Allathelges alisonae, Williams & Boyko, 2016

Williams, Jason D. & Boyko, Christopher B., 2015, Abdominal bopyrid parasites (Crustacea: Isopoda: Bopyridae: Athelginae) of diogenid hermit crabs from the western Pacific, with descriptions of a new genus and four new species, Raffles Bulletin of Zoology 64, pp. 33-69 : 37-40

Allathelges alisonae , new species

(Figs. 1, 2)

Material examined. Philippines: Mature holotype female (12.5 mm), mature allotype male (3.0 mm) ( USNM 1283370), infesting female Dardanus lagopodes (5.7 mm SL), inhabiting shell of Conus sp. , Batangas, Sombrero Island, coll. JDW, 30 January 1999; immature paratype female (6.9 mm) ( ZRC 2015.0498), mature paratype male (1.5 mm), infesting male Dardanus lagopodes (5.4 mm SL), inhabiting shell of Angaria delphinus (Linnaeus) , Cebu, Mactan Island, Maribago, coll. JDW, 9 July 1997.

Description. Female (Fig. 1): Body length 12.5 mm, maximal width 5.8 mm, head length 1.7 mm, head width 1.7 mm, pleon length 5.3 mm. Body longer than broad; pereon nearly symmetrical. All body regions and pereomeres distinctly segmented, except pereomeres I, II (Fig. 1A).

Head length, breadth subequal with convex lateral margins, anterior, posterior margins slightly flattened, overall shape of head circular. Eyes lacking. Antennule (Fig. 1D) of two articles, indistinctly separated; antenna (Fig. 1D) of four articles. Maxilliped (Fig. 1E) with elongate, subrectangular anterior lobe lacking palp; smaller, rounded posterior lobe bearing thin, acute spur. Barbula (Fig. 1F) with four short, smooth, distally acute lobes laterally on each side.

Pereon of five distinct pereomeres (first, second segments coalesced), broadest across pereomere IV, slightly tapering anteriorly and posteriorly. Pereomeres I, II medially anteriorly concave, posteriorly convex; pereomere III medially anteriorly concave, posteriorly sinuous with one posterolateral lobe on each side; pereomeres IV, V anteriorly and posteriorly medially sinuous with posterolateral lobes; pereomeres VI, VII anteriorly convex, posteriorly concave; pereomere VI with posterolateral lobes; pereomeres V, VI subequal in size. First oostegites extended beyond anterior margin of head (Fig. 1A, B). Oostegites completely enclosing brood pouch; posteriormost oostegite with fringe of setae on posterior margin (Fig. 1B). First oostegite anterior lobe laterally expanded and folded, posterior lobe with broad anterior region tapering to posterior rounded tip, internal ridge smooth (Fig. 1G, H). All pereopods subequal in size, dactyli slightly larger in anterior pairs, setae on distal end of carpus (Fig. 1I, J). Pereopods I–III parallel to head, evenly spaced with slightly broader gap between pereopods V, VI.

Pleon of six pleomeres, segmentation distinct. Pleomeres I–V (Fig. 1A) with elongate-ovate biramous pleopods, no lateral plates, arising from common peduncle; pleotelson narrow proximally, distally slightly expanded with rounded tip, lacking pleopods or lateral plates (Fig. 1A, C).

Male (Fig. 2): Length 3.0 mm, maximum width 1.3, head length 0.3 mm, head width 0.8 mm, pleon length 1.0 mm. Head subovate, narrow, evenly rounded distally, posterior margin nearly straight, distinct from pereomere I (Fig. 2A, B). Eye pigmentation present at lateral junction of head and first pereomere (Fig. 2A). Antennule of three articles; antenna of five articles (Fig. 2C), not extending posterolaterally beyond margin of head, distalmost article of each with tuft of long setae, penultimate article of each with few shorter setae.

Pereomere III broadest, slightly tapering anteriorly and posteriorly. All pereomeres directed posterolaterally with slightly tapered posterolateral margins. Anterior pereopods with slightly longer dactyli than posterior pairs, longer dactyli recurved and slightly twisted, touching base of propodus anterolateral to base of raised medial region on ventral surface of propodus (Fig. 2D), posterior shorter dactyli not twisted, touching base of propodus in median of ventral surface (Fig. 2E). Propodi and other segments of all pereopods subequal; carpi with setae on distal tip (Fig. 2B, D, E).

Pleon subtriangular, anteriorly laterally expanded, tapering posteriorly, broadly rounded at tip, all pleomeres fused but with lateral indication of fusion of first pleomere with remainder of pleotelson. No midventral tubercles, pleopods, or uropods (Fig. 2B).

Type locality. Philippines, Batangas: Sombrero Island (13°42’N, 120°50’E) .

Etymology. Named for Alison Carson, the wife of the first author who helped collect many of the Philippine specimens reported on herein.

Distribution. Known only from Batangas and Cebu provinces in the Philippines.

Host. Diogenidae : Dardanus lagopodes .

Size Range (Length). Females: to 11.75 mm, males: to 3.0 mm.

Remarks. This species has the same female pleopodal formula as the type species, Allathelges pakistanensis Kazmi & Markham, 1999 , as well as the reflexed first oostegites that extend forward over the head. However, the female pleopods of A. alisonae n. sp. are large, foliose and ovate (vs. very small and slender in A. pakistanensis ) and the pleotelson is elongated, terminally expanded and similar to the pleotelsons seen in species of Athelges (vs. short and terminally tapered in A. pakistanensis ). Barbula with four pairs of projections (vs. with two pairs of projections in A. pakistanensis ). The male of A. alisonae n. sp. has a lateral expansion anteriorly on the pleotelson with indication of first pleomere fusion (vs. no anterior lateral expansion and no indication of pleomere fusion in A. pakistanensis ). Dardanus lagopodes has not been previously recorded as a host for bopyrids.