Category: crustaceans

Readers’ wildlife photos

November 17, 2025 • 6:15 am

Intellectual hero and UC Davis math professor Abby Thompson again has a batch of lovely intertidal photos for us. Abby’s captions and IDs are indented, and you can enlarge her photos by clicking on them:

The first two pictures were taken on my cellphone at the Berkeley marina, where a friend was taking us sailing. Fortunately for me, the boat needed more than an hour of preparation, which I got to spend lying flat on the dock looking at the marine life growing underneath it. There’s an entire community on inaturalist devoted to observations of such “dock fouling”; it’s an incredibly rich environment. Because all I had was my phone, only a couple of the pictures I took were legible- next time I’ll bring a camera (and hope the boat needs even more work).

Clathria prolifera (red beard sponge). Most sponges can’t be identified from a photo, but apparently this brilliant one is an exception:

Genus Ciona (tunicate). Pretty much any blobby thing you see lying around the beach is some kind of tunicate, an animal with an inflow and an outflow, and usually not too much else to recommend them (unlike, say, clams, which are at least delicious). These at the marina were lovely, however, looking flower-like:

The rest of the pictures were taken in my usual spot on the coast, near or after sunset (that’s when the great winter low tides happen). At night it’s cold, wet, slippery and, of course, dark, which makes things a bit tricky.

Genus Crepidula; Slipper snail – this clings to the rock looking almost like a limpet:

Slipper snail top view:

Order Amphipoda; I liked this guy’s eyes:

   Genus Polycirrus; Spaghetti worm- it’s one worm, with many tentacles. The main body of the worm is curled up and coated in sand:

Dirona picta:  A nudibranch, munching on some matching bryozoans:

Cebidichthys violaceus (Monkeyface eel, or monkeyface prickleback) Despite its common name and looks, this is a fish, not an eel (all eels are fish, but not vice versa). Supposedly delicious, it’s one of the creatures for which I regularly see people foraging. They’re caught by “poke-poling”; a baited wire hook is just stuck into the end of a long pole, and the fishing method is to poke the hook into crevices under the rocks.    One of the advantages of nighttime tide-pooling is that there are a few creatures- this was one- that seem to get stunned by a flashlight, and they stay completely still.  In the daylight you seldom see one of these, and they’re gone in a flash, too quick to photograph:

Anthopleura xanthogrammica (tentative) (giant green anemone) Several species of anemone fluoresce like this under UV light:

For the second group of pictures [after number 4] the camera was my Olympus TG-7, in microscope mode, with a lot of extra lights.

Readers’ wildlife photos

May 21, 2025 • 8:15 am

We’re running low on this feature, so please send in some good photos. I won’t beg again for a while.

Today we have photos from Africa by Loretta Michaels.  Her captions and IDs are indented, and you can enlarge the photos by clicking on them.

Brief Introduction: I used to do a lot of business in Africa and so I almost always tried to tack on a weekend safari of some sort while there.  Most of these times I had only my iphone to take pictures, unlike the bigger safari vacations my husband & I take with all our camera gear.

While in Dar es Salaam on business, I spent a weekend on Chumbe Island, just off the coast of Zanzibar.  One of the more bizarre sightings was a Coconut Crab (Birgus latro), the largest land crab in the world, which is able  to climb coconut palms and easily crack coconuts with its claws.  These crabs also eat fleshy fruit and even prey on smaller crabs. This species of crabs has evolved to live on land from the sea, returning to water only to lay their eggs. On land, they live in underground holes made with fibers from coconut husks, and are generally only spotted at night. An adult crab can reach one meter in length. It has a curled-under abdomen that makes it look like a lobster. Coconut crabs supposedly have very tasty meat, so, unfortunately, they are hunted:

Three nicely aligned bush elephants (Loxodonta africana) I saw during a trip to Zambia:

A nice female African lion (Panthera leo), spotted during a night drive in Zambia:

A Komodo Dragon (Varanus komodoensis) spotted during a drive:

Two white rhino (Ceratotherium simum) in Nairobi National Park, a 45 square mile wildlife sanctuary established in 1946 just outside Nairobi:

