures lining the mantle margin (pallium) of limpets. . . The tips and shafts of these tentacles are covered in dense tufts of non-motile cilia, which act as sensory receptors.” (Google AI):

Seagulls at sunset:

As always, thanks to experts on inaturalist for help with some IDs.   Camera is an Olympus TG-7.

Readers’ wildlife photos and video

April 26, 2026 • 8:15 am

I now have three batches plus some singletons, and so we’ll have semi-regular photos for a while, at least.  Today’s batch of tidal invertebrate photos, and one video, comes from math professor Abby Thompson at UC Davis. Abby’s captions are indented, and you can enlarge the photos by clicking on them. The video is also hers.

April tidepools, and a mystery den.

Starting with a video of a Ctenophore, Pleurobrachia bachei (Pacific sea gooseberry, a ‘comb jelly’). All appearances to the contrary, this is in a different phylum (Ctenophora) from the “jellyfish” of my earlier post, which are in the phylum Cnidaria.   The flashing lights are the cilia in the “combs” that run down the sides, used for locomotion.  This one wasn’t moving very much, but I was surprised it was moving at all.   I picked it up off the sand quite a way above the water line, and dumped it into a shallow pool to take a photo.    It seemed to be recovering pretty well from what I thought was death.   It’s about the size of a walnut.

Sea urchin “test”, or internal skeleton. Probably Strongylocentrotus purpuratus:

Ophiopholis aculeata (daisy brittle star):

Bispira pacifica (feather duster worm):

Close up of ‘feathers’ of pacifica:

Genus Eupentacta (sea cucumber):

Phoronis ijimai (tentative- the white things). This is a species of horseshoe worm, which lives in tubes.   I haven’t seen this species before, and it was in an awkward spot, so it was hard to get a good photo.   The photo below that is from a few years ago of a worm from the same family, so you can see their general shape better:

Phoronopsis harmeri (from July 2021) (same family):

Anthopleura artemisia (moonglow anemone):

And a few nudibranchs:

Triopha maculata (nudibranch):

Tenellia laguna (nudibranch):

Acanthodoris rhodoceras (nudibranch):

Rostanga pulchra (nudibranch):

Lastly the mystery den. Our entire front yard seems to have been tunneled under, with at least three major entrances- this pair of holes is just one of them.  The holes are large, about 10 inches across.  We’re dreaming of badgers, would be very happy with foxes, and really hoping it’s not skunks (I love skunks, but not in the front yard).  A wildlife cam is the next purchase:

Camera: Olympus TG-7.   Thanks as usual to some experts on inaturalist.

Readers’ wildlife photos

March 29, 2026 • 8:15 am

Abby Thompson of UC Davis has sent in some pictures of California tidepool organisms, as well as a video. Abby’s captions are indented and you can enlarge her photos by clicking on them.

Late January-early March tidepools, plus an octopus.

Bryozoans:

Lepas anatifera (pelagic gooseneck barnacle).   Usually found clinging to something drifting around in the open ocean (the “pelagic” part of their name), these were on a large log washed up on shore:

Intertidal zones, illustrated.    A well-placed vertical rock face, like this one, exhibits the idea of the different intertidal “zones”, each of which has its own specific collection of inhabitants.  You can see mussels and barnacles clustered at the top (in the “high intertidal”), exposed to the air as soon as the tide goes out even a little. There are smaller colonial anemones next, beneath them the orange and purple ochre stars, and below those, arriving at the low intertidal level, some giant green anemones.   If you peer into the water under the open giant green anemone, you’ll see a crab, probably a rock crab.   There’s some back and forth- there are a few giant green anemones pretty high up in this photo- but the general idea holds.

