биота российских вод японского моря - Materials of Alexey Shipunov

proper) may be straight or calyciform; the eighth segment (propodus) may be straightor slightly curved; it bears a main, or terminal claw and a pair of auxiliary claws on itsend. There are several basal spines on the sole of the eighth segment's ventral side.Some species have a small protrusion (heel) with large spines at the proximal part ofthe sole.The digestive system of the pycnogonids consists of a pharynx (foregut), midintestine,and a hind-intestine. The pharynx is situated inside the proboscis that has atriangular mouth, provided with three cutting plates ("lips"), on its end. There is a socalled "filter" at the proximal part of the pharynx. The "filter" is a net of chitinousthreads, densely interlaced with one another, which holds back large particles comingthrough the mouth. The mid-intestine is situated in the trunk; it is quite short, but hasmany branches (diverticula), supplying nutrients to legs. The hind-intestine is veryshort and has no outgrowths. It extends through the abdomen and opens through theanus.There is no blood-vascular system, but there are lacunae through which liquidcirculates, transporting nutrients from the diverticula of the intestine to the muscles.The nervous system of the pycnogonids consists of two anterior ganglia(suprapharyngeal and subpharyngeal) innervating the eyes and the first to third pairsof appendages and of a chain of four ganglia innervating every segment of the trunk;nerves extending to the legs also originate from these ganglia.The reproductive system of the most pycnogonid species consists of a U-shapedtube, lateral outgrowths of which extend inside the first, second, third and fourthsegments of the legs, where germ-cells mature. Pycnogonids are dioecious animals.Sexual pores are situated on the second coxae of the legs on their ventral sides,females having such pores on all legs, males – on the third and fourth legs.Usually females are larger than males; their trunks are more robust. The males inmost species have thinner trunks, relatively more elongated and having strongerarmature of spines and setae. Males of the families Nymphonidae, Ammotheidae,Callipallenidae have longer ovigers than females, the fifth segments (the longestsegments of these appendages) are noticeably curved. As for the familiesPhoxichilidiidae and Pycnogonidae, only males have ovigers.During the period of breeding males wind mucous cords with eggs round theirovigers. The eggs stick together by the secretion of the male's cement glands situatedon the dorsal sides of the femurs. Growing larvae stay on the male's body for quite along time and seemingly feed on the organisms living on its surface. Larvae of themost species parasitize on hydroids.Adult pycnogonids are free-living animals, some species are ectoparasites. Theyfeed on soft tissues of hydroids, sea anemones, jelly-fishes, sponges, corals and, moreseldom, on mollusks, starfishes, and sea urchins; they also feed on benthic protistans(Komokiacea).The sea spiders are benthic animals that sometimes are able to swim. They can becaught by bottom trawls, dredges, sometimes they got into benthic traps; they mayrarely be taken by plankton nets and other pelagic fishing gear. The pycnogonidsshould be preserved in 70% alcohol, or at least in neutralized formalin. Preparation insome cases is necessary for the identification of a species. During this processappendages should be separated as whole units or divided into segments, withoutdestruction of the adjoining segments, because the correlation between the lengths ofsegments may be important for identification.93