Lunchtime at the Lilayi Elephant Nursery just outside Lusaka, Zambia.  The baby elephants are just adorable to watch, especially as they come running in from the fields when they see it’s feeding time:

A Golden Monkey (Cercopithecus mitis kandti) spotted in Volcanoes National Park in Rwanda:

A mother and baby mountain gorilla (Gorilla beringei beringei) in Volcanoes National Park in Rwanda, just outside Kigali. It is one of two subspecies of the Eastern Gorilla.  The other population lives in the Congo. The park is one of the 3 homes of the endangered mountain gorillas within the Virunga Mountains:

Dominant male gorilla in Volcanoes National Park:

Variable Sunbird (Cinnyris venustus) in Rwanda. The sunbirds are a group of small Old World passerine birds which feed largely on nectar, although they will also take insects, especially when feeding young. Flight is fast and direct on their short wings. Most species can take nectar by hovering like a hummingbird, but usually perch to feed most of the time:

Readers’ wildlife photos

January 20, 2025 • 8:15 am

Today’s photos come from mathematician and Hero of Intellectual Freedom Abby Thompson of UC Davis, whose avocation is photographing California tide pools and their invertebrates. Abby’s captions are indented, and you can enlarge her photos by clicking on them.

New year’s tidepool pictures from Dillon Beach in northern California, plus a few older photos.  It’s not that much colder during the winter here- August can be freezing, December delightful.   To see much in December you have to be willing to go out after dark, which is a little spooky, but has the advantage that you often get to see racoons foraging on the rocks.    Sadly the only pictures I get of them look like two red dots (their eyes) on a black background.

As usual I got help with some of the IDs from people on inaturalist.

Schuchertinia milleri (tentative):

This is through a microscope, taken with my iphone.  In the tidepools it appears as a small very pink blob stuck to a rock. These are hydroids, closely related to jellyfish, unlikely as that seems.

Kelp crab:

These crabs are one of the few things you should be cautious about in the tidepools here- they are reported to have a strong bite with their claws (I haven’t tested this), and they’re not shy.

The next four pictures are all nudibranchs. As you can see, their coloration is quite varied, but nevertheless they are all the same species. Keep this in mind for when we get to pictures 7,8 and 9.

Triopha maculata 1:

 

Triopha maculata 2:

 

Triopha maculata 3:

 

Triopha maculata 4:

 

Ok, the next two pictures are two distinct species of nudibranch.    To my eye, the difference in coloration here is a bit more subtle than for the Triophas; H. crassicornis has white “stripes” on the frilly stuff on its back.

Hermissenda opalescens:

Hermissenda crassicornis:

And the next picture is of these two local species of Hermissenda hanging out together.  Not exactly in flagrante (nudibranchs spend an awful lot of their time mating and laying eggs), but still, looking pretty friendly. Maybe Jerry will chime in with some info on delimiting species?  and how exactly it is done, for us non-experts. [JAC: two different forms copulating doesn’t resolve their species status!]

Hermissenda opalescens and Hermissenda crassicornis:

Clam siphons:

There is not enough appreciation of bivalves in the world, except as dinner,  Their siphons can be lovely (I admit this may be in the eye of the beholder).

Coryphella trilineata:

A pretty nudibranch. There are lots of this species at the moment.

Pycnogonid stearnsi:

There are several species of “sea spiders” locally.   They’re small (this one was less than an inch across), and lively.      This is the most common here.

Anthopleura artemisia (Moonglow anemone):

You may remember from earlier pictures that this is another species with many dramatically different color variants.

Camera info:  Mostly Olympus TG-7, in microscope mode, pictures taken from above the water.

Readers’ wildlife photos

December 18, 2024 • 8:15 am

Today we have some underwater photos from reader Peter Klaver. His captions and IDs are indented, and you can enlarge his photos by clicking on them.

My friends and I did 5 days of scuba diving from San Pedro in Belize. The coral reefs there are beautiful and are home to many animals.

