The Whelk Lobster

Adult specimens are usually between 5 and 10 centimeters in length, consisting of two tagmata: the cephalothorax and the abdomen. The cephalothorax has four pairs of perieopods, and two flagella, which are both sturdy and whip-like, which are presumably analogous to antennae.

The creature consists of 13 somites. The first somite is separate from the head, forming a stridulating organ. The organism is able to produce sound by moving its first pair of antennae throughout the ridge, functioning as a means of communication. The second somite has two lateral pigmented corneas, which lack eyestalks, and therefore give the organism a very limited range of vision. The third somite contains the jaw, a hard beak-like mouthpart. The dorsal mandible fits within the ventral mandible, and the two pieces come together in a scissor-like fashion; the mandibles can be referred to as a rostrum, due to their similarity to the mouth-parts of cephalopods. Somites 4-7 contain one pair of periopods each. These walking legs are used primarily for locomotion. Dorsally, the cephalothorax is covered in a hard carapace, extending from the rostrum to underneath the abdomen. Somite 8 contains the pair of flagella, the function of which is not completely known. The creatures have been seen using the organs for balance, as well as sensory perception. Their most important function is to help the creature bury itself in the sand, which the organisms do to hide from predators. The abdomen consists of the remaining 5 somites, which are distinct. Each has two prominent lateral pleura, which hide the organisms 5 pairs of swimmerets, or pleopods, which are used for locomotion as well as copulation.

The male F. sconoplos is generally larger than the female, but is similar in shape and behavior. The young whelk lobster passes through its larval stages within the egg, and is similar in anatomy to the mature specimens.

F. sconoplos thrives on sandy beaches, where it can easily bury down in the sand.They are scavengers, and will eat any fruit or fish that it comes across, making the lobster an important part of the ecosystem. The organism protects itself from predation by hiding in the sand, and like all arthropods on Cassus Atoll, having slight levels of toxicity when ingested.