Hyale spinidactyla Chevreux, 1925

Serejo, Cristiana S., 2001, A new species of amphipod from the Brazilian coast, with redescription of Hyale spinidactyla Chevreux, 1925 (Crustacea, Amphipoda, Hyalidae), Zoosystema 23 (3), pp. 479-492 : 480-484

Hyale spinidactyla Chevreux, 1925

( Figs 1 ; 2 )

Hyale spinidactyla Chevreux, 1925: 366 , figs 13; 14 (part, not fig. 15 = Hyale sp. ). — Reid 1951: 245, fig. 39. — Arresti 1996: 81, figs 2-8.

MATERIAL EXAMINED. — Canary Islands. Stn 290, lectotype 6.4 mm (MNHN-Am 5106) ; paralectotype, 1 and 1 (pieces apart) (MNHN-Am 5122).

Dakar. Hyale sp. , 1 (pieces apart) (MNHN-Am 5107).

B A

DISTRIBUTION. — Type locality: Canary Islands ( Chevreux 1925). Other localities: Rio do Ouro, São Tomé Island ( Pirlot 1939); Cape Verde ( Ruffo 1950); Fayal, Azores ( Reid 1951); coast of the Basque Country, northern Spain ( Arresti 1996).

DIAGNOSIS. — Eyes large, oval. Gnathopod 2 palm with small concavity and distal process, covered with few spines and setae. Pereopods 6-7, propodus posteri- or margin with group of setae. Pereopods 3-7 dactylus smooth on inner margin, sub-terminal seta very stout and striate, resembling bifid dactylus. Peduncle of uropod 1 with two well-developed disto-lateral spines. Peduncle of uropod 2 with row of seven to eight spines on lateral margin. Ramus of uropod 3 with seven to eight distal spines, no marginal spines.

REDESCRIPTION

Lectotype, male (6.4 mm)

Antenna 1 about one quarter of body length, flagellum with 12 articles. Antenna 2 about one third of body length, flagellum with 16-17 articles. Eyes large, oval ( Fig. 1A ). Epistome triangular. Upper lip rounded with row of distal setae. Right mandible with group of setae above molar; spine row with two spines. Spine row of left mandible with three spines, and indistinct group of setae above molar. Maxilla 1 with nine dentate spines on outer lobe, palp slightly constricted medially, reaching base of spines of outer margin. Lower lip and maxilla 2 as in H. youngi n. sp. Maxilliped, outer distal angle of inner and outer lobe, and palp articles 1-2 with 1/1/1-2/2 small spines, respectively; palp robust; inner margin of dactylus slightly concave, with setae not overlapping nail.

Gnathopod 1 ( Fig. 1B ), basis robust, posterior margin of propodus with medial group of setae; palm slightly oblique, defined by two spines; dactylus fitting palm. Gnathopod 2 ( Fig. 1C, D ), basis and ischium lobate; propodus with defined posterior margin, palm with a small concavity and a distal process, with few spines and setae, dactylus fitting palm. Coxae 1-4 with posterior processes slightly produced. Propodus of pereopods 3 and 4 with four spines sub-equal in length, third spine surrounded by long setae ( Fig. 1E, F ). Pereopods 5-7, basis expanded; propodus with three groups of spines followed by one spine surrounded by setae and a distal spine larger than the others, near dactylus articulation ( Fig. 2A ). Pereopod 5, propodus posterior margin with one to two medial setae. Pereopods 6-7, propodus posterior margin with a group of setae medially. Dactylus of pereopods 3-7 with inner margin smooth; sub-terminal setae very stout and striate, resembling bifid dactylus ( Fig. 2A ).

Epimera 2-3 with postero-ventral margin slightly sinuous. Uropod 1 ( Fig. 2B ), peduncle with five spines on outer margin, two spines on inner margin, and two well-developed disto-lateral spines, rami slightly shorter than peduncle, with two to three marginal spines. Uropod 2 ( Fig. 2C ), peduncle with seven to eight spines on outer margin and one spine on inner margin; rami with two to four marginal spines and two apical spines. Uropod 3 ( Fig. 2D ), peduncle with two distal spines, one spine less than half length of other, ramus with seven to eight distal spines. Telson lobes triangular and separated from base, as in H. youngi n. sp.

