Bresilia gibbosa, Komai, Tomoyuki & Yamada, Yusuke, 2010

Komai, Tomoyuki & Yamada, Yusuke, 2010, A new species of the rare caridean genus Bresilia Calman (Crustacea: Decapoda: Bresiliidae) from the Ryukyu Islands, Japan, representing a family new to the North Pacific marine fauna, Zootaxa 2450, pp. 41-52 : 42-51

Bresilia gibbosa n. sp.

[new Japanese name: Manza-sekiyou-ebi] ( Figs. 1–5 )

Material examined. Holotype: ovigerous female (cl 1.6 mm), CBM-ZC 9868, Apo-gama Cave, Onna Village, Okinawa Island, Ryukyu Islands, 30 m, 28 January 2010, coll. Y. Yamada. Paratype: male (cl 1.3 mm), CBM-ZC 9869, same locality, 9 February 2010, coll. Y. Yamada.

Diagnosis. Body integument with numerous short to very short, transverse or obliquely transverse striae. Rostrum about 0.6 times as long as carapace, nearly straight or slightly curved dorsally, reaching distal margin of antennular peduncle; dorsal margin armed with 6 or 7 spines, including 2 on carapace, posterior 3 or 4 spines basally articulated, posteriormost spine located at about 0.2 of carapace length; ventral margin with 2 or 3 spines on distal 0.3. Carapace with pterygostomial margin angulate. Third abdominal tergite strongly produced, but not carinate. Fourth abdominal pleuron with small posteroventral spine, fifth pleuron with 2 posterolateral spines. Telson with 5 pairs of dorsolateral spines; posterior margin narrowly convex, with 2 unequal pairs of spines. Epistome with elongate, acute median process. Eye tapering distally, cornea narrower than eyestalk, distinctly faceted, lightly pigmented. Third segment of antennal peduncle without elongate seta. First maxilliped with well-developed exopodal flagellum. First pereopod with ischium bearing sharply pointed distoventral angle; palm with 1 spine at midlength of ventral margin, but without grooming setae. Second pereopod with tips of fingers bearing tuft of minute setae.

Description. Female holotype. Body ( Fig. 1 ) moderately slender, generally subcylindrical; integument not firm. Rostrum ( Fig. 2 A, B) slender, slightly widened at base, about 0.6 of carapace length, directed forward, nearly straight, reaching distal end of antennular peduncle; dorsal margin with 6 teeth, of them posterior 3 basally articulated, posteriormost one located at about 0.2 of carapace length; ventral margin linear, with 3 tiny teeth on distal 0.3; lateral carina sharp, merging into orbital margin. Carapace ( Fig. 1 ) with numerous, scattered, short transverse striae on surfaces; dorsal surface rounded, straight in lateral view, with few setae medially; orbital margin evenly concave; antennal tooth moderately strong, acuminate ( Fig. 2 A); pterygostomial margin rectangular, without tooth ( Fig. 2 A).

Thoracic sternum ( Fig. 2 C) very narrow; third sternite with sharp median tooth directed anteriorly; fourth sternite with short median carina; fifth sternite with submedian pair of small teeth; sixth and seventh each with pair of long, slender processes, those on sixth sternite acute, those on seventh terminally rounded; eighth with terminally blunt median process, slightly dilated and dorsoventrally flattened distally.

Abdomen ( Fig. 1 ) also with covering of short to very short, transverse or obliquely transverse striae; terga all rounded dorsally, but third tergite strongly produced posterodorsally, angular in lateral view; few setae on third tergite (setae missing). Pleura of anterior three somites broadly rounded, fourth pleuron with small, sharp posteroventral tooth, fifth pleuron with 2 small teeth posterolaterally. Sixth somite tapering posteriorly in lateral view, about 0.6 times as long as carapace, 1.8 times longer than fifth somite, and 1.3 times longer than proximal height; posterolateral process terminating in acute tooth; posteroventral tooth very small. Telson ( Fig. 2 G) about 1.5 times longer than sixth somite, tapering distally to narrowly convex posterior margin; dorsal surface nearly flat, with 6 pairs of lateral spines including 1 pair at posterolateral angle; posterior margin with 2 pairs of long, unequal spines (mesial pair shorter than lateral pair).