This reflects each animal’s differing tolerance for specific conditions- time out of the water as the tide goes out, harshness of wave actions, etc.      The nudibranchs (next few pictures) are usually in the very low intertidal:

Orienthella piunca (nudibranch):

Hermissenda opalescens (nudibranch):

Doto amyra (nudibranch).  Visible through the translucent skin on its back are lobules of the “ovotestis” (thanks inaturalist expert! ).   From google AI: “Ovotestes in nudibranchs are specialized, hermaphroditic reproductive glands that produce both male (sperm) and female (oocytes/eggs) gametes simultaneously”:

More eggs, this time from a snail in the genus Amphissa. I like the pointy egg casings, like wizards’ hats:

And here’s an adult of the genus- almost certainly Amphissa versicolor, but it’s an unusual color (they’re usually shades of orange or brown/tan):

In honor of Ghost the octopus, and also because I’ve finally figured out how to include videos, below is a clip from 2021 of an East Pacific red octopus (Octopus rubescens), cruising around the rocks (out of the water!) at low tide.  I’ve only seen one twice, probably because they’re too cleverly camouflaged (possibly just too clever) for me to spot.    This guy was about the size of a human hand, a miniature compared to the 50 pound Ghost.

Point Reyes peninsula at sunset:

Camera: Olympus TG-7.

Readers’ wildlife photos

March 13, 2026 • 8:15 am

Abby Thompson, a UC Davis mathematician, is back with more photos (and a video!) from the intertidal of northern California. Abby’s captions and IDs are indented, and you can enlarge her photos by clicking on them.

Jellyfish!

I thought I’d throw some jellyfish into the lull between the great winter tides and the great summer ones.

The reproductive cycles of the tidepool creatures are wildly varied, with behaviors ranging from maternal (see Epiactis prolifera from my last post), chancy (see mussels), through incessant (see nudibranchs).   But for sheer baroque complication, I vote for the jellyfish.    Many who stroll on a beach will see the quivering gelatinous masses of jellyfish stranded by the tide, and the less fortunate will have encountered their stinging tentacles while in the water.  This describes, a little, how they get there.

There are several jellyfish species common on the Northern California beaches; here are some of them:

Aurelia labiata (Greater Moon Jelly):

Chrysaora fuscescens (Pacific sea nettle):

Chrysaora colorata (purple-striped sea nettle) These are big, about a foot across:

Another Chrysaora colorata (handsome creatures):

Genus Aequorea (crystal jelly):

Polyorchis haplus:

Scrippsia pacifica (giant bell jelly):

The Chrysaoras and Aurelia labiata are in the class Scyphozoa; the rest are in the class Hydrozoa.

For all of these, males and females get together in the same vicinity, and release eggs and sperm (see “chancy” above), which form little “planulae”.    Then things get complicated.     Because (usually) the planulae settle down and attach themselves to something, and become polyps.  Like these tiny things:

Genus Sarsia:

Hydrocoryne bodegensis:

But how do they get from here (e.g. something like Sarsia) to there (e.g. something like Polyorchis haplus)?   Well they don’t, always, and sometimes they don’t get from there to here, either, but here’s an illustration of the process when it goes through a “typical” complete cycle:

And in fact if you look closely at that photo of H. bodegensis, you can see a little medusa just budding off, circled in the photo below:

Here’s a video of a set of newly-formed “baby jellyfish” (they look excited) which swam into my microscope view.    I didn’t know what I was seeing, so don’t have a photo of the polyp from which they likely emerged.   This means I have no idea of the genus (or even the class- if these are Scyphozoa then these are really ephyrae which will turn into medusae).

There seem to be many species for which the complete reproductive  process is not documented –  for example, if you search for the polyp stage of Polyorchis haplus, the answer is that we don’t know what it is, nor where it can be found.

 

A final oddity of this elaborate reproductive process is the existence of the so-called “immortal” jellyfish. (not found in the cold waters of Northern California).  If damaged at the medusa phase, this one can revert to its earlier (genetically identical) polyp phase- and so on ad infinitum, apparently.  As though, when things go wrong in your life, you could go back to your childhood and try again.

I’m grateful for help with IDs from experts on inaturalist and elsewhere.    All mistakes are mine.

Readers’ wildlife photos

March 10, 2026 • 8:15 am

We have no more batches in the tank, so if you have photos, send them along. Thanks.

Today’s final tranche comes from reader Ephraim Heller, which will be in two parts. Ephraim’s captions and IDs are indented, and you can enlarge his photos by clicking on them:

Q: Why do chickens (Gallus gallus domesticus) in Trinidad & Tobago cross the roads?

A: To eat the tarantulas.

