Caligoneus cavernicola, Komai & Fujita, 2018

Komai, Tomoyuki & Fujita, Yoshihisa, 2018, A new genus and new species of alpheid shrimp from a marine cave in the Ryukyu Islands, Japan, with additional record of Salmoneus antricola Komai, Yamada & Yunokawa, 2015 (Crustacea: Decapoda: Caridea), Zootaxa 4369 (4), pp. 575-586 : 577-584

publication ID	https://doi.org/ 10.11646/zootaxa.4369.4.7
publication LSID	lsid:zoobank.org:pub:CE0D1E89-B2CC-4871-ACE3-23C41343AA5C
DOI	https://doi.org/10.5281/zenodo.5982862
persistent identifier	https://treatment.plazi.org/id/CD40D06F-FFD7-780C-658A-505BFAE6FAB8
treatment provided by	Plazi
scientific name	Caligoneus cavernicola
status	sp. nov.

Treatment

Caligoneus cavernicola View in CoL n. sp.

[New Japanese name: Kurayami-teppou-ebi] Figs 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5

Material examined. Holotype: CBM-ZC 14136, ovigerous individual (cl 5.7 mm), unnamed cave (sometimes called as “ Ohoba No. 2 Cave ”), Ie Island, Okinawa Islands, Ryukyu Islands, Japan, 12 m, 18 July 2015, SCUBA diving, coll. K. Yunokawa & Y. Fujita.

Paratypes: RUMF-ZC-02733, non-ovigerous individual (cl 5.6 mm), same data as holotype; CBM-ZC 14137, ovigerous individual (cl 5.8 mm), same locality as holotype, 12 m, 3 August 2015, SCUBA diving, coll. K. Yunokawa ; RUMF-ZC-04569, non-ovigerous individual (cl 5.7 mm), same locality as holotype, 12 m, 23 June 2017, SCUBA diving, coll. Y. Fujita ; RUMF-ZC-04570, ovigerous individual (cl 5.7 mm), same data as RUMF-ZC 0 4569.

Non-type: RUMF-ZC-04568, non-ovigerous individual (cl 6.0 mm; damaged for DNA extraction), same data as RUMF-ZC 0 4569.

Description. Holotype. Body ( Fig. 1 View FIGURE 1 ) moderately stout. Rostrum ( Fig. 2A–C View FIGURE 2 ) not reaching distal margin of article 1 of antennular peduncle, trigonal in cross-section with carinate dorsal and lateral margins, longer than wide at base, directed forward; tip sharply pointed; dorsal mid-line somewhat elevated, mid-dorsal carina extending to gastric region beyond postrostral spine; lateral carina not reaching rostral apex, merging into orbital margin; ventral surface slightly convex but not medially carinate, unarmed or armed with 1 minute subdistal spine; lateral margins nearly straight in dorsal view; ventral surface unarmed. Carapace ( Figs. 1 View FIGURE 1 , 2A–C View FIGURE 2 ) glabrous, with 1 small middorsal spine at postrostral position; anterolateral margin gently sinuous, with small extra-orbital spine lateral to eyestalk; cardiac notch shallow; orbital spine directed forward; pterygostomial angle broadly rounded.

Pleon ( Fig. 1 View FIGURE 1 ) with anterior 3 pleura rounded ventrally and posteroventrally; pleuron 4 somewhat produced posteriorly but unarmed; pleuron 5 with acutely pointed posteroventral angle. Pleomere 6 without articulated flap at posteroventral angle; preanal plate rounded; posterolateral process truncate. Telson ( Figs. 1 View FIGURE 1 , 2D View FIGURE 2 ) 1.1 times as long as pleomere 6, with 2 pairs of dorsolateral spiniform setae on posterior half situated laterally from blunt dorsolateral ridge; posterior margin with very deep, narrow, V-shaped cleft, remaining margin truncate, bearing 2 greatly unequal spiniform setae, lateral about twice as long as mesial ( Fig. 2E View FIGURE 2 ); dorsal surface with 2 shallow longitudinal sulci, one on each side of mid-line, reaching to posterior margin.

Eyestalks ( Fig. 2A, B View FIGURE 2 ) exposed both in dorsal and lateral views, each with small distal spinule at dorsomesial angle; cornea anterolateral, substantially reduced in size, darkly pigmented.

Antennular peduncle ( Fig. 2A, C View FIGURE 2 ) stout, overreaching distal margin of antennal scaphocerite by 0.3 length of article 3. Article 1 with small forwardly directed spine on ventromesial ridge at midlength; stylocerite terminating in slender, acute spine reaching to distal margin of article 1. Distomesial angle of article 2 somewhat produced distally. Flagella very long, more than twice body length; lateral flagellum ( Fig. 2A View FIGURE 2 ) biramous, fused portion very short; accessory ramus consisting of about 10 articles with aesthetascs.

