биота российских вод японского моря - Materials of Alexey Shipunov

SUBPHYLUM CHELICERATA HEYMONS, 1901 1CLASS PYCNOGONIDA Brunnich, 1764Elena P. TurpaevaGeneral characteristicsThe class Pycnogonida (the later accepted names are Pantopoda, or Podosomata)includes peculiar, exclusively marine animals which combine morphological featuresof the Crustacea and the Chelicerata. Owing to some exterior resemblance toterrestrial spiders they got the name “sea spiders”. In the pycnogonids some featuresof primitive organization are preserved, and this class represents an independentgroup, like the Chelicerata or the Mandibulata (Dunlop & Arango, 2004).The bodies of the pycnogonids, living in the Sea of Japan, consist of a foursegmentedtrunk, proboscis, small abdomen, and seven pairs of appendages (pl. I, fig.1). Some species have segmented trunks, in others, segments of trunks are fused.Every segment has a pair of lateral processes with which the legs articulate. The first(cephalic or ocular) segment has in addition small processes for the first, second, andthird pairs of appendages, as well as a protruding proboscis. There is an oculartubercle on the dorsal side of the cephalic segment, bearing four eyes – a pair ofanterior and a pair of posterior ones. Segment 4 bears a protruding abdomen with ananal opening on its end.The pycnogonids’ appendages consist of segments. The first pair of appendages(chelifori) of the Sea of Japan pycnogonids usually consist of two segments: thestraight cylindrical first segment (scape) and the second segment (chela) consisting ofa broadened proximal part (palm) with two fingers – movable and immovable (pl. I,fig. 2). Appendages of such a type serve for grasping and holding of prey, but in somespecies these appendages are reduced. The second pair of appendages (palpi) is tactileorgans; the number of segments of this pair ranges from one to ten (the species of thegenus Nymphonella have up to 20 segments). The third pair of appendages (ovigers) inmales is assigned to bear progeny, and both male and female ovigers also serve forcleaning the body of sessile organisms living on it (hydroids, alcionarii, bryozoans andothers). The oviger consists of five-ten segments, the seventh to tenth ones are armedwith thin flat compound spines with toothed or smooth edges, and the tenth one ofmany species has a small claw on its end.The next four pairs of appendages are legs. The legs of all pycnogonids consist ofeight segments, every one of which have its own name or named by its number (first,second, third, etc.). The first three segments, usually short, are called coxae. The nextthree segments are long: the fourth segment is a femur, the fifth and sixth segmentsform a tibia (they are called tibia 1 and tibia 2 correspondingly). Relatively shortseventh and eighth segments form a tarsus; the seventh segment (called the tarsus1 In the last decade specialists oppose the class Pycnogonida to the rest of the chelicerates (Euchelicerata)or regard it as a sister group to all other modern arthropods (Euarthropoda) –Editorial note.92