Alpheus ledoyeri, Anker, 2025
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publication ID |
https://doi.org/10.11646/zootaxa.5659.1.3 |
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publication LSID |
lsid:zoobank.org:pub:CF273210-0DEA-48FC-95D0-8181EE3BC596 |
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persistent identifier |
https://treatment.plazi.org/id/3777878E-AD0A-2B7E-8CA1-FAFE01E6FBC0 |
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treatment provided by |
Plazi |
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scientific name |
Alpheus ledoyeri |
| status |
sp. nov. |
Alpheus ledoyeri sp. nov.
( Figs. 5 View FIGURE 5 , 6 View FIGURE 6 )
Type material. Holotype: male (cl 8.3 mm), MNHN-IU-2018-5290, Madagascar, Nosy Bé , Ambatoloaka, Mission Cherbonnier, sta/nr. 142G, depth and habitat unknown, 10.06.1960.
Description. Carapace smooth, inconspicuously pitted, glabrous. Rostrum well developed, about 1.3 times as long as wide at base, horizontal, subacute distally, not reaching distal margin of first article of antennular peduncle, with two short setae; rostral carina well demarcated, blunt, not rising above orbital hoods in its anterior part, gently sloping into shallow adrostral furrows, continuing beyond level of eyes, then slightly widening and flattening, not extending beyond base of orbital hoods posteriorly ( Fig. 5A, B View FIGURE 5 ). Rostro-orbital region somewhat produced anteriorly ( Fig. 5A, B View FIGURE 5 ). Orbital hoods swollen, slightly projecting anteriorly in lateral view, unarmed; frontal margin between rostrum and orbital hood shallowly concave ( Fig. 5A, B View FIGURE 5 ). Pterygostomial angle rounded ( Fig. 5B View FIGURE 5 ); cardiac notch deep.
Telson moderately broad, subrectangular, tapering distally, about 1.9 times as long as maximal width; lateral margins slightly constricted at about 0.7 telson length, almost parallel in posterior third; dorsal surface with two pairs of very stout spiniform setae both inserted at considerable distance from lateral margin, first pair at about 0.4 telson mid-length, second pair at about 0.7 telson length, mid-dorsal groove not distinct; posterior margin broadly rounded, with row of short spiniform setae above long plumose setae; posterolateral angles each with one pair of spiniform setae, mesial spiniform setae almost three times as long as lateral ones ( Fig. 5C View FIGURE 5 ).
Cornea of eye large, well pigmented; eyes completely enclosed by orbital hoods ( Fig. 5A. B View FIGURE 5 ). Antennular peduncle moderately stout, not particularly elongate, ventromesial carina with wide tooth ending in small subacute point; stylocerite not particularly swollen laterally, ending in sharp point, latter falling short of distal margin of first article; second article 1.8–1.9 times as long as wide; dorsolateral antennular flagellum with accessory ramus fused to main ramus over most of its length, ending in short stump, with several groups of aesthetascs distally ( Fig. 5A, B, D View FIGURE 5 ). Antenna with basicerite short, stout, armed with sharp tooth on distoventral margin; scaphocerite overreaching distal end of antennular peduncle, blade moderately broad, distolateral tooth prominent, reaching well beyond distal margin of blade and separated from blade by deep cleft, lateral margin slightly concave; carpocerite not particularly elongate, stout, subcylindrical, reaching slightly beyond scaphocerite and well beyond end of antennular peduncle; flagellum not particularly thickened ( Fig. 5A, B View FIGURE 5 ).
Mouthparts not dissected, typical for genus in external observation. Third maxilliped rather stout; coxa with large, subacutely projecting lateral plate above strap-like epipod; antepenultimate article about 4.5 times as long as high, flattened on ventrolateral surface, with distinct longitudinal ridge running parallel to dorsal margin on lateral surface and ending in blunt distodorsal prominence; penultimate article very short, cup-shaped, wider distally than proximally, not bulging ventrally, not particularly setose; ultimate article about 0.7 length of antepenultimate article, compressed, very setose, more so distally, length of some distal setae exceeding length of ultimate article; arthrobranch well developed ( Fig. 5E, F View FIGURE 5 ).
