Dero tuna, Viviane, 2002

Righi, Gilberto & Hamoui, Viviane, 2002, Oligochaeta, Naididae Of The West Indies And Adjacent Regions, Papéis Avulsos de Zoologia 42 (6), pp. 119-167 : 133-134

Dero tuna n. sp.

( Fig. 2 A-D)

Material : Surinam 923: 4 specimens (Holotype ZU-1319). Habitat :

Limnetic.

Description: Length 2.0- 2.6 mm. Diameter 154-180 µm. Number of segments 20-26. Division zone in XV (2 specimens) or XVII (1 specimen). Eyes absent. Prostomium obtuse, wider than they are long. The very contracted branchial fossa leaves a small dorsal aperture making it difficult to see the gills, 2 or 3 pairs, contracted inside the fossa ( Fig. 2A ). Septal glands to V. Stomach in VII. Chloragogenous cells from VI backwards. Dorsal vessel displaced to the left; comissural vessels in V, VI-VIII. Dorsal setae from VI onwards, one hair and one needle setae per bundle. Hair setae straight, thin and smooth, length 122-130 µm. Needles 42-53 µm long, with straight proximal 2/3 and bowed distal 1/3, bicuspidate apex, distal tooth longer than the proximal, both of them are united by a thin membrane with convex margin and 10-12 longitudinal riblets (thicknings) in its distal half ( Fig. 2B ). Ventral bundles of II-V with 3-4 setae on each lessen to 1-2 in the last segments. The ventral setae of II-V are 72-79 µm long with proximal nodulus, thin teeth of similar thickness or the distal tooth is slightly thinner and always 1.5-2 times longer than the proximal ( Fig. 2C ). The relation between the lengths of the proximal: distal teeth varies from 7.8: 5.2-10.4: 6.5 µm. The ventral setae of VI backwards are 50-64 µm long with medial nodulus and teeth of alike length, 2.6-3.9 µm, the proximal tooth is thicker ( Fig. 2D ).

Remarks: Dero abranchiata Harman, 1977 (from south USA), D. righii Varela, 1990 (from north Argentina) and D. tuna constitute a very homogeneous group characterized by their ribbed palmate needles. D. tuna is separated from the other two species by the shape of the ventral setae of VI and following segments and by the number of gills. The name of the new species means “water” in the Iêconã indians’ dialect.

Figures

Fig. 2. Dero tuna: A, branchial fossa. B, needle. C-D, ventral setae of IV and IX. Aulophorus kalina: E, branchial fossa. F, needle. G-J, ventral setae of II, V, VI and XII. Aulophorus tridentatus: K-L, needles. M-R, ventral setae of II-VII. S, branchial fossa. Scales to Fig. A, E, S = 50 µm to other figures 10 µm.