Argyrodiaptomus furcatus (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 : 18-23

Taxon classification Animalia Calanoida Diaptomidae

Argyrodiaptomus furcatus (Sars, 1901) Figs 20, 21, 22, 23, 24

Diaptomus furcatus Sars, 1901

Diagnosis.

Adult male, body length 1354 µm. Modified seta of segment 13 of A1R with bifid apex, reaching or exceeding proximal border of segment 14 (Fig. 20K); spinous process on anterior margin of segment 15 present, or sometimes absent; distal process of segment 20 sometimes absent, if present, variable from short (Fig. 20G) to strong, long and curved (Fig. 21A, C, D). Basipodite of A2 with spinular ornamentation (Fig. 21B, I); Enp1A2 with row of spinules and single pore (Fig. 20F). Left BspP5 ornamented with setules and patches of small spinules (Fig. 20 H–J); left Exp2P5 with long lateral seta (Fig. 21F); right CxP5 with distal process, ornamented with fine spinules (Fig. 20D, E); right BspP5 with smooth surface, with simple distal process (Fig. 20 B); lateral spine of right Exp2P5 slightly curved at apex, inserted posterodistally on segment very close to base of claw (Figs 20 A–E, 21E), reaching about to middle of terminal claw; terminal claw curved and twisted, with torsion in three planes. Leg 1 with distinctive spinulation on coxa, basipodite and both rami (Fig. 21G, H).

Adult female, body length 1712 µm. Dorsal surface of Ped4 and Ped5 unornamented, lacking lines of spinules (Figs 22A, 23A). Incomplete suture present dorsally between Ped4 and Ped5; lateral wings slightly asymmetrical, left side larger than right (Fig. 23B); both wings with pair of sensillae, located at distal corner. GS asymmetrical, about twice as long as wide; slightly swollen anteriorly, more on left side than on right (Fig. 22A). P5 symmetrical, with small conical process at outer distal corner of CxP5 bearing short, triangular sensilla (Fig. 22B). BspP5 with short outer seta (Fig. 22C), measuring about 70-80% of external margin of EnpP5. EndP5 2-segmented, although suture only visible from certain angles (Figs 22C, 23 C–E). ExpP5 3-segmented; lateral spine of Exp2P5 short, not exceeding length of external margin of Exp3P5; external seta of Exp3P5 about ¼ (25%) length of internal seta; internal seta about 2/3 length of terminal claw (Fig. 23E).

Remarks.

The figured specimens were collected from the Iguaçu River at the reservoir of Foz do Areia (FARE-D) (Figure 24). This species was originally described from material collected in the state of São Paulo and, according to Wright (1927), occurs in Brazil (south and southeastern, and possibly also in the mid-west) and in Argentina. Santos-Silva (2008) and Previattelli et al. (2013) cited several records of Argyrodiaptomus furcatus from south and southeastern Brazil. Together these studies confirm the occurrence of this species mainly in reservoirs of southeastern and southern Brazil, and in northern Argentina. Along with other large species of this genus, this species can co-occur with Argyrodiaptomus azevedoi (in southeastern Brazil) and with Notodiaptomus spiniger (Brian, 1925) (in southern Brazil and northern Argentina). Argyrodiaptomus furcatus tends to be closer to Notodiaptomus spiniger in body size, whereas Argyrodiaptomus azevedoi is larger.