Major cheliped robust; ischium stout, smooth; merus very stout but not swollen, trigonal in cross-section, about 2.1 times as long as maximal width, setose (most notably, with long setae along dorsal, distal and ventromesial margins), distodorsal angle ending bluntly, dorsal and ventromesial margin crenulated, latter armed with short spiniform setae in proximal half and with large, stout, sharp distal tooth; carpus cup-shaped, short; chela not particularly elongate, stout; palm compressed, subrectangular in cross-section, smooth, about twice as long as wide, dorsal surface without pronounced ridges, distodorsal surface with deep, oblique transverse groove; fingers somewhat unequal in length with dactylus markedly longer than pollex, about 0.6 length of palm, not twisted or significantly deviating from chela axis; dactylus distally rounded, with plunger in form of prominent tooth, well demarcated from anterior occlusal edge; ventral surface of palm and pollex covered with long setae; adhesive disks small ( Fig. 6A–D View FIGURE 6 ).
Minor cheliped robust; ischium short, with shallow sulcus on lateral surface; merus somewhat swollen, about 2.2 times as long as maximal width, setose (most notably, with long setae along dorsal and ventral margins), distodorsal angle blunt, dorsal, ventrolateral and ventromesial margins somewhat crenulated, latter armed with short, stout spiniform setae in proximal half and with small, blunt distal tooth, lateral surface with faint sulcus proximally; carpus cup-shaped, longer than that of major chela, distally widening; chela moderately slender, not particularly elongate or swollen; palm subcylindrical, slightly compressed, smooth, about twice as long as high, distodorsal surface without transverse groove; fingers subequal in length with tip of dactylus slightly surpassing that of pollex, about 1.2 times as long as palm, somewhat gaping, tips strongly curved and crossing; dactylus not conspicuously expanded; rows of densely inserted, plumose balaeniceps setae present along occlusal margins on each side of dactylus and pollex; ventral and distal surfaces of palm, pollex and distal surface of dactylus densely covered with long setae, some reaching far beyond finger tips and forming long setal brush; adhesive disks small ( Fig. 6E–G View FIGURE 6 ).
Second pereiopod slender; ischium longer than merus; carpus with five subarticles, first and second subequal in length; chela noticeably longer than distal-most carpal subarticle ( Fig. 5G View FIGURE 5 ). Third pereiopod moderately robust; ischium with large, stout spiniform seta on ventrolateral surface; merus almost four times as long as maximal width, ventral margin unarmed, distal ventrolateral angle without tooth; carpus about 0.6 length of merus, more slender, unarmed; propodus slightly longer than carpus, with numerous spiniform setae of various size along ventral and ventrolateral margins and one distal pair of long spiniform setae near propodo-dactylar articulation; dactylus about half-length of propodus, gradually curving distally, with longitudinal keel, trigonal in cross-section, more conical than subspatulate ( Fig. 5H, I View FIGURE 5 ). Fourth pereiopod generally similar to third pereiopod, somewhat more slender. Fifth pereiopod much more slender than third and fourth; ischium with stout spiniform seta on ventrolateral surface; merus somewhat curved, about five times as long as wide; carpus not significantly narrower than merus, about 0.9 length of merus; propodus subequal to carpus in length, with several spiniform setae (some broken off in the holotype) along ventromesial margin and at least six rows of microserrulate setae forming grooming brush on distolateral surface; dactylus conical, slender, 0.6 times length of propodus ( Fig. 5J, K View FIGURE 5 ).
Male second pleopod with appendix masculina slightly exceeding appendix interna, densely covered with long, stiff setae, mainly on apex ( Fig. 5L View FIGURE 5 ). Uropod broad; mesial and lateral lobes of protopod each ending in sharp distal tooth; exopod and endopod broadly ovate, endopod noticeably smaller; exopod with strong distolateral tooth flanked mesially by long slender spiniform seta, latter not reaching distal margin of exopod; diaeresis somewhat uneven, with broad blunt lateral lobe adjacent to spiniform seta; endopod with row of small spiniform setae above plumose setae on distal margin ( Fig. 5M View FIGURE 5 ).
