Batella praecipua De Grave, 2004

Ashrafi, Hossein, Ďuriš, Zdeněk & Anker, Arthur, 2022, The first complete specimen of the deep-water shrimp Batella praecipua De Grave 2004 (Crustacea: Decapoda: Alpheidae), Zootaxa 5092 (3), pp. 378-386 : 379-385

publication ID	https://doi.org/ 10.11646/zootaxa.5092.3.8
publication LSID	lsid:zoobank.org:pub:E1B0A723-B78B-47FB-9D2B-75F32C63C56E
DOI	https://doi.org/10.5281/zenodo.5910455
persistent identifier	https://treatment.plazi.org/id/105287B9-FFC7-4C01-80CB-DC525047E166
treatment provided by	Plazi
scientific name	Batella praecipua De Grave, 2004
status

Treatment

Batella praecipua De Grave, 2004 View in CoL

( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Batella praecipua De Grave 2004: 504 View in CoL , figs. 1–3. View Cited Treatment

Material examined. 1 ovigerous female (cl 4.9 mm), MNHN-IU-2017-2930, KANADEEP 1 sta. CP5022, Coral Sea , north of Bellona Plateau, 20°23’S – 158°43’E, depth: 370–380 m, 21.09.2017. GoogleMaps

Description (based solely on the KANADEEP 1 specimen, for original description see De Grave 2004). Smallsized alpheid shrimp. Carapace ( Fig. 1A–C View FIGURE 1 ) glabrous, with one small tubercle on mid-dorsal line, at about 0.35 of carapace length; pterygostomial angle bluntly protruding anteriorly; cardiac notch deep. Rostrum ( Fig. 1A, B View FIGURE 1 ) reduced to shallow, broadly rounded projection, slightly upturned in lateral view. Orbital hoods ( Fig. 1A View FIGURE 1 ) broadly rounded anteriorly, feebly projecting forwards as shallow bumps; surface between orbital hoods and post-rostral area slightly depressed.

Pleura of first to fifth pleonites rounded antero- and posteroventrally; sixth pleonite ( Fig. 1D, E View FIGURE 1 ) with blunt distolateral lobes flanking base of telson. Telson ( Fig. 1D, E View FIGURE 1 ) subrectangular; lateral margins broadly convex, slightly tapering distally; dorsal surface with two pairs of minute dorsal spiniform setae situated at about 0.6 and 0.8 of telson length, respectively, distal pair located closer to lateral margin; posterior margin slightly convex centrally, furnished with about 12 plumose setae, armed with two pairs of spiniform setae, mesial spiniform setae stouter and at least 2.5 times as long as lateral ones; distolateral angles of posterior margin bluntly projecting.

Eyes fully covered by carapace both dorsally and laterally; cornea somewhat reduced and depigmented.

Antennule ( Fig. 1B, C View FIGURE 1 ) with peduncle relatively stout; first article longest, its ventromesial surface unarmed; stylocerite slightly overreaching first article, with blunt tip; second article slightly wider than long; third article as long as second one, as long as wide; lateral flagellum biramous, with fused portion composed of two subdivisions; accessory ramus well-developed, without discernible subdivisions, with two tufts of aesthetascs present on or near apex.

Antenna ( Fig. 1B, C View FIGURE 1 ) with basicerite bearing stout subacute distoventral tooth, latter falling short of end of first article of antennular peduncle; scaphocerite broad, with lateral margins feebly convex and distolateral tooth rounded, reaching to end of antennular peduncle; blade broad, with anterior margin convex, noticeably overreaching distolateral tooth; carpocerite relatively slender, reaching to about 0.8 of scaphocerite length.

