Bathypalaemonella pandaloides
Creators: name: Komai, Tomoyuki
name: Tsuchida, Shinji
name: Fujiwara, Yoshihiro
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Bathypalaemonellidae
Bathypalaemonella
Bathypalaemonella pandaloides

description: Bathypalaemonella pandaloides (Rathbun, 1906)
[New Japanese name: Madara-shinkai-tenaga-ebi]
(Figs. 1–5)
Palaemon pandaloides Rathbun, 1906: 924, fig. 73, pl. 22, fig. 4.
Leander pandaloides.— Kemp 1925: 290.
Bathypalaemonella pandaloides.— Holthuis 1949: 517, fig. 43.— De Grave & Fransen 2011: 306.
? Bathypalaemonella pandaloides.— Cleva 2001: 765, figs. 4, 10C.— Poupin 2010: 36 (list). See “Remarks”.
Material examined. JAMSTEC No. 106771 1 male (cl 10.0 mm), KM20-10 C, KM ROV dive #132, Ritto Seamount, 21°48.69’N, 142°02.67’E, 657 m, 8 December 2020, suction sampler, associated with antipatharian coral Leiopathes sp.
Description of newly collected specimen. Body (Fig. 1) moderately slender for genus, slightly compressed laterally; integument moderately firm, surface generally glabrous, but dorsally with 2 pairs of tufts of thin, fragile setae on carapace dorsum (Fig. 2A) and 1 pair of tuft of similar setae on pleomere 1 tergum (Fig. 2C).
Rostrum (Figs. 2A; 5A) elongate (1.6 times as long as carapace), noticeably curved dorsally, far overreaching distal margin of antennal scaphocerite; dorsal margin armed with 15 basally articulated, narrowly spaced teeth, including 11 on rostrum proper (anteriormost tooth located at 0.4 rostral length, and then anterior 0.6 leaving unarmed) and 4 postrostral (posteriormost tooth located at 0.2 of carapace length), and 1 small fixed tooth near apex; ventral blade narrow, deepest at proximal 0.4 length, margin serrated with 13 teeth decreasing in size distally; lateral carina obsolete. Carapace (Figs. 2A, B) with low postrostral ridge extending to midlength of carapace; orbital margin evenly concave; suborbital lobe small but distinct, rounded; antennal spine small, well exceeding beyond suborbital lobe; branchiostegal spine marginal, slightly smaller than antennal spine, margin between antennal and branchiostegal spines concave; pterygostomial margin rounded, unarmed; anterolateral margin between antennal and pterygostomial spines slightly sinuous; shallow depression present on hepatic region.
Pleon (Fig. 2C) with pleura 1–5 all rounded, unarmed. Pleomere 2 tergum with faint transverse groove anteriorly. Pleomere tergum 3 gently produced posterodorsal margin. Pleomere 6 1.8 times as long as pleomere 5, 2.0 times as long as high, unarmed on posteroventral margin; posterolateral process terminating in small spine. Telson (Fig. 2D, E) 1.2 times as long as pleomere 6, 4.1 times as long as basal width, armed with 2 pairs of small dorsolateral spiniform setae (anterior pair located at midlength of telson, posterior pair at 0.8 length); posterior margin rounded, with 4 pairs of unequal spiniform setae (second pair strongest).
Eye (Fig. 2A, B) subpyriform; cornea darkly pigmented, its maximum width 0.16 of carapace length; ocellus absent. Eyestalk cup-shaped.
Antennular peduncle (Fig. 2A, B) reaching midlength of antennal scaphocerite. Basal article longer than distal two articles combined; stylocerite tapering and terminating in spine, reaching distal margin of basal article, directed anterolaterally, mesial margin sinuous. Penultimate and ultimate articles subcylindrical, penultimate article 1.5 times as long as wide (measured along lateral margin). Lateral flagellum with thickened aesthetasc-bearing portion about 0.8 times as long as carapace; mesial flagellum distinctly slender than lateral flagellum.
Antenna (Fig. 2A, B, F) with basicerite stout, bearing small ventrolateral distal spine. Carpocerite subcylindrical, not reaching mid-length of scaphocerite. Scaphocerite 0.8 times as long as carapace and about 6 times as long as greatest width, widest at proximal one-fourth; lateral margin slightly concave; distolateral tooth falling slightly short of distal margin of well-produced, rounded blade. Flagellum well developed, slightly shorter than total body length.