Antenna ( Fig. 2A, C, F View FIGURE 2 ) with basicerite bearing small ventrolateral distal spine. Scaphocerite subovate with nearly straight lateral margin and gently convex mesial margin, 2.4 times as long as wide; distal blade broadly rounded, reaching well beyond small distolateral tooth. Carpocerite reaching mid-length of scaphocerite.

Epistomial sclerites unarmed. Labrum with non-crested median lobe.

Mandible ( Fig. 3A–C View FIGURE 3 ) with broad incisor process, terminal margin with 6 unequal blunt teeth; inner surface excavate, accommodate 2-articulated palp; distal article of palp subovate, marginally setose; molar process relatively narrow. Maxillule ( Fig. 3D View FIGURE 3 ) with basial endite bearing both spiniform and stiff setae, arranged in double row, on mesial margin. Maxilla ( Fig. 3E View FIGURE 3 ) with poorly developed, slightly bilobed, coxal endite; endopod short, curved mesially, not extending beyond distal margin of basial endite; posterior lobe of scaphognathite short, rounded. Maxilliped 1 ( Fig. 3F, G View FIGURE 3 ) with unequally bilobed coxal endite; basial endite generally oval, with longitudinal row of setae on mid-line of outer surface; exopod with narrow caridean lobe, flagellum well developed; epipod large, bilobed. Maxilliped 2 ( Fig. 3H View FIGURE 3 ) somewhat slender; basis and ischium fused; carpus with produced mesial angle; propodus and dactylus partially fused, with row of slender spiniform setae on mesial margin; epipod large, devoid of podobranch; exopodal flagellum well developed, with 1 long plumose seta arising at about mid-length.

Maxilliped 3 ( Fig. 4A, B View FIGURE 4 ) with endopod slender, not reaching distal margin of antennal scaphocerite. Coxa with lateral plate rounded-subquadrate ( Fig. 4B View FIGURE 4 ). Antepenultimate article sinuously curved in dorsal view, proximal half flattened dorsoventrally. Penultimate article subcylindrical. Ultimate article 1.5 times as long as penultimate article, tapering distally from mid-length, terminating in acute tip, latter bearing 1 long subterminal seta but no stout spiniform setae; mesial face with several transverse rows of stiff serrulate setae. Exopod not reaching distal end of antepenultimate article.

Pereopods 1 (= chelipeds) ( Fig. 4C, E View FIGURE 4 ) subequal in size, symmetrical in shape, slender, simple, carried extended or loosely folded, in full extension only slightly overreaching distal margin of antennal scaphocerite. Ischium with 4 (left) or 6 (right) spiniform setae on ventrolateral surface. Merus slightly longer than ischium, subcylindrical. Carpus subequal in length to merus, slightly widening distally, 8 times as long as distal width. Chela ( Fig. 4D, F View FIGURE 4 ) tapering distally, 0.7 times as long as carpus; palm subcylindrical; fingers 1.4 times as long as palm, not crossing distally; occlusal margin of fixed finger with 3 very small teeth proximal to mid-length, some teeth directed slightly backwards; dactylus slightly curved distally, unarmed on occlusal margin.

Pereopod 2 ( Fig. 4G View FIGURE 4 ) slender, overreaching distal margin of antennal scale by half-length of carpus. Ischium with 3 spiniform setae on ventrolateral surface. Merus subequal in length to ischium, flexor side slightly inflated distally. Carpus 0.8 times as long as ischium and merus combined, subdivided into 5 articles, ratio of carpal articles from proximal to distal equal to: 5: 0.8: 0.8: 1.3: 1. Chela slightly longer than distal-most carpal article, simple, with tufts of setae.

Pereopods 3–5 very slender, elongate, pereopods 3 and 4 subequal in length, pereopod 5 distinctly longer than each of pereopods 3 and 4. Pereopod 3 ( Fig. 4H View FIGURE 4 ) in full extension overreaching distal margin of antennal scaphocerite by 0.4 length of carpus; ischium without spiniform setae; merus unarmed, flexor side slightly inflated distally; carpus slenderer than merus, 1.3 times as long as merus, lacking distodorsal projection; propodus with 5 widely spaced, minute spiniform setae (including one adjacent to propodo-dactylar articulation) on flexor margin; dactylus 0.1 times as long as propodus, slender (9 times as long as wide), simple, almost straight ( Fig. 4I View FIGURE 4 ). Pereopod 4 ( Fig. 4J View FIGURE 4 ) similar to pereopod 3, overreaching distal margin of antennal scaphocerite by full length of propodus; ischium unarmed. Pereopod 5 ( Fig. 4K View FIGURE 4 ) overreaching distal margin of scaphocerite by 0.4 length of carpus; ischium unarmed; carpus and propodus elongate, with setal brush on distal 0.4 of flexor margin ( Fig. 4L View FIGURE 4 ); dactylus similar to those of pereopods 3 and 4, less than 0.2 times as long as propodus.