Epistome ( Fig. 2 D) with very long, slender median process, visible even in lateral view.

Eye ( Fig. 2 B) stout, weakly tapering to cornea; cornea small, well-faceted, but devoid of dark pigmentation; eyestalk with scattered transverse striae.

Antennular peduncle ( Fig. 2 B, D) reaching distal 0.2 of antennal scale. First segment with fringe of stiff setae directed dorsally or laterally; ventral surface slightly thickened mesially, unarmed; stylocerite terminating in sharp tooth, reaching distal margin of first segment. Distal two segments cylindrical, combined length shorter than first segment; third segment slightly shorter than second segment. Outer flagellum uniramous, consisting of about 10 articles, subequal in length to peduncle; inner flagellum subequal in length to outer flagellum, more slender.

Antennal peduncle ( Fig. 2 D) with stout basicerite bearing small ventrolateral and ventrodistal teeth. Third segment without prominent plumose seta. Carpocerite (fifth segment) cylindrical, reaching midlength of antennal scale. Antennal scale ( Fig. 2 B, D) elongate oval, about 0.6 times as long as carapace, about 1.8 times longer than wide; dorsal surface with scattered very short transverse striae; lateral margin slightly convex, terminating in small, acute distolateral spine; distal lamella strongly produced, far overreaching distolateral spine. Flagellum shorter than body (missing at time of examination).

Mandible ( Fig. 3 A) with broad incisor process bearing 9 closely set, acute teeth on mesial margin and 1 somewhat remote tooth at distomesial angle; molar process very slender, extending as far as incisor process, bearing row of microsopically minute setae distally; palp broad, 2-articulated, proximal article with 1 seta at outer angle; distal article subequal in length to proximal article, with several stiff setae on roundly truncate terminal margin. Maxillule ( Fig. 3 B) with moderately stout, short proximal endite bearing stiff setae distally; distal endite broadly oval, with double row of spiniform setae on mesial margin partially obscured by longer stiff setae; endopod divided in two unequal lobes terminally, mesial lobe very short, bearing apical bristle, lateral lobe elongate. Maxilla ( Fig. 3 C) with broad distal endite; proximal endite lost during dissection; endopod broad basally, but abruptly tapering distally at midlength, curved mesially; scaphognathite moderately broad, anterior lobe broadly rounded, posterior lobe rounded, not particularly elongate, bearing some greatly elongate setae posteriorly. First maxilliped ( Fig. 3 D) with endites apparently fused; endopod moderately slender, rather abruptly tapering distally at about midlength, reaching base of exopod; exopod with moderately broad caridean lobe and well-developed flagellum; epipod large, faintly bilobed. Second maxilliped ( Fig. 3 E) with endopod sub-pediform; coxa with small epipod lacking podobranch; basis and ischium incompletely fused (suture still discernible); merus with convex mesial margin; carpus short, but not cup-like; propodus with stiff setae on mesial margin; articulation between propodus and dactylus transverse, not oblique; dactylus subequal in length to propodus, rounded terminally, bearing short stiff setae distomesially. Third maxilliped ( Fig. 4 A) slender, reaching distal margin of antennal scale, consisting of 4 segments; coxa with small, papilla-like epipod ( Fig. 4 B); antepenultimate segment longest, sinuously curved in dorsal view, with 1 slender spiniform seta near ventrolateral angle; ultimate segment about 1.3 times longer than penultimate segment, slightly tapering distally to blunt tip, with sparse tufts of stiff setae and 2 long subterminal setae on ventral (flexor) margin ( Fig. 2 E); exopod flagellum-like, falling short of distal margin of antepenultimate segment, bearing terminal tuft of setae.

