Ctenocheloides almeidai, Anker, Arthur & Pachelle, Paulo P. G., 2013
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publication ID |
https://doi.org/ 10.11646/zootaxa.3613.5.4 |
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publication LSID |
lsid:zoobank.org:pub:EAED4151-DB27-4ABF-B3C5-6CD804FEFB34 |
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DOI |
https://doi.org/10.5281/zenodo.6155230 |
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persistent identifier |
https://treatment.plazi.org/id/03E987AD-FFAA-FF9E-82AB-FE7AC560E187 |
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treatment provided by |
Plazi |
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scientific name |
Ctenocheloides almeidai |
| status |
sp. nov. |
Ctenocheloides almeidai sp. nov.
Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4
Type material. Holotype: female (CL 3.75 mm), MZUSP 27617, Brazil, Alagoas, Maceió, Ponta Verde, rocky reef, in large and deep tide pool with some corals and sponges, in silt-cemented rock crevice, depth about 1 m, leg. A. Anker, P.P.G. Pachelle, 1 August 2012 [field collection and photo voucher number 12-249].
Description. Body moderately slender, pleon and telson together more than twice as long as carapace, latter about the same length as first and second pleomeres ( Fig. 1 View FIGURE 1 ). Frontal margin of carapace broadly convex, without anteriorly projecting rostrum; anterolateral projections broadly obtuse; postfrontal area with low rounded elevation ( Fig. 2 View FIGURE 2 a, b). Carapace with gastric region not noticeably elevated above cardiac region, latter with rounded bumplike prominence; cervical groove deep; linea thalassinica well-marked, running close to depressed lateral margin of dorsal elevation; anterolateral margin below anterolateral projection deeply notched; branchiostegial margin forming slightly elevated branchiostegial lip fringed with long setae ( Fig. 2 View FIGURE 2 a, b).
First pleomere longest, with some grooves and sutures laterally; second pleomere about 0.8 length of first, with some erect setae dorsally and rows of setae posteroventrally; third, fourth and fifth pleomeres similar in length, smaller and shorter than second somite, with numerous erect setae dorsally and fairly dense cover of plumose setae laterally and posteroventrally (especially on fourth pleuron); sixth pleomere about the same length as third, with some erect setae posterodorsally, near telson, without dense rows of setae laterally ( Fig. 2 View FIGURE 2 c).
Telson as long as wide at proximal margin, broadly triangular; lateral margin shallowly constricted at about 0.4 length from anterolateral angle; posterior margin broadly rounded, without spine-like setae; posterior half of lateral margin and posterior margin fringed with plumose setae; dorsal surface smooth, with a few conspicuously long setae ( Fig. 2 View FIGURE 2 d).
Eyestalks slightly overreaching distal margin of first segment of antennular peduncle; anteromesial margin bluntly rounded, protruding well beyond cornea; cornea more or less rounded, with numerous (>20) wellpigmented ommatidia ( Fig. 2 View FIGURE 2 a).
Antennular peduncle overreaching fourth article of antennal peduncle in full extension of both peduncles (note: appearing reaching only to distal margin of fourth article in dorsal view, with antennular peduncle directed slightly upwards in Fig. 2 View FIGURE 2 a); first article not visible in dorsal view being concealed by eyestalks; third article longest, about 2.5 times as long as wide; flagella much longer than peduncle; dorsal flagellum thicker and slightly shorter than ventral flagellum, with 12 joints, distal four joints gradually narrowing, furnished with thick aesthetascs on ventral margin; ventral flagellum with long slender setae, mainly along ventral margin, typically grouped in pairs at distoventral end of each joint ( Fig. 2 View FIGURE 2 a, b). Antennal peduncle longer than antennular peduncle by about 0.7 length of its fifth article; first article with large, anteriorly protruding, distally blunt lobe; second and third article separated by deep lateral furrow, distoventral lobe subacute; fourth article slender, elongate, longest of all articles of antennal peduncle; scaphocerite small, with minute acute point distally; antennal flagellum longer than dorsal antennular flagellum ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 a, b).
