Axianassa mineri Boone, 1931

Anker, Arthur & Pachelle, Paulo P. G., 2016, Mud-shrimps of the genus Axianassa Schmitt, 1924 from Panama, with description of two new species (Decapoda: Gebiidea: Laomediidae), Zootaxa 4111 (2), pp. 101-125 : 104

Axianassa mineri Boone, 1931

( Figs. 1 , 2 )

Axianassa mineri Boone 1931: 157 , fig. 10; Hernández-Aguilera 1998: 310; Kensley & Heard 1990: 563, fig. 4; Dworschak 2013: 44.

Material examined. 1 male (cl 8.9 mm), 1 female (cl 7.4 mm), MZUSP 34081, Pacific coast of Panama, Las Perlas Archipelago, Isla Contadora, Playa Larga, low tide, mid-intertidal, near water edge under rocks in muddy sand, coll. T. Kaji, A. Anker, A.R. Palmer, 17.iv.2015; 1 male (cl 3.1 mm), FLMNH UF 39751, Mexico, Baja California Sur, Los Frailes, 23.3827–109.4253, intertidal, coll. T.A. Ebert, D.M. Dexter, 28.i.1972.

Description. See Boone (1931) and Kensley & Heard (1990); additional illustrations and colour photographs are provided in Figs. 1 , 2 .

Colouration. Creamy whitish, with faint pale-yellow tinge; inner organs yellow-orange ( Fig. 2 ).

Distribution. Eastern Pacific: Mexico (Los Frailes, Baja California Sur; Islas Tres Marías and Isla Santa Isabel off Nayarit); Costa Rica ( Isla del Coco); Panama (Las Perlas Archipelago) ( Boone 1931; Hernández-Aguilera 1998; Dworschak 2013; present study).

Ecology. Mid- to lower intertidal of offshore islands and drier continental shores; in shallow horizontal or oblique burrows made in muddy sand under rocks and larger pieces of coral rubble.

Remarks. Axianassa mineri is a rather distinctive species of the genus, characterised by a broadly rounded frontal margin of the carapace, without a clear rostral projection ( Kensley & Heard 1990: fig. 4D); a very short antennal acicle bearing two distal teeth ( Fig. 1 A; see below); the presence of several rows of stout corneous spines throughout the full length of the dactylus of the third and fourth pereiopods ( Fig. 1 C); the third maxilliped carpus with a strong ventral tooth ( Kensley & Heard 1990: fig. 4A); and the presence of teeth on the posterior margins of the uropodal exopod and endopod ( Kensley & Heard 1990: fig. 4C). The distally bidentate tip of the antennal acicle, a unique configuration within the genus, is most probably a result of the extreme shortening of the main (lateral) tooth, with the distomesial tooth thus corresponding to the more proximally situated mesial tooth in several other species of Axianassa (see below).

The holotype of A. mineri is a female missing its left cheliped ( Boone 1931; Kensley & Heard 1990). The present material, composed of three complete specimens (two males and one female), suggests that the right cheliped of the holotype ( Boone 1931: fig. 10; Kensley & Heard 1990: fig. 4B) is most likely the female major cheliped ( Fig. 1 B). The male major cheliped (shown in situ in Fig. 2 C) appears to be stouter and with stronger teeth on the cutting edges of the fingers, but otherwise is very similar to that of the female ( Fig. 1 B, 2B). The female and male minor chelipeds (shown in situ in Fig. 2 B, C) are also similar, except for their proportions (stouter in male), and appear to be fairly typical for the genus. In both sexes, the minor cheliped pollex is armed with several strong subacute teeth on the cutting edges, in addition to a row of smaller blunt teeth (e.g., Fig. 2 C).

Axianassa mineri appears to be ecologically different from the other eastern Pacific species (see below) by inhabiting mixed rocky-sandy shores, where it can be most easily collected at low tide by flipping rocks or larger pieces of coral rubble dispersed on muddy sand.

Figures

FIGURE 1. Axianassa mineri Boone, 1931: male (cl 8.9 mm) from Isla Contadora, Las Perlas Archipelago, Panama (MZUSP 34081); A—proximal area of antennal peduncle, dorsal view; B—left (major) cheliped, lateral view; C—third pereiopod dactylus, dorsolateral view.

FIGURE 2. Axianassa mineri Boone, 1931: A, B—female (cl 7.4 mm) from Isla Contadora, Las Perlas Archipelago, Panama (MZUSP 34081), in dorsal (A) and lateral (B) views; C—male (cl 8.9 mm) from the same locality (MZUSP 34081), in lateral view.