Axianassa linda, Anker, Arthur & Pachelle, Paulo P. G., 2016

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: 112-117

publication ID

http://doi.org/10.11646/zootaxa.4111.2.1

publication LSID

lsid:zoobank.org:pub:0208587B-598C-4202-A4BA-8FDECD2C93B9

persistent identifier

http://treatment.plazi.org/id/895FDE15-FF05-9E6C-FF5A-FF01FAD4D3D9

treatment provided by

Plazi

scientific name

Axianassa linda
status

sp. nov.

Axianassa linda   sp. nov.

( Fig. 8–11 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11 )

Type material. Holotype: 1 male (cl 5.3 mm), MZUSP 34082, Pacific coast of Panama, Playa El Agallito, intertidal mud flat near mangroves, in burrow, coll. A. Anker, J.F. Lazarus, T. Kaji, 22.iii. 2015. Paratypes: 1 male (cl 5.0 mm), 1 female (cl 8.1 mm), MZUSP 34400, same collection data as for holotype; 1 male (cl 4.5 mm), MZUSP 34401, same collection data as for holotype.

Additional material. 1 male (cl 6.3 mm), MZUSP 34402, Pacific coast of Panama, Las Perlas Archipelago, Isla Casayeta, small bay with mud flat fringed by rocks and mangroves, 0.3 m, in burrow, coll. A. Anker, 20.iv. 2015.

Description. Carapace smooth, with occasional erect setae; rostrum subtriangular, broadly rounded distally, reaching well beyond anterior margin of eyestalks, lateral margins not toothed, fringed with setae; linea thalassinica straight, running entire length of carapace; cervical groove deep, crescent-shaped in dorsal view; branchiostegial margin slightly elevated; pterygostomial region rounded, not protruding, fringed with setae ( Fig. 8 View FIGURE 8 A –C).

Pleon thinly sclerotised, smooth; dorsal surface with scattered setae of various length; lateral surface of first pleuron with curved, broad, posteroventrally directed depression, ventral margin produced into small subacute process in males, with blunt lobe in females; second to sixth pleura with ventrolateral surface bearing broadly U-shaped depression, most conspicuous on second and third pleura, ventral margin unarmed, almost straight, fringed with some stiff setae locally ( Fig. 8 View FIGURE 8 D). Telson broad, convex proximally, smoothly tapering posteriorly, posterior margin broadly rounded, neither lateral nor posterior margin with armature ( Fig. 8 View FIGURE 8 E).

Eyestalks rounded distally; cornea moderately developed compared to eyestalk, in subterminal position, moderately pigmented ( Fig. 8 View FIGURE 8 B). Antennular peduncle with third article elongate, subcylindrical, slender, reaching half-length of fourth article of antenna; ventral flagellum slender, about half-length of much stouter dorsal flagellum ( Fig. 8 View FIGURE 8 A). Antennal acicle relatively broad at base, tapering distally, short, with tip not reaching 0.2 length of fourth article of antennal peduncle, mesial margin smooth or with variously developed tooth; fourth article of antennal peduncle subcylindrical, elongate, much more robust than third article ( Fig. 8 View FIGURE 8 A, F, 10 E, G).

Mouthparts typical for genus (cf. Kensley & Heard 1990; Rodrigues & Shimizu 1992; Anker 2011 a; Komai 2014). Third maxilliped pediform; coxa with projecting sharp dorsomesial tooth; basis with minute dorsomesial spinule on distal margin; ischium about as long as merus, with well-developed crista dentata consisting of about 13 teeth, proximal-most tooth much smaller, ventral margin occasionally with thick fusiform setae; merus with several rows of thick fusiform setae on distoventral surface; carpus vase-shaped, about half as long as merus; propodus as long as merus; dactylus about half-length of propodus; ventral margin of all articles with long fine setae ( Fig. 8 View FIGURE 8 G –J, 10 F, H, I).