Mouthparts not dissected.
Maxilliped 3 endopod (Fig. 3A, B) slender, not reaching midlength of antennal scaphocerite. Ultimate article gradually tapering to blunt apex, subequal in length to penultimate article (= carpus); mesial face with numerous transverse rows of stiff setae. Penultimate article subcylindrical, with row of sparse setae on mesial face. Antepenultimate article slightly tapering, gently bowed proximally in dorsal view, with tiny spiniform seta at ventrolateral distal angle; mesial margin with row of setae. Exopod well developed, flexible, not reaching distal end of antepenultimate article. Coxa stout, with small lateral process terminating in acute tip, devoid of strap-like epipod (Fig. 5B).
Pereopod 1 (Figs. 3C; 5C) slender, reaching midlength of scaphocerite by tip of chela. Chela 0.5 times as long as carpus, 7 times as long as wide; palm subcylindrical, 5 times as long as wide, with patch of stiff setae on flexor proximal portion, consisting of grooming apparatus together with setal cluster on flexor distal portion of carpus; dactylus 0.5 times as long as palm, tip concealed by tuft of stiff setae; fixed finger also with distal tuft of setae. Carpus widened distally, 9.5 times as long as greatest width. Merus 0.7 times as long as carpus dorsal margin; articulation to ischium nearly horizontal. Ischium 0.9 times as long as merus dorsal margin, with row of short setae ventrally.
Pereopods 2 grossly unequal and markedly dissimilar. Left major pereopod 2 (Fig. 4A–D) overreaching scaphocerite by length of chela and carpus. Chela relatively slender, 1.3 times as long as carapace, 7.3 times as long as greatest depth across midlength. Dactylus slightly directed inward, approximately 0.4 times as long as palm, 3.5 times as long as greatest breadth across level of distal one-third; extensor to distal margin keeled, distal margin broadly rounded in outline, with few setae; mesial surface shallowly concave; lateral surface slightly convex; occlusal margin nearly straight, not keeled or sharply edged. Palm fairly compressed laterally, gently narrowing proximally; lateral surface with shallow depression and longitudinal patch of fine setae near base of fixed finger, followed by short longitudinal groove along flexor margin; extensor surface flattened, faintly convex in general outline in lateral view; flexor margin distinctly carinate, smooth, faintly sinuous, forming low crest on base of fixed finger; mesial surface slightly sulcate along flexor margin to accommodate merus when cheliped flexed; fixed finger strongly hooked distally, with 3 small blunt teeth on proximal half of occlusal margin. Carpus slightly shorter than merus, slightly widened distally, 5 times as long as distal width; Merus linear, 6.5 times as long as distal width; ventral surface shallowly grooved to accommodate carpus when cheliped flexed. Ischium also linear, as wide as merus, approximately twice as long as merus, ventral margin with row of sparse short setae. Basis short, unarmed. Coxa very robust, without patch of setae on ventral surface.
Right minor second pereopod (Figs. 3D; 5D) overreaching scaphocerite by length of chela. Chela slender, halflength of carpus, 7.6 times as long as wide, linear; palm oval in cross section, 5 times as long as wide; dactylus 0.5 times as long as palm, slightly curved, terminating in acute tip, occlusal margin entire; fixed finger straight, with tufts of short setae, extending onto palm, on flexor margin. Carpus elongate, slightly widened distally, 15 times as long as distal width. Merus obliquely articulated with ischium, 0.9 times as long as carpus, 15 times as long as distal width. Ischium 0.7 times as long as merus, with sparse setae ventrally. Basis short, without special features. Coxa without patch of setae ventrally.
Pereopods 3–5 moderately slender, generally similar. Pereopod 3 (Figs. 3E; 5E, F) not reaching distal margin of scaphocerite. Dactylus slightly less than 0.2 times as long as propodus, partially obscured by terminal setae on propodus, strongly curved; unguis strong; flexor surface bearing 2 pairs of accessory spiniform setae, distal pair much stronger than proximal pair, arising slightly proximal to base of unguis. Propodus extensor surface with sparse long setae in distal 0.3, flexor surface with prominent tufts of setae in distal 0.3. Carpus subequal in length to propodus, slightly widened distally, unarmed. Merus 13.5 times as long as wide, with 1 strong, subdistal spiniform seta on lateral surface. Ischium approximately half-length of merus, unarmed. Basis and coxa without special features.
