CLASS CRUSTACEA 

 Subclass MALACOSTRACA 



ORDER AMPHIPODA 

 Suborder HYPERIIDEA 



Hyperiidea constitutes a fairly heterogeneous group. It is not always 

 possible to speak of its phylogenetic unity. Nevertheless, a series of 

 characters are available, which make it possible to separate hyperiideans 

 from the remaining Amphipoda. 



The following morphological features are typical of the suborder 

 Hyperiidea. The integument is thin, usually semitransparent but some- 

 times highly pigmented. The shape of the body is exceptionally diverse 

 and varies from spherical in some Physosomata and Platyscelidae to 

 acuminate in the Rhabdosoma. The eyes are very large, occupying the 

 entire lateral surface of the head and touching the vertex or, conversely, 

 very small, poorly developed, reduced, or totally absent. Sometimes the 

 eyes are devoid of crystalline lens or are modified into plates devoid of 

 receptor elements lining the bottom of the large eye cones. Antennae I 

 are always devoid of an accessory flagellum, their peduncle short, the 

 proximal flagellar segment usually strong, conical, longer than the rest of 

 the flagellum and peduncle; in some groups, antennae I and II in males 

 may be very thin and long. Sexual dimorphism is distinct, with a few 

 exceptions in the structure of antennae II. Often, especially in females, 

 they are reduced and sometimes totally absent. 



The oral appendages are small, reduced to a variable extent, and 

 weakly armed. The mandibles often lack a dental process and palp. Max- 

 illae I sometimes lack an inner lobe; the lobes of maxillae II are often 

 fused; the maxillipeds usually lack a palp, their inner lobes may be fused 

 and reduced or totally absent. 



The pereon is usually enlarged, sometimes spherically inflated. The 

 coxal plates are small, usually weakly developed, low, of one type, 

 not overlapping, and sometimes fused with the corresponding pereon 

 somites. The coxal plates never form a lateral shield; in groups where 

 such a shield is present, the same is formed by the enlarged 2nd segment 

 of the posterior pereopods. 