Gill-exopod formula typical for genus ( Coutière 1899; Chace 1988).
Colour pattern. Unknown.
Etymology. The new species is named after the late Michel Ledoyer (1937–2015) (formerly associated with Station Marine d’Endoume, Marseille), a well-known French carcinologist specialised in Peracarida, for his numerous contributions to the taxonomic knowledge of the crustacean fauna of Madagascar, including two major studies on caridean shrimps ( Ledoyer 1969, 1970).
Type locality. Nosy Bé , north-western Madagascar .
Distribution. Presently known only from the type locality in north-western Madagascar.
Ecology. Unknown.
Remarks. Alpheus ledoyeri sp. nov. belongs to the A. brevirostris ( Olivier, 1811) species group, defined mainly by the compressed, more or less elongate major chela, with the palm subrectangular in cross-section ( Coutière 1899). Several species originally placed in this group by Coutière (1899) and subsequent workers (e.g., Crosnier & Forest 1966; Banner & Banner 1982; Chace 1988; Bruce 1994), such as A. glaber ( Olivi, 1792) and A. barbatus Coutière, 1897 [ Coutière (1897a)], were recovered outside of the main A. brevirostris clade in the most recent molecular phylogeny of Alpheus ( Hurt et al. 2021) , pointing to the necessity for a redefinition of the A. brevirostris group. Nevertheless, all morphological characters of A. ledoyeri sp. nov. suggest that it belongs to the “core” A. brevirostris group.
Within the A. brevirostris group, A. ledoyeri sp. nov. must be first of all compared with several Indo-West Pacific species having the following characteristics: (1) carapace and pleon glabrous, not pubescent; (2) orbital hoods rounded, unarmed; (3) mid-dorsal carina of carapace moderately developed, not reaching beyond orbital hoods; (4) major chela not extremely elongate and slender; (5) major chela palm with a deep transverse notch on distodorsal surface; (6) minor chela fingers not gaping, with rows of balaeniceps setae, dactylus not conspicuously broadened; (7) second pereiopod carpus with first and second subarticles subequal in length; and (8) dactylus of the third, fourth and fifth pereiopods trigonal, only slightly expanded, subspatulate. Using the incomplete and now also outdated key to the Indo-West Pacific members of the A. brevirostris group in Bruce (1994), A. ledoyeri sp. nov. keys out to the A. djeddensis Coutière, 1897 [ Coutière (1897b)] – A. djiboutensis De Man, 1909 species complex, which was partly revised by Anker (2022b, 2022c, 2024).
The new species can be immediately separated from all species of the A. djeddensis – A. djiboutensis complex by the distal portion of the minor chela fingers, especially pollex, carrying unusually long, far-reaching setae, forming a loose brush (cf. Fig. 6E, G View FIGURE 6 ; illustrations in Banner & Banner 1982; Purushothaman et al. 2021; Anker 2022b, 2022c, 2024). In addition, in A. ledoyeri sp. nov., the rostral carina is short and not continued by a strong mid-dorsal carina beyond the base of orbital hoods, as in A. djeddensis and allied forms (cf. Fig. 5A View FIGURE 5 ; Anker 2022b, 2022c, 2024), being similar in length to the carina in A. mannarensis Purushothaman, Abhilash, Ajith Kumar & Lal, 2021 ( Purushothaman et al. 2021: fig. 2B). Another difference between A. ledoyeri sp. nov. and most species of the A. djeddensis – A. djiboutensis complex is the relative length of the first and second carpal subarticles in the second pereiopod: they are subequal in the new species, whereas in A. djeddensis and most related species, the first subarticle is noticeably longer than the second (cf. Fig. 5E, G View FIGURE 5 ; same references as above). The only exceptions are A. thompsoni Anker, 2022 , in which the first and second subarticles are subequal in length, and A. mannarensis , in which the second subarticle is much longer than the first ( Purushothaman et al. 2021: fig. 3G; Anker 2022b: fig. 1F). The distomesial tooth of the major cheliped merus is very prominent and stout in A. ledoyeri sp. nov. ( Fig. 6B View FIGURE 6 ); this tooth is reduced or at most moderately developed in most species of the A. djeddensis – A. djiboutensis complex (same references as above), except for the Red Sea species tentatively identified as A. cf. djiboutensis in Anker (2024: fig. 32G). Finally, A. ledoyeri sp. nov. can be separated from each of the species treated and illustrated by Anker (2022b, 2022c, 2024), as well as from A. mannarensis in Purushothaman et al. (2021), by at least three additional characters, including proportions of the minor chela, third pereiopod merus and telson, shape of the antennal scaphocerite, length and stoutness of the ultimate article of the third maxilliped, etc.
