Leptalpheus cf. forceps Williams, 1965

Anker, Arthur, 2008, The shrimp genus Leptalpheus Williams, 1965 in the southwestern Caribbean Sea, with description of one new species from Panama (Crustacea, Decapoda, Alpheidae), Zoosystema 30 (4), pp. 781-794 : 788-792

Leptalpheus cf. forceps Williams, 1965

( Figs 4 ; 5 ; 6A, B )

Leptalpheus forceps Williams, 1965: 194 ; 1984: 101. — Dawson 1967: 224. — Saloman 1971: 67. — Chace 1972: 77. — Abele & Kim 1986: 194, 228. — Felder & Rodrigues 1993: 366. — Holthuis 1993: 203. — Anker et al. 2006b: 686 .

(?) Leptalpheus forceps – Christoffersen 1980: 135; 1998: 361. — Hermoso-Salazar 2001: 1278.

MATERIAL EXAMINED. — Costa Rica. Caribbean coast, Cahuita, Punta Uva, small mangrove river, coarse sand, from burrow of Lepidophthalmus richardi (host fcn 05- 118, will be deposited in MNHN), bait suction pump, depth 10-30 cm, coll. A. Anker, I. Wehrtmann and L. Harris, 26.XI.2005, fcn 05-119, 1 ♂, CL 8.2, TL 22.2 (MNHN-Na 17066). — Same collection data, from burrow of Lepidophthalmus richardi (host fcn 05-120, UCRMZ 2420-02 ), fcn 05-121, 1 ♂, CL 6.1, TL 15.3 ( UCRMZ 2420-01 ) ; 1 specimen (CL and TL not measured, sex not determined) preserved in Ambion RNA-later for molecular studies (fcn 05-006).

DESCRIPTION For complete description see Williams (1965, 1984). Detailed drawings of Cahuita specimens are provided in Figures 4 and 5 .

Size

The two Costa Rican male specimens were 6.1 mm CL, 15.3 mm TL, and 8.2 mm, 22.2 mm TL. Williams’ (1965) type specimens were 7.8 mm CL (female holotype) and 5.2 mm CL (male paratype).

Colour pattern

Semitransparent with yellowish and reddish chromatophores, more intense on tail fan, antennular peduncles,eyestalk and along posterior margins of the carapace and abdominal somites, forming transverse bands; some pale blue and greenish chromatophores present on the antennal scaphocerite and antennular peduncle; merus and carpus of major cheliped with reddish and some bluish chromatophores, major chela hyaline-whitish. Th e above-described pattern is much less conspicuous on a dark background: the shrimp appears as uniform whitish, with pale reddish bands on the abdomen and tail fan (see black-and-white photographs in Figure 6A, B ). The specimens from Fort Pierce, Florida (previously deposited in the MNHN) had pale greenish transverse bands on the abdomen; the antennules and the antennae were pale lettuce-greenish; the tail fan had locally pinkish, bluish and greenish tinge ( Anker et al. 2006b). Williams (1984) described the colour of L. forceps as “translucent, colorless in life; eggs light green in formalin”.

ECOLOGY

The present specimens were collected from burrows along the sea-side of a small river estuary, about 5 m wide, fringed with mangrove.Two specimens were collected together with their hosts, the callianassid ghostshrimp Lepidophthalmus richardi Felder &

A

Manning, 1997 ( Fig. 6C ). Elsewhere, L. forceps was found in burrows of the present host’s congeners, L. siriboia Felder & Rodrigues, 1993 ( Christoffersen 1980, as Callianassa jamaicensis ) and L. louisianensis (Schmitt, 1935) ( Felder & Rodrigues 1993) , as well as the upogebiid mudshrimp, Upogebia affinis

(Say, 1818) ( Williams 1965). Williams (1965, 1984) provided a brief summary of the biology of L. forceps .

HOST

Lepidopthalmus richardi ( Fig. 6C ) was previously known only from the type locality in Belize ( Felder & Manning 1997). Th e record from Cahuita represents a second finding of this species and a considerable extension of its distribution range from Belize southward to Costa Rica.

