Description:
Idotea wosnesenskii is a small marine crustacean (Phylum Arthropoda, Order Isopoda). They have a segmented, rectangular body that can reach 40 mm in length. Like all isopods, their body is flattened for top to bottom (dorsoventrally) and they have seven pairs of visible legs. They are typically an olive-green colour, but can also be tan, brown, black or pink. Their colour depends upon the type of algae that they are associated with. Their body colour can change colour with time, but scientists do not yet understand how this happens; but, it is not related to their diet.
Their head appears to only have one pair of antennae, but there are actually two pairs. The first, smaller pair of antennae, are used for smell and detect odors. The second, larger pair of antenna are used for touch. They also have two small kidney-shaped compound eyes. These eyes are likely highly sensitive to movement, which would allow I. wosnesenskii to detect the movement of fast moving predators. Chewing mouthparts are located on the bottom surface of the head.
The many overlapping plates protect I. wosnesenskii from predators, but also allow for flexibility. Each segment contains a pair of legs with hooked-tips, which I. wosnesenskii can use for walking and to latch onto algae and other objects. Each leg is approximately the same size, hence the name isopod (iso = same, poda = foot). The hindmost five pairs of legs are flattened and are used for gas exchange. I. wosnesenskii can also use these appendages to swim gracefully through the water.
Their head appears to only have one pair of antennae, but there are actually two pairs. The first, smaller pair of antennae, are used for smell and detect odors. The second, larger pair of antenna are used for touch. They also have two small kidney-shaped compound eyes. These eyes are likely highly sensitive to movement, which would allow I. wosnesenskii to detect the movement of fast moving predators. Chewing mouthparts are located on the bottom surface of the head.
The many overlapping plates protect I. wosnesenskii from predators, but also allow for flexibility. Each segment contains a pair of legs with hooked-tips, which I. wosnesenskii can use for walking and to latch onto algae and other objects. Each leg is approximately the same size, hence the name isopod (iso = same, poda = foot). The hindmost five pairs of legs are flattened and are used for gas exchange. I. wosnesenskii can also use these appendages to swim gracefully through the water.
Ecology:
Idotea wosnesenskii inhabits the mid intertidal zone to water depths of 16 m from Alaska (and Russia) to Southern California. They are found clinging to various macroalgae and sea grasses, in mussel beds, under rocks, in rock crevices, and in empty shells.
I. wosnesenskii is primarily an herbivore that feeds on macroalgae and sea grasses. However, they are known to also feed on snail eggs. They secrete a distasteful compound that deters other herbivores from feeding on sea grasses.
I. wosnesenskii are preyed upon by at least twenty species of fish, birds and mammals. They rely on blending into the substratum to avoid being detected by these visual predators.
I. wosnesenskii is primarily an herbivore that feeds on macroalgae and sea grasses. However, they are known to also feed on snail eggs. They secrete a distasteful compound that deters other herbivores from feeding on sea grasses.
I. wosnesenskii are preyed upon by at least twenty species of fish, birds and mammals. They rely on blending into the substratum to avoid being detected by these visual predators.
Life History:
I. wosnesenskii has separate sexes. Males tend to be larger and paler than females. Females carry their fertilized eggs in a special fluid-filled pouch on their ventral surface, which protects the eggs from drying out. The eggs hatch into small individuals that look like adults. There is no larval stage.
To learn more:
Hultgren, K.M. and Mittlestaedt, H. 2005. Color change in a marine isopod is adaptive in reducing predation. Current Zoology, 64(4): 739-748.