Mouthparts not dissected (see De Grave 2004 for description and illustrations). Third maxilliped ( Fig. 3A, B View FIGURE 3 ) with lateral plate of coxa feebly developed; antepenultimate article slender, slightly wider basally, about six times as long as wide, with one subdistal spiniform seta on ventromesial margin; penultimate article about 0.4 times as long as antepenultimate article, about four times as long as wide; ultimate article elongate, only slightly shorter than antepenultimate article, tapering distally, with numerous transverse rows of serrulate setae on dorsomesial surface, one stout subdistal spiniform seta on dorsal margin and three stout spiniform setae on apex; exopod well developed, about 0.6 times as long as long as antepenultimate article; arthrobranch absent

First pereiopods = chelipeds ( Fig. 2A–D View FIGURE 2 ) slightly unequal in size and somewhat asymmetrical, with left cheliped slightly larger than right one and with slightly different armature on finger cutting edges. Left cheliped ( Fig. 2A, B View FIGURE 2 ) with coxa bearing anteriorly pointing projection on ventromesial surface; ischium with oblique distal margin, about twice as long as wide; merus nearly three times as long as wide, nearly twice as long as ischium, slightly depressed both dorsally and ventrally; carpus cup-shaped, unarmed distally; palm robust, subcylindrical, smooth, about twice as long as high, about 1.5 times as long as merus; fingers about 0.3 length of palm, slightly turned ventrally from main axis of palm, with crossing tips and slightly gaping when closed; pollex with five broad, blunt, irregularly shaped teeth on cutting edge; dactylus moderately curved, with five blunt teeth, central tooth (third from either proximal or distal end) more triangular and much stronger than others. Right cheliped ( Fig. 2C, D View FIGURE 2 ) generally similar to left cheliped, slightly smaller and less robust; cutting edges of fingers with three to four blunt, irregularly shaped teeth.

Second pereiopod ( Fig. 3C View FIGURE 3 ) with all articles slender; ischium nearly five times as long as wide; merus slightly shorter than ischium, about 4.5 times as long as wide; carpus subequal to ischium in length, with five subarticles, proximal and distal segments subequal, twice longer than three subequal intermediate segments; palm slender, elongate, 0.7 times as long as carpus, about five times as long as own broadest part; fingers small, about 0.2 times as long as palm, with tufts of long serrulate setae forming conspicuous brush.

Third pereiopod ( Fig. 3D View FIGURE 3 ) with ischium more than twice as long as broad, with one spiniform seta on ventrolateral surface; merus relatively stout, slightly swollen, about 1.6 times as long as ischium, carpus much more slender than merus, about half-length of merus, slightly broadening distally, almost three times as long as distal width; propodus more slender than carpus, slightly shorter than merus, with seven small spinifrom setae along ventral margin and one distoventral pair of spiniform setae; dactylus simple, nearly 0.2 times as long as propodus, unguis demarcated, with minute serrations on distal third.

Fourth pereiopod ( Fig. 3E View FIGURE 3 ) generally similar to third pereiopod, slightly less robust; ischium with two spiniform setae on ventrolateral surface; propodus armed with nine short spiniform setae on ventral margin, in addition to distal pair of longer spiniform setae.

Fifth pereiopods missing in the present specimen [described as generally similar to third and fourth pereiopods, but more slender, by De Grave (2004)].

Uropod ( Fig. 1D, E View FIGURE 1 ) with protopod bearing two subacute teeth distally, lateral tooth slightly stronger than mesial one; exopod with distolateral margin terminating in blunt angle with stout spiniform seta, latter slightly surpassing distal margin of exopod; diaeresis shallowly U-shaped, lacking lateral tooth; endopod slightly overreaching exopod.

Colour in life unknown.

Gill-exopod formula: 5 pleurobranchs (P1–5); 0 arthrobranchs; 0 podobranchs; 2 finger- or sac-shaped epipods (Mxp1–2), 0 strap-like epipods (mastigobranchs), 0 setobranchs, 3 exopods (Mxp1–3).

GenBank accession number. MZ695832 View Materials for barcode fragment of MT-CO1; MZ700228 View Materials for partial fragment of 16S rRNA.

Distribution. South-West Pacific, presently known only from south-east off New Caledonia (east of the southern tip of the lagoon and south-west of Île des Pins) and Bellona Plateau in the Coral Sea mid-way between New Caledonia and Queensland, Australia ( De Grave 2004; present study).

