Psechrus

Palmgren, P., 1980, Some comments on the anatomy of spiders, Ann. Zool. Fennici 17, pp. 161-173 : 167-172

3. Psechrus

Professor H. W. Levi kindly provided me with a specimen of the not readily accessible Psechrus argentatus (Doleschall) from New Guinea, Wau

(Figs. 29-38). It is apparently a not fully mature (J, abnormal in that the left palp bears a typical combed claw (female character); the tarsus of the right clawless palp is 30 % longer than that of the left, but not turgid. The specimen was preserved in Bouin’s fluid and in good condition. Lehtinen (1967) remarks on the lack of anatomical information concerning this isolated group.

The lateralis muscle forms a continuous sheet of median height and strength from the pedipalps to the petiolus. Two somewhat individualized fibre bundles are inserted on triangular sclerites in the pleurae behind the first and second coxae. From these sclerites small muscles of the type called "posterior rotators" by earlier authors, c 4 in my nomenclature (Palmgren 1978a), run to the hind margins of coxae I and II.

The tergo-coxal muscles (ci-%) are bulky. Their shape is reminiscent of Tegenaria (Palmgren 1978a, fig. 12:8-9). Tegenaria also displays the two foremost "posterior rotators" c 4. No systematic conclusions should be attempted. Suspensor I is very weak, suspensor III has two fans which partly cross each other. Suspensor IV and the suspensor centralis are unusually strong. The endosterno-coxal muscles do not deviate in any way from the normal and the same is true of the intrinsic coxotrochanteric muscles.

The pedipalp has a differentiated set of tergal muscles: An externus muscle (pe) is present, the posterior and median muscles are cleft (pp and pm) and the anterior muscle (pa) is strong. The set of endosterno-pedipalpal muscles (ai, as, pi, ps) is of the usual pattern. The intrinsic coxotrochanteric muscles are depicted.

As would be expected, the bulky chelicers are served by powerful muscles of the usual configuration. The intrinsic cheliceral muscles are very simple; the flexor is not composed of many converging tracts.

The opisthosoma (Figs. 34-36) is encased in a sheet of circular integumental muscle fibres, strongest near the pulmonary furrow and decreasing in strength towards the spinnerets. The fibres are rather flat and divided into compartments (Fig. 35). The muscles between the segmental apodemes and between them and the integumental insertion points do not deviate from the general type (cf. e.g. Whitehead & Rempel 1959). The same applies to the muscles of the spinnerets.

The pockets of the lungs are very narrow. The pericardial sac, which originates from the space surrounding the lungs and receives the blood from the petiolus, is narrow. The heart has three

pairs of ostia, the third being almost rudimentary. Unfortunately, all but the hindmost part of the tracheal tubes was destroyed.

In the middle of the intestinal tract a large pouch-like structure gives off diverticula which ramify and form the dorsal digestive parenchyma. The bladder was filled with faecal crumbs. The point of origin of the ventral part of the parenchyma could not be detected. The anal bladder is conspicuous. Owing to poor preservation the ramification of the Malpighian vessels remained obscure.

Only three kinds of silk glands could be discerned. The cribellar glands are bushlike and aciniform. The mass of the glands are lengthy and ampullate. Only a few typical tubuliform glands are found.

Owing to the imperfect penetration of the fixative ( Bouin’s fluid) the structure of the genital organs could not be established in full detail. On the whole, it corresponds to the findings of Crome (1951). The testes are digitated, however. The long and coiled vas deferens incorporates a bulky structure to be regarded as the vesicula seminalis. Between this and the testis is an intercalated enlargement. The vesiculae and the vasa deferentia are strongly sclerotized, the later being covered by a soft, apparently glandular tissue. The part of the duct between the vesicula and the "uterus masculinus" is much narrower than the part between the vesicula and the testis, and the ultimate part has no glandular investment.

Dr. F. R. Wanless has kindly provided me with two undetermined Psechrus females from the collections of the British Museum of Natural History. One is apparently P. himalayanus (Nepal, Darsan, 3000', 16. VI. 1954, leg. K. H. Hyatt). The identity of the other remains obscure (Saravak, Dee Cave 24. IV. 1978, leg. P. Chapman, Mulu Expedition). The epigynes and “vulvae” are depicted in Figs. 42 and 44. The muscular anatomy of the prosoma corresponds closely, of course, to the anatomy of the P. argentatus male. The intestinal caecal pouch seems not to extend narrowly into the chelicerae, as in the male, perhaps corresponding to the bulkier state of the poison glands in the females. In the opisthosoma, the ovaries (filled with eggs) are in close contact. The other organs were rather poorly preserved.