First pereopod ( Figs. 1 , 4 C–E) overreaching antennal scale by about half length of chela; articulation between basis and ischium distinct; ischium widened distally, distoventral angle produced, terminating in small tooth; merus slightly widened distally, dorsodistal margin produced in strong tooth, ventral margin with distinct notch proximally adjacent to articulation to ischium; carpus short, cup-like, dorsal surface with 1 subterminal spine, ventral surface with 1 spine located at midlength, dorsodistal and ventrolateral distal angles produced in strong teeth, distomesial margin with 1 prominent triangular process; chela about 0.8 times as long as carapace; palm oval in cross section, slightly increasing in depth distally, armed with 1 long spine at midlength of ventral margin; fingers somewhat deflexed, forming deep concavity on outer side ( Fig. 4 E), terminating in acute tips; cutting edge of fixed finger bordered by thin chitinous plate; inner side of chitinous plate with fossae to accommodate chitinous spines on cutting edge of dactylus; dactylus curving, about 0.6 times as long as palm, cutting edge pectinate with row of small chitinous spines; exopod flagellum-like, overreaching distal margin of ischium. Second pereopod ( Fig. 4 F, G) slender, overreaching antennal scale by half length of chela; ischium with 3 spines on lateral face; merus subequal in length to ischium, with row of 3 spines on lateral surface; carpus about 0.4 times as long as chela, with tiny distolateral spine; chela slightly arcuate in lateral view; fixed finger very slightly deflexed in extensor view, with sparse microscopically minute spinules on cutting edge, tipped by tuft of minute setae ( Fig. 2 F); dactylus slightly shorter than palm, tapering to acute tip, slightly curving in lateral view, tipped by tuft of minute setae, cutting edge with row of microscopically minute spinules ( Fig. 2 F); exopod flagellum-like, reaching to distal margin of ischium, with terminal tuft of setae. Third to fifth pereopods lacking exopod. Third pereopod ( Fig. 4 H, I) falling short of distal margin of antennal scale; ischium with 1 spine on lateral surface at midlength; merus longer than ischium, unarmed; carpus about 0.3 times as long as propodus; propodus with few setae and few spinules on flexor margin (distalmost one located at distal margin); dactylus slightly curving, 0.25 times as long as propodus, terminating in sharp unguis, bearing 5 accessory spinules over entire length of flexor margin. Fourth pereopod ( Fig. 4 J, K) with ischium bearing 2 spines on lateral surface, otherwise similar to third pereopod. Fifth pereopod ( Fig. 4 L, M) with ischium unarmed; propodus with row of long setae on dorsal (extensor) margin.

Thoracis somites 1 2 3 4 5 6 7 8

Maxillipeds Pereopods

Appendages 1 2 3 1 2 3 4 5 Pleurobranchs 0 0 0 1 1 1 1 0 Arthrobranchs 0 0 0 0 0 0 0 0 Podobranchs 0 0 0 0 0 0 0 0 Epipods 1 1 r 0 0 0 0 0 Exopods 1 1 1 1 1 0 0 0

Gill formula summarized in Table 1. Pleurobranch on seventh thoracic somite very large, but other pleurobranchs greatly diminishing in size anteriorly.

Pleopods without distinctive feature. Uropod ( Fig. 2 G) falling short of tip of telson; endopod slender, tapering distally, with row of stiff setae directed laterally on lateral margin anterior to midlength; exopod slightly shorter than endopod, not tapering distally, bearing sharp posterolateral spine and 1 slender spine just mesial to posterolateral spine, distal lamella rounded; protopod sharply pointed posterolaterally.

Eggs about 0.4 mm in diameter (about 0.25 of carapace length); number not precisely counted, but about 20.

Male paratype. Generally similar to female holotype. Rostrum with 7 teeth on dorsal margin including 2 on carapace, posterior 4 basally articulated; ventral margin with 3 small teeth. Dactyli of third to fifth pereopods each with 5 accessory spinules as in holotype ( Fig. 3 F). Endopod of first pleopod ( Fig. 3 G) tapering distally to rather slender distal part; lateral margin strongly sinuous, with 3 simple stiff setae at around midlength; mesial margin also sinuous, with few adhesive hooks distally. Second pleopod with endopod ( Fig. 3 H) bearing sparse setae marginally; appendix masculina distinctly longer than appendix interna, bearing 2 setulose elongate setae apically and 3 simple spiniform setae directed outward on distal half of dorsal surface; 1 spiniform seta proximal to base of appendices interna and masculina.

TABLE 2. Comparison among five speccies of the Bresilia antipodarum group.