The large animals we saw most often were nurse sharks (Ginglymostoma cirratum):

They are quite tame and if we spotted them lying on the sea floor, we could move in quite close to them:

The other type of sharks we saw were reef sharks:

There were lobsters:

And turtles. I’m not 100% sure, but I thin this is a green sea turtle (Chelonia mydas):

There were rays of wildly varying size. This was a larger one:

And there were these almost entirely white fish whose name I don’t know:

45 million red crabs migrate to the sea

November 8, 2024 • 12:30 pm

To end, the week, we have some stunning videos from BBC Earth and other places, depicting the migratory behavior of the red crabs of Christmas Island, a small Australian territory (135 km², pop. 1692 ) near Indonesia: encircled below. Their vernacular name is The Christmas Island red crab, the Latin binomial is Gecarcoidea natalis, and they are  endemic to that island and the Cocos (Keeling) Islands in the Indian Ocean.

TUBS, CC BY-SA 3.0, via Wikimedia Commons

The life cycle of this crustacean is described here, but the videos are more impressive. Here are the basic facts:

The migration starts with the first rainfall of the wet season. This is usually in October or November, but can sometimes be as late as December or January.

Red crabs all over the island leave their homes at the same time and start marching towards the ocean to mate and spawn. Male crabs lead the migration and are joined by females along the way.

The exact timing and speed of the migration is determined by the phase of the moon. Red crabs always spawn before dawn on a receding high-tide during the last quarter of the moon. Incredibly, they know exactly when to leave their burrows to make this lunar date.

However, because crabs wait until the first rainfall to start their trek, they sometimes have to hurry. If the rains arrive close to the optimal spawning date, they will move rapidly. But if the rain comes early they may take their time, stopping to eat and drink on their way to the coast.

If it begins raining too late to make the spawning date, some crabs will stay in their burrows and migrate the following month instead.

And from BBC Earth, narrated by Attenborough. Note that the crabs breathe through gills, which must be kept moist. They live on land, but in moist habitats, but a remnant of their evolutionary origin is their need to go back to the ocean to spawn. Note that they walk sideways.

Note that they mate during the migration, too, so it’s not just females who are drawn to the sea at this time. A similar video, but also showing one of their predators and some of the other dangers they face.

I especially like this video because it shows how the island’s human inhabitants care for and protect the crabs:

Readers’ wildlife photos

March 28, 2024 • 8:15 am

Today we have some photos from the Galápagos by Ephraim Heller. His narration and IDs are indented, and you can enlarge the photos by clicking on them.

You have published lots of photos from the Galapagos Islands over the years. Here is my contribution to the genre. I took these photos on a March 2022 trip. They are divided into two classes first identified by Linnaeus: birds and non-birds. Each will be posted separately. First the non-birds.
Galapagos sea lions (Zalophus wollebaeki). Sea lions use whiskers for social communication (from Chilling Seals):
Sea lions, like other pinnipeds, have a highly developed sense of touch, which they utilize both in their aquatic and terrestrial environments. They possess long, sensitive whiskers known as vibrissae, which are dense clusters of sensory hair follicles. These vibrissae play a crucial role in the sea lion’s ability to navigate through their environment, locate and capture prey, and communicate with conspecifics.
Research suggests that sea lions do, in fact, use their vibrissae to recognize each other. These whiskers are rich in nerve endings, allowing them to perceive even subtle tactile cues. When sea lions come into close contact, they engage in a behavior known as ‘whisker touching,’ where they gently touch each other’s vibrissae. This behavior is considered a form of non-vocal communication and is thought to serve as a means of social bonding and identification.
Each sea lion’s whisker pattern is unique, similar to a human fingerprint, allowing for individual identification. Sea lions use their whiskers to recognize each other by comparing the unique pattern and structure of the vibrissae. This recognition process involves a combination of tactile exploration and visual inspection. Sea lions often nuzzle or touch each other’s whiskers to gather information about the individual they are interacting with.
Furthermore, sea lions possess a specialized neural network in their brain known as the somatosensory system, which processes information from their vibrissae. This system allows them to discriminate between different whisker patterns, aiding in the recognition and identification of conspecifics.

