Alpheus websteri Kingsley 1880

Alpheus websteri Kingsley, 1880

Alpheus websteri Kingsley, 1880:416.—Wicksten, 1983:42.

Alpheus Ridleyi Pocock, 1890:518.

Alpheus nigro-spinatus Rankin, 1898:249, pl. 30: fig. 6.

Alpheus ridleyi.—Chace, 1972:69.

Crangon arenensis Chace, 1937:119, fig. 4.

MATERIAL EXAMINED.—Costa Rica: Guanacaste, Playa del Coco (sta 1566: 1 , 1 ovig); Puntarenas, Golfo de Nicoya, Isla Tolinga (sta 1567: 5 , 1 ovig).

Panama: Pedro Gonzales, Perlas Islands (sta 33-4: 2 ).

TYPE-SPECIMEN.—USNM 84329, male, cl 6.5 mm, Key West, Florida.

MEASUREMENTS.—Males, cl 6.1–10.0 mm; females, cl 4.5–9.0 mm; ovigerous females, cl 6.6–6.7 mm.

DESCRIPTION.—Rostrum (Figure 11a,b) narrowly triangular, almost reaching to middle of visible part of first antennular segment and bearing several setae near base; rostrum extending posteriorly as narrowly raised carina, passing to posterior end of eye.

Ocular hood strongly inflated dorsally, separated from rostral carina by rather deep, distinct depression and armed with sharp tooth directing inward at tip. Ocular tooth reaching to distal of rostrum. Anterior inner margin of ocular hood strongly slanting anteriorly from base of rostrum to ocular tooth, very concave near base of rostrum.

First antennular segment bearing shallow, round carina extending from ventral inner margin (Figure 11c). Second segment about 2.1 times as long as broad, almost as long as visible part of first segment and 1.5 to 2 times as long as third segment. Stylocerite narrowing to long sharp point, scarcely reaching to distal margin of first segment.

Scaphocerite with lateral margin strongly concave at middle. Distal spine overreaching distal end of antennular peduncle and slightly falling short of distal end of carpocerite. Inner blade narrower than adjacent distal spine, reaching to distal of scaphocerite. Cleft between inner blade and distal spine deep, arising from distal of scaphocerite.

Carpocerite overreaching distal end of antennular peduncle by length of third antennular segment. Basicerite with sharp, triangular lateral spine; spine long, very broad at base, reaching to or overreaching distal margin of first antennular segment.

Third maxilliped (Figure 11d) overreaching distal end of carpocerite by to entire length of ultimate segment. Ultimate segment truncate at distal end, about 3.4 times as long as broad at proximal end and 2.1 times as long as penultimate, bearing long setae on distal margin. Penultimate segment about 1.5 times as long as broad at distal end. Exopod reaching to distal end of ultimate segment. Precoxa with one arthrobranch near distal end but with no supplementary arthrobranch.

Major chela of first pereopods (Figure 11e,f) about 2.3 times as long as broad with fingers occupying distal 0.3. Movable finger opening and closing in almost vertical plane, regularly arched in profile, compressed laterally, bluntly rounded distally and extending somewhat beyond tip of immovable finger. Immovable finger with inferior margin slightly sinuous, with very slight longitudinal groove in outer face; groove arising from region above inferior shallow transverse depression. Palm with trace of longitudinal depression behind dactylar articulation on outer face and with obliquely transverse superior groove most marked on inner face, but terminating abruptly without extending far onto either lateral face. Inferior transverse depression at base of immovable finger very shallow. Merus about 2.2 times as long as broad with no distinct spine (or with trace of very small spine) on distal end of inferior inner margin.

Minor chela of first pereopods (Figure 11 g,h) about 2.9 times as long as broad, fingers occupying 0.54 length of chela. Inner face of palm bearing acute, subrectangular tooth flanking dactylar articulation. Palm with no trace of sculpturing except trace of very slight depression on inferior margin at base of immovable finger. Entire chela, especially fingers provided with numerous tufts of setae on inner face. Merus about 2.3 times as long as broad with no distinct spine on distal end of inferior inner margin.

Second pereopod (Figure 11i) reaching distal end of carpocerite beyond part of merus. Fingers of chela almost as long as palm. First segment of carpus about 2.1 times as long as second; second segment 1.5 times as long as third; third segment subequal to fourth; fifth segment slightly shorter than second and 1.4 times as long as third.

Dactylus of third pereopod (Figure 11j) about length of propodus, with very small tooth on distal of inferior margin. Propodus about 1.1 times as long as carpus, with 7 movable spines on inferior margin and pair at distal end, and its superior margin provided with tufts of long setae and bearing one movable spine at distal end. Merus fairly stout, about 3.1 times as long as broad and bearing several tufts of long setae on inferior margin. Ischium with no movable spine.

Fourth pereopod almost same as third pereopod. Dactylus with small tooth on inferior margin. Ischium with no movable spine.

Fifth pereopod much narrower than third pereopod. Ischium with no movable spine.

Pleura (Figure 11k) of abdominal somites broadly rounded. Abdominal sternite with no spine at midline. Appendix masculina clearly overreaching distal end of appendix interna.

Telson (Figure 11l) about 1.4 times as long as broad at anterior end, armed with two pairs of rather stout dorsal spines (color of spine brown in some specimens preserved in alcohol) and with no longitudinal median depression on dorsal surface. Posterior margin produced at middle, armed with pair of spines at each lateral end; inner spine almost 2 times as long as outer one.

Uropodal endopod with inner depression at anterior half invisible. Uropodal exopod with lateral margin terminating in two immovable teeth, and strong dark colored movable spine overreaching distal margin of uropodal exopod, flanked internally by strong immovable tooth; transverse suture forming two convex lobes, outer one much more narrow and convex.

VARIATIONS.—The rostrum of this species is longer than the ocular tooth, but one male specimen shows that the rostrum is shorter than the ocular tooth. The relative length of the second antennular segment varies from 1.5 times to 2 times as long as the third segment.

HABITAT.—Rock, sand beach, tide pools. Intertidal zone to 6 m, among rocks or coral (Wicksten, 1983:42).

TYPE-LOCALITY.—Key West, Florida.

DISTRIBUTION.—Eastern Atlantic; Caribbean region; southern Gulf of California; Isla Socorro; Costa Rica; Panama; Colombia and Galapagos Islands.

Shallow-waters (0-100 m)

Hard bottom (rock and rubbles)