Characters/species B. gibossa n. sp. B. antipodarum B. briankensleyi B. plumifera B. saldanhai

Rostrum

Extension reaching distal margin reaching nearly to reaching nearly not reaching distal reaching to distal margin of of antennular distal margin of to distal end of margin of first second segment of antennular peduncle first segment of antennular segment of peduncle antennular peduncle antennular

peduncle peduncle

Armature on with 6 or 7 teeth, with 9 small teeth, 8 small teeth, all 4 small teeth, all 10-13 small teeth, all fixed, 1 on

dorsal margin posterior 3 or 4 all fixed, none on fixed, none on fixed, 1 on carapace basally articulated, 2 carapace carapace carapace

on carapace

Pterygostromial angular with sharp tooth with sharp tooth with sharp tooth with sharp tooth

angle of carapace

Abdomen

Third tergite non-carinate carinate carinate carinate non-carinate

Fourth pleuron with posteroventral with rounded rounded with posteroventral tooth tooth posteroventral

tooth

Fifth pleuron with 2 teeth with with with with 2 teeth posteriorly posteriorly posteroventral ponsteroventral ponsteroventral tooth tooth tooth

Telson posterior narrowly convex angulate no information no information truncate

margin

Antennal peduncle third segment without third segment third segment third segment with third segment with elongate

elongate plumose seta without elongate without elongate elongate plumose plumose seta plumose seta plumose seta seta

Third maxilliped without elongate seta no information no information with elongate without elongate seta at at dorsodistal margin plumose seta at dorsodistal margin of of antepenultimate dorsodistal margin antepenultimate segment segment of antepenultimate segment

First pereopod

Ischium terminating in acute terminating in no information terminating in rounded, non-produced at

tooth distoventrally acute tooth acute tooth distoventral margin distoventrally distoventrally

Ventral surface of with only 1 long with 3 transverse no information with 3 transverse with 2 transverse rows of

palm movable spine located rows of grooming rows of grooming grooming setae and 1 movable at midlength setae setae and 1 spine located distal to midlength movable spine at midlength

Distribution Okinawa Island, Tasman Sea, Egyptian Red Tasman Sea, Madeira, northeast Atlantic

Ryukyus Australia and New Sea Australia

Caledonia

Depth range 30 m 770–830 m 750–753 m 133 m 15 m

Color in life. See Fig. 5 . Body whitish or transparent; cephalothorax reddish or orangish ventrally; third abdominal tergite with white patch and reddish brown spot laterally. Cornea of eye light yellowish gray. Antennular flagellum whitish. Antennal also whitish; flagellum generally brown, with narrow white bands. Pereopods generally transparent, but chela of first pereopod generally whitish; bases of third to fifth pereopods with tinge of reddish brown. Eggs yellow.

Size. Ovigerous female cl 1.6 mm; male cl 1.3 mm.

Distribution. Known only from Okinawa Island, Ryukyu Islands, Japan; found in marine cave at depth of 30 m.

Ecology. The two specimens were collected at about 5 m from the entrance of the cave. They were found under rocks on a substrate consisting mainly of coral rubble. When disturbed, the shrimp moved forward slowly. The holotype moved its first pereopods horizontally during brief observation in situ, although the function is unknown. Other fauna found in the same habitat included Acanthanas sp. (Caridea: Alpheidae ), Calaxius sp. (Axiidea: Axiidae ), Pylopaguropsis fimbriata McLaughlin and Haig, 1989 and P. speciosa McLaughlin and Haig, 1989 (Anomura: Paguridae ). It is unclear if the new species is endemic to cave environment, but the small cornea on the distally tapering eyestalk and the lack of dark pigments may be of suggestive that the new species prefers aphotic environment.

Remarks. Bresilia gibbosa sp. nov. is readily distinguished from other four species of the B. antipodarum group in the posterior three or four spines on the dorsal rostral series being movable and the angular pterygostomial angle of the carapace. In other four species, the dorsal rostral spines are all fixed; and the pterygostomial angle terminates in an acute tooth. Other differentiating characters are summarized in Table 2. Furthermore, Bresilia gibbosa is very similar to Bresilia sp. reported by Bruce (2005b), particularly in having three spines of the rostral dorsal series and an angulated pterygostomial margin of the carapace. Nevertheless, the present two specimens differs from the specimen reported by Bruce (2005b) in the lack of prominent setae on the dorsum of the carapace and abdomen, spinose pleura of the fourth and fifth somites and the possession of six pairs of dorsolateral spines on the telson, instead of two pairs. Nevertheless, Bruce (2005b) noted that his original drawings bore annotations suggesting re-examination of the pterygostomial angle and the posteroventral angles of the fourth and fifth abdominal pleura. It is difficult to further comment on the identity between the present specimens and the specimen reported by Bruce (2005b), because the whereabouts of Bruce’s specimen remains unknown.