Sea lion pup being cute. They are experts at this:

Nursing sea lion pup:

Galápagos green turtle (Chelonia mydas). Per Wikipedia:
A subspecies of the green sea turtle. The species’ common name does not derive from any particular green external coloration of the turtle. Its name comes from the greenish color of the turtles’ fat, which is only found in a layer between their inner organs and their shell.
Since green sea turtles migrate long distances during breeding seasons, they have special adaptive systems in order to navigate. In the open ocean, the turtles navigate using wave directions, sun light, and temperatures. The sea turtles also contain an internal magnetic compass. They can detect magnetic information by using magnetic forces acting on the magnetic crystals in their brains. Through these crystals, they can sense the intensity of Earth’s magnetic field and are able to make their way back to their nesting grounds or preferred feeding grounds.

Galápagos giant tortoise (Chelonoidis niger). Per Wikipedia:
The species comprises 15 subspecies (13 extant and 2 extinct). It is the largest living species of tortoise, and can weigh up to 417 kg (919 lb). They are also the largest extant terrestrial cold-blooded animals (ectotherms). With lifespans in the wild of over 100 years, it is one of the longest-lived vertebrates. Captive Galapagos tortoises can live up to 177 years.
Galápagos tortoises are native to seven of the Galápagos Islands. Shell size and shape vary between subspecies and populations. On islands with humid highlands, the tortoises are larger, with domed shells and short necks; on islands with dry lowlands, the tortoises are smaller, with “saddleback” shells and long necks. Charles Darwin’s observations of these differences on the second voyage of the Beagle in 1835, contributed to the development of his theory of evolution.

Galapagos marine iguanas (Amblyrhynchus cristatus). Per Wikipedia:
Unique among modern lizards, it is a marine reptile that has the ability to forage in the sea for algae, which makes up almost all of its diet.
Researchers theorize that land iguanas (genus Conolophus) and marine iguanas evolved from a common ancestor since arriving on the islands from Central or South America, presumably by rafting. The land and marine iguanas of the Galápagos form a clade, the nearest relatives of which are the Ctenosaura iguanas of Mexico and Central America. Based on a study that relied on mtDNA, the marine iguana was estimated to have diverged from land iguanas some 8–10 million years ago, which is older than any of the extant Galápagos islands. It has therefore traditionally been thought that the ancestral species inhabited parts of the volcanic archipelago that are now submerged. However, a more recent study that included both mtDNA and nDNA indicates that the two split about 4.5 million years ago, which is near the age of the oldest extant Galápagos islands (Española and San Cristóbal).
The different marine iguana populations fall into three main clades: western islands, northeastern islands and southeastern islands. These can be further divided, each subclade generally matching marine iguanas from one or two primary island, except on San Cristóbal where there are two subclades (a northeastern and a southwestern). However, even the oldest divergence between marine iguana populations is quite recent; no more than 230,000 years and likely less than 50,000 years. On occasion one makes it to another island than its home island, resulting in hybridization between different marine iguana populations.

Galapagos land iguana (Conolophus subcristatus).
Charles Darwin personally disparaged these beauties as “ugly animals, of a yellowish orange beneath, and of a brownish-red colour above: from their low facial angle they have a singularly stupid appearance.” But what did he know, anyway?
Per Wikipedia:
Because fresh water is scarce on its island habitats, the Galápagos land iguana obtains the majority of its moisture from the prickly-pear cactus, which makes up 80% of its diet. All parts of the plant are consumed, including the fruit, flowers, pads, and even spines.
The Galápagos land iguana has a 60 to 69 year lifespan.

I’m pretty sure that Captain Kirk engaged in hand-to-hand combat with the Gorn subspecies:

Galapagos lava lizard (Microlophus albemarlens). Per Wikipedia:
There are seven species within the Galapagos lava lizard population and these species are found on several islands.
The major defense mechanism used by these lizards involves dropping their tail; their tail continues to move and thus distracts their predators while the actual lizard will camouflage or flee.

Painted ghost crab (Ocypode gaudichaudii). I love the eye stalks.

