Argestes mollis Sars, 1910

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 : 240-248

Redescription of Argestes mollis Sars, 1910

Figs. 15–20

Material. Collected by G.O. Sars (1910) at Bukken, eastern Norway. The material comprises of 10 individuals, 9 of which resulting as A. mollis females, the 10th corresponds to another harpacticoid family. One female was dissected and placed on 13 slides, labelled as “Zool. Mus. Oslo, F. 20352 b­n, Mp. 435g ”. It is designated as lectotype, as no holotype exists. During dissection it was noted that the specimen showed minor damage, i.e. to the mouthparts and P5. A second female was selected for completion of illustrations (lateral habitus, telson/FR) without dissection, and returned into alcohol.

The male was described based on material from the Langian Collection of the Swedish Museum of Natural History, Department of Invertebrate Zoology, coll. no. SMNH – 54818. K. Lang collected the material on July 21st, 1937 in Bohuslän, Gullmaren, Sweden, at 80m depth. It includes 28 representatives of A. mollis (and additionally 5 specimens of other harpacticoid species) One male and one (badly damaged) female were dissected and placed on 7 and 5 slides, respectively.

Female.

Habitus ( Figs. 15 A, B) dorsolaterally slightly depressed. Total body length including FR approximately 980µm. Similar to A. angolaensis sp. nov., cphth reaches approximately 1/3 of whole body length. Urosoma smaller than prosoma, markings varied within the examined specimens. All body somites including telson covered with small spinules, which decrease in density in the genital double somite, the dorsal parts of cphth and second and third thoracic somite. Cphth dorsally with tube pores, and at its posterior margin with a row of larger spinules. Whole body with sensilla, mainly at the posterior margin of the somites, with several arising from tubercles.

Telson ( Figs. 15 A, B, 17A) almost square in shape, reaching length of preceding 2 abdominal somites together, dorsally with small anal operculum bearing a row of spinules at distal margin, ventrally with proximal row of larger spinules.

FR ( Fig. 17 A) small, square, and covered with small spinules. 7 setae: I, II, and III of almost same length, all inserting in distal half of FR. IV and V longest setae, inserting terminally. VI longer than I–III, inserting terminally on inner margin. VII arising from small knob­like projection on dorsal side, subterminal. Setae I– III, and VI of rat­tail shape.

A1 ( Figs. 16 A, A’) 7­segmented, first and second segment covered with small spinules, forming rows in second segment. Second segment at its outer margin with few long spinules. All segments with bipinnate setae, seventh segment additionally with bare setae. Fourth segment with aes, sixth segment terminally with 1 very long and tripinnate seta. Seventh segment terminally with small aes and 1 strong but short seta.

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

A2 ( Fig. 15 C) with allobasis and 1­segmented exp bearing 1 bare seta, accompanied by 4 spinules. Allobasis covered with small spinules, anterior margin with some longer spinules. Enp as long as basis, bearing several spinules and anteriorly 2 bipinnate setae. Terminally with 6 setae, 1 of which is fused with tube pore at its base.

Md ( Fig. 16 B, B’) palpus missing, not drawn. Gnathobase massive and broad, with several strongly cuticularized teeth. In male, 1 small subterminal seta discernable (triangular arrow in Fig. 16 B’), but not in female ( Fig. 16 B).

Mxl ( Fig. 17 B) with several spinulose fields and massive precoxal arthrite, showing terminally 6 big spines, subterminally 1 bipinnate seta, and on its surface 2 long and slender bare setae. Coxa terminally with 2 bare and 1 bipinnate seta. Basis distinct, incorporating enp and exp, and bearing in total 5 setae, one of which is unipinnate.

Mx ( Fig. 17 C, C’) syncoxa with 2 endites (Fig. C), the proximal one with 1 bipinnate seta ( Fig. 17 C’), the distal one with 3 setae. Basis distinct, fused with 1 terminal seta, additionally with 3 setae. Enp distinct, with 2 bare and 1 bipinnate setae.

Mxp ( Fig. 15 D) syncoxa small, terminally with 2 bipinnate setae. Basis approximately 3 times longer than syncoxa, with several small spinules. Enp produced into long and slender claw accompanied by 1 bare seta.

P1 ( Fig. 18 A) with 3­segmented exp and enp. Coxa and basis of almost same size, coxa with some long spinules at outer margin. Intercoxal sclerite ( Fig. 18 A’) elongate. All exopodal segments of same size, exp2 with inner seta, exp3 with 5 setae/spines. Endopodal segments also of nearly same size, enp3 with 1 outer spine and 2 terminal setae. For setal formula see table 2.

P2–P4 ( Figs. 18 B, 19A, B) with 3­segmented exps and enps. Intercoxal sclerites ( Figs. 18 B’, 19B) bowlike. Coxae about 2 times bigger than bases, with few spinules. Bases broader than long, appendages turned outward. At inner margin, bases with a few long setules. Exps bigger and longer than enps, setation as shown in table 2. P3 exp and enp as well as P4 exp2 covered with small spinules.

TABLE 2: Argestes mollis Sars, 1910 , female, setation of P1–P4 (no. outer spines in roman numbers).

FIGURE 19: Argestes mollis , female. A. P3, B. P4. Scale: 50µm.

P5 ( Fig. 20 A) benp lost, not drawn. Exp approximately 3 times longer than broad, covered with spinules of different sizes, some reaching size of setae. Terminally with 4 setae and 1 long tube pore. Laterally on outer margin with 1 bare seta. Subterminally on inner margin with small tube pore.

Male:

Habitus and most characteristics as in female, but differing in the following features:

A1 ( Fig. 20 B) 10­segmented, haplocer, aes on fifth segment. First segment with 1 seta, fifth, sixth, and seventh segments each with 1 additional short and thick multipinnate seta. Eighth segment with just 1 big seta. Setal formula: 1/1; 2/6; 3/3; 4/1; 5/5 + aes; 6/1; 7/3; 8/1; 9/4; 10/6 + aes.

P5 ( Fig. 20 C) benp fused, endopodal lobe virtually absent, represented by 1 long and 1 smaller bipinnate seta. Exp approximately 4 times longer than broad, with 7 setae, outer margin with long tube pore. (Sub­)Terminally no tube pore discernible.

P6 ( Fig. 20 D) small, with 2 bare setae and row of spinules at proximal margin.

Figures

FIGURE 15: Argestes mollis, female. A. Habitus, dorsal view, B. Habitus, lateral view, C. A 2, D. Mxp. Scales: A, B. 100 µm, C, D. 50 µm.

FIGURE 16: Argestes mollis. A. A 1 female, general shape, A’. A 1 female, setation of single segments, B. Md gnathobase, palpus not drawn, B’. male Md gnathobase, triangular arrow pointing to small subterminal seta. Scales: 50 µm.

FIGURE 17: Argestes mollis, female. A. Telson and FR, ventral view, B. Mxl, C. Mx, C’. Mx of counterpart. Scales: A. 100 µm, B – C, C’. 50 µm.

FIGURE 18: Argestes mollis, female. A. P 1, A’. P 1 intercoxal sclerite, B. P 2, B’. P 2 intercoxal sclerite. Scale: 50 µm.

FIGURE 20: Argestes mollis. A. Female P 5 exp, enp not drawn, B. Male A 1, C. Male P 5, D. Male P 6. Scales: 50 µm.