The present new species has characteristic transverse striae on the body integument, but this character is not known in other species of Bresilia . Nevertheless, without staining, the transverse striae will be easily overlooked. It needs to be verified if the transverse striae are really absent in other congeneric species.

Previously, Bresilia was considered to be a deep-water genus, but the recent studies ( Bruce 1990b; Calado et al. 2004) have shown that the genus occurs in rather various environments: Bresilia plumifera was collected at sublittoral zone (133 m deep); B. saldanhai and the present new species occur in shallow water caves. Bresilia sp. of Bruce (2005b) was recorded at a reef edge of 27 m depth, although the habitat was not clearly indicated. There is little doubt that the genus is more widespread than we have suspected. One of the reasons of the rareness of the genus may be due to the small size and the free but cryptic habitats. The two specimens of the present new species were found to live under rocks, where collection is possible only by SCUBA divers. As mentioned above, this new species is the first species of Bresiliidae to be known from the North Pacific Ocean. It is clearly suggested that the cryptic macrobenthos fauna in shallow reefs in the tropics remains insufficiently sampled. There is no doubt that cooperation with skilful divers provides opportunities to better understand the diversity and ecology of the cryptic fauna.

Etymology. From the Latin gibbosus (= hump-backed) in reference to the strongly produced third abdominal tergite.

Figures

FIGURE 1. Bresilia gibbosa n. sp., holotype, ovigerous female (cl 1.6 mm), CBM-ZC 9868. Entire animal in lateral view. Scale bar: 1 mm.

FIGURE 2. Bresilia gibbosa n. sp., holotype, ovigerous female (cl 1.6 mm), CBM-ZC 9868. A, rostrum and anterior part of carapace, lateral view; B, rostrum, anterior part of carapace and cephalic appendages, dorsal view (setae partially omitted; distal part of outer flagellum of left antennule broken off); C, third to eighth thoracic sternites, ventral view (left pereopods and right fourth and fifth pereopods removed); D, epistome and left antennae, ventral view (setae and antennular flagella omitted; antennal flagellum missing); E, close up of distal part of ultimate segment of third maxilliped, lateral view; F, close up of fingers of second pereopod, lateral view; G, telson and left uropod, dorsal view. Scale bars: 0.5 mm for A – D, G; 0.25 mm for E, F.

FIGURE 3. Bresilia gibbosa n. sp. A – E, holotype, ovigerous female (cl 1.6 mm), CBM-ZC 9868; F – H, paratype, male (cl 1.3 mm), CBM-ZC 9869. Left appendages. A, mandible, inner view; B, maxillule, outer view; C, maxilla, outer view (proximal endite broken off); D, first maxilliped, outer view; E, second maxilliped, outer view; F, dactylus and distal part of propodus of third pereopod, lateral view; G, endopod of first pleopod, dorsal view; H, endopod and appendices internal and masculina of second pleopod, ventral view (setae on endopod omitted). Scale bars: 0.25 mm.

FIGURE 4. Bresilia gibbosa n. sp., holotype, ovigerous female (cl 1.6 mm), CBM-ZC 9868. Left appendages. A, third maxilliped, lateral view; B, same, proximal part of antepenultimate segment of endopod and exopod, dorsal view; C, first pereopod, lateral view; D, same, dorsomesial view; E, same, fingers, ventrolateral view; F, second pereopod, lateral view; G, same, chela, extensor view; H, third pereopod, lateral view; I, same, propodus and dactylus, lateral view; J, fourth pereopod, lateral view; K, same, propodus and dactylus, lateral view; L, fifth pereopod, lateral view; M, same, propodus and dactylus, lateral view. Scale bar: 0.5 mm.

FIGURE 5. Bresilia gibbosa n. sp., underwater photographs in situ, showing living animals. A, holotype, ovigerous female (cl 1.6 mm), CBM-ZC 9868; B, paratype, male (cl 1.3 mm), CBM-ZC 9869. Photography by Y. Yamada.