Female

Gnathopod 2 carpus well-developed, palm oblique with several long setae, defined by two large spines. Oostegites 2-5 as H. youngi n. sp. Second oostegite triangular, third and fourth oostegites rectangular, and fifth oostegite sub-triangular and smaller than other ones.

REMARKS

Chevreux (1925) provided only a brief description and poorly detailed illustration of H. spinidactyla . Some important characters were examined in the syntypes, which were not indicated by Chevreux’ (1925) description. These were: the oval eyes; the coxae 1-4 bearing a posterior process; the peduncle of uropod 1 with marginal spines and two well-developed disto-lateral spines; the peduncle of uropod 2 with a row of seven to eight spines on the outer margin and one spine on the inner margin; and the ramus of uropod 3 with seven to eight distal spines.

The specimen observed by Chevreux (1925: 368, fig. 15) with designation of station from Dakar are definitely not H. spinidactyla . Chevreux (1925) suggested that this specimen might be an adult form of H. spinidactyla , although it had a different ornamentation on the male gnathopod 2 palm. Moreover, this specimen lacked the row of seven to eight spines on the peduncle of uropod 2 and the characteristic stout striate seta on the dactylus of pereopods 3-7.

Arresti (1996) cited some distinctions between Chevreux’ (1925) description and his specimens from the Basque Country coast, Spain. Most divergences actually resulted from the brief and incomplete description of Chevreux (1925). Only two characters still differ from the type material: the propodus of gnathopod 2, which lacks a defined posterior margin, and the palm extends over the entire propodus and the presence of an anterior acute process on coxa 7. The different structure of gnathopod 2 illustrated by Arresti (1996: fig. 8e) for his H. spinidactyla , probably resulted from the larger size of his specimens (adult 8.3 mm). In the juvenile form (7.8 mm) ( Arresti 1996: fig. 8d), the gnathopod 2 is similar to the lectotype observed here (6.4 mm), suggesting that Chevreux (1925) had only juvenile forms. This type of dimorphism between the juvenile and adult male gnathopod 2 is common, and was observed also in H. youngi n. sp. and H. macrodactyla ( Serejo 1999) .

Some differences indicated as diagnostic for H. spinidactyloides ( Schellenberg 1939: figs 17- 20) were found to be present also in H. spinidactyla . For instance, as coxae 1-4 have posterior processes, and peduncle of uropod 1 has two disto-lateral spines. The former species still differs from H. spinidactyla in the smaller antenna 1, about one fifth of the body length, and the straight palm of gnathopod 2.

Hyale spinidactyla is here included in the H. spinidactyla complex, which encompasses H. spinidactyloides Schellenberg, 1939 , H. ramalhoi Reid, 1939 , and H. youngi n. sp. This complex is characterized by a stout striate seta on the dactylus of pereopods 3-7, which is unique within Hyale . The large eyes and the two disto-lateral spines on peduncle of uropod 1 could also characterized this complex, however, these features were not described in the succinct description of H. ramalhoi .

Figures

FIG. 1. — Hyale spinidactyla Chevreux, 1925; A-C, lectotype 6.4 mm, Canary Islands (MNHN-Am 5106); D, paralectotype (MNHN-Am 5122) entire gnathopod 2. Abbreviations: gn, gnathopod; hd, head; p, pereopod. Scale bars: A, 0.5 mm; B, C, E, 0.2 mm; D, 0.3 mm; F, 0.1 mm.

FIG. 2. — Hyale spinidactyla Chevreux, 1925; A-D, lectotype 6.4 mm, Canary Islands (MNHN-Am 5106). Abbreviations: p, pereopod; u, uropod. Scale bars: A-C, 0.2 mm; D, 0.1 mm.