Bresilia cinctus Komai & Kohtsuka 2017, n. sp.
Creators: name: Komai, Tomoyuki
name: Kohtsuka, Hisanori
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Bresiliidae
Bresilia
Bresilia cinctus

description: Bresilia cinctus n. sp.
[New Japanese name: Obimaki-sekiyou-ebi] Figs. 1–5
Material examined. Holotype: ovigerous female (cl 4.4 mm), Sagami Bay, SW of Jogashima, Miura Peninsula, 35°06.10’N, 139°34.25’E to 35°05.68’N, 139°34.06’E, 218–318 m, 10 January 2012, RV “ Rinkai-maru ”, dredge, coll. H. Kohtsuka, CBM-ZC 13987.
Diagnosis. Body integument soft, apparently without microscopic pits on surface. Rostrum 0.4 times as long as carapace, straight, reaching distal margin of article 1 of antennular peduncle; dorsal margin armed with 10 spines, including 2 postrostral, none basally articulated, postrostral spines located slightly posterior to rostral base; ventral margin with 1 minute spine at distal 0.25. Carapace with pterygostomial margin weakly produced, obtusely angulate. Pleon gibbous with tergite 3 somewhat elevated, but not carinate or cristate; pleuron 4 with minute posteroventral denticle; pleuron 5 with 1 posteroventral and 1 posterolateral spines. Epistome with short but prominent, acute median process. Eyestalk normal, directed anterolaterally, with cornea subequal in width to eyestalk, distinctly faceted, darkly pigmented. Article 3 of antennal peduncle without elongate seta. Maxilliped 1 with well-developed exopodal flagellum. Pereopod 1 with ischium bearing minute denticle at distoventral angle; merus unarmed on dorsodistal margin; palm with 1 spiniform seta at midlength of flexor margin; dactylus sinuous, longer than fixed finger, lateral occlusal margin with row of minute chitinous spines. Pereopod 2 fingers with minute setae on tips; ischium and merus with row of spiniform setae (4 in number on respective article).
Description. Female holotype. Body (Figs. 1; 2A, B) moderately slender, generally subcylindrical; integument soft but not membranous.
Rostrum (Figs. 2 A; 3A) slender, widened at base, 0.4 as long as carapace, directed forward, straight, reaching distal end of article 1 of antennular peduncle; dorsal margin with 10 spines over entire length, none basally articulated, 2 postrostral, posteriormost spine located slightly posterior to rostral base; ventral margin linear, with 1 tiny spine at distal 0.25; lateral carina sharp, merging into orbital margin. Carapace (Figs. 2 A, 3A) glabrous, apparently without microscopic pits on surface; low postrostral ridge extending to anterior 0.1 of carapace, remaining dorsum rounded; dorsal outline straight in lateral view; orbital margin evenly concave; suborbital angle produced in rounded lobe, strongly depressed (Fig. 3 B); antennal spine moderately strong, acuminate; pterygostomial margin produced as far as antennal spine, obtusely angulate (Fig. 2 A).
Thoracic sternum very narrow; sternite 3 with sharp median tooth directed anteriorly; sternite 4 with short median carina; sternite 5 with median pair of small teeth; sternites 6 and 7 each with pair of long, slender processes, those on sternite 6 acute, those on sternite 7 terminally rounded; sternite 8 with slender, terminally subacute median process.
Pleon (Fig. 2 B) glabrous; terga all rounded dorsally, tergite 3 fairly elevated, making pleon gibbous; no prominent setae on any tergite. Pleura of anterior three pleomeres rounded, pleuron 4 with minute posteroventral denticle, pleuron 5 with 1 small posteroventral and 1 posterolateral spines. Pleomere 6 0.7 times as long as carapace, twice longer than fifth somite, and approximately twice as long as high; posterolateral process terminating in tiny spine; posteroventral angle bluntly pointed, without spine. Telson damaged, most part missing.
Epistome (Fig. 3 C) with short but prominent, acute median process.
Eyestalk (Figs. 2 A; 3A) stout, subcylindrical; cornea moderately large, subequal in width and as long as eyestalk, well-faceted, with dark pigmentation.
Antennular peduncle (Figs. 2 A; 3A) reaching distal 0.2 of antennal scale. Article 1 not reaching midlength of antennal scale; ventral surface slightly thickened mesially, unarmed; stylocerite slender, tapering to acute tip, slightly diverging, reaching distal margin of article 1. Distal two articles cylindrical, combined length shorter than article 1; article 3 more than half length of article 2. Flagella damaged.
