Austinixa chacei (Wass 1955)

Pinnixa chacei Wass, 1955

FRONTISPIECE, FIGURE 5

Pinnixa sp.—Wass, 1949:11.

Pinnixa chacei Wass, 1955:138, 160, figs. 5–9 [part, Florida records only].—Schmitt, McCain, and Davidson, 1973:104.—Abele and Kim, 1986:xvi, 64, 683, 694, 756, fig. b,c on p. 695.

Pinnixa chaecei.—Menzel, 1956:81.

PREVIOUS RECORDS.—Florida: Florida (Abele and Kim, 1986). Alligator Harbor (Wass, 1949, 1955). Alligator Point, Franklin County (Wass, 1955). Appalachee Bay and St. George's Sound area (Menzel, 1956).

MATERIAL.—Florida: Outer beach of Alligator Point, Franklin County; from Callianassa burrows; 4 Oct 1952; M.L. Wass; 5 males (paratypes, USNM 98905). Same data; 1 male (holotype, USNM 95694). Same data; 1 female (allotype, USNM 205683). Gulf beach across from marine lab, Alligator Point; 30 Aug 1952; M.L. Wass; 7 females (2 ovigerous) (paratypes, USNM 95695). Kevins Beach, Highway 98, east of Florida State University Marine Laboratory; 12 Jun 1987; K. Carmen and F. Dobbs; 1 female (USLZ 1963). From Callichirus burrows, immediately east of Florida State University Marine Laboratory; J. Martin and F. Dobbs; 1 male, 1 female (USLZ 2964). Ft. Pickens end of Gulf Beach, Santa Rosa Island, Pensacola; from burrows of Callichirus islagrande; 10 Oct 1980; D. Felder and R. Heard; 12 males, 13 females (USLZ 2952; largest specimens are photo vouchers).

Alabama: Dixie Bar, off Mobile Bay east of Dauphin Island; bucket dredge on sand bar in 1 m depth; 20 Jan 1977; M. Dardeau; 2 males (MESC).

DIAGNOSIS.—Carapace 1.8 to 2.9 (mean 2.3, based on 17 specimens larger than cb 5.0 mm) times broader than long in adults, with high, sharp cardiac crest extending from side to side above posterior margin. Branchial regions each crossed by distinct tuberculate ridge, not extending to orbits, laterally with sharp turn to posterior, extending almost to posterolateral margin. Distinct ridge extending mesially from each orbit, diminished or interrupted along midline.

Chelipeds of male and female dissimilar, those of male larger. In male, distal margin of palm almost perpendicular, with broad, rectangular median tooth; gape setose above tooth. Fixed finger very short, deflexed, distally serrate. Dactylus strongly deflexed, lacking distinct tooth, distally serrate on opposable margin. Female chela like that of juveniles, fingers extended, cutting edges serrate but lacking distinct teeth, few setae in gape.

Third walking leg (P-4) strongest, merus 1.1 to 2.3 times longer than high, lower margin fringed with setae, posterior face otherwise naked. Propodus about 1.2 to 2.5 times longer than high, ventral (opposable) margin with single carina. Dactylus with low but distinct longitidinal ridge on posterior face, anterior face lacking ridge.

Male and female abdomens with 7 free somites. Male abdomen with first somite trapezoidal, wider than second, tapering slightly from second to fifth somites, corners of somites not markedly produced at articulations. Sixth somite with sides concave. Telson broader and longer than sixth somite, cordiform, widest posterior to base.

Gonopod as illustrated (Figure 5h–k), apex blunt.

SIZE.—Males, cl 1.7 to 3.5 mm, cb 4.5 to 8.9 mm; non-ovigerous females, cl 1.5 to 2.7 mm, cb 4.1 to 6.3 mm; ovigerous females, cl 2.2 to 2.6 mm, cb 5.6 to 6.0 mm.

The largest specimen examined is a male measuring 3.5 × 8.9 mm.

COLOR IN LIFE.—“In life, males white, with brown specking; females slate grey, with translucent legs; juveniles paler” (Wass, 1955:161).

Color very similar to that of P. behreae in pattern and variation. Chelipeds diffuse white to translucent, white sometimes concentrated on merus and carpus, sometimes extending to superior and distal areas of manus. Walking legs largely translucent to diffuse white, white areas when developed usually confined to distal or superodistal extremes of carpus and propodus.

Dorsal pattern of carapace varying between two extremes, one dominated by white chromatophores, the other by dark grey to black chromatophores, with intervening areas appearing as traces of translucent tan.

DISTRIBUTION.—Apparently restricted to the northeastern Gulf of Mexico, from near Apalachee Bay, Florida, to Alabama. Usually intertidal, occasionally to a depth of several meters.