Pereopods 4 (Figs. 3F; 5G) and 5 (Figs. 3G; 5H) very similar to pereopod 3.
Branchial formula including pleurobranchs on thoracomeres 4–8, arthrobranchs on thoracopod 3–4 (maxilliped 3 and pereopods 1–4) and podobranch on maxilliped 2; epipods only on maxilliped 1 and 2; exopods on maxilliped 1–3, no exopod on pereopods.
Male pleopod 1 endopod (Fig. 5I) flattened, with prominent, rounded lobe arising from proximal 0.3 length of mesial margin; mesial margin distal to lobe faintly concave, with row of numerous minute, hooked setae, mesial margin proximal to lobe slightly convex, with row of setae; distal margin rounded; lateral margin nearly straight, with row of setae in proximal 0.6. Male pleopod 2 with appendix masculina slightly longer than appendix interna (Fig. 5J), bearing numerous stiff setae on distal portion and mesial face.
Uropod (Fig. 2E, D) with protopod posterolateral angle produced into acute tooth. Exopod with lateral margin slightly convex, bearing minute spiniform seta just mesial to base of small posterolateral spine; diaeresis distinct. Endopod slightly longer than exopod, falling slightly short of posterior margin of telson, with some transverse rows of short setae anteriorly.
Coloration in life. Carapace and pleon mottled with red and pink (Fig. 1); rostrum red generally except for white distal part; telson and uropods pale; antennular peduncle pale pink with scattered dots, flagella pale; antennal scaphocerite reddish in distal half, much paler in proximal half; major pereopod 2 generally light orange-red, more intense on fingers; maxilliped 3 and other pereopods generally pinkish, darker in distal parts of propodi and ischia of pereopods 3–5; protopods of pleopods 1–5 reddish, rami paler.
Distribution. Heretofore known with certainty only from Hawaii, at depths of 950 m (see “Remarks”). The present specimen greatly extends the geographical range of the species to the northwestern Pacific.
Habitat. The present specimen was collected by a suction sampler from a colony of Leiopathes sp. (Cnidaria: Octocoralia: Antipatharia) (Fig. 6), suggesting a symbiotic association of the shrimp with the octocoral, although video record did not depict the shrimp. In fact, the association with octocorals has been reported for congeneric species, as mentioned above.
Remarks. Bathypalaemonella pandaloides was originally described on the basis of a heterosexual pair of specimens from vicinity of Kauai Island, Hawaii, at depth of 528 fathoms (= 950 m) (Rathbun 1906, as Palaemon). The original description is brief, accompanied only by a figure of the left pereopod 2 (fig. 73) and a black-white photograph of a habitus (pl. 22, fig. 4). In his key to species of the genus Palaemon (as Leander), Kemp (1925) inserted Rathbun’s (1906) taxon under the name Leander pandaloides without examining specimens. Holthuis (1949) reexamined the two type specimens (syntypes), reassigning the species to Bathypalaemonella. Chace (1997) stated that he examined the type specimens, but no further information was provided. Cleva (2001) reported one specimen he identified with B. pandaloides, collected from the Marquesas Islands, French Polynesia, in comparison with the type specimens.
The present specimen agrees generally with the redescription of the two type specimens by Holthuis (1949), particularly in the following diagnostic features: rostrum elongate (distinctly longer than carapace), far overreaching distal margin of antennal scaphocerite, armed ventrally with 10 or more teeth; telson with four pairs of spiniform setae on posterior margin; pereopods 3–5 dactyli each armed with less than 3 pairs of accessory spiniform setae on flexor margin. Holthuis (1949) illustrated the dorsal rostral series as if they are fixed, but later, it was clarified that those rostral dorsal teeth are all basally articulated (Cleva 2001). The dactyli of pereopods 3–5 are each armed with two pairs of spiniform setae on the flexor surfaces in our specimen, whereas Holthuis (1949) noted that there was only one pair of flexor spiniform setae on those dactyli in the type specimens, which was confirmed by Cleva (2001). The posterior margin of the telson was said to be “truncate” by Holthuis (1949), but in our specimen, it is roundly truncate (Fig. 2E). In addition, the mesial lobe of the pleopod 1 endopod seems to be better developed in our specimen than one of the two type specimens (Fig. 5I versus Holthuis 1949: fig. 43i). These differences are minor, and for the time being, we regard them as intraspecific variation.