Antennal peduncle (Figs. 2 A; 3A, D) with stout basicerite bearing small ventrolateral and ventrodistal spines; dorsolateral distal angle also produced into small spine. Article 3 without prominent plumose seta. Carpocerite (article 5) slender, cylindrical, reaching to base of distolateral spine of antennal scale. Antennal scale (Fig. 3 A, D) elongate oval, 0.6 times as long as carapace, 2.7 times as long as wide; lateral margin very faintly concave, terminating in small, acute distolateral spine; distal lamella strongly produced, narrowing to rounded distal margin, far overreaching distolateral spine. Flagellum missing.
Mandible (Fig. 3 E) with broad incisor process bearing 5 closely set, acute teeth on mesial margin and 1 somewhat remote tooth at distomesial angle; molar process broken off; palp 2-articulated, distal article subequal slightly shorter than proximal article, with several short to long setae on roundly truncate terminal margin to outer margin. Maxillule (Fig. 3 F) with short proximal endite bearing stiff setae terminally; distal endite with double row of spiniform setae, partially obscured by short submarginal setae, on truncate mesial margin; endopod slender, arcuate, inner margin with slight shoulder and 2 subterminal stiff setae. Maxilla (Fig. 3 G) with broad distal endite divided into 2 lobes; proximal endite extending as far as distal endite; 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. Maxilliped 1 (Fig. 3 H) with distal endite broad, with slightly concave mesial margin; proximal endite narrow, roundly truncate; endopod moderately slender, rather abruptly tapering distally at about midlength, reaching base of exopodal flagellum; exopod with narrow caridean lobe and well-developed flagellum; epipod large, faintly bilobed. Maxilliped 2 (Fig. 3 I) with endopod sub-pediform; coxa with small, rounded epipod, lacking podobranch; basis and ischium completely fused; merus subcylindrical; sparse setae on mesial margin of basis-ischium fused article and merus; carpus short, subquadrate; propodus elongate; articulation between propodus and dactylus transverse, not oblique; dactylus slightly more than half-length of propodus, rounded terminally, bearing numerous setae on extensor surface to tip (setae on extensor surface erect). Maxilliped 3 (Figs. 4 A; 5A) endopod slender, reaching slightly beyond distal margin of antennal scale; coxa with small, papilla-like epipod; antepenultimate article longest, sinuously curved in dorsal view, with 1 slender spiniform seta near ventrolateral distal angle; penultimate article with transverse tracts of slender spiniform setae on mesial surface (Fig. 5 A); ultimate article 1.3 times as long as penultimate article, slightly tapering distally to obliquely truncate tip, with sparse tufts of stiff setae on mesial face and 2 long stiff setae on terminus; exopod flagellum-like, falling short of distal margin of antepenultimate article.
Pereopod 1 (Fig. 4 B) overreaching antennal scale by about half length of chela; articulation between basis and ischium distinct. Ischium slightly widened distally, distoventral angle with minute denticle. Merus fairly compressed laterally, not particularly widened distally, dorsodistal margin unarmed. Carpus short, cup-like, dorsolateral distal margin with 1 minute spiniform seta, ventrodistal margin also with 1 small spiniform seta; dorsomesial distal angle produced into rounded lobe (Fig. 5 B). Chela (Fig. 5 C) 0.75 times as long as carapace; palm oval in cross section, 3.3 times as long as central width, armed with 1 tiny spiniform seta at midlength of ventral margin, dorsodistal margin (articulation to dactylus) with minute spine; fingers somewhat deflexed, forming deep concavity on outer side (Fig. 5 D, E); fixed finger narrowly triangular, 2.4 times as long as basal width, terminating in subacute tip; occlusal margin medial, nearly straight, with line of slit-like fossae opposing dactylar teeth, each fossa with short, microscopic chitinous spinules on outer side (these spinules becoming distally directed toward distal). Dactylus slightly sinuous with recurved distal part, 0.9 times as long as palm, acute tip distinctly exceeding tip of fixed finger; main occlusal margin strongly medially situated, nearly straight, with row of closely spaced, acutely triangular, compressed chitinous teeth not extending to distal part, with distalmost teeth markedly smaller than proximal series; outer occlusal margin slightly sinuous, with row of spaced, minute subconical, chitinous spines decreasing in size distally. Grooming apparatus consisting of short, subdistal transverse row of stiff setae on carpus and 4 short transverse rows of short stiff setae on ventral proximal part of palm. Exopod well developed, flagellum-like, overreaching midlength of merus.
