Alpheus pacificus Dana 1852

Alpheus pacificus Dana, 1852

Alpheus pacificus Dana, 1852:544; 1855: pl. 34: fig. 5.—Coutière, 1899:16, fig. 290; 1905:909, pl. 85: fig. 47, 47a, 47b,b′, pl. 86: fig. 47c,c′,—Chace, 1962:610.—Tiwari, 1963:315, fig. 30.—A. Banner and D. Banner, 1966:143, fig. 54.—Gillett and Yaldwyn, 1969:70, 110, fig. 41.—Luke, 1977:4.—D. Banner and A. Banner, 1981:37; 1982:217, fig. 68.—A. Banner and D. Banner, 1984:42.

Alpheus gracilidigitus Miers, 1884:287.—Nobili, 1899:233.

Crangon pacifica.—Banner, 1953:138, fig. 50 [neotype established].

Crangon pacificus.—Schmitt, 1939:12.

MATERIAL EXAMINED.—Mexico: Braithwaite Bay, Socorro Island (sta 130-34: 1 ovig).

Costa Rica: Isla del Coco, Wafer Bay (sta 105-33: 1 , 1 ovig).

Galapagos Islands: Gardner Bay, Hood Island (sta 27-33: 1 , 1 ovig).

MEASUREMENTS.—Males, cl 5.1-12.3 mm; ovigerous females, cl 8.0-14.0 mm.

DESCRIPTION.—Rostrum (Figure 42a,b) elongate, slightly overreaching middle of visible part of first antennular segment and bearing few short setae on lateral margins proximally. Rostral carina rounded dorsally, extending backwards beyond posterior end of ocular hood.

Ocular hood slightly inflated dorsally above level of rostral carina and produced anteriorly to middle of rostrum. Orbitorostral groove moderately deep and reaching far posterior to eye. Anterior margin of ocular hood rounded, very concave near base of rostrum.

First antennular segment bearing very shallow, broadly V-shaped carina extending from ventral inner margin (Figure 42c). Second segment about 2.3 times as long as broad, 1.7 times as long as visible part of first segment and 1.6 times as long as third segment. Stylocerite broad proximally, abruptly narrowing to sharp point, almost reaching to distal margin of first segment.

Scaphocerite about 2.6 times as long as broad with lateral margin slightly concave at proximal . Distal spine at least reaching to distal end of antennular peduncle and falling short of distal end of carpocerite. Inner blade regularly narrowing distally, far shorter than adjacent distal spine. Cleft between inner blade and distal spine deep, arising from slightly more than distal 0.4 of scaphocerite.

Carpocerite overreaching distal end of antennular peduncle by length of third antennular segment. Basicerite bearing sharp, triangular lateral spine; spine broad at base, almost reaching to tip of stylocerite.

Third maxilliped (Figure 42d) slightly overreaching distal end of carpocerite. Ultimate segment about 5.2 times as long as broad at proximal end and 1.7 times as long as penultimate; distal margin truncate, not much narrower than proximal end and bearing long setae on superior and inferior margins as well as on distal margin; tufts of setae on inner surface dense. Penultimate segment about 2.5 times as long as broad, with dense long setae on superior and inferior margins, especially distally. Antepenultimate segment with sparse setae on inferior margin and few long setae on superior distal margin. Exopod slightly overreaching distal end of antepenultimate segment. Precoxa with one arthrobranch near distal end and also with small supplementary arthrobranch near proximal end.

Major first pereopod (Figure 42e-g) overreaching distal end of carpocerite by length of chela. Major chela about 2.3 times as long as broad with fingers occupying distal . Movable finger regularly arched in profile, compressed laterally and acutely rounded at tip. Immovable finger with tip directed upward; superior margin just before tip very concave; outer face with very slight longitudinal median depression leading posteriorly below anterior part of superior outer palmar depression. Palm with superior transverse groove very deep with proximal shoulder well overhanging groove. Superior outer palmar depression well defined, quadrangular, extending to oblique suture. Superior inner palmar depression elongated triangular in shape, reaching proximally just past middle of palm, and directing toward superior margin. Inferior transverse groove very deep, slightly slanting posteriorly; proximal shoulder heavy, rounded, slanted distally and bearing small granules. Inferior outer palmar depression very narrow, obliquely inverse V-shaped. Inferior inner palmar depression very broad and not well defined superiorly and anteriorly. Inner face of palm with shallow longitudinal depression near bottom of palm. Merus about 1.8 times as long as broad with inferior inner margin bearing very short setae and no spine at distal end.

