Ophidonais
Ophidonais Gervais, 1838 (ref. ID; 1257, 3692)
Family Naididae (ref. ID; 1928, 5876, 5939, 7854)
Family Naididae: Subfamily Naidinae Lastockin, 1924 (ref. ID; 1257) reported author and year? (ref. ID; 6648)
ref. ID; 1663
Segment III not elongated. All dorsal setae aciculate. Capilliform setae lacking. Dorsal and ventral setae with different tips. The ventral setae hooked bifurcate, the dorsal weakly bifurcate or uncinate. Four dark anterior pigment bands. Pair of eyespots. Body more or less covered with debris. Usually in mud substrates. Up to 30 mm long. (ref. ID; 1663)
ref. ID; 1923
Dorsal setae nearly straight, slightly toothed or simple pointed, begin in segment 6 with 1 per bundle. (ref. ID; 1923)
- Ophidonais reckei Floericke, 1892 (ref. ID; 1257) reported year? (ref. ID; 1928)
- Ophidonais serpentina (O.F. Muller, 1773) (ref. ID; 1257, 1663, 1923, 3692, 6648, 6773, 7854) reported year? (ref. ID; 1928, 7098) reported author and year? (ref. ID; 5939)
Syn; Ophidonais reckei Floericke, 1892 in Southern (1909) (ref. ID; 1257)
Ophidonais reckei Floericke, 1892 (ref. ID; 1257) reported year? (ref. ID; 1928)
Diagnosis
The brief description of this species given by Floericke refers mainly to the character of the dorsal setae, which differ from those O. serpentina in being pointed, and not bifid, at the distal end. In other respect the two species are said to be similar. (ref. ID; 1928)
Descriptions
This species are enveloped in a very fine tube, probably of mucus secreted by the whole body. To this tube, fine particles of mud are attached. The whole tube is quite flexible, and allows the worm to wriggle about without apparently incommoding it. When the tube is removed, the body of the worm is seen to be quite transparent. The eyes consist of large irregular masses of dark pigment, just in front of the corners of the mouth. The brain is concave in front, and deeply cut behind. The dorsal bundles commence in the sixth segment, and contain a single short, thick, pointed seta, having a node near the distal end. The ventral bundles contain 3-5 setae. In the anterior bundles the node is in the proximal half. Behind the fifth segment, it is in the centre; and in the posterior setae, it is in the distal half. This appears to be the opposite arrangement to that found in O. serpentia. (ref. ID; 1928)
Measurements
Body length 10-15 mm. (ref. ID; 1928)
Ophidonais serpentina (O.F. Muller, 1773) (ref. ID; 1257, 1663, 1923, 3692, 6648, 6773, 7854) reported year? (ref. ID; 1928, 7098) reported author and year? (ref. ID; 5939)
Synonym
Ophidonais reckei Floericke, 1892 in Southern (1909) (ref. ID; 1257)
Descriptions
This species easily recognized by the small irregularly distributed dorsal setae, the 4 large transverse pigmented areas on the anterior region, and the relatively large size. (ref. ID; 1923)
This species were enveloped in a very delicate tube, coated with fine particles of mud. (ref. ID; 1928)
In fixed state, single worm 8-20 mm long, 0.4-0.5 mm wide, segments 63-126. Several anterior segments swollen. The body with thin covering of foreign matter. 3-4 transverse dark brown pigment stripes on anterior dorsal and lateral body wall; each usually distributed on chaetal line of II, IV, V, and (if the fourth is present) on VI, respectively, but often disordered. Prostomium short and conical. Eye rectangular in shape situated laterally to the mouth. The ventral chaetae 2-4 per bundle; these in II 180-208 µm long, longer than the rest with the nodulus situated proximally; those in III-V 152-168 µm long, often smaller than the following ones, the nodulus situated medially or somewhat proximally; those from VI on 152-180 µm long, with the nodulus situated medially or slightly distally. Distal end of the ventral chaetae bifurcated: the upper tooth longer and thinner than the lower one is anterior segments; but thinner and almost as long as the lower in posterior segments. 