Slime star

This is Pteraster tesselatus, commonly known as a slime star. As its name implies, when disturbed this star can produce copious amounts of slime, which may protect it from predators [1]. It eats sponges and the like and lives in the colder waters off the west coast of the US.

It also has an interesting feature common to many members of its family. It has a 'brood pouch'. The surface that you see is actually a soft covering which covers the true surface of the sea star. In other members of the family, females will release their eggs from their gonopores (like all other sea stars), but retain them under that covering until they develop into juvenile sea stars and crawl out. In this particular species, they do not brood their young, and instead send them shooting out of the osculum, an opening in the covering. The osculum is generally used for exchanging water from the water vascular system to the outside, and can be seen opening and closing even in individuals who are not spawning.

Life Photo Meme: Secret

What is the secret behind the demise of this coral? I don't know for sure, but I can make a pretty good guess based on the picture. Can you?

It looks like this coral has been the victim of that famous corallivore, the crown of thorns starfish (Acanthaster sp.). You can see part of the culprit in the center bottom of the picture. What looks like a patch of grey, red-tipped spines is actually the starfish. The crown of thorns is infamous for eating corals. They crawl on top and digest the fleshy parts, leaving the stripped white skeleton of the coral behind. Their spines are also a painful irritant to humans.

The crown of thorns is distributed throughout the indo-pacific, and has been thought to consist of single species, Acanthaster planci. However recent molecular evidence suggests that there are actually four species of Acanthaster [1].

This coral-eating starfish can devastate reefs when they appear in high numbers, but there is hope from a coral eating starfish.

Kingdom: Animalia

Phylum: Echinodermata

Class: Asteroidea

Order: Spinulosida

Family: Acanthasteridae

Life photo meme: Bat star

Kingdom: Animalia

Phylum: Echinodermata

Class: Asteroidea

Order: Spinulosida

Family: Asterinidae

It's hard for me to think of anything more voracious than a sea star. I like to refer to them as the walking stomachs of the sea. If you open one up, you will see the digestive gland and little else. This particular sea star is a bat star (Asterina miniata), and it eats plants (like surf grass), animals (anything it can catch, dead or alive), and even the thinnest biofilms (bacterial, protozoan). It basically everts its stomach on anything organic and digests it. The thin tissue in the picture is the bat star's stomach.

Bat stars will fight each other whenever they come into contact. A battle consists of one star trying to put its arm on another. So both stars will rear an arm up and very slowly try to lay it on top, like a slow-motion thumb war (you remember that game, right?). It's rather amusing to watch, if you have the time.

Photohunter: Colorful Cucumber

This is a violet sea cucumber (also called a sea apple). They are native to the western pacific and eastern indian oceans. They get their name from the violet ring around their feeding tentacles. Their body may be violet as well (like this guy's) or may be yellow, red, or blue. They use their bright yellow tube feet to move around the ocean floor, and the feeding tentacles to pick up detritus from the sea floor, or filter it from the water column.

The color of the violet sea cucumber is not just for show. When disturbed, like being picked on by a fish, the violet sea cucumber release toxic mucus. Fish and other animals learn quickly not to upset anything that looks like them.

Photohunter: pointy

What is more pointy than a sea urchin? In addition to the spines that most people see, sea urchins have small pinchers in between their spines called pedicillaria. The pedicillaria are used to pinch off any creature which tries to settle on them (like barnacles or algae) for a free ride. They can also be used as a defense against predators who aren't deterred by the spines, like sea stars. The urchin will fold down their spines and use the pedicillaria to pinch the sea star's tube feet and stomach.


They also have super pointy teeth. There are five teeth that continuously grow and are held in a structure called Aristotle's lantern. They use these teeth to scrape algae off of rocks, and to form little pockets in the rock where they live. Sea urchins kept in aquariums can cause lots of damage to the acrylic by chewing it up, and if they are kept in a concrete and fiberglass touch tank, they can chew right through it.

Animalpedia: Heart Urchin

This is a heart urchin, most likely Lovenia cordifornis. This particular species is relatively shallow-water dwelling, from the intertidal down to 60 feet (18m). It has long guard spines that can be raised when disturbed and folded back when resting. It likes to bury under the sand, but it can scoot around on top of the sand, using its longer spines. They eat detritus, and can create a mucous strand to capture falling particles.

Unlike most urchins, the heart urchin’s test is very fragile, and can be broken easily. This is why they tend to live in deeper calmer waters and under sand and not in rocky areas where you find regular urchins. Like thier sand dollar relatives, they have a the five petaliods, through which most gas diffusion takes place. Unlike most other echinoderms, such as sea stars and 'regular' urchins, heart urchins are not radically symmetrical .

Animalpedia: Criniods

This is a picture of a crinoid. Crinoids are in the same phylum as sea urchins, cucumbers, and sea stars, the echinoderms (spiny-skin). Basically, if you imagine an upside-down brittle star with lots of arms, you’ve got a crinoid. There are two types, stalked crinoids, which have a stalk giving them the common name of ‘sea lilies’, and stalk-less crinoids, which have claw like cirri that they use to walk with.

Both types are filter feeders, and you often find them in deeper waters where they catch ‘marine snow’ detritus and dead matter that falls from the upper surface. Their tube feet are modified to assist in filter feeding, they lack the suction cups on the end that most other members of the echinoderm phyla posses. Also, they are one of the few members of the echinoderms whose anus is on the same side as their mouth, instead of the opposite side. (The other group that has the same arrangement is the sand dollars)

They first appeared in the oceans around 510 million years ago, around the middle of the Cambrian beginning of the Ordovician periods. They were incredibly abundant from the Silurian to the Carboniferous periods (435-290 mya), such that whole layers of ocean limestone are made up entirely of their fossils.

While modern stalked crinoids only reach a height of 60cm (23 inches), some fossil forms reached 20 meters in height (60 feet)!