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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Teneridrilus

Teneridrilus Holmquist (ref. ID; 7098)

Family Tubificidae: Subfamily Tubificinae (ref. ID; 6648)
  1. Teneridrilus calvus Ers. & Br., 1990 (ref. ID; 6651)
  2. Teneridrilus columbiensis (Br., 1985) (ref. ID; 6651)
  3. Teneridrilus mastix (Brinkhurst, 1978) (ref. ID; 6648, 7098) reported year? (ref. ID; 6600)

Teneridrilus mastix (Brinkhurst, 1978) (ref. ID; 6648, 7098) reported year? (ref. ID; 6600)

Descriptions

Lake Biwa material: In mature and fixed state, body 10-25 mm long, becoming slender posteriorly. Segments 56-80. No coelomocytes. Prostomium small. Mouth enlarged, becoming narrower when fixed. Buccal cavity large and densely covered with pear-shaped gland cells. Pharynx in II and III, large, folded and eversible devoid of pharyngeal glands. Oesophagus in IV and V. Intestine beginning in VI, covered with chloragogen cells, becoming wider in VIII-XI. Dorsal chaetal bundles consisting of hairs and bifurcate crotchets except in II and III (occasionally only in II) where hair chaetae absent. Hair chaetae short and bayonet-shaped, almost smooth or finely hispid distally, 2-5 per bundle, 84-124 µm long anteriorly, 2-4 per bundle, 64-100 µm long posteriorly. Dorsal and ventral crotchets with nodulus at 1/4 from distal end; upper tooth almost as long as but thinner than lower in II and III, while upper tooth a little long and thinner than lower in the following segments. Dorsal crotchets 2-6 per bundle, 56-80 µm long anteriorly, 2-3 per bundle, 60-78 µm posteriorly. Ventral chaetae 2-7 per bundle, 56-74 µm long anteriorly and 2-4 per bundle, 50-66 µm long posteriorly. No modified genital chaetae. Clitellum from X to XII, thin. Testes in X, very small. Ovaries in XI, large. Sperm sac and spermathecae absent. Ovisac large in XI-XIII. Male ducts in XI, but often missing. Male funnels on 10/11, 80 µm in diameter. Vasa deferentia thin (8-10 µm in diameter) and hardly winding, entering atria almost apically. Atria elongate tubular with thick wall, 200 µm long and 50 µm wide medially. Prostate glands small (90 µm in maximum width), connected with atria near apical end. Penes protrusible without penis sheaths, 70 µm long, opening ventrally. (ref. ID; 6648)

Remarks

Teneridrilus mastix has been recorded from Pacific North America (Brinkhurst 1978, 1986), China (Erseus & Qi 1985), and two central Japanese lakes, L. Biwa and L. Suwa (Ohtaka & Nishino 1995; present study). The present examination of the type material and topotypes (from Fraser River, B.C., Canada) confirmed that their chaetae are stouter in II than in the following segments, and that, in II also, the upper teeth are shorter than the lower. The caetae of II in the topotypes are usually single as in the original description (Brinkhurst 1978), however, 2 chaetae per bundle were often found (5 out of 15 specimens examined). Chinese specimens from Pearl River coincide with the topotypes in the number and distal form of chaetae of II, on the other hand, they have strongly hispid hairs which has not been reported in the topotypes. One Chinese specimen was mature; its spermathecal ampullae are spherical with sperm as loose bundles while the ducts were not detected; atria are cylindrical with large prostates and large protruded penes. Consequently, the Chinese form resembles the Canada one in chaetal characteristics, as already noted by Erseus & Qi (1985), while it differs from the latter in having hispid hairs, larger penes and spermathecae. The present Japanese form is, on the other hand, different from the Canadian and Chinese specimens in that the chaetae of II are not modified, while it is intermediate between the latter two forms with regard to the degree of hispid condition of hairs and the size of the penes. Teneridrilus sp. recorded from Sumatra (Ohtaka & Usman 1997) closely resembles the Japanese form in the number and distal form of chaetae in II, but its hair chaetae are not hispid. We regard all the above forms compared as a single taxon T. mastix because the diagnostic characteristics overlap with each other. Erseus et al. (1990) proposed the modification of chaetae in II and the eversible pharynx as synapomorphies for the genus, but the former character should be cancelled because Japanese and Sumatran materials never show such a modification. This may also apply to the taxonomy of Varichaetadrilus species without hair chaetae; they also have a modification of chaetae in anterior segments (Brinkhurst, pers. comm.). The modifications in anterior ventral chaetae may be caused by chemical conditions of water, as in the Spanish form of another tubificid, Tubifex tubifex (Tubifex sp. in Rodriguez & Armas 1983), whose anterior ventral chaetae were enlarged related to be very high mineralized waters (Rodriguez 1986). All Japanese material examined have no spermatheca. In addition, the male duct are also often missing, although the clitellum and ova are fully developed. Among 50 mature specimens from Lake Biwa examined, only six had male ducts. This species may be able to reproduce facultatively by parthenogenesis as suggested by Erseus & Qi (1985). (ref. ID; 6648)

T. mastix have been recorded from Pacific North America (Brinkhurst 1978, 1986), China (Qi & Erseus 1985; Erseus & Qi 1985; Qi 1987) and now from Japan. It is widespread in Lake Biwa, occurring from the littoral to the deep profundal (Nishino et al. unpubl.). All of the present specimens examined had no spermatheca as in the original description. In addition, the male duct was also often missing just as pointed out by Erseus and Qi (1985) for Chinese specimens. (ref. ID; 7098)

Material examined

One mature and 25 immature individuals, off Hayasaki (the northern lake), 10-90 m depth, 26th January, 29th September, 1992, 26th February, 1993. Ten mature and 10 immature individuals, off Ayamehana (the northern lake), 10 m depth, 3rd April, 1990. Twenty-five immature individuals, off Wani (the northern lake), 3-76 m depth, 27th January, 25th October, 1992. Nineteen immature individuals, Lake Suwa, Nagano Prefecture (exact locality unknown), 8th December, 1983, 11th November, 1984, 9th, 19th, 23rd November, 1985, collected by K. Takada. USNM55375 (holotype) and USNM55375 (paratype), Fraser River, B.C., Canada, 1972, collected by R.O. Brinkhurst. Sixteen immature and one mature individuals, the type locality (R.O. Brinkhurst collection). One mature and 12 immature individuals, Pearl River, People's Republic of China, July 1988, January, 1989, collected by Qi Sang (R.O. Brinkhurst collection). (ref. ID; 6648)