Alpheus paludicola Kemp 1915

Alpheus paludicola Kemp, 1915

(Figs. 3A–G, 43, 52D)

Alpheus paludicola Kemp 1915: 303; Yeo & Ng 1996: 39, figs. 2, 3.

(?) Not Alpheus paludicola. — Kemp 1918: 273 (= possibly A. microrhynchus De Man, 1897).

Not Alpheus paludosus (lap. cal.).— Johnson 1965: 9 (part. = A. cyanoteles Yeo & Ng, 1996).

Type material. Lectotype, male (cl 5.5 mm, tl 18.0 mm, chl 10.0 mm), NHM 1919.11.1.1, India, Orissa, Chilika (= Chilka) Lake, Outer Channel, leg. S. Kemp, 1914; paralecotype, male (cl 5.2 mm, tl 14.0 mm, chl 9.7 mm), NHM 1919.11.1.2, same collection data as for lectotype.

Description. See Kemp (1915) for original description and illustrations (Fig. 3A–G), and Yeo & Ng (1996) for full redescription and additional figures; complementary illustrations of the type material are provided in Fig. 43.

Colour pattern. Overall translucent with brownish red rostrum; antennular peduncle and lateral margin of scaphocerite tinged with reddish brown; posterior edge of carapace and each pleonite with transverse brownish to bluish green band; telson and uropods dusky (adapted from Kemp 1915).

Type locality. Chilika Lake (formerly Chilka Lake), Orissa, India.

Distribution. Northern Indian Ocean: currently known only from the type locality in Orissa, northeastern India (Fig. 52D). The material from Lake Thale Sap Thailand reported by Kemp (1918) as A. paludicola most likely represents another, perhaps undescribed species (see also comments in Yeo & Ng 1996).

Common name proposed. Chilika snapping shrimp.

Ecology and biology. Alpheus paludicola is confined to brackish lagoons, where it lives in burrows on soft mud, at a depth range of 1– 4 m. The species can be classified as euryhaline, being able to tolerate fluctuations in salinity (Kemp 1915). The small number of eggs and their large size (diameter about 1.4 mm) suggest an abbreviated larval development, as seen in A. microrhynchus and A. cyanoteles (see above).

Taxonomic remarks. In their very detailed redescription of A. paludicola, Yeo & Ng (1996) noted that the stylocerite is missing its distal point on both sides in the lectotype (see Yeo & Ng 1996: fig. 2c) vs. terminating in a small acute point in the paralectotype. The major chela was illustrated by Yeo & Ng (1996: fig. 2e) without a mesial subdistal ridge on the pollex, whereas the fine granulation of the major chela observed by Kemp (1915) was “not visible” according to these authors. However, the reexamination of the lectotype and paralectotype of A. paludicola by the present author revealed that the major chela pollex of the lectotype has a small mesial subdistal ridge, whereas the distal portion of the mesial side of the major chela palm and the adjacent area of the pollex are indeed covered with minute granules, as correctly observed by Kemp (1915). Another possible small inaccuracy in Yeo & Ng’s (1996) illustrations of the major cheliped of A. paludicola is the absence of a mesial longitudinal groove connecting with the dorsal transverse groove, which is present, albeit very shallow, in the lectotype.

Alpheus paludicola (Figs. 3A–G, 43) can be separated from A. euphrosyne, A. eurydactylus, A. richardsoni, A. microrhynchus, A. cyanoteles, A. nomurai sp. nov., A. takla sp. nov., A. mangalis sp. nov. and A. songkla by the extremely short rostrum (which is noticeably longer in most other species, except for A. microrhynchus); the development of the rostro-orbital furrows (absent in A. paludicola vs. present in most other species, although very shallow in A. eurphrosyne and not distinct in A. microrhynchus); the distally unarmed antennal basicerite (vs. armed with a more or less strong tooth in A. richardsoni, A. cyanoteles, A. nomurai sp. nov., A. mangalis sp. nov. and A. takla sp. nov., occasionally with a minute tooth also in A. microrhynchus); the shape of the dorsal shoulder of the major chela (gently sloping in A. paludicola vs. with an overhanging tooth in A. euphrosyne); the proportions of the fingers to the palm in the major chela (0.4 in A. paludicola vs. 0.6–1.0 in all the other species); the development of the mesial subdistal ridge on the major chela pollex (feebly developed in A. paludicola vs. very strong in A. euphrosyne, A. eurydactylus, A. microrhynchus, A. cyanoteles and A. takla sp. nov.); the degree of granulation on the mesial surface of the major chela (weak and restricted to the distal portion of the palm and pollex in A. paludicola vs. much stronger and extensive in A. euphrosyne and A. eurydactylus, or absent in A. microrhynchus, A. cyanoteles and A. mangalis sp. nov.); the sculpture of the palm of the male minor chela (with weak dorsal and ventral transverse grooves in A. paludicola vs. with much stronger ones in A. euphrosyne and A. eurydactylus, or without a distinct dorsal notch in A. richardsoni and A. takla sp. nov.); the shape of the dactylus of the third to fifth pereiopods (spatulate in A. paludicola vs. trigonal-subspatulate in A. microrhynchus and A. cyanoteles); the armature of the ischium of the third pereiopod (unarmed in A. paludicola vs. armed with a spiniform seta in A. euphrosyne, A. eurydactylus, A. richardsoni, A. nomurai sp. nov. and A. mangalis sp. nov., although variable in some taxa); and the number and size of eggs in females (few and very large in A. paludicola vs. numerous and small in the other species, except for A. microrhynchus and A. cyanoteles). In addition, A. paludicola differs from A. mangalis sp. nov. by the distally unarmed ventromesial margin of the chelipeds. The type specimens, with maximal cl 5.5 mm / tl 22.0 mm, are also much smaller than all the above-listed species of the A. euphrosyne — A. microrhynchus complex. In life, A. paludicola may be easily separated from A. euphrosyne, A. richardsoni, A. cyanoteles and A. nomurai sp. nov., by its duller and more uniform colour pattern (Kemp 1915), although young or paler individuals of A. microrhynchus, A. eurydactylus, A. mangalis sp. nov. and A. takla sp. nov. may bear some resemblance with A. paludicola.