Odontozona ganzu, Saito & Fujita, 2022

Saito, Tomomi & Fujita, Yoshihisa, 2022, A new shrimp of the genus Odontozona Holthuis, 1946 (Decapoda: Stenopodidea Stenopodidae) from a submarine cave of the Ryukyu Islands, Indo-West Pacific, Zootaxa 5175 (4), pp. 439-452 : 441-450

publication ID	https://doi.org/ 10.11646/zootaxa.5175.4.2
publication LSID	lsid:zoobank.org:pub:48F8A9C4-E5A8-42F2-97B5-CF849802B988
DOI	https://doi.org/10.5281/zenodo.7011087
persistent identifier	https://treatment.plazi.org/id/03F387AF-FFB1-FFB9-FBC6-017EFD624304
treatment provided by	Plazi
scientific name	Odontozona ganzu
status	sp. nov.

Treatment

Odontozona ganzu sp. nov.

( Figs. 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Type material. Japan, the Ryukyu Islands . Holotype: male, cl 3.6 mm (RUMF-ZC-6111), submarine cave called “Akuma-no-yakata” (Devil’s Hole), at Shimoji-jima Island , Miyako Island Group , Ryukyu Islands, 24°49’22.51”N, 125°08’07.84”E, rubble-covered rocky substrate, 80–90 m from the entrance, depth 18 m, SCUBA diving, coll. Y. Fujita, 31 August 2017 GoogleMaps .

Diagnosis. Small-sized stenopodid shrimp with subcylindrical body. Rostral dorsal margin armed with 6 teeth, ventral margin with 4 teeth. Carapace with indistinct cervical groove, bearing cincture of several spines of various sizes; supraorbital region armed with 2 pairs of stout spines; branchiohepatic and postcervial grooves indistinct; anterolateral region with scattered stout spines. Pleonites not sculptured. First and second pleura with transverse carina. Sixth pleuron armed with 2 lateral spines but lacked transverse row of posterior small spines. Telson lanceolate; dorsal surface with dorsolateral carinae each bearing 6 large spines; lateral margins each with 1 strong tooth; posterior margin with 2 submarginal posterolateral and 1 posterior teeth. Cornea pigmented, smaller than eyestalk. Antennal scale bearing 7–8 lateral teeth. Third pereopod palm subcylindrical, armed with irregular longitudinal row of several large spines and their interspaced several small spines on dorsolateral margin. Fourth and fifth pereopods with propodi indistinctly subdivided into 5 segments; carpi indistinctly subdivided into 5– 6 segments. Uropodal exopod with lateral margin nearly straight, armed with row of 8–9 teeth, with 2 smooth longitudinal carinae; endopod lateral margin and dorsal surface unarmed, with 2 smooth longitudinal carinae.

Description of holotype male. Rostrum ( Figs. 1 View FIGURE 1 , 2A, B View FIGURE 2 ) moderately long and slender, anterior two fifths directed obliquely upward slightly, reaching mid-length of antennal scale, about half of carapace length, narrowly rod-like in dorsal view; dorsal margin armed with 6 strong, anteriorly directed teeth, 5 of which situated anterior to orbital margin; ventral margin armed with 4 strong teeth; lateral margins unarmed.

Carapace ( Figs. 1 View FIGURE 1 , 2A, B View FIGURE 2 ) with postrostral median ridge extending to epigastric region; supraorbital region armed with 2 pairs of stout spines; orbital margin concave, unarmed; inferior orbital angle triangular, armed with large, acuminate, submarginal antennal spine; anterolateral margin armed with 3 (right) or 4 (left) large, acuminate, submarginal branchiostegal spines; pterygostomial angle produced anteriorly and ending in tooth; cervical groove dorsally distinct, laterally indistinct, posterior margin bearing with cincture of 14 large spines, directed anteriorly, ending in hepatic region; dorsal surface of gastric region armed with 4 pairs of large spines, directed anteriorly, decreasing in size posteriorly; postcervical groove indistinct, merging into branchiohepatic groove, posterior margin bearing with cincture of several small spines; suprahepatic region with indistinct groove, bearing row of a few small stout spines; anterolateral and branchial regions armed with scattered several stout spines, directed anteriorly.

Sixth thoracic sternite ( Fig. 2C View FIGURE 2 ) with medially jointed pair of subrectangular, contiguous lobes; each distomesial angle ending in spine; anterolateral margin each armed with 2 spines; ventral surface concave, unarmed. Seventh thoracic sternite with pair of broad subrectangular plates; distolateral angle produced; lateral and anteromesial margins armed with several teeth, respectively; ventral surface concave, unarmed. Eighth thoracic sternite with pair of smaller trapezoid plates; distolateral angle produced; lateral margin armed with a few teeth; anteromesial margin unarmed; ventral surface concave, unarmed.