Mandible, maxillule and maxilla not dissected. First maxilliped with broad, distally setose endites; endopod narrow, elongate, non-segmented; exopod broad, distally truncate; epipod large, bilobed ( Fig. 2 View FIGURE 2 e). Second maxilliped with large, stout coxa, without epipod (see discussion below); basis with long setae on ventral margin and rudimentary exopod (see discussion below); ischiomerus furnished with long, flexible setae; carpus shorter than wide; propodus longer than carpus, about 1.6 times as long as wide; dactylus more slender than propodus, distally with thickened setae ( Fig. 2 View FIGURE 2 f). Third maxilliped pediform, moderately slender, not operculate; ischium approximately twice as long as wide, ventromesial margin with prominent crista dentata consisting of 10 subtriangular, mostly subacute teeth; merus about 2.8 times as long as wide in lateral view, ventrolateral margin with subacute tooth subdistally, ventromesial margin with small blunt tooth at about 0.6 length of merus; carpus as long as merus, slightly widening distally, unarmed; propodus about the same length as carpus, slightly tapering distally; dactylus shorter and much narrower than propodus, about three times as long as wide, increasingly more setose distally; exopod absent ( Fig. 2 View FIGURE 2 h, i); two arthrobranchs present, one of them (smaller) shown in Fig. 2 View FIGURE 2 h.
First pereiopods (chelipeds) unequal in size and asymmetrical in shape ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 ). Major cheliped with ischium distally widening, approximately four times as long as wide at base, ventral margin armed with nine widely spaced teeth increasing in size distally, most proximal teeth minute, most-distal tooth conspicuously larger than remaining teeth; merus about twice as long as wide, somewhat inflated, ventral surface distally excavated, ventral margin with two large teeth at about mid-length; carpus short, about three times as wide as long, cupshaped, unarmed; chela suboval, 1.5 times as long as greatest width, not markedly compressed, ovoid in crosssection, smooth; fingers slender, moderately elongate, approximately same length as palm, distally markedly twisted mesially, tips crossing; cutting edges of fingers strongly pectinate, with 23 teeth on dactylus and 22 teeth on pollex, most teeth subtriangular, distally sharp, three teeth on each finger significantly longer and stronger than others, separated from each other by several smaller teeth, some teeth minute, proximal portion of both fingers without teeth, forming a broad gap when fingers are closed ( Fig. 3 View FIGURE 3 a–f). Minor cheliped smaller and shorter than major cheliped by about 80%; ischium generally similar to that of major cheliped; merus with one subdistal tooth on ventral margin; carpus longer compared to that of major cheliped, about 1.7 times as wide as long; minor chela smaller in size than major chela, about 1.7 times as long as greatest width; fingers about 0.9 length of chela; cutting edges of both fingers with prominent teeth, 10 teeth on dactylus and 13 teeth on pollex, most teeth broadly triangular or molar-shaped, some slightly larger than others ( Fig. 3 View FIGURE 3 g–i).
Second to fifth pereiopods relatively stout. Second pereopod with short ischium; merus long, robust, at least three times as long as wide at base, ventral margin fringed with row of long flexible setae; carpus vase-shaped, widening distally, fringed with some long flexible setae on ventral margin; chela with subrectangular, very short palm, palm length inferior to palm width, ventral margin with numerous long setae, fingers much longer than palm, straight, feebly gaping when closed ( Fig. 4 View FIGURE 4 a). Third pereiopod with short ischium; merus about three times as long as wide; carpus 0.6 length of merus, widening distally, distoventral margin furnished with long setae; propodus as long as carpus, subrectangular, about three times as long as wide, with numerous long and short setae on dorsal and lateral surfaces, ventral margin with numerous long, thick, stiff setae, some arranged in four short rows, and one stout spiniform seta at distal end, opposed to dactylus; dactylus stout, about half length of propodus, slightly curved ventrally, with groups and tufts of setae, tip subacute ( Fig. 4 View FIGURE 4 b, c). Fourth pereiopod generally similar to third, with proportionally longer ischium and carpus; merus about slightly more than three times as long as wide; carpus more than 0.7 length of merus, widening distally, without long stiff setae on distoventral margin; propodus almost four three times as long as wide, subequal in length to carpus, distodorsal margin with tufts of long slender setae, ventral margin furnished with groups of long, thick, stiff setae, numerous slender, flexible setae, and one stout spiniform seta at distal end, opposed to dactylus; dactylus moderately stout, about 0.6 length of propodus, slightly curved ventrally, with groups and tufts of setae, tip subacute ( Fig. 4 View FIGURE 4 d). Fifth pereiopod noticeably more slender than third and fourth pereiopods; ischium subrectangular; merus about four times as long as greatest width; carpus dorsally convex, about 0.8 length of merus, widening distally, without long stiff setae on distoventral margin; propodus as long as carpus, but more slender, about 3.5 times as long as wide in lateral view, ventral margin furnished with long, stiff, serrulate setae on distal half, distoventral margin protruding below dactylus, with small acute corneous point; dactylus relatively slender, about half-length of propodus, somewhat concave ventromesially, slightly curved, furnished with setae, tip subacute ( Fig. 4 View FIGURE 4 e, f).
