Dero magna Harman, 1974

Righi, Gilberto & Hamoui, Viviane, 2002, Oligochaeta, Naididae Of The West Indies And Adjacent Regions, Papéis Avulsos de Zoologia 42 (6), pp. 119-167 : 128-129

Dero magna Harman, 1974

( Fig. 1 D-F)

Dero (D.) magna Harman, 1974: 23 , fig. 4A-C.

Material: Surinam 642,2 specimens (ZU-1315). Habitat: Limnetic; salinity 0.2%.

Description: Length 6.9-16.5 mm. Diameter 385-424 µm. Number of segments 130. Division-zone lacking. Prostomium like an obtuse cone. Very contracted branchial fossa with dorsal opening and 2 or 3 pairs of short gills. Bundles of dorsal setae begining at V in one specimen and VI in the other; one hair and one needle setae per bundle. The hairs are straight, smooth, thin and 256-328 µm long. The needles ( Fig. 1D ) are 88-108 µm long; the nodulus separates the straight proximal 2/3 from the bowed distal 1/3. The apex presents the proximal and distal teeth of equal length, 4 µm, and the thickness or the proximal tooth is somewhat longer; there are 2-5 intermediate teeth. The ventral bundles have 4, occasionally 3, setae in segments II-V, in the following segments there are 3 setae per bundle and 2 in the last segments. The length of the setae in II-V is 107-111 µm, the nodulus is medial and the teeth are alike in length, 10 µm, or the distal tooth is a little longer; the proximal tooth is the thickest ( Fig. 1E ). From VI onwards the length of the setae is 100-141 µm, the nodulus is proximal and the teeth have similar length or the proximal is a little longer. The proximal tooth is always the thickest ( Fig. 1F ).

Remarks: Dero magna is known only be the type specimen and the two worms described here, the three of them from Surinam. Dero magna and D. asiatica Cernosvitov (1930) are distinguished from the other species of the genus by the size of the setae and by the posterior setae of similar length or longer than the anterior ones. There is a great possibility that D. magna is just an aberrant form of Aulophorus pectinatus Stephenson, 1931a (= A. intermedia Loden & Harman, 1982 ).

Figures

Fig. 1. Nais barua: A, needle. B-C, ventral setae of III and XVII. Dero magna: D, needle. E-F, Ventral setae of V and XII. Dero trifida: G, branchial fossa. H, needle. I-J, ventral setae of II and VIII. Dero scalariformis: K, branchial fossa. L-M, ventral satae of II and XI. N, needle. O, hair and needle. Scales to Fig. G, K = 50 µm, to other figures 10 µm.