REMARKS

The two male specimens from Costa Rica ( Figs 4 ; 5 ) agree reasonably well with the illustrated female holotype from North Carolina (cf. Williams 1965), except for the more robust antennular peduncles (compare Fig. 4 A and Williams 1965: fig. 1B); the slightly shorter scaphocerite, reaching to about 2/3 length of the second segment of the antennular peduncle ( Fig. 4A ) vs. reaching almost to the end of this segment in the type ( Williams 1965: fig. 1B); and the more elongate lateral plate on the coxa of the third maxilliped (compare Fig. 4D and Williams 1965: fig. 2F). Williams (1965) noted that “the fingers of the major chela are slightly less gaping in females than in males” and that “there is a slight variation in the number of teeth on the fingers of the major cheliped”, however, without providing the exact range of this variation. Th e dentition of the type includes six teeth ( Williams 1965: fig.1G), whereas the two examined Costa Rican specimens have six and seven teeth, respectively (not counting the small most proximal tooth visible only when chela is widely opened) ( Fig. 5 F-H, L). Th e most distal tooth on the pollex may be more protruding than the others ( Fig. 5L ). However, the most important difference between the specimens from Costa Rica and North Carolina lies in the development of a segmented appendix on each uropodal endopod. These appendices (caudal filaments) are present in both males from Cahuita ( Fig. 4J ), and absent in the female holotype and apparently also in all paratypes of L. forceps ( Williams 1965: fig. 2L). Similar caudal filaments were observed in one male specimen of L. felderi from Isla Margarita, Venezuela ( Anker et al. 2006b: fig. 5C); however, in other males and in females of this species, the distal margin of the uropodal endopod was rounded. Th e function of these structures, if there is any, as well as their occurrence in some individuals and absence in others remain unexplained. Thus L. felderi appears to be a highly variable species, but more specimens and DNA sequencing are needed to determine the full extension and the genetic base of this variation, and to decide whether L. cf. felderi from Costa Rica is conspecific with L. felderi from North Carolina and Florida.

Figures

FIG. 4. — Leptalpheus cf. forceps Williams, 1965, larger ♂ from Cahuita, Caribbean coast of Costa Rica (MNHN-Na 17066): A, frontal region, dorsal view;B, same,lateral view; C, tooth on ventromesial carina of first segment of antennular peduncle,lateral view;D, third maxilliped, lateral view; E, second pereiopod, lateral view; F, third pereiopod, lateral view; G, fifth pereiopod, lateral view; H, second pleopod, mesial view; I, same, detail of appendix masculina and appendix interna; J, uropod, dorsal view; K, telson, dorsal view; L, same, detail of posterior margin. Scale bars: 1 mm.

FIG. 5. — Leptalpheus cf. forceps Williams, 1965, larger ♂ (A-K) from Cahuita, Caribbean coast of Costa Rica (MNHN-Na 17066), smaller ♂ (L) from the same locality (UCRMZ 2420-01): A, major (left) cheliped, mesial view; B, same, lateral view; C, same, detail of ischium, mesial view; D, same, detail of carpus, mesial view; E, same, lateral view; F, same, chela fingers, lateral view; G, same, mesial view; H, same, fingers opened; I, minor (right) cheliped, lateral view (mastigobranch accidentally detached); J, same, chela and carpus, ventrolateral view; K, same, chela fingers opened; L, major (left) cheliped of smaller male, chela fingers, mesial view. Scale bars: 1 mm.

FIG. 6. — A, B, Leptalpheus cf. forceps Williams, 1965, larger ♂ from Cahuita, Caribbean coast of Costa Rica (MNHN-Na 17066); A, habitus in lateral view; B, same in dorsal view; C, Lepidophthalmus richardi Felder & Manning, 1997 (Callianassidae), host (UCRMZ 2420-02) of smaller ♂ from Cahuita (UCRMZ 2420-01), habitus in dorsal view.