First pleopod (female) with long setae distally on protopod, along lateral margin of ramus, and on apex of ramus ( Fig. 2 View FIGURE 2 j). Second pleopod (female) with endopod slightly longer than exopod, both endopod and exopod elongate, ovoid, margins fringed with plumose setae; endopod with well-developed, rod-shaped appendix interna ( Fig. 2 View FIGURE 2 k). Third to fifth pleopods (female) with exopods and endopods elongate-oval, margins densely fringed with plumose setae; endopods with rod-shaped appendices internae. Uropod with exopod and endopod broadly ovate, both with low median elevations, margins densely fringed with plumose setae; exopod distinctly expanded laterally, narrowing distally, with row of stout, short, spiniform setae inserted above plumose setae, extending from about 0.4 length of lateral margin to distal margin; lateral incision absent ( Fig. 2 View FIGURE 2 l).
Gill/exopod formula summarised in following Table; for (?) see remarks below
Colour. Body hyaline-whitish, ovary yolk-yellow ( Fig. 1 View FIGURE 1 ).
Etymology. The new species is named after our friend and colleague, the Brazilian carcinologist Dr. Alexandre Oliveira de Almeida (Universidade Estadual de Santa Cruz, Ilhéus, Bahia).
Distribution. Presently known only from the type locality in Ponta Verde, Maceió, Alagoas, northeastern Brazil.
Ecology. The type locality is a shallow rocky reef with numerous tide pools, some very large (10 m or more across and 30 m or more long) and deep (1.5–2 m), but also numerous small tide pools and deep cracks. The tide pools walls are covered with dead and living corals, sponges, and algae. The holotype specimen was extracted from a deep crevice cemented with compacted, clay-like silt, in a large coral rock collected near the base of the tide pool wall, at about 1 m. The same rock was also inhabited by a pair of mud shrimps, Upogebia cf. omissa Gomes Corrêa, 1968 (Upogebiidae) .
Remarks. Ctenocheloides almeidai sp. nov. is undoubtedly closely related to C. attenboroughi , the type species and the only other presently known species of Ctenocheloides . One of the main differences between the two species lies in the configuration of the crista dentata on the ischium of the third maxilliped. In C. almeidai sp. nov., the crista dentata is conspicuously protruding and armed with 10 teeth, eight of them very strong ( Fig. 2 View FIGURE 2 h. i), whereas in C. attenboroughi , the crista dentata is not protruding and bears only five, relatively weak teeth (cf. Anker 2010: fig. 3H, I). In addition, in the new species, the ventromesial margin of the third maxilliped merus bears a small bump ( Fig. 2 View FIGURE 2 i) instead of a very stout, projecting tooth, as in C. attenboroughi (cf. Anker 2010: fig. 3H, I).
The two species also differ in the armature of the major and minor chelipeds. In C. almeidai sp. nov., the major cheliped ischium is armed with eight smaller teeth and one much larger subdistal tooth on the ventral margin, whilst the merus is armed with two large teeth ( Fig. 3 View FIGURE 3 d); in contrast, in C. attenboroughi , the major cheliped ischium is armed with four small teeth and two much larger teeth more distally, whilst the merus is armed with only one tooth (cf. Anker 2010: fig. 4A, B). The dentition on the cutting edges of the cheliped fingers, although generally similar between the two species, presents some important differences. For instance, the major chela of C. almeidai sp. nov. is characterised by the absence of teeth in the proximal one fifth or so of the cutting edge length, resulting in a conspicuous gap between the fingers when they are closed ( Fig. 3 View FIGURE 3 e); this gap is much less conspicuous in C. attenboroughi (Anker 2010: fig. 4A, B). The fingers of the minor chela of C. almeidai sp. nov. are armed with 10-13 teeth ( Fig. 3 View FIGURE 3 i), which is far less than in C. attenboroughi (24-25 teeth, cf. Anker 2010: fig. 5C). In addition, in C. almeidai sp. nov., both the major and the minor chelipeds appear to be slightly stouter and their fingers shorter than in the type species (e.g., palm/fingers ratio ~1 vs. ~ 1.3 in C. attenboroughi ; see Figs. 3 View FIGURE 3 a, b, h, g; cf. Anker 2010: figs. 4A, B, 5A).