During my recent visit to Trinidad and Tobago, a local birding guide explained that one of the reasons people commonly keep free-range chickens in their yards is to eat the tarantulas. This gave me a new respect for these domestic fowl, as I witnessed venomous tarantulas larger than my XXL-size hands, such as this female Trinidad chevron tarantula (Psalmopoeus cambridgei):

Trinidad harbors a diversity of arachnids that rivals anywhere in the Neotropics. On my night walks with my new macro lens I observed spiders (order Araneae) and harvestmen, also known as daddy long legs (order Opiliones). Both arachnids are eight-legged members of the class Arachnida, but they belong to entirely separate orders and are not closely related within that class.

Returning to the Trinidad Chevron tarantula: it constructs silken tube retreats in tree crevices, behind bark, and among epiphytic plants. It also readily adapts to human structures (e.g., tin roofs, metal pipes, and abandoned buildings) making it something of a synanthrope:

Females are large and fast-growing, reaching 18 cm (7 inches) in leg span, with striking chevron-shaped dark markings on the abdomen and green-brown coloration accented by red or orange flashes on the legs. Males are smaller, with a more uniform grey-brown appearance, and can mature in as little as one year. The species is notable for its broad diet: bats, frogs, lizards, grasshoppers, mice, and other insects have all been documented as prey.

Pharmacologically, the Trinidad chevron tarantula is of medical interest. Its venom is the source of psalmotoxin and vanillotoxin – inhibitor cystine knot (ICK) peptides that may have therapeutic applications in stroke treatment.

The pinktoe tarantula (Avicularia avicularia), is the most commonly encountered tarantula in Trinidad and Tobago. This arboreal species is named for the distinctive pink coloration on the tips of its legs in adults:

Adults reach about six inches in leg span. They are ambush predators that construct silken retreats and trip lines in tree canopies, using webbing as both trap and sensor. Unlike most tarantulas, pinktoes can jump short distances (3-4 cm), and their defensive repertoire includes propelling feces at threats, a behavior that, while unglamorous, is effective. Their venom is mild, even by New World tarantula standards. Here’s a closeup from the previous photo focused on the body:

The Giant Fishing Spider (Ancylometes bogotensis) is a semi-aquatic giant. Females reach roughly 26 mm in body length with an impressive leg span, while males are somewhat smaller at about 21 mm. These spiders walk on water using air-trapping hydrophobic hairs on their leg tips, much like water striders. When disturbed, they can dive below the surface and remain submerged for over 20 minutes by breathing air trapped in the hairs surrounding their book lungs. Their diet ranges from aquatic insects to small fish, frogs, lizards, and geckos:

Ancylometes bogotensis is sometimes confused with the infamous Brazilian wandering spider (genus Phoneutria, photo below): both are large, ground-active, nocturnal hunters with similar body plans. The name Phoneutria translates from Greek as “murderer,” and the genus has appeared in the Guinness World Records as containing the world’s most venomous spider. There are eight described species, found primarily in tropical South America with one extending into Central America.

Phoneutria species are best known for their potent neurotoxic venom, their characteristic threat display (raising the first two pairs of legs high to reveal banded leg patterns) and their wandering, non-web-building habits. They famously hide in banana bunches, boots, clothing, and dark shelters, which brings them into frequent contact with humans. Their venom contains a cocktail of neurotoxins, but fatalities are rare with modern medical treatment.

Though Ancylometes and Phoneutria were both historically placed in the family Ctenidae, Ancylometes was transferred to its own family (Ancylometidae) in 2025, reflecting the growing understanding that these semi-aquatic fishing spiders represent a distinct evolutionary lineage:

We now turn to a species of orb-weaver. The golden silk spider (Trichonephila clavipes) is one of the most conspicuous spiders in the Caribbean and Neotropical forests. Sexual dimorphism in this species is extreme: males are tiny (5-9 mm body length) and weigh roughly one-thousandth what a female does. Here is a female:

The silk itself is remarkable. It has a golden hue visible to the naked eye and is the strongest natural fiber known. Researchers have fully annotated the T. clavipes genome, identifying 28 unique silk protein genes. These spiders produce and utilize seven different types of silk. Their large, asymmetric orb webs can exceed a meter in diameter, and in the South Pacific, relatives of Trichonephila spin webs strong enough to be used as fishing nets by indigenous communities: