Hyale youngi, Serejo, 2001

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 : 484-491

Hyale youngi n. sp.

( Figs 3-7 )

TYPE MATERIAL. — Holotype 7.5 mm, Praia Rasa, Búzios, Rio de Janeiro (RJ), Brazil, intertidal, on Ulva sp. , VIII.1996, coll. R. Donato ( MNRJ 13475). Paratypes: same locality, 9, 13, and 14 juveniles ( MNRJ 13476).

ETYMOLOGY. — Named in honor of my husband, Paulo S. Young, who works with barnacles and always encourages me in this wonderful profession.

OTHER MATERIAL EXAMINED. — Praia Rasa. Búzios, Rio de Janeiro (RJ), Brazil, 1 and 1 (USNM 306873). Same locality, 1 and 1 (MNHN-Am 5123).

Praia das Conchas. Cabo Frio, RJ, Brazil, 2, 13, and 3 juveniles (MNRJ 10448).

Ogiva. Cabo Frio, RJ, Brazil, 1 and 1 (MNRJ 10449).

Enseada da Ferradura. Búzios, RJ, Brazil, 2, 4

and 1 juvenile (MNRJ 14003).

Central channel of Ilha Grande Island. Angra dos Reis, RJ, Brazil, 3, 8, and 2 juveniles, on the bivalve Isognomon sp. (MNRJ 14870).

Praia do Poço. Itanhaém, São Paulo, Brazil, 7

and 4 on Ceramiales sp. (MNRJ 14871).

Morro de São Paulo, Bahia, Brazil, 1, on algae (MNRJ 13474).

DISTRIBUTION. — Brazil, States of Bahia, Rio de Janeiro, and São Paulo.

DIAGNOSIS. — Eyes large, oval. Antenna 2 reaching about one quarter of body length. Adult male gnathopod 2 palm straight, parallel to anterior margin, with few spines and setae and medially rugose; posterior margin of propodus inconspicuous. Pereopods 3-7, dactylus castellate, sub-terminal seta very stout and striate. Peduncle of uropod 1 with two well-developed disto-lateral spines. Uropod 3 with one marginal and six distal spines.

DESCRIPTION

Holotype, male (7.5 mm)

Antenna 1 reaching about one fifth of body length, flagellum with 9-11 articles. Antenna 2 reaching about one quarter of body length, flagellum with 12-13 articles. Eyes large and oval ( Fig. 3A ). Epistome triangular. Upper lip rounded with row of distal setae. Mandibles ( Fig. 3B, C ) with a group of setae above the molar; spine row of right mandible with two spines. Left mandible, spine row with three spines; lacinia mobilis with eight to nine teeth. Outer lobe of lower lip apically setose ( Fig. 3D ). Inner lobe of maxilla 2, with seven dentate spines, several simple setae, and two plumose setae, one of these considerably longer than others ( Fig. 3E ). Maxilla 1 ( Fig. 3F ) with nine dentate spines on outer lobe. Maxilliped ( Fig. 4A ), outer distal angle of inner and outer lobe, and palp articles 1-2 with 1/1/2/2 small spines, respectively; palp robust; dactylus inner margin straight, setae not overlapping nail.

Gnathopod 1 ( Fig. 4B ), basis robust, posterior margin of propodus with medial group of setae; palm slightly oblique, defined by stout spine; dactylus fitting palm. Gnathopod 2 ( Fig. 4C, D ), basis and ischium lobate; palm straight, parallel to the anterior margin, with few spines and setae, proximally with concavity to fit dactylus, bordered by two spines (these spines visible only from inner side); inner side of palm rugose. Coxae 1-4 with posterior processes acutely produced. Propodus of pereopods 3 and 4 with three spines about the same size, second spine surrounded by long setae ( Fig. 4E, F ). Pereopods 5-7 ( Fig. 5 A-C), basis expanded; propodus with three groups of spines followed by one large spine surrounded by setae and one tiny spine near dactylus articulation, posterior margin lacking setae. Inner margin of dactylus of pereopods 3-7 castellate, sub-terminal setae very stout and striate, resembling bifid dactylus ( Figs 4F ; 5 A-D).

