INVERTEBRATE ZOOLOGY IN THREE BOOKS - BOOK 2 - G.I. Shcherbak - 1996

PHYLUM ARTHROPODA

SUBPHYLUM BRANCHIATA, OR CRUSTACEA

CLASS MAXILLOPODA

Representatives of this Class are distributed worldwide. They inhabit both marine and fresh waters, living on the bottom and in the Water Column at various depths, as well as in capillary water between sand grains. Alongside free-living forms, there are species with sessile and parasitic modes of life.

The body of maxillopods consists of a syncephalon, Thorax, and abdomen terminating in a telson. The syncephalon incorporates the HEAD segments and the first thoracic segment, with the latter bearing maxillipeds. The antennules are uniramous and elongated; the antennae and mandibles are biramous, both pairs of maxillae are uniramous and multi-

jointed; an unpaired labrum is present. The maxillipeds vary in Structure (uniramous or biramous).

The thorax consists of six, rarely four or five segments, of which the first is incorporated into the syncephalon. The thoracic limbs are predominantly biramous and serve a locomotor function, adapted for swimming or generating water currents. The abdomen has a variable number of segments (3–5) and lacks appendages; the telson bears various articulated outgrowths ("caudal appendages"). In most species, only the unpaired (naupliar) eye is developed; the Circulatory system is highly reduced. A nauplius hatches from the egg.

The class Maxillopoda comprises four subclasses encompassing 14 orders. Let us examine the most important representatives of these subclasses.