Pleonites ( Fig. 1 View FIGURE 1 ) not sculptured; second to fifth pleura each terminating in tooth, in addition to 2–4 smaller anterior and posterior teeth. First pleonite short, divided into two sections by distinct transverse carina; anterior section with pleuron unarmed laterally, posteroventrally ending in short process; posterior section with pleuron unarmed laterally, its posteroventral margin armed with a few small teeth. Second pleonite rather long, with distinct short transverse carina. Third pleonite longest, without transverse groove nor carina. Sixth pleonite with long, sharp, posteriorly directed 2 spines on lateral region; posterior surface without any spines.

Telson ( Fig. 2D View FIGURE 2 ) lanceolate, slightly constricted near base, gradually tapering distally, 2.5 times as long as maximum width; dorsal surface with shallow median groove flanked by dorsolateral carinae each bearing 6 strong, symmetrically located spines, and 1 pair of large proximal submedian spines; lateral margins each armed with 1 strong tooth on mid-length; posterior margin generally convex, armed with 2 long submarginal posterolateral and 1 posterior teeth.

Eyes ( Figs. 2A, B View FIGURE 2 , 3A View FIGURE 3 ) well developed; cornea slightly smaller than peduncle, hemispherical, pigmented; anterodorsal and posterodorsal surfaces and mesial margin of eyestalk each armed with several small spines.

Antennular peduncle ( Figs. 2A, B View FIGURE 2 , 3B, C View FIGURE 3 ) overreaching mid-length of antennal scale. First article slightly longer than distal 2 articles combined, armed with 1 dorsomesial spine; stylocerite strongly curved inwards, distally acute. Second article armed with 2 dorsomesial and 1 distolateral spines. Third article unarmed. Flagella slender, long, about 9 times as long as carapace.

Antenna ( Figs. 2A, B View FIGURE 2 , 3D, E View FIGURE 3 ) with stout basicerite bearing 2 moderately large, distolateral spines, and several additional spines of various sizes on ventrolateral surface; mesial margin with laminate process. Antennal scale 2.8 times longer than broad, lateral margin slightly concave, armed with 8 (left) or 7 (right) large teeth; dorsal surface with 2 longitudinal carinae, otherwise unarmed. Carpocerite short, reaching level of antennular peduncle, armed with several spines on mesial and lateral margins. Flagellum slender, long, about 13 times as long as carapace.

Mandible ( Fig. 3F, G View FIGURE 3 ) robust; palp composed of 3 articles, distal article oval, intermediate article subequal to distal article in length; molar and incisor processes clearly separated.

Maxillule ( Fig. 3H View FIGURE 3 ) with simple, slender endopod; coxal endite suboval; basal endite moderately broad, truncate distally.

Maxilla ( Fig. 3I View FIGURE 3 ) with slender endopod; coxal and basal endites bilobed; scaphognathite well developed, anterior lobe subquadrate distally, posterior lobe short, subquadrate, widening posteromesially.

First maxilliped ( Fig. 3J View FIGURE 3 ) with endopod subdivided into 2 articles, distal article with 1 sharp spine, considerably narrower than proximal article; basal endite large, subtriangular, with concave mesial margin; coxal endite short, unilobed; exopod with well-developed flagellum; epipod large, feebly bilobed.

Second maxilliped ( Fig.3K View FIGURE 3 ) with moderately broad endopod; dactylus tapering distally; propodus anteromesially truncate, as long as dactylus, produced on ventromesial angle posteriorly; carpus slightly elongate, subquadrate; merus 2.2 times as long as carpus, oblong; ischiobasis compressed laterally; 1 arthrobranch present; epipod elongate, with well-developed podobranch; exopod with well-developed flagellum.

Third maxilliped ( Fig. 3L, M View FIGURE 3 ) overreaching tip of antennal scale by length of dactylus; dactylus tapering distally; propodus with shallow depression furnished with dense grooming setae at distomesial angle ( Fig. 3M View FIGURE 3 ); carpus subequal to propodus in length, unarmed; merus armed with 4 strong spines on dorsolateral margin and row of several small spines on ventrolateral margin; ischium compressed laterally, armed with rows of several equally spaced moderately small spines on ventromesial and ventrolateral margins; epipod elongate, rod-like; exopod with well-developed flagellum.

First pereopod ( Fig. 4A, B View FIGURE 4 ) slender, overreaching tip of antennal scale by length of chela, with well-developed carpo-propodal grooming apparatus ( Fig. 4B View FIGURE 4 ); all articles unarmed; fingers about half of chela length, pectinate with many teeth on opposable margins; palm subcylindrical; carpus slender, 2.2 of chela length; merus 0.8 of carpal length; ischium about half of meral length.

