Palaemonetes texanus

Palaemonetes texanus

DISPOSITION OF TYPES.—Male holotype, USNM 152395, and one male and one female paratype, USNM 152396; one male and one female paratype, Rijksmuseum van Natuurlijke Historic Leiden, The Netherlands.

TYPE-LOCALITY.—San Marcos River within the city limits of San Marcos, Hays County, Texas.

DESCRIPTION.—Rostrum (Figure 2a) straight; slightly overreaching anterior margin of scaphocerite; dorsal margin bearing five to eight teeth, one of which is placed behind orbit; lower margin with two to four teeth. Antennal spine sharp, distinct, and extending beyond anterior margin of carapace. Branchiostegal spine just below branchiostegal groove on anterior margin of carapace and extending anteriorly.

Pleura of fourth and fifth somites forming acute to right angle; sixth somite 1.5 times as long as fifth. Telson (Figure 2b) subequal in length to sixth somite; anterior pair of dorsal spines posterior to midlength of telson; posterior pair usually near posterior margin. Posterior margin of telson with sharp median point flanked by one pair of plumose setae and two pair of spines; mesial pair of spines elongate and extending beyond median point.

Eyes (Figure 2a) well developed; cornea globular and well pigmented.

Stylocerite (Figure 2e) sharp and extending one-third length of basal segment of antennular peduncle; distolateral spine strong. Lateral antennular flagellum with proximal 19 to 29 articles of rami fused; free portion of shorter ramus consisting of three to six articles.

Scaphocerite (Figure 2d) about three times as long as wide, lateral margin straight; blade well overreaching lateral tooth.

Mouthparts (Figures 2f–k) typical.

First pereiopod (Figure 2l) extending to distal margin of scaphocerite; palm and finger bearing numerous setae distally; carpus twice as long as chela and slightly longer than merus. Second pereiopod (Figure 2m) longer than first, overreaching scaphocerite by most of chela; carpus 1.4 times as long as chela and 1.5 times as long as merus. Third pereiopod (Figure 2n) extending to base of third segment of antennular peduncle; propodus and merus of equal length with carpus 0.6 length of propodus. Fourth pereiopod reaching anterior margin of scaphocerite; fifth pereiopod overreaching anterior margin of scaphocerite by length of dactyl.

Appendix masculina (Figure 2c) of male with six apical spines. Eggs of gravid females few and large; 1.2 mm to 1.5 mm in length. Lateral branch of uropod with or without movable spine between fixed distolateral tooth and margin of blade.

SIZE.—Male with carapace length to 8 mm (including rostrum, to 14 mm); females, to 11 mm (including rostrum, to 18 mm).

VARIATION.—The movable spine of the lateral ramus of the uropod is quite variable; both movable spines may be present, both may be absent, or only a left or right one may be present.

RANGE.—This species is known from the San Marcos River in the city of San Marcos, Hays County and Comal River in the city of New Braunfels, Comal County, Texas. Both of these rivers are fed by large springs associated with the Balcones Escarpment.