Potamalpheops yamakawai Yamashita, Komai & Koreeda, 2024, sp. nov.
Year: 2024
Type: other
Abstract: Potamalpheops yamakawai sp. nov. [New Japanese name: Uzumi-bi-yobi-mizu-teppou-ebi] (Figures 1–3, 4D) Type material. Japan. Holotype: CBM-ZC 17507, ovigerous female (cl 3.9 mm), DNA voucher, mouth of Minami-no River, Ao-no River system, Teishi, Minami-izu Town, Shizuoka Prefecture, 34°38.50’N, 138°52.38’E, hand net, coll. R. Yamashita, 11 July 2021. Paratypes: i) CBM-ZC 17508, male (cl 3.8 mm), same data as holotype; CBM-ZC 17850, 1 female (cl 2.5 mm), Mizunari River, Beppu, Ei Town, Minami-kyushu City, Kagoshima Prefecture, 31°15.16’N, 130°26.05’E, yabby pump, coll. R. Koreeda, 28 September 2022; ii) KAUM-AT 3422–3424, 1 male (cl 3.2 mm), 2 ovigerous females (cl 3.8–4.4 mm), same locality as CBM-ZC 17850, yabby pump, coll. R. Koreeda, 22 July 2023; iii) CBM-ZC 17851– 17867, 6 females (cl 3.5–4.6 mm), 8 ovigerous females (cl 3.6–4.9 mm), 3 males (cl 3.2–3.8 mm), 3 DNA vouchers, Arata River, Kotsuki River system, Simoarata, Kagoshima City, Kagoshima Prefecture, 31°34.23’N 130°33.20’E, hand net, coll. R. Koreeda, 05 August 2023; iv) KAUM-AT 3425–3427, 4 ovigerous females (cl 4.4–4.8 mm), same data as previous specimens. Diagnosis. Carapace glabrous, without distinct grooves on lateral surface. Rostrum almost as long as broad, short, not reaching or slightly exceeding distal corneal margins, ventral margin unarmed; extra-corneal spine directed slightly upward, located lateral to cornea. Telson with 2 spiniform setae on each posterolateral angle. Cornea well developed, darkly pigmented; anteromesial margin of eyestalk unarmed or with minute, sharply pointed tubercle, without setae or at most with 1 or 2 minute setae. Antennular peduncle with basal article serrated on dorsodistal margin; penultimate article slightly shorter than visible portion of basal article in dorsal view. Antennal carpocerite reaching 0.8–0.9 length of scaphocerite. Chelipeds equal in length, similar, not particularly enlarged; carpus with several rows of grooming setae ventromesially; chela subequal in length to carpus. Pereopod 5 ischium and merus unarmed. Uropodal exopod with 1 posterolateral tooth; diaeresis serrated with 20–25 teeth. Description. Holotype female. Body (Fig. 1, 2A, C) moderately stout, not particularly compressed. Carapace (Fig. 2A, B) smooth, glabrous, without distinct grooves on lateral surface, subequal in length to anterior 3 pleomeres combined. Dorsum slightly domed due to development of ovary. Rostrum triangular, nearly as long as broad, short, slightly exceeding distal margin of cornea, distally acute; dorsal surface non-carinate; ventral margin unarmed. Extra-corneal teeth directed slightly upward, located lateral to cornea; infra-corneal margin broadly rounded, reaching as far as extra-corneal teeth. Pterygostomial margin broadly rounded, slightly projecting anteriorly, without setae; ventrolateral margin without setae. Posterior margin with deep cardiac notch. Pleon (Figs. 1, 2C) with anterior 4 pleura rounded; pleuron 5 with posteroventral angle angular but not sharply pointed. Pleomere 6 with triangular articulated plate posteroventrally; posterolateral process rounded; anal tubercles absent. Telson (Fig. 2C, D) subrectangular, slightly tapering posteriorly; dorsal surface with 2 pairs of strong spiniform setae, first pair inserted at about 0.3 of telson length, second pair at about 0.6 length; posterior margin with median part rounded, somewhat projecting, with about 15 plumose setae; each posterolateral angle with 2 strong spiniform setae, lateral distinctly shorter than mesial. Eyestalks (Fig. 2A, B) largely exposed in dorsal and lateral views; cornea darkly pigmented, oval-shaped, occupying most of eyestalk except for mesial and anteromesial portions; anteromesial margin of eyestalk with minute setae and minute tubercle. Ocellar beak not visible in lateral view. Antennular peduncle (Fig. 2A, B) moderately slender, about half-length of carapace, slightly exceeding distal margin of antennal scaphocerite. Basal article with distodorsal margin serrated (Fig. 2B); dorsal surface with 2 spiniform setae (Fig. 2A); stylocerite acute, slightly exceeding distal margin of basal article; ventromesial carina with anteriorly directed tooth. Penultimate article slightly shorter than visible portion of basal article in dorsal view. Ultimate article distinctly shorter than penultimate article. Lateral flagellum biramous, bearing 8 tufts of aesthetascs; fused portion consisting of 10 segments; accessory branch with 4 segments; mesial flagellum about twice as long as carapace. Antenna (Fig. 2A) with basicerite bearing acute ventrolateral distal tooth. Carpocerite moderately long, reaching 0.8 length of scaphocerite. Scaphocerite ovate, about 3 times as long as wide; lateral margin nearly straight, terminating distally in robust spine, latter slightly overreaching distal margin of rounded lamella. Flagellum not particularly thickened, slender, about 3 times as long as carapace. Epistomial sclerite without visibly projecting process. Mouthparts typical for genus (not illustrated). Maxilliped 3 (Fig. 3A) slender. Ultimate article twice as long as penultimate article (= carpus), with 2 and 1 small spiniform setae on apex and anterolateral margin, respectively. Antepenultimate article depressed in proximal half. Coxal lateral plate somewhat ear-shaped, distally subacute. Exopod flagellum-like, slightly overreaching distal margin of antepenultimate article. Pereopods 1 (chelipeds) (Fig. 3B–D) symmetrical, not particularly enlarged or elongate, slightly exceeding distal margin of basal article of antennular peduncle. Ischium slightly widened distally. Merus distinctly longer than ischium and carpus. Carpus vase-shaped, widened distally, with 5 transverse rows of setae on ventromesial surface (= grooming apparatus). Chela subcylindrical, subequal in length to carpus, 3 times as long as wide; fixed finger with occlusal margin nearly straight, unarmed; dactylus slightly shorter than palm, with short setae distally, unarmed on occlusal margin. Pereopod 2 (Fig. 3E) slender, not exceeding distal margin of penultimate article of antennular peduncle. Ischium and merus subequal in length. Carpus divided into 5 segments; ratio of carpal segmentts approximately equal to (proximal to distal): 4.3: 1.2: 1.5: 1.0: 2.5. Chela almost as long as distalmost carpal segment; fingers subequal in length to palm, with short setae distally. Pereopod 3 (Fig. 3F) slender. Ischium armed with 1 spiniform seta on ventrolateral surface. Merus armed with 2 widely spaced spiniform setae. Carpus unarmed, distally with stiff seta. Propodus armed with 6 minute spiniform setae on flexor margin and 1 pair of spiniform setae on flexor distal margin. Dactylus 0.4 length of propodus, subconical, simple, slender, slightly curving distally. Pereopod 4 (Fig. 3G) similar to pereopod 3, slightly longer. Pereopod 5 (Fig. 3H) longer than pereopods 3 and 4; ischium and merus unarmed; propodus with 4 minute spiniform setae on proximal half of flexor margin; grooming apparatus consisting of long distal setae and 6 rows of shorter stiff setae in distal half of flexor margin. Pleopod 1 with endopod about 0.4 length of exopod. Pleopods 2–5 each with appendix interna on endopod. Uropod (Fig. 2C, E) with posterolateral lobe of protopod ending in strong tooth. Exopod longer than endopod; lateral margin nearly straight, with 1 small acute posterolateral tooth; posterolateral spiniform seta strong, distinctly longer than posterolateral tooth but not reaching posterior margin of exopod; diaeresis not reaching to mesial margin of exopod, serrated with 20 minute teeth between lateral margin and abrupt mesial incision at about one-third of diaeresis length. Gill formula typical for genus (cf. Powell 1979; Anker 2003). Eggs: 75 in number, 0.56–0.79 mm in diameter. Paratypes. Body less stout in males than in ovigerous females. Carapace dorsum slightly domed in mature females, not in males and younger females. Rostrum varying in length, from not reaching distal margin of cornea to overreaching mid-length of basal article of antennular peduncle. Tubercle on anteromesial angle of eyestalk absent or present, if present, minute but sharp; 1 or 2 minute setae present or absent on anteromesial angle of eyestalk, sometimes barely visible. Antennular peduncle with basal article bearing 2 or 3 (usually 2) spiniform setae on dorsal surface; lateral flagellum bearing 7–13 tufts of aesthetascs, fused portion consisting of 8–12 segments, accessory branch constantly with 4 segments. Carpocerite reaching 0.8–0.9 length of scaphocerite. Pereopod 1 with ischium 0.6–0.9 length of merus. Pereopod 3 and 4 propodi armed each with 6–8 minute spiniform setae on flexor margin and 2 on flexor distal margin. Pereopod 5 propodus armed with 4–6 minute spiniform setae on flexor margin and grooming apparatus of 6–8 rows of short stiff setae on flexor margin. Male pleopod 1 with endopod small, less than 0.2 length of exopod. Male pleopod 2 with appendix masculina twice as long as appendix interna (Fig. 3I), with 4 long distal setae and 1 subdistal seta on mesial margin. Uropodal exopod with diaeresis serrated with 20–25 minute teeth. Size. Largest female cl 4.9 mm, ovigerous females cl 3.6–4.9 mm; largest male cl 3.8 mm. Colour pattern in life. Body and appendages generally translucent, occasionally with pale orange tinge; anterolateral margin of carapace reddish; pleomere 1 with 2 red or purple transverse bands, pleomeres 2–6 each with red or purple transverse bands posteriorly; cornea dark grey; antennular peduncle with tinge of red; eggs yellowish brown or yellowish green at non-eyed stage (Fig. 1). Distribution. Presently known only from three locations on two Japanese main islands: Minami-no River in Aono River system, Minami-izu Town, Shizuoka Prefecture, Honshu (type locality); Arata River in Kotsuki River system in Kagoshima City, and Mizunari River, Minami-kyushu City, Kagoshima Prefecture, Kyushu. Ecology. Minami-no
Authors: Yamashita, Ryunosuke, Komai, Tomoyuki, Koreeda, Reo
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6968074529
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