Anatomy & Physiology

External Morphology

As has been previously discussed, the first pair of periopods on C. biunguiculatus possess tufts of small hairs that are used for the catching if particles from the water. Other than this, the first set of periopods is fairly representative of other shrimp species.

The most telling anatomical traits of C. biunguiculatus are their adapted feeding appendages, which are permanently extended. The rostrum of the shrimp is quite reduced, consisting of a small triangular protrusion from the head. The antennae of the shrimp possess a single joint and do not appear to possess any specific adaptations. However the antennules present to either side of the rostrum are highly derived. Each antennule is separated into two sections, with one remaining a simple antennae-like structure, while the other has developed a series of fine hairs in a fan-like shape at the tip.

The eyes of C. biunguiculatus do not appear to be in any way reduced.

The head and thorax are fused into a cephalothorax in the same manner as other shrimp. Indeed, the cephalothorax possesses 5 sets of walking legs just like other shrimp. The cephalothorax of females is significantly wider than that of males in order to accommodate for eggs.

The tail of C. biunguiculatus is also fairly similar to that of other shrimp in that it contains 5 sets of pereopods for swimming. The one difference in the tail being that it is often seen tucked underneath the cephalothorax. Males tend to have a more developed tail and thus tend to be more powerful swimmers.

                                         

Image7: The large swimming tail of the male (left) in comparison to the bulky abdomen of the female (right). The abdomen of the female can often be seen holding eggs, although females possess a much smaller tail.

Image 8: The mouth parts of C. biunguiculatus are permanently extended. Note the first leg visible in the left of frame possessing several small hairs. These hairs are also present on some of the feeding limbs.

Internal Anatomy:

Hemal System: The hemal system of arthropods is comprised of an open circulatory system. The heart sits within the pericardial sinus and can exist in a variety of shapes and sizes. Given the size of C. biunguiculatus, some level of isolation between the heart and the hemal cavity may be present. (Ruppert et al. 2004)

Respiratory System:Gas exchange occurs in the same way as most crustaceans - via the gills which are located on the thoracic maxilla. These act as pumps for the gills while, in C. biunguiculatus, simultaneously being used as swimming apparatus. (Ruppert et al. 2004)

Digestive System: The guts of crustaceans are complete, with different levels of complexity depending on the diets of the species. Thus it is likely that C. biunguiculatus has a gut typical of other plankton feeders. (Ruppert et al. 2004)