Bannereus chani Anker & Pachelle 2020, sp. nov.
Creators: name: Anker, Arthur
name: Pachelle, Paulo P. G.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Alpheidae
Bannereus
Bannereus chani

description: Bannereus chani sp. nov.
Figs 1–4
(?) Bannereus anomalus – Bruce 1988: 140 (partim, male specimen), figs. 2D–K, 3, 4H–J (as on figure, legend erroneous), 5B–D, G–J, 6C [not B. anomalus Bruce, 1988].
Type material. holotype, ovigerous female (cl 6.3 mm), MNHN-IU-2017-11749, Taiwan, off south-eastern coast, Campaign TAIWAN 2002, N/O “Ocean Researcher”, Sta. DW 151, 22°18.8’N 121°29.6’E, depth: 301–356 m, leg. T.Y. Chan, R. von Cosel and B. Richer de Forges, 20 May 2002.
Description. Medium-sized alpheid shrimp. Carapace glabrous, somewhat swollen, not compressed laterally. Rostrum present as small median convexity of frontal margin; orbital teeth absent (Fig. 1A, B). Pterygostomial angle broadly rounded (Fig. 1B). Cardiac notch moderately deep.
First to fourth pleonites with pleura rounded posteroventrally, second greatly expanded in females; fifth pleuron with posteroventral margin somewhat more angular; sixth pleonite with blunt posterolateral projection near telson base, without articulated plate (Fig. 4A). Telson subrectangular, considerably tapering distally, nearly twice as long as proximal width, with 2 pairs of small cuspidate setae (one of them minute) both situated in posterior half of telson; posterior margin straight, with 2 pairs of spiniform setae, mesial almost twice as long as lateral (Fig. 4B).
Eyes completely concealed by frontal projection of carapace in dorsal view, partly visible in lateral view, relatively well-developed, with normally pigmented corneas, latter occupying most of distolateral area of short stout eyestalk; anteromesial margin rounded, without tubercle (Fig. 1A, B).
Antennular peduncle with dorsally visible portion of first article subequal to second article in length (Fig. 1A). First article with stylocerite stout, rounded distally, not reaching distal margin of first article; ventromesial carina with large blunt tooth (Fig. 1 A–C). Second article about 1.3 times as long as wide, ventral surface with small subacute tooth distally (Fig. 1A, C). Third article shortest. Lateral flagellum with fused portion composed of 4 units, accessory ramus very stout, subdivided into at least 3 units (tip broken off); several groups of aesthetascs extending from last unit of fused portion to last unit of accessory ramus; main ramus very slender distal to bifurcation (Fig. 1B).
Antenna with basicerite moderately robust, armed with small subacute distoventral tooth (Fig. 1B). Scaphocerite very broad, ovate, reaching to mid-length of third article of antennular peduncle; lateral margin broadly convex; blade strongly convex anteriorly, overreaching greatly reduced, blunt distolateral tooth (Fig. 1A, B, D, E). Carpocerite fairly slender, cylindrical, overreaching both scaphocerite and antennular peduncle (Fig. 1A, B, D).
Mouthparts not dissected, seemingly typical for genus in external observation. Third maxilliped pediform, robust, coxa with small rounded lateral plate; exopod moderately developed, not reaching penultimate article; antepenultimate article about 4 times as long as greatest width, somewhat curved, ventromesial margin slightly rugose, with several slender spiniform setae; penultimate article subcylindrical, about 2.5 times as long as distal width, with clusters of stout setae on ventromesial and distodorsal surface; ultimate article slender, elongate, tapering distally, tip with stout spiniform setae (Fig. 1 F–H).
Only left (major) cheliped present (preserved) in holotype (Fig. 2). Major cheliped robust, greatly enlarged relative to body. Ischium short, unarmed (Fig. 2A, D). Merus subtriangular in cross-section, widening distally; ventromesial surface adjacent to margin with numerous spiniform setae inserted in irregular row; distomesial margin unarmed; distodorsal margin blunt (Fig. 2A, D, E). Carpus very short, much broader than long, cup-shaped (Fig. 2A, D). Chela with palm smooth, without ridges or other sculpture, swollen, elongate-ovoid in shape (Fig. 2A, B). Fingers about half-length of palm, not twisted mesially or laterally; fingertips strongly curved and crossing distally; pollex slightly shorter than dactylus; cutting surface deeply excavated, channel-like; mesial cutting margin with 2 rounded teeth proximally; lateral cutting margin with single low bump proximally; dactylus with cutting surface distinctly bulging, fitting into excavation of pollex (Fig. 2A, B, C, F).
Second pereiopod relatively short, stout (Fig. 1I). Merus somewhat longer than ischium. Carpus slightly shorter than merus, subdivided into 5 units (subarticles), proximal longest, their ratio approximately equal to 3: 1: 0.8: 0.8: 2 (Fig. 1I). Chela slightly shorter than carpus, with fingers about 0.7 length of palm; both fingers with dense fan-like tufts of setae near bifid tips; cutting edges unarmed (Fig. 1 I–L).
