Notodiaptomus conifer (Sars, 1901)

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 : 28-32

Taxon classification Animalia Calanoida Diaptomidae

Notodiaptomus conifer (Sars, 1901) Figs 35, 36, 37, 38

Diaptomus conifer Sars, 1901

Diagnosis.

Adult male, body length 1548 µm. Segment 1 of A1R with spinule row (Fig. 36F, G); segment 15 typically with well-developed spinous process reach ing to end of segment (Figs 35A, 36A, B, E); process sometimes absent; segment 20 of A1R lacking distal projection. Enp1 of A2 ornamented with spinule row and single pore (Figs 35G, 36J). Right BspP5 with longitudinal fissure ornamented with surface granulations (Fig. 36H, I); Right Exp2P5 twice as long as wide (Figs 35B, 36C, D); lateral spine positioned close to outer distal angle of segment and directed posteriorly relative to longitudinal axis of body, length of lateral spine less than width of segment; terminal claw long and slightly curved (Fig. 35 C–F), more slender than in Notodiaptomus cearensis .

Adult female, body length 1734 µm. Ped4 and Ped5 separated by complete suture; lateral wings slightly asymmetrical, each wing with sensilla at apex (Fig. 37A). GS asymmetrical, about 1.5 times longer than wide; slightly dilated anteriorly, with swelling on left side larger than on right, left swelling hemispherical with sensilla directed slightly posteriorly; right swelling more pronounced, sensilla located on dorsal surface, not on lateral margin; right lateral margin of GS with small projection about at 2/3 length and with small notch at posterior border (Fig. 37A). P5 symmetrical (Fig. 37B), with small expansion at outer distal corner of Cx, bearing large robust, triangular sensilla, approximately 1.5 times longer than wide. BspP5 with long outer seta, almost reaching distal margin of Exp1P5. EnpP5 with incomplete suture, similar in length to inner margin of Exp1P5. Exp 3-segmented; lateral spine of Exp2P5 similar in length to external margin of Exp3P5; external seta of Exp3P5 about 1/5 (20%) length of internal seta; internal seta attaining 3/4 length of terminal claw.

Remarks.

The illustrated specimens were collected from the upper Tiete River, at the Barra Bonita Reservoir. In addition to the well-developed spinous process on segment 15 of A1R of the male, Notodiaptomus conifer can be distinguished from other congeners like Notodiaptomus iheringi and Notodiaptomus cearensis , by its larger body size. These species also differ in their relative lengths of the lateral spines on the right Exp3P5 of the male.

Earlier studies ( Nogueira 2001, Nogueira et al. 2008; Matsumura-Tundisi and Tundisi 2003), which sampled several rivers in São Paulo State (Brazil) between 1970 and 2005 noted changes in the abundance of Notodiaptomus conifer . Matsumura-Tundisi and Tundisi (2003) suggested that such changes might be in response to variations in the ionic concentrations resulting from decreasing water quality and increasing conductivity over the surveyed period. Notodiaptomus conifer was found in the current study (based on samples taken in 2010) in only two reservoirs (JUR and BBON) (Fig. 38), and in both of these Matsumura-Tundisi and Tundisi (2003) had indicated that the species had disappeared. Studies on long time series (e.g. Polli and Simona 1992) have demonstrated cycles of 25 years for some diaptomid species, over which they dramatically decrease in population density but subsequently recover to become dominant again. It is necessary to sample extensively before putative disappearances can be confirmed.

Notodiaptomus conifer has been reported from Argentina to the northeast of Brazil, thus suggesting a widespread but scattered occurrence across South America.