Allonais japonica ( Kondô, 1936 )

Righi, Gilberto & Hamoui, Viviane, 2002, Oligochaeta, Naididae Of The West Indies And Adjacent Regions, Papéis Avulsos de Zoologia 42 (6), pp. 119-167 : 139-140

Allonais japonica ( Kondô, 1936)

( Fig. 3 E-G)

Nais japonica Kondô, 1936: 385 , pl. 23, fig. 12.

Material : St. Vincent 858: 1 specimen (ZU-1323). Habitat: Limnetic; salinity 0.05 %.

Description: Length 2,8 mm. Diameter 167 µm. Number of segments 24 plus a long posterior growing-zone. Eyes and division-zone are missing. Obtuse prostomium as long as wide. Septal gland to VI. Dorsal vessel dislodged to the left side; commissural vessels in VII-VIII. Dorsal setae from V backwards, one hair and one needle setae per bundle. The hairs are straight, smooth, 113- 155 µm long. The needles ( Fig. 3E ) are 50-57 µm long, the proximal 2/3 are straight and the distal 1/3 is slightly curved; the bicuspidate apex has teeth of similar length, the proximal tooth is a little thicker. There are 4, occasionally 3 ventral setae per bundle diminishing to 2 and 1 in the last segments. These setae are alike one another throughout the body ( Fig. 3 F-G). The length of the setae is 50-58 µm in II-V and 52-61 µm from Vl backwards; the nodulus is medial to slightly distal; the distal tooth is 1.5 times longer than the proximal tooth, which is a little thicker.

Remarks: The species is known only by the original description based on specimens collected at a station of water treatment in Osaka, Japan. Sperber (1948) put it in doubt under Nais variabilis and wrote - “ Nais japonica Kondô (1936) is remarkable, having no eyes, and dorsal bundles from V onwards. The stomachal dilatation is gentle, the setae seem to resemble those of N. communis and N. variabilis . Possibly it may represent abnormal or prematurely separated individuals of the latter, as it was found together with it”. We can not say anything about the stomach because our specimen has the digestive tube ruptured in VII. Our worm has no signs of anterior regeneration; however, it is regenerating the posterior end, which suggests it is an old individual and the most anterior of an eventual chain of assexual reprodution. As Kondô (1936) said - “It is well characterized by the absence of eye-spots and the presence of the dorsal setae in all segments from the fifth onwards”. The species was transfered to Allonais due to the absence of eyes, dorsal setae begining at V, and ventral setae similar throughout the body. A. japonica has similarites with A. gwaliorensis Stephenson (1920) but it is distinguished by the origin of the dorsal setae and by the teeth of the posterior ventral setae.

Figures

Fig. 3. Aulophorus barbatus: A, hair and needle. B-D, ventral setae of V, VIII and XXXV.Allonais japonica: E, needle. F-G, ventral setae of II and XII. Scale = 10 µm. Pristina sima: H-I, needles. J- K, ventral setae of IV and X. Scale = 10 µm.