Furthermore, C. almeidai sp. nov. and C. attenboroughi can also be distinguished from each other by the shape of the telson (posteriorly broader in C. almeidai sp. nov.) and especially of the uropodal exopod (posteriorly narrower in C. almeidai sp. nov.) ( Fig. 2 View FIGURE 2 d, l, cf. Anker 2010: fig. 7F, E). Finally, the two species also differ, albeit insignificantly, in the length of the antennular peduncle, which in the new species reaches slightly past the distal margin of the third antennal article in full extension ( Fig. 2 View FIGURE 2 b, note: peduncle not fully extended in Fig. 2 View FIGURE 2 a), whilst reaching far beyond this margin in the type species (cf. Anker 2010: fig. 1A).
Anker (2010) provided a gill/exopod formula for C. attenboroughi , where the author listed (1) two arthrobranchs associated with the fifth pereiopod, and (2) a rudimentary epipod on the second maxilliped. Ctenocheloides almeidai sp. nov. does not have arthrobranchs above the fifth pereiopod; the position of the last arthrobranch is above the posterior margin of the coxa of the fourth pereiopod, although adjacent to the base of the fifth pereiopod. As no other callianassoid has a gill above the fifth pereiopod, it is very likely that Anker (2010) made a type error in the gill/exopod table and that the actual arthrobranch number and position in C. attenboroughi are the same as in C. almeidai sp. nov. and Ctenocheles , i.e. without two arthrobranchs above the fifth pereiopod (Rodrigues 1978). Reinforcing this hypothesis is the fact that Anker (2010) did not use the presence or absence of arthrobranchs at the fifth pereiopod to separate Ctenocheles from Ctenocheloides .
With respect to the second maxilliped, a fairly large, rounded, epipod-like lobe with a short basal attachment ( Fig. 2 View FIGURE 2 g), was accidentally separated during the dissection of the right second maxilliped in C. almeidai sp. nov. This structure was initially assumed to represent a detached epipod of the right second maxilliped. However, an external (in situ) observation of the left second maxilliped did not reveal the presence of such a lobe on the coxa of this appendage. In addition, Anker (2010) did not find such a lobe in C. attenboroughi , whereas Rodrigues (1978) did not illustrate an epipod on the second maxilliped in Ctenocheles holthuisi nor did he list it in the gill/exopod table. Therefore, the nature and the position of this lobe remain unknown. On the other hand, the second maxilliped of both C. almeidai sp. nov. and C. attenboroughi is characterised by a rudimentary lobe at the base of the endopod, which was tentatively considered to be a rudimentary epipod in Anker (2010). The small size of the second maxilliped and the complex structure of its coxo-basal articulation make it difficult to determine the exact insertion point of this lobe. However, as this lobe is very near the basis and the endopod, it could also represent a rudimentary exopod. Thus, the absence or presence of an epipod on the second maxilliped, the nature of the detached rounded lobe ( Fig. 2 View FIGURE 2 g), and the homology of the rudimentary lobe (epipod or exopod) remain to be confirmed for both species of Ctenocheloides , preferably when more material is found in the future (it appears to be most sensible not to damage further the small, partly dissected, increasingly fragile holotypes of C. almeidai sp. nov. and C. attenboroughi ).
Noteworthy, C. almeidai sp. nov. from Brazil and C. attenboroughi from Madagascar are found in the same type of microhabitat. Both species seem to inhabit galleries made in rock crevices cemented with compact clay-like silt, at very shallow depths (1–1.5 m). Thus, the two species of Ctenocheloides are ecologically different from the much larger species of Ctenocheles , which all live, presumably in self-made burrows, on sand and mud bottoms at greater depths (10–400 m, sometimes as deep as 800 m, see Anker 2010 and references therein). The biology of both genera, including size and configuration of burrows, feeding mode, diet, and reproductive patterns, remains largely unknown.
The discovery of C. almeidai sp. nov. adds a previously unreported genus, Ctenocheloides , to the Atlantic decapod fauna, thus being also a new genus record for the western Atlantic and Brazil. In the western Atlantic, the family Ctenochelidae (including Gourretiidae Sakai, 1999 ) is now represented by four genera and six species: Dawsonius Manning & Felder, 1991 (1 species: D. latispina (Dawson, 1967)) , Gourretia de Saint-Laurent, 1973 (2 species: G. l a re s i Blanco Rambla & Liñero Arana, 1994 and G. biffari Blanco Rambla & Liñero Arana, 1994 ), Ctenocheles (2 species: C. leviceps Rabalais, 1979 and C. holthuisi Rodrigues, 1978 ), and Ctenocheloides (1 species: C. almeidai sp. nov.). These genera and species can be distinguished using the following key:
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