Notodiaptomus isabelae (Wright, 1936)

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 : 50-53

Taxon classification Animalia Calanoida Diaptomidae

Notodiaptomus isabelae (Wright, 1936) Figs 66, 67, 68

Diaptomus isabelae Wright, 1936

Diagnosis.

Adult male, body length 919 µm. Transverse row of strong spinules present along posterior margin of Ped4 (Fig. 66B, C). Modified seta on segment 13 of A1R extending beyond middle of segment 14, but not reaching end of segment; spinous process present on segments 15 and 16 of A1R (Fig. 66G). Two small expansions present proximally on internal margin of right BspP5 (arrowed in Fig. 66A); right Exp1P5 with wide distal expansion on margin (Fig. 66D, F); right Exp2P5 broad, with width about ¾ length (Fig. 66A, E); lateral spine short, inserted distally, close to insertion of terminal claw.

Adult female, body length 1056 µm. Complete suture present between Ped4 and Ped5, ornamented with row of strong spinules dorsally (Fig. 67A); lateral wings asymmetrical, left wing smaller and located anterior to right wing; two pairs of sensillae present on each wing, large sensilla on left positioned on small dorsal projection; large sensilla on right positioned at apex of wing. GS asymmetrical, approximately 2.5 times longer than wide; anterior part slightly dilated, with swelling on right side larger than that on left; left swelling rounded with strong sensilla at apex, approximately 1.5 times long than wide; anterior swelling on right side with strong sensilla at apex, approximately twice as long as wide; anterior swelling extending back along two thirds of lateral margin to acute indentation; margin straight posterior to indentation (Fig. 67A). P5 symmetrical (Fig. 67B) with small conical process at outer distal corner of CxP5, bearing sensilla with rounded apex, barely longer than wide. BspP5 with external seta reaching middle of external margin of Exp1P5. EnpP5 one-segmented, about as long as inner margin of Exp1P5. ExpP5 three-segmented; lateral spine of Exp2P5 almost reaching distal tip of external margin of Exp3P5; external seta of Exp3P5 about one third length of internal seta; internal seta about two thirds length of terminal claw.

Remarks.

The specimens were collected in the middle section of the Paraná River at Yaciretá Reservoir (Fig. 68, YACI-D). The type locality of this species is in the state of Pernambuco (northeastern Brazil) but this species is distributed across much of Brazil and Argentina, with its southernmost boundary in the middle region of the Paraná River. It does not seem to occur in the Iguaçu and Uruguay rivers, and the low winter temperatures in this region may be a factor limiting its distribution. Dussart and Frutos (1986) recorded this species in the middle section of the Paraná River.

This species can be easily distinguished from its congeners by the proximal processes on the internal margin of the male right BspP5 and by the shape of the wings and GS of females. A comparison with the description by Paggi (1976) revealed minor differences in the shape of segment 20 of the male A1R. No falciform process was found on this segment in our specimens, but this absence can occur in some populations, and a similar range of variability of this process has been noted for other species ( Ringuelet and Martínez de Ferrato 1967, Paggi 1976).