Second pereopod ( Fig. 4C View FIGURE 4 ) longer than first pereopod, reaching tip of antennal scale by length of chela and carpus; all articles unarmed; fingers 0.4 of chela length, pectinate with many teeth on opposable margins; palm subcylindrical; carpus treble as long as chela; merus 0.8 of carpal length; ischium about half of meral length.

Third pereopod ( Fig. 4D, E View FIGURE 4 ) longest and strongest, reaching tip of antennal scale by lengths of chela, carpus and half of merus. Chela 1.8 times as long as carapace. Dactylus 0.4 of chela length, slightly curved, cutting edge proximally with large triangular tooth, posterodorsal margin with 2 large strong spines. Fixed finger slightly shorter than dactylus, hooked distally, cutting edge proximally with large subquadrate tooth fitting into hiatus on opposed cutting edge of dactylus. Palm subcylindrical, 2.7 times as long as wide; lateral and mesial margins not carinate; dorsolateral margin armed with irregular longitudinal row of several strong spines and several minute spines in their interspaces; lateral and mesial surfaces and ventral margin armed with scattered small spines or granules. Carpus slightly widening distally, 6.3 times as long as wide, 0.8 of chela length; dorsolateral surface armed with row of widely spaced, strong spines of various sizes, distal-most strongest; ventromesial surface armed with 9 strong spines. Merus 1.1 of carpal length; dorsal margin with row of well-spaced 3 strong spines; ventral margin with row of 6 stronger spines, distal-most spine strongest; length ratio of third pereopod chela against carpus and merus 1.0: 0.8: 0.9. Ischium about half of meral length; distodorsal angle bluntly projecting and with 1 strong spine.

Fourth and fifth pereopods ( Fig. 5A–D View FIGURE 5 ) similar in shape and length. Dactyli compressed laterally, 4.0 times as long as wide, biunguiculate. Propodi about 5 times as long as dactyli, indistinctly subdivided into 5 segments; ventral margin armed with 19–20 movable spines. Carpi 2.7 times as long as propodi, indistinctly subdivided into 5–6 segments; distal 3 joints ending in ventral movable spine. Meri 0.7 of carpal length, not subdivided. Ischia 0.4 length of meri.

First pleopod ( Fig. 5E View FIGURE 5 ) uniramous, shorter than other pleopods. Second to fifth pleopods biramous. Second pleopod ( Fig. 5F View FIGURE 5 ) with protopod shorter than both rami, armed with several teeth on mesial and lateral margins. Third to fifth pleopods generally similar, decreasing in size posteriorly.

Uropod ( Fig. 2D View FIGURE 2 ) with stout protopod, its lateral margin terminating in blunt process, posteroventral margin armed with several small teeth. Exopod relatively broad, slightly overreaching posterior margins of telson and endopod; lateral margin nearly straight, armed with 8 (left) or 9 (right) teeth; dorsal surface unarmed, with 2 smooth longitudinal carinae. Endopod tapering distally; lateral margin unarmed, distal part unarmed; dorsal surface unarmed, with 2 longitudinal carinae.

Gills trichobranchiate, gill formula as shown in Table 2 View TABLE 2 .

Color in life ( Fig. 6 View FIGURE 6 ). Rostrum red anterolaterally and ventrally. Carapace generally semitransparent, but forming red patches on supraorbital to epigastric, antennal to hepatic and anterolateral regions; posterior cervical groove to gastric region forming red crescent moon and larger transverse band; inframarginal region of postcervical groove ranging wider red patch to scattered red chromatophores in hepatic region; branchial region forming wider red band; posterior margin forming red transverse band; cervical, branchiohepatic and postcervical grooves semitransparent. First to sixth pleonites semitransparent, each with red transverse band posteriorly, extending to ventral margins; second to sixth pleura with short red longitudinal bands. Telson and uropods with red chromatophores proximally and on distal halves; uropodal protopods with red chromatophores proximally. Eyestalks semitransparent, proximal and posterior regions with red bands. Antennular and antennal peduncles pale red marginally; antennular and antennal flagella semitransparent. Third maxillipeds generally pale red. First and second pereopods generally semitransparent. Third pereopod chela generally pale red; anterior halves of fingers white; palm, carpus and merus pale red; ischium semitransparent. Fourth and fifth pereopods generally semitransparent, but carpi and meri pale red.

Etymology. While other species of the genus Odontozona have delicate impressions in the third pereopods, this species has a robust appearance. Therefore, the species name is adapted from “ganzu”, which is a dialect of Miyako Island, originally meaning sturdy, and now has the nuance of healthy.

