Argyrodiaptomus denticulatus (Pesta, 1927)

Perbiche-Neves, Gilmar, Boxshall, Geoffrey Allan, Previattelli, Daniel, Nogueira, Marcos Gomes & da Rocha, Carlos Eduardo Falavigna, 2015, Identification guide to some Diaptomid species (Crustacea, Copepoda, Calanoida, Diaptomidae) of " de la Plata " River Basin (South America), ZooKeys 497, pp. 1-111 : 12-16

Taxon classification Animalia Calanoida Diaptomidae

Argyrodiaptomus denticulatus (Pesta, 1927) Figs 10, 11, 12, 13, 14

Diaptomus denticulatus Pesta, 1927

Diagnosis.

Adult male, body length 1657 µm. Dorsal surface of Ped5 ornamented with irregular rows of spinules (Figs 10D, 11A). Ur4 with rows of spinules on dorsal surface. Antennules (Fig. 11D) long, reaching beyond posterior margin of Ur2 but not exceeding CR. Modified seta of segment 13 of A1R with acute apex and reaching middle of segment 14 (Figs 10A, 11C); spinous process on anterior margin of segment 15 always present and well developed, slightly curved. Segment 20 typically with long, curved distal process (Figs 10C, 11B). Enp1A2 with row of spinules on dorsal margin and single pore. BspP5R with proximal expansion on internal margin, overlapping BspP5L (Fig. 10B); BspP5R ornamented with small spinules on surface of rounded distal process on inner margin; inner surface of BspP5L with spinules. Exp2P5 or namented with minute spinules on process on outer margin proximal to insertion of lateral seta (Fig. 11 E–H).

Adult female, body length 1753 µm. Spinules present dorsally along posterior margins of Ped3 and Ped4 (Fig. 13A). Complete suture present between Ped4 and Ped 5. Lateral wings on Ped5 slightly asymmetrical, left wing longer than right; both wings projecting posteriorly, carrying two sensillae each, one at postero-distal corner (Fig. 13B). GS slightly asymmetrical, about twice as long as wide and slightly swollen anteriorly (Fig. 12A). P5 symmetrical (Fig. 12B), with small conical process at outer distal corner of Cx, bearing short triangular sensilla, bifid apically. BspP5 with short external seta, approximately one third length of Exp1P5. EnpP5 2-segmented, with two apical setae and distal row of spinules (Fig. 12B, C). ExpP5 3-segmented; lateral spine of Exp2P5 short, extending only to middle of Exp3P5; internal seta of Exp3P5 reaching beyond middle of terminal claw (Fig. 13E); external seta of Exp3P5 about 1/4 length of inner seta; terminal claw with two rows of 10-15 strong spinules (Fig. 13 C–D).

Remarks.

The male illustrated was collected from the Salto Grande reservoir (SGRA-D), Uruguay River. The female illustrated here belongs to the collection of the Museo Argentino de Ciencias Naturales (Buenos Aires) (MACN-In 29733), and was examined because of the scarcity of females in the samples from de la Plata river basin. This species can be readily identified because of the distinctive structure of its P5 and the presence of dorsal rows of spinules on the male pedigers, which are lacking in other species of Argyrodiaptomus .

This species is common in the lower regions of the basins of the Paraná and Uruguay rivers (Figure 14), and has been reported in several studies, particularly by Argentinian researchers. Santos-Silva (2008) recorded this species in southern Brazil, in the state of Rio Grande do Sul. Previattelli et al. (2013) included a record of this species from Bolivia, a distance of about 1,300 km north of the previous northernmost record. It is possible that the distribution of this species extends beyond this northern limit to at least the line of latitude 35°, but verification is needed.