Several other Indo-West Pacific shallow-water species of the A. brevirostrris group have a certain number of characters in common with A. ledoyeri sp. nov., most notably the presence of a deep notch on the distodorsal surface of the major chela and/or well-developed balaeniceps condition on the minor chela fingers. These species are: A. platyunguiculatus ( Banner, 1953) ; A. cythereus Banner & Banner, 1966 ; A. arenicolus Banner & Banner, 1983 ; A. moretensis Banner & Banner, 1982 ; A. savuensis De Man, 1908 ; A. pubescens De Man, 1908 ; A. tenuicarpus De Man, 1908 ; A. williamsi Bruce, 1994 ; A. fenneri Bruce, 1994 ; A. stephensoni Banner & Smalley, 1969 ; and A. zulfaquiri Kazmi, 1982 . Among them, only A. arenicolus , A. tenuicarpus and A. zulfaquiri are known from the western Indian Ocean ( Banner & Banner 1981, 1983; Kazmi 1982). However, each of these species differs from A. ledoyeri sp. nov. by a combination of several characters. Most of them don’t have a conspicuous brush of long setae on the minor chela fingers, which is characteristic for the new species (cf. De Man 1908, 1911; Banner 1953; Banner & Banner 1966, 1982; Banner & Smalley 1969; Kazmi 1982). Further, A. pubescens and A. williamsi have pubescent carapaces, which is not the case of A. ledoyeri sp. nov.; A. fenneri has a greatly reduced and feebly bulging plunger on the major chela dactylus, whereas in A. ledoyeri sp. nov., the plunger is very distinct; A. platyunguiculatus and A. savuensis both have very short, stout minor chelae, compared to the much longer minor chela in the new species; A. cythereus differs from A. ledoyeri sp. nov. by the minor chela fingers more conspicuously gaping, the distally twisted major chela, and the second subarticle of the second pereiopod much longer than the first; in A. arenicolus (holotype examined, see comparative material), the major chela palm does not have a deep oblique notch, as in the new species, but rather a broad shallow sinus, whilst the antennular peduncle is noticeably longer; in A. tenuicarpus , in which the minor cheliped fingers have some elongate setae distally (although by far not as numerous and long as in A. ledoyeri sp. nov.), the major chela palm has no trace of a distodorsal notch; the minor chela of the species described as A. zulfaquiri (see below) has proportionally much longer fingers, whereas the major chela dactylus has a large bulge in front of the plunger, a feature not observed in A. ledoyeri sp. nov.; A. moretensis has a posteriorly far-reaching mid-dorsal carina (which is very short in the new species) and the plunger of the major chela dactylus is lower and anteriorly more confluent with the occlusal margin; finally, A. stephensoni greatly differs from A. ledoyeri sp. nov., for example, by the conspicuously granulated carapace and chelipeds, and the much longer antennular peduncle. Most of the above-listed species seem to be only distantly related to the new species, with the possible exception of A. tenuicarpus and A. arenicolus . It must be noted that the taxonomic status of A. zulfaquiri , which for some reason was not included in Bruce’s (1994) key to the Indo-West Pacific species of the A. brevirostris group, needs to be reassessed. More precisely, this taxon needs to be carefully compared with the holotype of A. dispar Randall, 1840 , the dried chelipeds of which were illustrated by Bruce (1994: fig. 6D). The identity of specimens from Singapore identified as A. dispar in Anker & De Grave (2016) also needs confirmation.
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