First pereiopods (chelipeds) stout, somewhat unequal in size, asymmetrical in shape ( Fig. 9 View FIGURE 9 ), weaker in females ( Fig. 11 View FIGURE 11 C). Major cheliped robust; ischium with several widely spaced minute tubercles or denticles on ventrolateral margin, without strong teeth; merus inflated, with strongly convex dorsal margin and slightly convex ventromesial and ventrolateral margins; ventromesial margin with row of widely spaced small tubercles or denticles; carpus cupshaped, ventral margin with large blunt projection; chela ovate, somewhat compressed laterally; palm about 1.8 times as long as high in males, covered with minute granules near base of pollex and dactylus, on both mesial and lateral surfaces, ventral margin rugose proximally; fingers about 0.6 length of palm, very stout, pollex slightly shorter than dactylus; cutting edge of pollex with one very stout tooth proximal to mid-length and some rugosities or very low teeth in proximal half; cutting edge of dactylus with shallow hiatus at about mid-length and several blunt teeth distal to this hiatus ( Fig. 9 View FIGURE 9 A –C, G). Minor cheliped slightly smaller and less robust than major cheliped; ischium and merus similar to those of major cheliped; carpus without conspicuously projecting ventral margin; chela somewhat more slender compared to major chela; palm with granules present only on mesial side; fingers slightly shorter than palm; cutting edges of pollex and dactylus with blunt, irregularly shaped teeth, most rounded or subtriangular, without large and protruding teeth ( Fig. 9 View FIGURE 9 D –F, H).

Second pereiopod stout; merus, carpus and propodus smooth, with numerous long thin setae along ventral margin; dactylus about half as long as propodus, with crenulated ventral margin ( Fig. 10 View FIGURE 10 A). Third pereiopod relatively robust; ischium, merus and carpus smooth, with few setae; propodus with distoventral brush of stiff setae; dactylus slightly shorter than propodus, dorsal margin with row of corneous spines, distoventral margin slightly expanded, with comb-like row of minute spiniform setae ( Fig. 10 View FIGURE 10 B). Fourth pereiopod similar to third in general configuration, more slender ( Fig. 10 View FIGURE 10 C). Fifth pereiopod more slender than third and fourth; propodus subchelate, ending in short blunt tooth, latter concealed by dense stiff setae; dactylus subspatulate, somewhat twisted and excavated mesially, with row of minute setae on edge subdistally ( Fig. 10 View FIGURE 10 D).

First pleopod absent in males; first pleopod in females consisting of short base and longer distal article, latter fringed with setae along margins. Second to fifth pleopods similar, biramous; protopods unarmed. Uropod with broadly ovoid exopod and endopod, both unarmed dorsally; exopod without diaeresis, distolateral margin with two or three posteriorly directed teeth, distal-most strongest ( Fig. 8 View FIGURE 8 K). Gill/exopod formula typical for genus (cf. Kensley & Heard 1990; Komai 2014); first maxilliped without podobranch.

Colouration. Hyaline white with pale straw-yellowish tinge; inner organs yellowish or reddish ( Fig. 11 View FIGURE 11 ).

Etymology. The new species’ name is derived from the Spanish word “ linda   ”, meaning pretty or beautiful, referring to its elegant appearance; used as a noun in apposition.

Type locality. Playa El Agallito, Azuero   Peninsula, Pacific coast of Panama [note: accidentally misspelled as “Playa El Aguillito” in the original descriptions of Leptalpheus azuero Anker, 2011   and L. hendrickxi Anker, 2011   , in Anker (2011 b)].

Distribution. Eastern Pacific: presently known only from Panama ( Azuero   Peninsula and Las Perlas Archipelago).

Ecology. Intertidal and shallow subtidal (less than 0.5 m) mud flats near mangroves or mangrove creeks; in burrows in mud.

Remarks. Axianassa linda   sp. nov. appears to be variable in one important character commonly used in the taxonomy of the genus, which is the presence or absence of a tooth on the mesial margin of the antennal acicle ( Fig. 8 View FIGURE 8 F, 10 E, G). The new species can be easily separated from the other three eastern Pacific species of the genus, viz. A. canalis   , A. darrylfelderi   and A. mineri   , by the presence of thick fusiform setae on the distoventral margin of the third maxilliped merus (absent in the other three species); from A. canalis   and A. darrylfelderi   by the ventrally unarmed first pleuron in females (vs. with a strong ventral process in both sexes in A. canalis   and A. darrylfelderi   ); specifically from A. canalis   by the ventromesial margin of the cheliped merus finely denticulate (vs. with a stout sharp tooth in A. canalis   ); specifically from A. darrylfelderi   by the significantly shorter antennal acicle, not reaching 0.2 length of the fourth article of the antennal peduncle (vs. reaching 0.3 length of this article in A. darrylfelderi   ); the ventrolateral margin of the cheliped ischium finely denticulate (vs. armed with several strong sharp teeth in A. darrylfelderi   ); and the pale-yellowish colour (vs. reddish pink in A. darrylfelderi   ); and specifically from A. mineri   by the dagger-shaped antennal acicle (vs. distally bidentate in A. mineri   ); the presence of a single row of corneous spinules on the dactyli of the third and fourth pereiopods (vs. with several rows in A. mineri   ); and the third maxilliped merus and carpus unarmed ventrally (vs. armed with sharp teeth on ventral margin in A. mineri   ) (cf. Kensley & Heard 1990; Anker & Lazarus 2015; see also Figs. 1 –5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 , 7 View FIGURE 7 ).

