Species New to Science's Journal

[Crustacea • 2022] Hexapanopeus klausruetzleri • A New Shallow-water Mud Crab of the Genus Hexapanopeus Rathbun, 1898 (Decapoda: Panopeidae) from Belize

Hexapanopeus klausruetzleri

Felder & Thoma, 2022

DOI: 10.11646/zootaxa.5168.5.3

Abstract

A new species of panopeid crab from shallow coastal waters of Belize is formally described and named based upon comparative study of three small specimens obtained in the course of a regional biodiversity survey of decapod crustaceans. The herein designated holotype of Hexapanopeus klausruetzleri n. sp. is a specimen previously included in a comparative molecular phylogenetic analysis that showed it to be closely related to, but genetically distinct from, the western Atlantic species Hexapanopeus angustifrons (Benedict & Rathbun, 1891). Hexapanopeus klausruetzleri n. sp. differs from this widely reported warm-temperate species in both its smoother carapace and pereopod surfaces and its generally more lobiform anterolateral teeth. The unique male first gonopod of the new species also strongly supports its morphological separation from all known congeners and other superficially similar western Atlantic panopeids with which it might be confused. To date, mature females have not been found, and the limited available collections are restricted to the vicinity of Carrie Bow Cay and nearby waters. Fourteen additional species of small panopeid and pseudorhombilid crabs, similar to Hexapanopeus klausruetzleri n. sp. in size and general habitus, were taken in the course of our studies in Belize. Most have not been previously reported from these waters, and several warrant further study to confirm their identifications.

Keywords: Crustacea, Decapoda, Panopeidae

Hexapanopeus klausruetzleri n. sp.,
A, male holotype, USNM 1546469 (= ULLZ 12526-A) cw 9.9 mm, Belize;
B, juvenile male paratype, USNM 1661745 (= ULLZ 12526-B) cw 7.2 mm, Belize;
C, juvenile female paratype, USNM 1549828 (= ULLZ 16524) cw 5.2 mm, Belize.

Hexapanopeus klausruetzleri n. sp., male holotype, USNM 1546469 (= ULLZ 12526-A).
A, right side of carapace, dorsal surface; B, left side of carapace, ventral surface; C, right third maxilliped detached, external surface (arthrobranch gill pair not shown); D, right third maxilliped detached, internal surface; E, major (left) chela, external surface; F, major (left) cheliped, supero-internal surface. Scale bars = 1.0 mm.

Hexapanopeus klausruetzleri n. sp.

Diagnosis. Carapace dorsal surface weakly convex, ovoid to weakly subhexagonal outline, wider than long (including anterolateral teeth), fronto-orbital width slightly exceeding 0.6 carapace width; front broadly convex with small median V-shaped notch separating shallow unimarginate lobes to each side, frontal margin of each lobe bearing slightly enlarged granules, lateral tooth of each frontal lobe obsolesent, lateral margin deflected to intersect antennal sinus; dorsal regions weakly defined, furrows of mesogastric, gastric, and anterior cardiac most evident; five anterolateral teeth, first tooth (outer orbital corner) subacutely angular, weakly separated from lobiform second by shallow depression of margin, third and fourth broadly lobiform to somewhat rounded or subrectangular, fifth small, subacutely angular. Third maxilliped merus distal margin sinuous, slightly produced to form small prominence near articulation with carpus. Cheliped merus superolateral margin with rough row of denticles, variably grouped to form serrate teeth, in major cheliped some forming sharp serrate teeth; carpus superior and lateral surfaces smooth to minutely granulate, microgranules forming weakly defined lines or surmounting weak elevations, supero-external surface marked by depression parallel to distal margin, internal margin with proximal angle weak, surmounted by line of low granules, distal angle stronger, forming blunt distally directed tooth. Major chela propodus mostly smooth to microgranulate, superior longitudinal crest weak, unarmed, adjacent external furrow shallow; dactylus opposable margin with slightly enlarged, lobiform basal tooth proximally. Ambulatory pereopods 2–5 relatively narrow, 2–4 subequal in size, merus length in all greater than 3 times greatest width, merus length approximating or slightly exceeding 1/2 carapace length; pereopod 5 smaller, propodus stouter than in other ambulatory pereopods, merus length not exceeding 1/2 length of carapace; merus in all ambulatory pereopods with superior margin unarmed, at most with dentiform granules variably concealed by plumose setae, inferior margin finely granulate; carpus superior margin with dense tract of short stout papilliform setae along crest; propodus superior margin with dense field of papilliform setae, dactylar-propodal locking mechanism not developed; dactylus stout proximally, inferior margin lacking subterminal prehensile tooth, superior margin densely covered by short papilliform setae, inferior margin with less dense slightly longer stiff simple setae. Male anterior thoracic sternum length (sternites 1–4) about 2/3 greatest width of fourth sternite (including episternites), eighth sternite exposed in subquadrate gap between lateral margin of flexed second pleonite and pereopod 5 coxa, exposure narrowly extending to anterior of condyle. Pleon of male with third through fifth pleonites fused, widest reach of first pleonite at its articulation with carapace, laterally rounded to articulation with second pleonite; telson subtriangularly rounded, widest in proximal one-third. Male first gonopod tip of highly modified panopeid form, subterminal tooth triangular, trunk in distal 1/4 of pleonal side bearing elongate field of heavy, rounded tubercles and granules extending to base of subterminal tooth. Male second gonopod less than one-third length of first gonopod.

Etymology. The species name is assigned in recognition of Klaus Ruetzler, world authority on marine sponge biology, who also led the establishment of the Smithsonian Marine Field Station at Carrie Bow Cay, Belize and for many years directed the Caribbean Coral Reef Ecosystems (CCRE) program based there. His encouragement and support of collaborators and colleagues brought many to focus years of work in Belize, including the senior author of this paper.

Distribution. At present known only from tropical waters in the vicinity of South Water Cay and Twin Cays along the barrier reef of Belize.

Habitat. Thus far known from only high salinity shallow subtidal calcareous sand habitats (1–4 m depth), occupying dead gastropod shells on wash-over fans and back-reef flats of coral reefs, sometimes between patches of turtle grass and sponges.

Darryl L. Felder and Brent P. Thoma. 2022. A New Shallow-water Mud Crab of the Genus Hexapanopeus Rathbun, 1898 from Belize (Crustacea: Decapoda: Panopeidae). Zootaxa. 5168(5); 541-552. DOI: 10.11646/zootaxa.5168.5.3