Sally Lightfoot crab (Grapsus grapsus). Quite beautiful, IMHO.

Terrestrial hermit crab (superfamily Paguroidea). This individual seems very pleased to have his photo taken.

Readers’ wildlife photos

January 1, 2024 • 8:15 am

I have but three batches of wildlife photos left, so we’ll run out on Thursday—and then I’ll have to stop this feature (the website is moribund anyway). Please send in your high-quality wildlife pictures if you have them.

Fortunately, Mark Sturtevant is here today with a good batch of insect photos (and one crustacean). His captions and IDs are indented, and you can enlarge his photos by clicking on them.

Over a year ago, the family traveled to New Jersey to visit family. I had already posted pictures from that trip some months ago, but I had lost track of another set. Here is that set.

We had not been to the area for about 8 years, and since then the invasive Spotted Lanternfly (Lycorma delicatula) had arrived. I expected that I would be photographing them, and I admit to some initial excitement about that since they are very large for planthoppers and are quite beautiful. There was certainly no problem locating some, since the buggers were just about everywhere! They decorated my brother-in-law’s house and most of the trees, and they often aggregated in solid patches in shady areas. Lanternflies were meanwhile also flying through the air like locusts. Here are adults and nymphs. Younger nymphs are black and white spotted, but this was late summer so I did not see those. Photographing them was slightly challenging since they are powerful jumpers, but with so many opportunities to get pictures it was still like shooting fish in a barrel.

Although the nymphs and the hind wings of the adults are quite colorful, I have not found anything about the colors being a warning that they are toxic.

As I said, I was at first looking forward to photographing these exotic insects, but it did not take me long to develop a strong dislike for Spotted Lanternflies! They were a constant presence when simply walking down a street or exploring a park. We even had to shoo them away when trying to enter a local restaurant, and taking care to not let any of the damn things fly inside

The Spotted Lanternfly is native to China, where it is under control by parasitic wasps. There seems no prospect of replicating that here, and I am not sure why. But such means of pest control do often fail because they are not cost effective, and similar approaches have resulted in unintended consequences. Spotted Lanternflies were first detected in the U.S. in 2014, and they have spread mainly because their egg masses can be accidentally transported on anything man-made. Now much of the eastern half of the country has them, and there are isolated populations out west as well. I understand that the main eastern population has now spread to my state of Michigan, and it’s probably only a matter of time before they turn up in my area, like the Spongy Moths (formerly Gypsy Moths), and Japanese Beetles before them.

These plant-sucking insects will feed on almost 200 plant species, and are considered a serious pest on grape vines. But many of our ornamental trees are fair game as well, and besides being obnoxious to humans, their large numbers are stressful for their host plants. But by far their preferred host is Tree of Heaven (Ailanthus), a rather attractive invasive tree that has become widespread in the U.S. for at least a century. So with a favored host plant already well established, there is little to slow further migration of the Spotted Lanternfly! The last picture is a typical scene on an Ailanthus sapling. But I have seen gatherings far denser than this.

Well, let’s move on. At a nearby park (also awash with Lanternflies), there were several of these Yellow-legged Mud Dauber Wasps (Sceliphron caementarium) collecting mud to build their nests. I had to hang head down on a steep river bank and hold the camera way out to get close pictures. When she completes her mud-pot nest, this wasp will stock it with paralyzed spiders for her young. [

On another outing near the ocean, I visited some tide pool areas where there were large numbers of these Atlantic Marsh Fiddler Crabs (Uca pugnax). They would all scatter to their burrows when I approached, so I had to wait in hiding. When some crept back into range, I was able to dive on this one for pictures. It’s the males that have the super-sized claw, which they wave at females to attract them. They will also use the claw to ritualistically arm wrestle other males.

 

In the same area there were numerous dragonflies, and on that one day I scored two new species from the Skimmer family. Here are Seaside Dragonlets (female and male, respectively) Erythrodiplax berenice.

And finally, a male Great Blue Skimmer (Libellula vibrans). This is one of our largest Skimmers, and I was very excited to get this picture!