Pleopod 1 ( Fig. 2G View FIGURE 2 ) with endopod about 0.3 length of exopod, gently curved inward, tapering to blunt apex ( Fig. 2H View FIGURE 2 ). Pleopod 2 ( Fig. 2I View FIGURE 2 ) with appendices interna and masculina present in both non-ovigerous and ovigerous individuals; appendix masculina ( Fig. 2J View FIGURE 2 ) about 0.8 length of appendix interna, slightly widened to distal 0.2, then tapering to subacute apex, with row of setae distolaterally; endopod about 0.8 times as long as exopod.

Uropod ( Fig. 2D View FIGURE 2 ) with lateral lobe of protopod unarmed. Endopod and exopod narrowly subovoid, former shorter than latter, reaching posterior margin of telson. Exopod with faintly concave, setose lateral margin terminating distally in minute spine covering base of minute distolateral spiniform seta; diaeresis sinuous, without spine mesial to distolateral spine; distal lamella extending far beyond distolateral spine.

Eggs at stage near hatching 0.9× 0.5 mm.

Variation. The remaining five specimens (four paratypes and one non-type) are generally very similar to the holotype. One of them (paratype, CBM-ZC 14137) has two postrostral spines ( Fig. 2B View FIGURE 2 ), whilst the other four have one postrostral spine, as in the holotype. In three specimens (two paratypes, RUMF-ZC 0 4569, 0 4570, and one non-type, RUMF-ZC 04568), the rostrum has a minuscule subdistal tooth on the ventral margin, such a tooth being absent in the holotype and the remaining two paratypes (CBM-ZC 14137, RUMF-ZC-02733). The ischia of the pereopods 1 and 2 are quite variable in the armature, having four to six and three or four spiniform setae, respectively. The ischium of the pereopod 3 can be either unarmed [holotype and two paratypes (CBM-ZC 14137, RUMF-ZC-02733)] or armed with one or two spiniform setae [two paratypes (RUMF-ZC 0 4569, 04570) and one non-type (RUMF-ZC 04568)]. Eggs in non-eyed stage measure 0.7× 0.4 mm.

Colour in life. Body and appendages ( Fig. 5A, B View FIGURE 5 ) generally semi-translucent with scattered red dots, sometimes more intense on carapace and pleomeres to telson, forming diffuse transverse bands ( Fig. 5B View FIGURE 5 ); yellowish ovary and hepatopancreas visible throughout integument; cornea darkly pigmented.

Distribution. At present known only from a marine cave off Ie Island, Okinawa Islands, Japan, at depths of 12– 17 m.

Habitat. The type locality of Caligoneus cavernicola n. sp. is a deep marine cave located on a reef slope off northeastern coast of Ie Island. The entrance to the cave lies at a depth of about 17 m below the sea level. The interior of the cave is 45 m long and bifurcated into “main tube” and “large hall” at about 30 m from the entrance. The “large hall” is about 200 m 2 and its height to the roof is about 12 m (the roof is about 8 m below the sea level). Shrimps were mostly found in small holes inside the “large hall”. The syntopic decapod fauna includes Salmoneus antricola (Caridea: Alpheidae ), Bresilia rufioculus Komai & Yamada, 2011 (Caridea: Bresiliidae ), Catoptrus iejima Fujita & Naruse, 2011 (Brachyura: Portunidae ), Atoportunus gustavi Ng & Takeda, 2003 (Brachyura: Portunidae ), and Lipkemera iejima Naruse & Fujita, 2015 (Xanthidae) .

Etymology. Named after the cave habitat of the new species, the Latin cavern (= cave) and –cola (suffix, meaning dweller). Used as a noun in apposition.

Remarks. Among the six specimens examined, three are ovigerous. Like species of Salmoneus and Triacanthoneus , all individuals including the ovigerous ones have a well-developed appendix masculina just next to the appendix interna ( Fig. 2J View FIGURE 2 ), on the pleopod 2, indicating a possibility of some form of hermaphroditism. Several morphological features of the new species clearly represent adaptations to cave environments, such as the reduced cornea located at the distolateral portion of the eyestalk and the very slender elongate pereopods 3–5.