Argestes reductus ( Itô, 1983 ), Ito, 1983

George, Kai Horst, 2008, Argestes angolaensis sp. nov. (Copepoda: Harpacticoida: Argestidae) from the Angola Basin (Southeast Atlantic), and the phylogenetic characterization of the taxon Argestes Sars, including the redescription of A. mollis Sars, 1910, and A. reductus (Itô, 1983) *, Zootaxa 1866, pp. 223-262 : 248-254

Redesription of Argestes reductus ( Itô, 1983)

Figs. 21 –25

The description is based on the type material collected by Itô (1983). It consists of 3 male specimens, all of which are dissected and mounted on slides: Holotype on six slides, labelled 6­II­1979, KH­79­1, St. 5, A­1/1­ 6, paratype 1 on six slides, labelled 6­II­1979, KH­79­1, St. 5, A­2/1­6, paratype 3 on six slides, labelled 6­II­ 1979, KH­79­1, St. 5, A­3/1­6. Due to the bad conditions of the embedded urosomes, no telson and FR of A. reductus could be illustrated.

Male.

Habitus not drawn, as well as telson and FR, the latter due to the bad conditions of the slide material.

A1 ( Fig. 21 A) 11­segmented, all segments covered with small spinules. Ninth segment terminally with 1 very strong seta.

Setal formula: 1/1; 2/1; 3/6; 4/6; 5/1; 6/8 + aes; 7/1; 8/2; 9/1; 10/3; 11/6 + aes.

A2 ( Fig. 21 B) with allobasis, covered in small spinules and bearing 1­segmented exp with 1 seta, additionally with long hair­like spinules. Enp at its anterior margin laterally with 2 bipinnate setae. Terminally with 6 setae, 5 of which are “rat­tail”­like, and 1 small tube pore which is fused to longest seta basally (triangular arrow in Fig. 21 B).

Md (Fig. 22A) with strong palp but weak, reduced gnathobase. Palpus with enp and exp. Basis with a few spinules and 2 bipinnate setae. Enp also with some spinules, laterally with 1 bipinnate seta, terminally with 4 bipinnate and 2 bare setae. Exp smaller than enp, each laterally and terminally with 2 bipinnate setae.

Mxl (Fig. 22B) atrophied, poorly sclerotized. Precoxal arthrite laterally with 1 bare seta, terminally with 7 setae. Coxa(?) terminally with 3 bare setae, no more structures discernible.

Mx not drawn, due to inability to determine it clearly.

Mxp (Fig. 22C) weak, basis longer than syncoxa, the latter covered with spinules and bearing 2 setae (1 of which is broken). Basis laterally with row of spinules. Enp produced into long and slender seta, which is accompanied by a second seta.

P1 ( Fig. 23 A) with 3­segmented rami. Coxa bigger than basis, intercoxal sclerite boomerang­like in shape. Basis with inner and outer seta, and with long spinules at inner margin. All segments covered with small spinules. Exp2 with inner seta. Outer setae of exps 1–3 subterminally with tube pores. Terminal setae “rat tail”­like at their distal half. Enps 1 and 2 with 1 bipinnate inner seta, whose spinules are remarkably long. Enp3 terminally with 2 long setae, showing “rat­tail” shape in their distal half, and with 1 shorter outer seta with a tube pore subterminally.

Argestes reductus , male. A. Md, arrow indicates single enp showing setation, B. Mxl, C. Mxp. Scales:

50µm.

FIGURE 25: Argestes reductus , male. A. P3, B. P4. Scale: 50µm.

P2–P4 ( Figs. 24 , 25A, B) with 3­segmented rami and bow­like intercoxal sclerites (cf. Fig. 24 ). All segments covered with small spinules. Coxa much bigger than basis, the latter with 1 outer seta and long spinules on the inner margin. Last exopodal and endopodal segments approximately as long as preceding segments together. Outer setae of P2 tripinnate and at P3 and P4 tetrapinnate. Setation as shown in table 3.

P5 ( Fig. 23 B) benps fused, endopodal lobe reduced, represented by 2 small, bipinnate setae. Exp distinct, approximately 4 times longer than broad, covered with spinules and bearing 6 setae, 2 of which are “rat tail”­ like. Each with 1 tube pore proximally and terminally.

Female unknown.

Figures

FIGURE 21: Argestes reductus, male. A. A 1, arrow indicates single sixth segment showing position of aes and accompanying seta, B. A 2, arrow indicates distal part of enp, showing tube pore (triangular arrow). Scale: 100 µm.

FIGURE 23: Argestes reductus, male. A. P 1 with corresponding intercoxal sclerite, B. P 5. Scale: 50 µm.

FIGURE 24: Argestes reductus, male P 2 with corresponding intercoxal sclerite. Scale: 50 µm.