Pereopod 2 (Fig. 4 C, D; 5F) long and slender, overreaching antennal scale by length of chela. Ischium with 4 spiniform setae on lateral face ventrally. Merus distinctly longer than ischium, with row of 4 spiniform setae on distal half of lateral surface. Carpus approximately 5 times as long as distal width, slightly widened distally, unarmed. Chela gently arcuate; palm subcylindrical, 5.1 times as long as central width; fixed finger tipped by tuft of few minute stout setae, occlusal margin pectinated with row of minute, slender, chitinous spines. Dactylus 1.1 times as long as palm; tip with few minute stout setae; occlusal margin with row of minute chitinous spinules. Exopod broken off.
Pereopods 3–5 all missing (except for non-articulated, rod-like right pereopod 4 in process of regeneration). Gill formula summarized in Table 1. Pleurobranch on seventh thoracic somite large, but other pleurobranchs greatly diminishing in size anteriorly.
Thoracic 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 1 0 0 0 0 0 Exopods 1 1 1 1 b 0 0 0 Pleopods without distinctive feature. Uropod with protopod bearing small posterolateral spine; endopod slender, tapering distally; exopod slightly shorter than endopod, not tapering distally, bearing minute posterolateral spine and 1 slender spiniform seta, distinctly longer than posterolateral spine, just mesial to posterolateral spine, distal lamella rounded.
Eggs small, 1.1 mm x 0.9 mm.
Colour in life. Body (Fig. 1) generally orange, pleomere 3 with obliquely transverse white band running from posterior part of tergum to anterior part of pleuron. Pereopod 1 also orange; pereopod 2 translucent.
Size. Ovigerous female cl 4.4 mm.
Distribution. Known only from Sagami Bay, central Japan, at depths of 218– 318 m.
Remarks. The holotype is not intact: the telson is damaged, with the distal half missing; the antennular flagella are broken off; the antennal flagella are missing; right pereopods 1–3, 5 and left pereopods 3–5 are missing; the right pereopod 4 is in the process of regeneration, non-articulated, rod-like; the distal part of the left uropod is also damaged.
Important features in assessing the taxonomic position of Bresilia cinctus n. sp. are (1) the possession of 10 dorsal spines on the rostrum of which the posteriormost two are slightly postorbital; (2) the well-developed suborbital lobe of the carapace; (3) the obtusely angulate pterygostomial angle of the carapace; (4) the nonproduced and non-carinate tergum of the pleomere 3; and (5) the presence of an exopodal flagellum of the maxilliped 1. The second feature (the well developed suborbital lobe of the carapace) might be unique within the genus and has not been mentioned in the description of the previously known species (Calman 1896; Forest & Cals 1977; Bruce 1990a, 1990b, 2005b; Calado et al. 2004; Komai & Yamada 2010, 2011; Hendrickx 2014). The other features are shared particularly with B. rufioculus (cf. Komai & Yamada 2011). Nevertheless, the new species differs from B. rufioculus in many morphological aspects: (1) the rostrum is relatively shorter in B. cinctus n. sp. than in B. rufioculus (reaching only to the distal end of the article 1 of the antennular peduncle vs. overreaching the distal end of the article 2 of the antennular peduncle; (2) the suborbital lobe of the carapace is well developed in B. cinctus, but is absent in B. rufioculus; (3) the tergum of the pleomere 3 is more strongly elevated in B. cinctus n. sp. than in B. rufioculus (cf. Fig. 2 B vs. Komai & Yamada, 2011: fig. 1); (4) the eyestalk is directed anterolaterally with a well developed, darkly pigmented cornea in B. cinctus n. sp., vs. directed anteriorly with the cornea narrowing distally and non-darkly pigmented in B. rufioculus; (5) the epistomal process is much shorter in the new species than in B. rufioculus; (6) the ischium of the pereopod 1 is armed with a minute spine at the ventrodistal angle in B. cinctus n. sp., vs. unarmed and merely obtusely angular in B. rufioculus; (7) the palm of the pereopod 1 is armed with a small spiniform seta at the midlength of the flexor margin in B. cinctus n. sp., whereas such a spiniform seta is absent in B. rufioculus; (8) the dactylus of the pereopod 1 is sinuous and longer than the fixed finger in B. cinctus n. sp., vs. gently arcuate and subequal in length to the fixed finger in B. rufioculus; (8) the outer occlusal margin of the pereopod 1 dactylus is armed with a row of chitinous spines in B. cinctus n. sp., vs. unarmed in B. rufioculus. Furthermore, in B. cinctus n. sp., there is apparently no trace of tegumental scales while these are present on the carapace, pleon, telson, eyestalk and the antennal basicerite in B. rufioculus. The habitat is also considerably different. The holotype of the new species was collected from deep-sea soft substrates at 218–318 m depth, while the type specimens of B. rufioculus were collected from shallow water cave (14–17 m deep) in the coral reefs (Komai & Yamada 2011).