Common name. Ganzu boxer shrimp (new English name), ganzu-subesube-otohime-ebi (new Japanese name).

Distribution. Presently known only from the type locality (Shimoji-jima Island, Miyako Island Group) in Ryukyu Islands, southwestern Japan.

Ecology. The type material of Odontozona ganzu sp. nov. was collected from a submarine cave called “Akumano-Yakata” at Shimoji-jima Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. Detailed information on the cave systems of the Islands was provided by Osawa & Fujita (2019). In the cave, the middle to innermost parts are known to be completely dark and anchialine environment (low salinity: 24–28 ppt., see Osawa & Fujita, 2019), and following unusual cave-dwelling decapod species are found: Odontozona fasciata Okuno, 2003 ( Stenopodidea : Stenopodidae ), Calliasmata pholidota Holthuis, 1973 (Caridea: Barbouriidae ), Bresilia rufioculus Komai & Yamada, 2011 (Caridea: Bresiliidae ), Neoliomera cerasinus Ng, 2002 (Brachyura: Xanthidae ) and Atoportunus gustavi Ng & Takeda, 2003 (Brachyura: Portunidae ) [see Fujita et al., 2013, 2017; Anker & Fujita, 2014; Fujita, 2018].

The present specimen of Odontozona ganzu sp. nov. was found under boulders in the cave. Two congeners, O. fasciata and O. okunoi are known to be occurred from submarine caves, and both found usually on the substratum and/or a crevice in caves ( Saito & Fujita, 2018; Fujita, personal observation). On the other hand, many of the smallsized species of Odontozona are known to be found under boulders ( Minemizu, 2000, 2013; Saito et al., 2017), and therefore this new species may not necessarily to live in cave environment.

Remarks. Odontozona ganzu sp. nov. is the only species of Odontozona lacking transverse row of posterior small spines on sixth pleuron. Except for the armature of the pleuron, the new species appears to be morphologically most similar to O. stigmatica Saito, Okuno & Anker, 2017 known only by the holotype from Ishigaki-jima Island, Ryukyu Islands, Japan, West Pacific Ocean. However, the present new species can be distinguished from O. stigmatica by several morphological features, including (1) the absence of the row of small spines on the posterior margin of the carapace (vs. present in O. stigmatica ), (2) the absence of the distinct transverse carina on the third pleuron (vs. present in O. stigmatica ), (3) the presence of the posterior tooth of telson (vs. absent in O. stigmatica ), (4) the absence of the lateral tooth of the uropodal endopod (vs. having 2 lateral teeth in O. stigmatica ), (5) the dorsolataral margin of the third maxilliped ischium is armed with a row of minute spines (vs. naked in O. stigmatica ), and (6) the length ratio of the male third pereopod chela against carpus and merus is 1.0: 0.8: 0.9 (vs. 1.0: 0.6–0.7: 0.5–0.6 in O. stigmatica ).

Several species of Odontozona share the red colored chela on the third pereopod in life; the male of Odontozona ganzu sp. nov. (this study), the male of O. stigmatica (cf. Saito et al., 2017, Fig. 13F), the males of O. arbur (cf. Saito et al., 2017, Fig. 13B, C, D), O. crinoidicola (cf. Saito & Fujita, 2009, Fig. 1A, B View FIGURE 1 ; Saito et al. 2017, Fig. 14B), O. ensifera (cf. Kawamoto & Okuno, 2003, 14), O. fasciata (cf. Kawamoto & Okuno, 2003, 15, referred as Odontozona sp. A ), Odontozona sp. B (cf. Kawamoto & Okuno, 2003, 15), Odontozona sp. 1 and 2 (cf. Minemizu, 2000, 116) and Odontozona sp. 2 (cf. Minemizu, 2013, 21). As a whole, many species of the genus Odontozona have a transparent body with a red pattern as the base color, it is difficult to distinguish the species of the genus by color pattern. O. arbur can be easily separated from O. ganzu sp. nov. in having sculpture on the pleon. O. crinoidicola has depressed body form, instead of compressed one in the new species. O. ensifera has cincture of about 70 slender spines just behind the postcervical groove, whereas the indistinct postcervical groove has only several small spines in the new species. Moreover, the third pereopod palm is unarmed in O. fasciata , but armed with many spines or granules in the new species. The specimen reported as Odontozona sp. 2 . in Minemizu (2013) was not available for the current study, however, its color pattern is in many ways very similar to that of the new species.

The present study increases the total number of species in the genus Odontozona to 23, with 11 species present in the Indo-West Pacific, three in the eastern Pacific, six in the western-central Atlantic, and three in the eastern Atlantic, two being endemic to the Mediterranean Sea.