Baicalarctiinae with genital pore opening into mouth tube; with pharynx plicatus; with wall of pharynx lumen including muscle layers oriented in two directions, longitudinal (under basement membrane) and circular; with reverse situation of longitudinal and circular muscle layers in the opposite wall of pharynx (Figs. 1, 2, 5-7, 9-14). All muscle layers in pharynx walls very poorly developed (both circular and longitudinal layers being, as a rule, in one or two rows), except for P. ermakovi sp. n., with two to three rows of circular and longitudinal muscles in wall of pharynx lumen)3. Distal end of pharynx body without any specialized papillae, where ducts of pharyngeal glands could open. Nuclei homogeneously distributed in pharynx body except distal third, which is nearly free of them in some species. Oesophagus well developed, its epithelial cells with insunken nuclei (except for so-called “external oesophagus” in P. minima (TIMOSHKIN et ZABROVSKAYA, 1985) and P. ermakovi sp. n. - see Figs. 2.2, 2.7, oee). Dorso-laterally situated vitellaria and testes distributed from anterior end of body back to the caudal part (except tail). Ovaries paired, well separated from vitellaria; each mature oocyte surrounded by one layer of accessory cells (elementary kind of oogenesis?). Accessory cells prism-shaped, on cross sections five- or six-sided. Vitellaria situated closely to sacklike intestine, forming net with a few large meshes around whole of intestine except for ventral side in front of pharynx, and consisting of several longitudinal branches joined by frontal, dorsal, caudal and ventral commissures (Fig. 4); with tunica propria; right behind pharynx lateral branches opening by several pores into paired proximal parts of oviducts, and latter ventrally joining into one ovovitelloduct. Female genital opening in ventral part of common atrium. Penis represented by cone-shaped, soft papilla (without any cuticular structures), formed as central enlargement of epithelial cells of male atrium (Fig. 3, pp) and separated from parenchyma by thin muscle septum (Fig. 3, msp). All nuclei of cells situated in basal part of papilla. Ducts of abundant prostatic glands passing through septum, cells of papilla, and epithelial cells of male atrium (ciliated) around papilla, and hence opening into atrium. Paired vesiculae seminalis of mature worms voluminous and opening via two symmetrical pores, one on each side of papilla basis (Fig. 3, vso). Epidermis with extremelly numerous rhabdoids (seen in nearly every epidermal cell in histological sections from the dorsal side), often equally numerous on dorsal and ventral sides of body, except for area around frontal gland opening, which is very different in structure and nearly free of rhabdoids. Epidermis cellular, homogeneously ciliated; cells and nuclei not insunken. Subepithelial rhabdoid glands very abundant. Body color white, light grey, light green, light yellow (some species lemon-yellow), pale orange, or intense orange-red4. Body length of sexually mature specimens 800-1900 ?m in fixed condition; maximum length of living worms up to 3000-3500 ?m; in this case, width about 300-500 ?m.
At least 7 species are known: P. minima, P. schirobokovi sp. n., P. ermakovi sp. n., P. kawanabei sp. n., P. barguzinensis sp. n., P. bathyalis sp. n., and P. xantha sp. n. In addition, another form, preliminarily described as species incertae sedis, has been recognized.
Additional notes on diagnosis. Only thin circular and strong longitudinal muscles are clearly identified in the body wall beneath the basement membrane. Only extrapharyngeal glands are found in the pharynx. It seems very likely that at least some species of Porfirievia have 2 types of prostate glands. Glands of the “first type” (the most abundant one) have a homogeneous, fine-grained, and greyish-blue secretion (Heidenhein’s azocarmine staining). Their cells are about 32-43 X 12-20 ?m in size, the ducts open through the penis papilla and the proximal part of the male atrium, and their bodies broadly surround the pharynx cavity behind and laterally (Fig. 3, pgl1). The ducts of the “second type” of glands open through the most distal part of the atrium, have a clear, intense blue, coarse-grained or reticulate, vacuolized secretion; the cell bodies not numerous and lie ventro-laterally, under the glands of the “first type” (Fig. 3, pgl2 ).
[From Timoshkin OA (1997): 153-154]
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