Epimera 2-3 ( Fig. 5E ) with postero-ventral margin slightly sinuous. Uropod 1 ( Fig. 5F ), peduncle with four large spines on outer margin, one spine on inner margin and two welldeveloped disto-lateral spines; rami as long as peduncle, with two to three marginal spines and several distal spines. Uropod 2 ( Fig. 5G ), peduncle with four spines on outer margin and one spine on inner margin; rami with three marginal and three apical spines. Uropod 3 ( Fig. 6A), peduncle with two distal spines, one spine slightly shorter than the other; ramus with one marginal and six distal spines. Telson ( Fig. 6B) deeply cleft, each lobe bearing one pair of sub-apical setae and a pair of marginal setae.

Female (6.2 mm)

Gnathopod 1 ( Fig. 6C), palm oblique with several long setae, defined by two large spines. Gnathopod 2 ( Fig. 6D, E) slightly larger than gnathopod 1, carpus well-developed, palm as in gnathopod 1. Oostegites 2-5 ( Fig. 7 A-D) with short curl-tip setae. Second oostegite triangular, third and fourth rectangular, and fifth sub-triangular and smaller than others.

Variations

The palm of gnathopod 2 in juvenile males varies according to the stage of development. In the specimen 5.1 mm long, the palm is oblique, with the carpal lobe well-developed ( Fig. 7E). In larger specimens (6.0 mm), the carpal lobe disappears completely, but the palm is still oblique ( Fig. 7F). In adults, the palm is large, and extends over the entire propodus, with the defining spines in a more proximal position ( Fig. 4D ). The uropod 3 ( Fig. 7G) also varies in juvenile forms. It has only one distal peduncular spine, and the ramus bears only distal spines. A disjunct spine was observed on the ramus of juvenile forms, but it seems not to be homologous to that in the adult, considering the different position of these spines.

REMARKS

Hyale youngi n. sp. is also a member of the H. spinidactyla complex as discussed above, but can be distinguished from the other species complex as shown in Table 1.

The H. spinidactyla complex is confined to the Atlantic Ocean (Fig. 8), indicating a recent evolution of these species. Hyale spinidactyla was first recorded from the Canary Islands and then from other regions of the northeastern Atlantic. Later, H. spinidactyloides was described from near the mouth of Congo river (Landana and Malembe) ( Schellenberg 1939) and recently to t h e A s c e n s i o n I s l a n d (B i e r n b a u m 1 9 9 6). H. ramalhoi w a s r e c o r d e d o n l y f r o m t h e Madeira Island ( Reid 1939). Unfortunately, the types of H. spinidactyloides and H. ramalhoi were not available, and the descriptions and illustrations are incomplete, limiting the comparative analysis. Detailed examination of the

D

A E

A B A C

types would clarify the diagnostic characters and the validity of these species, as was done with H. spinidactyla .

Hyale youngi n. sp. was observed on sheltered rocky shores of estuarine areas. In same samples it occurred together with Parhyale hawaiensis .

Figures

FIG. 3. — Hyale youngi n. sp.; A-F, holotype 7.5 mm, Praia Rasa, Búzios, RJ, Brazil (MNRJ 13475). Abbreviations: ll, lower lip; rmd, right mandible; lmd, left mandible; mx, maxilla. Scale bars: A, 0.5 mm; B-F, 0.1 mm.

FIG. 4. — Hyale youngi n. sp.; A-F, holotype 7.5 mm, Praia Rasa, Búzios, RJ (MNRJ 13475). Abbreviations: gn, gnathopod; mxp, maxilliped; p, pereopod, pa, palm. Scale bars: A, F, 0.1 mm; B, D, E, 0.2 mm; C, 0.5 mm.

FIG. 5. — Hyale youngi n. sp.; A-G, holotype 7.5 mm, Praia Rasa, Búzios, RJ (MNRJ 13475). Abbreviations: ep, epimera; p, pereopod; U, uropod. Scale bars: A, B, 0.5 mm; C, 0.25 mm, D-G, 0.2 mm.