Notodiaptomus henseni (Dahl, 1894)

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 : 38-41

Taxon classification Animalia Calanoida Diaptomidae

Notodiaptomus henseni (Dahl, 1894) Figs 47, 48, 49, 50, 51, 52, 53, 54

Diaptomus henseni Dahl, 1894

Notodiaptomus oliveirai Matsumura-Tundisi, Espindola, Tundisi, Souza-Soares & Degani, 2010 [new synonym]

Diagnosis.

Adult male, body length 1123 µm. Dorsal suture between Ped4 and Ped5 incomplete (Fig. 48B); surface of Ped3, Ped4, and Ped5 ornamented postero-dorsally and laterally with fine covering of slender spinules (Fig. 48 C–D). Lateral wings small, slightly asymmetrical, directed posteriorly; left side larger than right; both lateral wings with short, posteriorly-directed sensilla at distal corner, left sensilla better developed than right (Fig. 48B). GS slightly asymmetrical. Rostrum asymmetrical (Fig. 48H). Segment 1 of A1R ornamented with spinule row (Fig. 48E, F); modified seta on segment 13 reaching to end of segment 14 (Figs 47A, 48A, I). Bsp of A2 ornamented with spinules (Fig. 48G, J); Enp1 of A2 with spinule row (Fig. 47E). Cx and Bsp of P1 ornamented with long setules laterally (Fig. 49A). Right CxP5 with conical process bearing sensilla at apex (Figs 47H, J, 49G). Inner margin of right BspP5 with sclerotized knob, covered with tiny granulations (Figs 47C, D, 49C, E, F); right BspP5 with oblique fissure ornamented with small surface granulations (Fig. 47C); external seta of right BspP5 inserted subdistally, short, typically shorter than outer margin of Exp1P5. Right Exp1P5 bearing triangular process distally; right Exp2P5 with internal margin concave proximally, lateral spine slightly curved (Figs 47K, 49D) and inserted sub-terminally on external margin, less than 1/3 length of terminal claw (Fig. 47 G–K). CxP5L with small conical process at outer distal corner bearing short apical sensilla; BspP5L with short external seta inserted distally; internal margin of BspP5L slightly concave, bearing two small sclerotized knobs proximally (Figs 47 B–D, 49B, G), each ornamented with tiny granulations (Fig. 49C, E, F). EndP5 one-segmented, with row of spinules on inner distal margin (Fig. 47B, F). Exp2P5L with digitiform and sclerotized terminal process, lacking ornamentation.

Adult female, body length 1275 µm. Complete suture present between Ped4 and Ped5 (Fig. 50A); lateral surfaces of Ped3, Ped4 and Ped5 ornamented with covering of fine spinules (Fig. 51C); lateral wings more or less symmetrical (Fig. 51A); both wings with two sensillae, larger sensilla located at apex of wing and about 1.5 times longer than wide, smaller sensilla located near posterior margin of wing (Fig. 50A). GS asymmetrical, about 1.9 to 2 times longer than wide; slightly dilated anteriorly, with swelling of similar size on each side; each swelling with sensilla at apex; sensilla on right side of GS located at apex of hemispherical swelling; small lobe located at posterior end of right margin of GS (Figs 50A, 51A). Rostrum symmetrical (Fig. 51B). Fine setules present on segments 1 and 3 to 5 of A1 (Fig. 51E, F). P5 symmetrical (Fig. 50B) with small conical process at outer distal angle of CxP5, with short and strong sensilla, barely longer than wide. BspP5 with long external seta, extending beyond middle of external margin of Exp1P5. EnpP5 extending to middle of internal margin of Exp1P5, with incomplete suture (Fig. 51D). Exp 3-segmented; external seta of Exp2P5 exceeding length of external margin of Exp3P5 and similar in length to external seta of Exp3P5; external seta of Exp3P5 about 40% length of internal seta. Internal seta about 2/3 length of terminal claw.

Remarks.

The specimens depicted here were collected in Furnas Reservoir on the Grande River (Fig. 52, FUR-U). Wright (1936) commented on the possible confusion between Notodiaptomus amazonicus (Wright, 1935) and Notodiaptomus henseni . However, comparisons between the specimens of Notodiaptomus henseni found in this work and Notodiaptomus amazonicus collected in Balbina Reservoir ( Uatumã River, Amazonas) showed clear differences in the structure of P5 (Fig. 53), the dorsal spinular ornamentation of the prosomal somites, and in body length. In the present study, specimens of Notodiaptomus amazonicus similar to those obtained in the Amazon region were not found, but Notodiaptomus henseni was found to be widely distributed in the Upper Paraná River. There are significant differences in size range between Notodiaptomus henseni and Notodiaptomus amazonicus (Fig. 54). Notodiaptomus amazonicus males had a body length of 1608 µm and a body width of 397 µm, both significantly larger than Notodiaptomus henseni , whose body length does not exceed 1300 µm. It is possible that some records of Notodiaptomus amazonicus from de la Plata basin are erroneous, reflecting the taxonomic confusion between this species and Notodiaptomus henseni . For example, Ringuelet and Martinez de Ferrato (1967) reported a body length of about 1270 µm for a diaptomid identified as Notodiaptomus amazonicus in Argentina. However, this length is much less than would be expected for this species and falls within the typical size range of Notodiaptomus henseni .

In addition, Ringuelet and Martinez de Ferrato (1967) mentioned that their specimens of Notodiaptomus amazonicus that carried a process on segment 20 of the male A1R were larger (about 1375 µm), a condition which is closer to the expected size of Notodiaptomus amazonicus from the Amazon region, although still relatively small. More comparisons are needed between specimens of Notodiaptomus amazonicus from the Amazon basin and those reported by other researchers from de la Plata River Basin.

Recently, Matsumura-Tundisi et al. (2010) described a new species, Notodiaptomus oliveirai Matsumura-Tundisi, Espindola, Tundisi, Souza-Soares & Degani, 2010, which shows a close similarity to Notodiaptomus henseni , and stated that many records of Notodiaptomus henseni from the state of São Paulo (Brazil) would represent records of Notodiaptomus oliveirai . However, their description is supported by illustrations lacking many important details (e.g. description of A1 formula, dorsal spinules) and the diagnostic difference between these two species as stated by these authors was based only on the curvature of the outer margin of the second segment of the exopod of right P5 (Exp2P5R). We consider this evidence insufficient to justify the establishment of a new species. The form of the P5 appears to vary according to the angle of observation (e.g. Fig. 47G to 47K), and this can be misleading. The degree of curvature alone does not provide adequate evidence upon which to base the establishment of a new species. The typical sclerotized processes on internal margins of left and right BspP5 of Notodiaptomus henseni are visible in the photograph of Notodiaptomus oliveirai included by Matsumura-Tundisi et al. (2010) and their presence provides further evidence pointing to the synonymy of this nominal species. We formally propose the recognition of Notodiaptomus oliveirai as a junior subjective synonym of Notodiaptomus henseni .