Minor chela of first pereopods (Figure 42h,i about 3.5 times as long as broad, fingers occupying slightly more than distal 0.6. Inferior margin of palm with broad transverse notch below level of dactylar articulation. Inner face of palm with very blunt tooth flanking dactylar articulation. Both fingers slender and with acute tips. Movable finger not balaeniceps, bearing on lateral cutting edge dense series of long, forward-sweeping setae; setae crossing similar series of setae on immovable finger. Cutting surface of movable finger with two thin crests near articulation, longer crest placed in proximal of cutting surface and fitting into shallow groove in immovable finger when fingers closed; smaller crest not touching superior margin of immovable finger when fingers closed; fingers with tips overlapping, but gaping between tips and crests on movable finger when closed. Minor chela of female smaller, 3.7 times as long as broad with fingers occupying distal 0.6 and bearing only scattered setae instead of rows of long hairs. Merus about 2.5 times as long as broad with very short setae on inferior inner margin and without spine at distal end.

Second pereopod (Figure 42j) overreaching distal end of carpocerite by of first carpal segment. Fingers of chela almost as long as palm. First segment of carpus about 1.6 times as long as second; second segment 2.6 times as long as third; third segment subequal to fourth; fifth segment shorter than second and 1.8 times as long as fourth.

Dactylus of third pereopod (Figure 42k) simple, about 0.4 times as long as propodus. Propodus almost as long as carpus, with 7 movable spines and pair at distal end. Merus about 4.5 times as long as broad, 1.5 times as long as carpus, bearing few stiff setae on inferior margin. Ischium with movable spine.

Fourth pereopod almost same as third pereopod. Ischium with movable spine.

Ischium of fifth pereopod with no movable spine.

Pleura (Figure 42l) of first four abdominal somites broadly rounded in both sexes, but pleuron of fifth somite more triangular on posterior ventral margin. Abdominal sternites bearing spine at midline of each sternite of first three somites. Appendix masculina almost as long as Appendix interna.

Telson (Figure 42m) about 1.6 times as long as broad at anterior end, armed with two pairs of rather stout dorsal spines and with no longitudinal median depression on dorsal surface. Posterior margin rounded, bearing seta-like spines and armed with pair of spines at each lateral end; inner spine almost as long and wide as outer one.

Uropodal endopod with seta-like spines on distal margin and with inner depression at anterior half fairly distinct. Uropodal exopod with seta-like spines on distal margin and bearing rather slender movable spine flanked laterally by acute immovable tooth and internally by blunt lobe; movable spine not overreaching distal margin of uropodal exopod; transverse suture forming two convex lobes, inner one slightly flattened.

HABITAT.—Largely intertidal, living under rocks. From dead coral in water up to 20 meters (D. Banner and A. Banner, 1982:220). Shore; rock shingle, and rock spit.

COLOR.—Tip of major chela brown, rest of fingers and palm banded with irregular white, olive-green, and blue-green. Fingers of small chela light green, distal three-fourths of palm white and olive-green at base. Carpus and dactylus blue. Thoracic pereopods blue with white band at meral-carpal joint. Antennae blue, antennules olive-green. Scaphocerite and carpocerite blue. Carapace and abdomen reddish brown with faint brown line extending from middle of carapace to sixth abdominal somite. On the lateral margins where each abdominal somite meets the next is a diffuse white spot. Telson same color as abdomen, uropods light green (D. Banner and A. Banner, 1982:220).

TYPE-LOCALITY.—Hawaii.

DISTRIBUTION.—Throughout the Indo-Pacific area; Australia; Red Sea and Madagascar; Mombasa, Kenya; eastern Pacific from Gulf of California, Costa Rica, Clipperton Island, and Galapagos Islands.

太平洋槍蝦（学名：Alpheus pacificus）为槍蝦科槍蝦屬下的一个种。