Of the other eight previously described species of Bresilia, B. antipodarum, B. briankensleyi and B. plumifera are characteristic in having a strongly produced, carinate or crested tergite of the pleomere 3 (Bruce 1990a, 1990b, 2005). Bresilia atlantica, B. corsicana and B. pacifica are characterized by the lack of an exopodal flagellum of the maxilliped 1 and the unarmed ischium and merus of the pereopod 2 (Calman 1896; Forest & Cals 1977; Hendrickx 2014), which separates those three species from the other congeneric species, including B. cinctus n. sp. Bresilia atlantica and B. corsicana are also characteristic in the lack of an epistomal process (Komai & Yamada 2010). The pterygostomial angle of the carapace is acutely pointed, forming a branchiostegal spine in B. antipodarum, B. atlantica, B. briankensleyi, B. corsicana, B. pacifica, B. plumifera, B. saldanhai, while it is obtusely angulate in B. gibbosa, as well as the new species and B. rufioculus. Bresilia atlantica and B. pacifica have non-darkly pigmented and poorly faceted cornea. Bresilia gibbosa is easily distinguished from B. cinctus n. sp. by the fewer dorsal spines on the rostrum (six or seven), of which the posteriormost three or four spines are basally articulated, and the more strongly elevated, posteriorly angular tergum of the pleomere 3. Bresilia saldanhai further differs from the new species by the more strongly elevated tergum of the pleomere 3.
Komai & Yamada (2010) proposed to divide Bresilia into two informal species groups on the basis of the development of the epistomal process, the structure of the pleonal tergite 3 and the presence or absence of an exopodal flagellum of the maxilliped 1: B. antipodarum species group was characterized by the possession of an elongate, acute epistomal process, the strongly elevated tergum of the pleomere 3, making the pleon gibbous, and the presence of an exopodal flagellum of the maxilliped 1; B. atlantica species group was characterized by the absence of an epistomal process, not particularly elevated tergum of the pleomere 3 and the lack of an exopodal flagellum of the maxilliped 1. However, careful literature survey revealed that in fact B. antipodarum does not have an epistomal process (Bruce 1990, 2005a), although Bruce (2005b) stated that “The epistomal process, first described in B. antipodarum, has now also been reported in B. plumifera, B. saldanhai and B. briankensleyi.” The lack of the epistomal process in B. antipodarum reduces the significance of the subdivision of Bresilia proposed by Komai & Yamada (2010). Furthermore, the recently described Bresilia pacifica appears intermediate between the two informal species groups, because the species is linked to the B. atlantica group in the lack of an exopodal flagellum of the maxilliped 1, but is similar to members of the B. antipodarum group in the possession of the epistomal process (although much shorter than in the other species) and the somewhat elevated tergum of the pleomere 3. Now the subdivision of the genus seems to have no merit.
Etymology. From the Latin cinctus (= belt), in reference to the belt-like transverse band on the pleomere 3 seen in the new species.
description: Published as part of Komai, Tomoyuki & Kohtsuka, Hisanori, 2017, A new deep-sea species of the caridean genus Bresilia Calman, 1896 (Crustacea: Decapoda: Bresiliidae) from Sagami Bay, central Japan, pp. 405-414 in Zootaxa 4299 (3) on pages 406-413, DOI: 10.11646/zootaxa.4299.3.6, http://zenodo.org/record/836056