биота российских вод японского моря - Materials of Alexey Shipunov

SUBPHYLUM CRUSTACEACLASS BRANCHIOPODA Latreille, 1817Superorder CLADOCERAMilne-Edwards, 1840 sensu Negrea et al., 1999Irina K. Rivier 1 , Larissa S. Shkoldina 2General characteristics 3Cladocerans (superorder Cladocera) is a peculiar group of very small (usuallysmaller than 1 mm, rarer up to 4 mm) planktonic crustaceans of freshwater origin.They inhabit various continental and marine waters, where they are abundant and oftendominate.The body of most cladocerans is enclosed in a thin transparent shell, the dorsalpart of which (brood pouch) bears embryos, while the lateral parts (valves) protectthoracic limbs in filter-feeding cladocerans; in predatory cladocerans the valves arenot developed. Marine forms (Penilia and Podonidae) have the enclosed brood pouchcovered by shell, which isolates embryos from the external environment. In the Podonidaethe shell containing the brood pouch is enlarged; it grows together with embryosand has a hydrostatic function as well.The body of cladocerans is divided into a head, a thorax, a usually reduced abdomen,and a postabdomen (cauda). There is a compound eye and an ocellus (“naupliuseye”), which is reduced in some taxa. The first pair of antennae (antennules)represents sense organs provided with papillae (aestetascs) and short sensory setae,obviously performing a tactile function. In males the antennules are usually movableand longer than in females. Antennae 2 are locomotory organs. The mouth parts(mandibles, maxillulae and maxillae) are situated posteriorly. They are used to manipulateand push food particles into the gut. The body is indistinctly segmented andprovided with four to six pairs of thoracic limbs, being filtering organs in most cladoceransand grasping organs in predators. The postabdomen is situated posteriorly andusually provided with claws and “swimming” setae (setae natatoriae).The distinctive feature of the cladocerans’ life cycle is direct development (excludingthe genus Leptodora, which has the stage of a metanauplius larva; the Leptodoridaeare presently separated in the superorder Leptodorida) and the alternation ofgamogenetic and parthenogenetic reproduction, including the stage of a resting (latent)egg. Hatching newborn cladocerans (the first generation) from resting eggs give rise toseveral parthenogenetic generations. In most cladocerans parthenogenetic eggs devel-1 I.K. Rivier is the author of the systematic part of the chapter “Podonidae” and of the figuresof Podonidae (excluding figs. 1–3, 5 in pl. VIII).2 L.S. Shkoldina is the author of the chapter “Sididae” and figures 1–4 in plate I (Penilia avirostris).3 The chapter “General description” and the parts concerning distribution, biology, and ecologyare written by the authors in collaboration.9