Axianassa linda   sp. nov. also differs from its four western Atlantic congeners, viz. A. jamaicensis   , A. australis   , A. arenaria Kensley & Heard, 1990   , and A. intermedia Schmitt, 1924   . For instance, the new species can be separated from A. jamaicensis   , A. australis   and A. arenaria   by the presence of thick fusiform setae on the distoventral margin of the third maxilliped merus and sometimes ischium (absent in the other three species); from A. australis   and A. arenaria   by the first pleuron ventrally unarmed in females (vs. armed with a strong ventral process in both sexes in A. australis   and A. arenaria   ); from A. jamaicensis   , A. australis   and A. arenaria   by the ventrolateral margin of the cheliped ischium finely denticulate, without strong teeth (vs. armed with strong teeth in the other three species); from A. jamaicensis   , A. arenaria   and A. intermedia Schmitt, 1924   by the ventrolateral margin of the cheliped merus finely denticulate (vs. denticulate and additionally with a small top medium-sized tooth in A. jamaicensis   and A. arenaria   or with rough distal serrations in A. intermedia   ); from A. jamaicensis   and A. australis   by the pale-yellowish colour (vs. reddish pink in A. jamaicensis   and A. australis   ); specifically from A. arenaria   by the ventrally unarmed second to fifth pleura (vs. each armed with a small tooth in A. arenaria   ) and the lateral margins of the telson without a small notch proximally (with such a notch in A. arenaria   ); and specifically from A. intermedia   , to which it has most resemblance, by the crista dentata of the third maxilliped bearing several conspicuously larger teeth among smaller teeth (vs. bearing all small, and also more numerous, teeth in A. intermedia   ); and the comparatively longer major cheliped fingers in males, being at least 0.6 times as long as palm (vs. less than 0.5 times in A. intermedia   ) (cf. Kensley & Heard 1990; Rodrigues & Shimizu 1992; see also Fig. 6 View FIGURE 6 ).

The new species can be separated from the four western Pacific species of Axianassa   , most easily from A. heardi Anker, 2011   and A. japonica Komai, 2014   , by the uropodal exopod lacking a toothed diaeresis (vs. with a toothed diaeresis in A. heardi   and A. japonica   ) and the lateral margins of the rostrum without teeth (vs. conspicuously dentate in A. heardi   and A. japonica   ). It differs from A. sinica Liu & Liu, 2010   and A. ngochoae Anker, 2010   by the shorter antennal acicle, not reaching 0.2 length of the fourth article of the antennal peduncle (vs. reaching or overreaching 0.25 length of this article in A. ngochoae   and A. sinica   ), and the major cheliped carpus bearing a blunt ventral projection (absent in the other two species); and specifically from A. sinica   by the broadly rounded rostrum (vs. distinctly pointed in A. sinica   ) (cf. Anker 2010, 2011a; Liu & Liu 2010; Komai 2014).

It is interesting to note that the peculiar fusiform (or villiform) setae are present on the third maxillipeds of A. linda   sp. nov., A. intermedia   and A. canalis   . However, they are present on different articles of the third maxilliped, i.e. on the merus and sometimes also on the ischium in A. linda   sp. nov. ( Fig. 8 View FIGURE 8 G, H, 10 F, H, I), on the merus only in A. intermedia   (de Man 1928: fig. 2 a –c; Kensley & Heard 1990: fig. 2 J), and on the ischium only in A. canalis   ( Fig. 3 View FIGURE 3 B; see also Kensley & Heard 1990: fig. 7 D). A similar dense field of thickened setae was also observed in the snapping shrimp Alpheus villus Kim & Abele, 1988   , where it is found on the penultimate (= carpal) article of the third maxilliped ( Kim & Abele 1988: fig. 34 d). Their function in these four taxa remains enigmatic.

MZUSP

Museu de Zoologia da Universidade de Sao Paulo

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

Family

Laomediidae

Genus

Axianassa

Loc

Axianassa linda

Anker, Arthur & Pachelle, Paulo P. G. 2016
2016
Loc

A. japonica

Komai 2014
2014
Loc

A. heardi

Anker 2011
2011
Loc

A. sinica

Liu & Liu 2010
2010
Loc

A. ngochoae

Anker 2010
2010
Loc

A. arenaria

Kensley 1990
1990
Loc

Alpheus villus

Kim & Abele 1988
1988
Loc

A. intermedia

Schmitt 1924
1924
Loc

A. intermedia

Schmitt 1924
1924