3-4 penial chaetae present on VI in mature specimens, the heads close together; each 160-192 µm in length with distal nodule and with swelling and hollow head. The dorsal chaetal bundles beginning in VI, each represented by single needle chaeta 140-172 µm in length. The dorsal chaetae stout and straight with nodulus situated at 1/4 from the tips, and the distal end bluntly simple pointed or shortly bifid. The dorsal chaetae often lacking but, when present, sometimes larger (up to 200 µm in length) at various locations along the body. Clitellum from beginning of V to 1/2 VII, lacking around male pores. Male duct in VI; vas deferens long and narrow, densely coverd with prostate cells 25-35 µm in height, connected with atrium at frontal and proximal portions of the atrium; the atrium ovoid, 100 µm high and 75 µm wide, devoid of ejaculatory duct, and opening laterally from penial chaetal bundle in VI. Spermatheca in V; the ampulla large and ovoid with thin wall; the duct 160 µm long, well marked off from ampulla, opening in front of ventral chaetal bundle. Both slender spermatozeugmata and loose sperms found in spermathecal ampullae. Chloragogen cells from VI, thinly covered the gut. (ref. ID; 6773)
Remarks
Living worm crawls and never swims. Among 15 individuals from Shimosakamoto (the southern lake) examined, three lacked dorsal needles throughout the segments, and the remainder also had lost them in a variable number of segments. The absence of dorsal chaetae in some segments of this species were also reported from another Japanese lake (Ohtaka & Iwakuma 1993). (ref. ID; 6648)
The form and structure of chaetae and reproductive organs in the Lake Yunoko specimens closely agree with previous descriptions. Sperber (1948) described the length of chaetae in Swedish specimens as follows: the ventral chaetae 147-150 µm in II, 114-120 µm in the rest; the doral needles 150-168 µm. By comparison, the ventral chaetae in the present specimens are longer (180-208 µm in II and 152-180 µm in the rest) while the dorsal needles are about the same size (140-172 µm in the present specimens). It is noticeable that the present specimens show high variability in distribution and size of chaetae. That is, the dorsal needle chaetae were randomly missing in a majority of the present specimens. Among twenty five specimens examined, only two individuals have dorsal needles in all the segments from VI on; in the remainder, however, the needles appear from one to six segments later and/or are randomly absent in various segments. Further, as enlarged dorsal needle over 200 µm in length was found in one specimen; the chaeta was almost the same shape as the normal needle, and distributed on XII. In addition, the ventral chaetae in IV and V were also entirely missing in one specimens. Such variations have not been reported in this species, although similar ones have been found in some other naidid species. Loden and Harman (1980) induced giant chaetae in a naidid, Pristina aequiseta, by control of aquatic environments in the laboratory. Among our specimens collected monthly from 1988 to 1990, sexually mature individuals were found only in July 1988 at a low proportion (2.6%) of the population. Timm (1970) also reported that this species matured in June-July in Estonia waters. The present species has been recorded from Europe, North and South America, Siberia and Turkey (Brinkhurst and Jamieson 1971). In east Asian, the only findings recorded were from Lake Baikal (Sokolskaya, 1962) and the outlet, Angara River (Akinschina and Tomilov 1976). However it has not been previously reported from the vicinity of Japan, the Amur basin (Sokolskaya 1958, 1961), Kamchatka (Sokolskaya 1961), Sakhalin (Sokolskaya 1964), southern Primorye in Russia (Timm 1990) or China (Brinkhurst et al. 1990). The fact of that this is the first instance recorded from the Pacific Asian region suggests that this species is cosmopolitan. (ref. ID; 6773)
Material examined
Ten immature individuals, a ditch at Otsu, leading to the southern lake, mud with dense submerged vegetation, 21st October, 1992. Sixty-two immature individuals, off Shimosakamoto (the southern lake), 3 m depth, mud with submerged vegetation, 2nd August, 1995. (ref. ID; 6648)
Lake Yunoko, Nikko National Park, Tochigi Prefecture, Central Japan, 2-10 m deep, 23 May, 22 July 1988, six mature and over 500 immature individuals collected by T. Iwakuma. (ref. ID; 6773)