Third pereiopod relatively stout (Fig. 3A). Ischium with 1 or 2 stout cuspidate seta(e) on ventrolateral surface (Fig. 3A, C). Merus about twice as long as ischium, somewhat inflated, with both dorsal and ventral margins slightly convex, about 3.5 times as long as maximal width, with small spiniform seta at about mid-length of ventral margin (Fig. 3A, C). Carpus much slenderer than merus, about 0.4 length of merus, unarmed (Fig. 3A). Propodus elongate; ventral margin armed with row of 15 short spiniform setae, sometimes inserted by pairs, including 1 pair of longer spiniform setae distally, adjacent to dactylar base (Fig. 3A). Dactylus stout, about 0.2 length of propodus, biunguiculate; terminal unguis much longer than secondary unguis; both unguis directed slightly ventral relative to main dactylar axis and more or less parallel to each other; ventral margin with 4 minute, apparently articulated spinules, distal-most spinule situated near secondary unguis, proximal-most spinule situated at about mid-length of dactylus; dorsal margin with tuft of thickened setae (Fig. 3A, B).
Fourth pereiopod generally similar to third, much slenderer (Fig. 3D). Ischium bearing 1 or 2 cuspidate seta(e) on ventrolateral surface (Fig. 3D, F). Merus about 3.2 times as long as wide, less swollen, with margins less convex than in third pereiopod, unarmed or armed with 1 small cuspidate seta slightly proximal to mid-length (Fig. 3D, F). Carpus half-length of propodus, unarmed (Fig. 3D). Propodus elongate, with ventral margin armed with row of 11 short spiniform setae, including 1 pair of longer spiniform setae distally, adjacent to dactylar base (Fig. 3D). Dactylus less stout than that of third pereiopod but otherwise similar, about 0.2 length of propodus, biunguiculate; ventral margin with 4 minute, apparently articulated spinules, distal-most spinule located near secondary unguis (Fig. 3D, E).
Fifth pereiopod shortest and slenderest (Fig. 3G). Ischium unarmed (Fig. 3G). Merus about three times as long as wide, slightly less than twice as long as ischium, unarmed or armed with 1 small cuspidate seta between 0.3 and 0.4 of merus length (Fig. 3G, I). Carpus about 0.6 length of merus (Fig. 3G). Propodus with ventromesial margin armed with 9 spiniform setae, including 1 pair of longer spiniform setae distally, adjacent to dactylar base, and 5 –6 rows of grooming serrulate setae on distolateral surface; distodorsal margin with or without 1 spiniform seta at articulation with dactylus (Fig. 3G, H). Dactylus similar to that of fourth pereiopod in proportions, biunguiculate; ventral margin with 3 minute, probably articulated spinules (Fig. 3G, H).
Female first pleopod with well-developed endopod, overreaching mid-length of exopod, furnished with setae distally (Fig. 4C). Female second pleopod with short, stubby appendix interna (Fig. 4D). Uropod with lateral lobe of protopod blunt; exopod broad, truncate distally, with distolateral tooth poorly marked; adjacent spiniform seta well developed, reaching beyond distal margin of exopod; diaeresis not distinct; endopod broadly ovate, about same length as exopod; distal area of both exopod and endopod with fields of stiff setae, in addition to marginal setae (Fig. 4E, F).
Gill-exopod formula: 5 pleurobranchs (above bases of P1–5); 0 podobranchs; 1 arthrobranch (at base of Mxp3); 1 mastigobranch = strap-like epipod (on coxa of Mxp3); 0 setobranchs; 3 exopods (on Mxp1–3).
Colour in life. Unknown.
Distribution. Western Pacific: presently known with certainty only from type locality off south-eastern Taiwan; possibly also in the Coral Sea off eastern Australia (Bruce 1988; see below).
Ecology. The holotype was dredged from a depth of 301–356 m, without any further field notes, e.g. mentioning a possible association with hexactinellid sponges. The male from the Coral Sea reported by Bruce (1988) as B. anomalus was found inside a hexactinellid sponge brought up from a depth of 360 m.
Etymology. The new species is named after our colleague Dr. Tin-Yam Chan (National Taiwan Ocean University) for his immense contribution to decapod taxonomy, especially deep-water shrimps and lobsters.