As noted by Cleva (2001), his specimen from French Polynesia differs from the two type specimens and the present specimen in the more slender and longer pereopods 3–5 (cf. Cleva 2001: fig. 10C). The living colouration is also different between our specimen (Fig. 1) and the specimen reported by Cleva (2001: fig. 10C): the body is mottled with red-orange in our specimen, but in contrast, in Cleva’s (2001) specimen, the body is generally reddish, of which the pleon is obscurely banded. It is likely that Cleva’s (2001) specimen might represent a species other than B. pandaloides.
Bathypalaemonella pandaloides appears close to B. zimmeri in the elongate rostrum, being noticeably curved dorsally and distinctly longer than the carapace, the presence of 10 or more ventral rostral teeth and the entire, unarmed flexor margin of the pereopod 2 palm (cf. Balss 1914, 1925). In the other six congeneric species, the rostrum is subequal to or shorter than the carapace, with at most six ventral teeth (Zarenkov 1968; Pequegnat 1970; Wicksten & Mendéz 1983; Komai 1995; Cleva 2001; Cardoso 2010). Bathypalaemonella hayashii and B. serratipalma are readily distinguished from the other congeneric species in the possession of a row of tubercles on the flexor margin of the major pereopod 2 palm. In addition, the major cheliped 2 carpus is relatively slender in B. pandaloides, B. serratipalma, B. texana and B. zimmeri than in B. adenensis, B. hayashii and B. delsolari (cf. Balss 1925; Bruce 1966; Pequegnat 1970; Wicksten & Mendéz 1983; Komai 1995; Cleva 2001).
Bathypalaemonella zimmeri is represented only by the female holotype from off Somalia, western Indian Ocean, at depth of 1079 m (Balss 1914, 1925). As already noted by previous workers (Bruce 1966; Wicksten & Mendéz 1983; Cleva 2001; Cardoso 2010), B. pandaloides differs from B. zimmeri in having fewer flexor spiniform setae on the pereopods 3–5 dactyli (one or two pairs versus four pairs). In addition, the distal blade of the antennal scaphocerite seems to be less produced in B. pandaloides than in B. zimmeri (Fig. 2B, F versus Balss 1925: fig. 41). Otherwise, the two species are very similar for each other, as far as compared with the description by Balss (1925).
Five COI sequences attributed to Bathypalaemonella taxa, including three sequences referred to B. serratipalma and two referred to unidentified taxa, were available in the GenBank database (Table 1). We sequenced 658 bp of the barcoding region of the partial COI gene from our specimen of B. pandaloides. K2P divergence among the six sequences is 13.0–27.3%, and that between B. pandaloides and the other taxa is 23.9–27.3% (Table 2). There is no doubt that B. pandaloides is distinct from the other taxa registered in the GenBank database (cf. Lefébure et al. 2006). The two sequences referred to Bathypalaemonella sp. are identical (Table 2), clearly indicating that the voucher specimens represent a same species. On the other hand, it is obvious that two species are represented under B. serratipalma (the genetic divergence between KP759387 and KP759385 - KP759386 is 13.2%; Table 2), although the three voucher specimens all came from New Caledonia. In addition, B. serratipalma is the sole species of Bathypalaemonella recorded from both Pacific and Atlantic oceans. Reassessment of B. serratipalma based on an integrative approach would be advisable.
Four 16S sequences attributed to Bathypalaemonella, including sequences of B. hayashii, B. serratipalma, and two referred to unidentified species, were available in the GenBank database (Table 3). We sequenced 537 bp of the partial segment of 16S from the present specimen of B. pandaloides. K2P divergence among the five sequences is 5.5–10.9% (Table 3), suggesting that those sequences represent five species.
description: Published as part of Komai, Tomoyuki, Tsuchida, Shinji & Fujiwara, Yoshihiro, 2022, New record of a rarely collected caridean shrimp Bathypalaemonella pandaloides (Rathbun, 1906) (Decapoda: Bathypalaemonellidae) from the West Mariana Ridge, northwestern Pacific, pp. 272-284 in Zootaxa 5129 (2) on pages 274-282, DOI: 10.11646/zootaxa.5129.2.7, http://zenodo.org/record/6500958