Ecology. According to Bruce’s (1988) hypothesis, all members of the genus Batella are associates of glass sponges (Hexactinellida) (see also Anker & Pachelle 2020). As to the present specimen of B. praecipua , no association with a particular sponge was noted in the field, i.e. during the preservation of the trawled material. However, the trawl haul of the station CP5022, in which this alpheid shrimp was found, contained large dead coral blocks with sponges, among them several hexactinellid sponges ( Fig. 4 View FIGURE 4 ). The type material of B. praecipua was also found in association with “sponges”, most likely Hexactinellida ( De Grave 2004).

Remarks. This single ovigerous specimen collected during the KANADEEP 1 expedition corresponds very well with the original description of B. praecipua by De Grave (2004) and was collected in the same region, the Coral Sea between New Caledonia and Australia, and at a similar depth as the type material, e.g. close to 400 m.

The cardiac notch of the carapace of B. praecipua was described by De Grave (2004) as “shallow” and used as one of the differentiating characters of the species. However, both the present specimen and the holotype have a normally developed, i.e. fairly deep cardiac notch, thereby eliminating the “shallow cardiac notch” from the characters distinguishing B. praecipua from the other two species. The distoventral margin of the antepenultimate article of the third maxilliped was illustrated as unarmed by De Grave (2004: fig. 2B), whereas the present specimen and also the holotype possess a slender subdistal spiniform seta on the ventral margin of this article ( Fig. 3A View FIGURE 3 ). The ischia of the three last pereiopods were each described to be armed with two spiniform setae ( De Grave 2004: fig. 2G). However, only one such spiniform seta is present on the ventrolateral margin of the ischium of the third pereiopod in our specimen, in contrast to two spiniform setae present on the ischium of the fourth pereiopod, as in the type material. These differences are insignificant and represent either an expected intraspecific variation and/or slight inaccuracies in the original description of B. praecipua .

As discussed by De Grave (2004), B. praecipua can be easily distinguished from the two congeners, viz. B. parvimanus and B. leptocarpus , for instance, by the rostrum reduced to a broadly rounded projection (vs. acutely produced in the other two species), the absence of orbital teeth (vs. their presence in the other two species), and the three last pereiopods with monounguiculate dactyli (vs. biunguiculate in the other two species) (cf. Miya & Miyake 1968; Chace 1988). The previously unknown chelipeds of B. praecipua ( Fig. 2 View FIGURE 2 ) differ from those of B. parvimanus and B. leptocarpus mainly by the much shorter fingers of the chela, being approximately 0.3 length of the palm (vs. 0.5 length of the palm in B. leptocarpus and almost 0.7 length of the palm, at least for the dactylus, in B. parvimanus , see Chace 1988: figs. 17l, 18m). In addition, the second maxilliped bears a well-developed epipod in both the present specimen and in the holotype of B. praecipua , whereas the epipod was described as “rudimentary” in the holotype of B. bifurcata (now a junior synonym of B. parvimanus ) by Miya and Miyake (1968) and is clearly reduced in B. leptocarpus , judging from the illustrations in Chace (1988: fig. 17i).

Despite the fact that the mouthparts of Batella have been described and/or illustrated several times ( Miya 1984; Chace 1988; De Grave 2004), only Miya and Miyake (1968) included an arthrobranch at the base of the third maxilliped in the gill-exopod formula of B. bifurcata (= B. parvimanus ), illustrating a rudimentary arthrobranch in their fig. 3F. Both third maxillipeds of the present specimen of B. praecipua are in good condition (one of them still attached to the body, the other one detached) and neither of them possesses an arthrobranch. Therefore, the absence / presence of a small arthrobranch at the third maxilliped contributes to separate B. praecipua at least from B. parvimanus . However, if the presence of an arthrobranch at the third maxilliped is eventually also confirmed in B. leptocarpus , its absence in B. praecipua may represent yet another distinguishing feature between the latter species and its two previously described congeners.

Spence Bate’s (1888) original record of B. parvimanus from a depth of 15 m must be considered as questionable. Hexactinellid sponges are mainly found in deeper waters (200–6000 m), with only rare occurrences in shallow, scuba-accessible depths, for instance in the marine caves in the Mediterranean Sea and off British Columbia, Canada ( Van Soest et al. 2012). Since all three species of Batella seem to be associated with glass sponges and since all other records are from much deeper water (below 150 m), a labeling error (for instance, depth record) during or after the Challenger Expedition cannot be excluded.