Remarks. Bruce (1988) noted several important differences between the female holotype and the non-type male of Bannereus anomalus, which was the reason why the latter specimen was not given the paratype status. According to the author, “these differences appear sufficient to suggest that the male may represent a species distinct from the female, but on account of its damaged and incomplete nature, this cannot be stated with certainty”. Indeed, the differences between the female holotype and the non-type male appear to be rather significant. These differences include (i) the shape of the frontal margins of the carapace, rounded in the female vs. with a blunt rostral projection in the male (Bruce 1988: fig. 2B, E); (ii) the absence of a strap-like epipod on the third maxilliped coxa in the female (not illustrated) vs. its presence in the male (Bruce 1988: fig. 3J); (iii) the minor chela palm with bumps in the female vs. smooth in the single male chela (Bruce 1988: fig. 4G, H, mind a series of errors in the figure legend and in the text, e.g. confusion between the female and male minor cheliped or the cheliped accidentally called “minor second pereiopod”); (iv) the cheliped meri unarmed in the female (Bruce 1988: fig. 4G) vs. armed with about 10 spiniform setae on the mesioventral margin of the single male cheliped (described as “ventrally spinose merus”, but not illustrated); (v) the fifth pereiopod merus and ischium unarmed in the female (not illustrated, but generally similar to those of the third pereiopod, Bruce 1988: fig. 5E) vs. armed with ventral spiniform setae (“spines”) in the male (Bruce 1988: fig. 5G, but see below); and (vi) the dactylus of the ambulatory (third to fifth) pereiopods stout, with single terminal unguis, with corpus armed with five to six small teeth on the ventral margin and one to two dorsal spinules at the base of the terminal unguis (Bruce 1988: fig. 6A, B), in marked contrast to the noticeably slenderer dactylus of the male, with its terminal unguis bifurcated (with a stout ventral tooth), the corpus armed with only two teeth on the ventral margin and without dorsal spinules at the base of the terminal unguis (Bruce 1988: figs. 5H, 6C).
The above-listed differences, especially those involving the chelipeds, ambulatory pereiopods and epipod, are significant, strongly supporting Bruce’s (1988) suspicions that the male does not belong to the same species as the female holotype of B. anomalus. The main problem of Bruce’s (1988) description lies in the fact that the accompanying illustrations were made from both specimens (see synonymy above). Therefore, all comparisons between B. chani sp. nov. and B. anomalus refer only to the female holotype of B. anomalus (Bruce 1988: figs. 1, 2A–C, 4A–F, 5A, E, F, 6A, B) which was examined by the senior author in 2001, as well as a series of specimens from New Caledonia deposited in the MNNH. The latter include a complete female specimen collected relatively recently (in 2016), which corresponds particularly well to the holotype (see under comparative material above).
The differences between B. chani sp. nov. and B. anomalus are essentially the same as between Bruce’s male specimen and the holotype of the type species: the presence/absence of a blunt rostral projection [character (i) above]; the presence/absence of a strap-like epipod on the third maxilliped coxa [character (ii)]; the merus of at least one of the chelipeds armed with a row of spiniform setae or unarmed [character (iv)]; and obvious differences in the proportions of the dactyli of the third to fifth pereiopods [character (vi)]. The afore-mentioned character (iii) can be added to this series as well, because the palm of the major chela is smooth, i.e. without bumps, in B. chani sp. nov. vs. with bumps in the holotype of B. anomalus; the only difference is that Bruce (1988) was comparing the minor chelae for this same feature. As to the character (v), Bruce’s (1988) tentative assignment of the detached walking leg illustrated in his figure 5G, H to the fifth pereiopod is not correct. In almost all alpheid shrimps, the fifth pereiopod has a grooming brush on the propodus, as illustrated for B. chani sp. nov. (Fig. 3G). The walking leg of the male specimen in Bruce (1988) appears to be the fourth pereiopod, based on its general proportions and armature. Nevertheless, the holotype of B. chani sp. nov. clearly differs from the holotype of B. anomalus in the ischium and merus of the third pereiopod being armed with spiniform setae (one or two on the ischium and one on the merus, Fig. 3A, C). In B. anomalus, both of these articles are unarmed (Bruce 1988: fig. 5E).
In summary, multiple lines of evidence suggest that Bruce’s (1988) non-type male specimen may indeed belong to the same taxon as the species described herein as B. chani sp. nov., which differs from B. anomalus in at least six morphological details. If this hypothesis is eventually confirmed, it would imply that B. chani sp. nov. is a widely distributed western Pacific deep-water alpheid shrimp, ranging from Taiwan to north-eastern Australia. However, the general scarcity of the material of Bannereus precludes us from making more firm conclusions at this stage. With regard to B. anomalus, this species is presently known only from a few localities in the Coral Sea off Queensland, Australia (Bruce 1988), and off New Caledonia (present study, see Comparative material).
description: Published as part of Anker, Arthur & Pachelle, Paulo P. G., 2020, Description of a second deep-water species in the alpheid shrimp genus Bannereus Bruce, 1988 (Malacostraca: Caridea), pp. 133-142 in Zootaxa 4894 (1) on pages 136-141, DOI: 10.11646/zootaxa.4894.1.8, http://zenodo.org/record/4315588