Fenneralpheus Felder & Manning, 1986

Anker, Arthur, 2011, Six new species and three new records of infaunal alpheid shrimps from the genera Leptalpheus Williams, 1965 and Fenneralpheus Felder & Manning, 1986 (Crustacea, Decapoda), Zootaxa 3041, pp. 1-38 : 27-28

Fenneralpheus Felder & Manning, 1986

Fenneralpheus Felder & Manning, 1986: 497 .

Emended diagnosis. Carapace glabrous, not setose; frontal margin rounded, without orbital teeth, rostral projection, orbital crests; anterolateral suture present; pterygostomial angle subacutely protruding anteriorly or broadly rounded; branchiostegial margin with broad, somewhat membranous ventral lip; posterior margin with deep cardiac notch. Sixth abdominal somite with posteroventral articulated plate. Telson with two pairs of spiniform setae dorsally; posterior margin rounded, with two pairs of posterolateral spiniform setae; anal tubercles present. Eyes concealed in dorsal and lateral views; anteromesial margin bluntly projecting. Antennular peduncles flattened dorsoventrally; ventromesial carina of first article with large tooth; stylocerite appressed, not exceeding distal margin of first article; second article elongate, much longer than wide; lateral antennular flagellum with short secondary ramus. Antenna with stout basicerite bearing distoventral tooth; scaphocerite with small distolateral tooth; carpocerite overreaching scaphocerite. Mouthparts not especially modified; mandible with two-articulated palp; first maxilliped with elongate palp and broad caridean lobe; second maxilliped with elongate epipod. Third maxilliped with lateral plate on coxa moderately produced dorsally; tip of ultimate article unarmed. First pereiopods (chelipeds) very unequal in size and asymmetrical in shape, carried flexed; major cheliped stout, with enlarged, elongate chela; merus depressed ventrally, margins smooth; carpus short, more or less cup-shaped; chela with palm smooth, excavated ventromesially; fingers with armature consisting of large teeth with distal ridges, tooth-fossa system absent; adhesive discs, if present, feebly developed. Second pereiopod with carpus composed of five articles. Third pereiopod and fourth pereiopods very stout, strongly compressed laterally; ischium unarmed or with small spiniform seta; carpus short, with strong distoventral spiniform seta; propodus with strong spiniform setae on ventral margin; dactylus simple, subconical or subspatulate. Fifth pereiopod not compressed, shorter and more slender than third and fourth pereiopods; propodus with several setal rows distolaterally. Male second pleopod with appendix masculina exceeding appendix interna; female second pleopod with appendix interna only. Uropod with lateral lobe of protopod bifid distally; exopod distally truncate; diaeresis with deep incision and large triangular tooth near mesial margin of exopod. Gill/exopod formula: 5 pleurobranchs (P1–5), 1 arthrobranch (Mxp3), 2 lobe-like epipods (Mxp1–2), 0 podobranchs, 5 mastigobranchs (Mxp3, P1–4), 5 setobranchs (P1–5), 3–4 exopods (always Mxp1–3, sometimes P1).

Species included. F. chacei Felder & Manning, 1986 (type species), F. orabovis sp. nov.

Distribution. Western Atlantic: southeastern USA (Florida) and Panama.

Remark s. Felder & Manning (1986) listed the following differences between Fenneralpheus and Leptalpheus : (1) the pterygostomial angle strongly produced anteriorly in Fenneralpheus (not in Leptalpheus ); (2) the branchiostegial margin with a distinct ventral lip in Fenneralpheus (not in Leptalpheus ); (3) the antennular peduncles depressed and with the second article “much the longest” in Fenneralpheus (not in Leptapheus); (4) the scaphocerite “spatulate” and without “anterolateral spine” (= distolateral tooth), but with an “anterior emargination” in Fenneralpheus (vs. scaphocerite non-spatulate and with a well-developed distolateral tooth in Leptalpheus ); (5) the fingers of the major chela much longer, evenly toothed, not gaping in Fenneralpheus (vs. with the fingers shorter and gaping in Leptalpheus ); (6) the much stouter third and fourth pereiopods in Fenneralpheus (relatively slender in Leptalpheus ); and (7) the much larger size of Fenneralpheus (cl 9.2-12.8 mm in F. chacei vs. 2.9-7.8 mm in Leptalpheus spp. known to date).

The pterygostomial angle is not anteriorly produced in the below-described new species of Fenneralpheus , thus eliminating the first difference between the two genera. The antennular peduncles are somewhat depressed and the second article distinctly longer than the first or third in L. forceps ; therefore the third difference is also invalid. The size of the distolateral tooth and the shape of the blade of the scaphocerite appear to be quite variable in species of Leptalpheus , whilst a small but distinct tooth is present in the new species of Fenneralpheus , making the fourth difference unreliable. The fingers of the major cheliped are not gaping in several species of Leptalpheus , e.g. L.

marginalis sp. nov. and L. hendrickxi sp. nov. (see above), and only slightly gaping in L. pierrenoeli ( Anker 2008, fig. 2C, D). In fact, the major cheliped of L. pierrenoeli has some similarities to that of F. chacei , especially in the general shape and proportions of the fingers to the palm, however, differing in the armature of the finger cutting edges ( Anker 2008, fig. 2A–D). Finally, the difference in size is eliminated by the fairly large Indo-West Pacific L. pacificus and L. denticulatus , with the paratype of the latter species, at cl 14.5 mm ( Anker & Marin 2009), being larger than the largest known specimen of F. chacei . Generally, size cannot be a character of generic importance, as exemplified by extreme variation within the genera Alpheus Fabricius, 1798 and Synalpheus Bate, 1888 (A. Anker, pers. obs.).

Thus, the only morphological characters that allow distinguishing effectively Fenneralpheus from Leptalpheus (as currently defined) are the presence of a large ventral lip on the branchiostegial margin and the very stout third and fourth pereiopods, with short carpi and propodi, both armed with unusually robust spiniform setae. The presence of a large, somewhat membranous lip on the branchiostegial margin is shared with the Indo-West Pacific Richalpheus Anker & Jeng, 2006 , which can be easily distinguished from Fenneralpheus by the absence of the mastigobranch-setobranch complex (Mxp3, P1-5) and the very different shape and finger armature of the major cheliped ( Anker & Jeng 2006).