Alpheus nomurai, Anker, 2023

Anker, Arthur, 2023, Revision of Alpheus euphrosyne De Man, 1897 and A. microrhynchus De Man, 1897, with description of three new species and taxonomic remarks on several other morphologically and ecologically similar snapping shrimps (Malacostraca: Decapoda: Alpheidae), Zootaxa 5282 (1), pp. 1-115 : 50-57

Alpheus nomurai sp. nov.

( Figs. 25–28 , 51F )

Alpheus bis-incisus (or A. bisincisus ).— Dôtu 1961: 136, fig. 1; Kim & Park 1972: 198; Kim 1976: 142; Kim 1977: 247, figs. 100, 101, pl. 24, fig. 44 [not A. bisincisus De Haan, 1844 ].

Alpheus euphrosyne .— Jeng & Chang 1985: 248, fig. 23 [not A. euphrosyne De Man, 1897 ].

Alpheus euphrosyne richardsoni .— Miya 1995: 275, fig. 2; Yang & Kim 1996: 106, figs. 1-3; Hayashi 1998: 292, figs. 353c, g, 354c, 355c, e [not A. richardsoni Yaldwyn, 1971 ].

Alpheus richardsoni .— Yoshigou 2009: 249, fig. 12m, 13m, 14m, 15m,. 16m, 17m, 18m, pl. III 1-4; Koyama et al. 2017: 132 [not A. richardsoni Yaldwyn, 1971 ].

Alpheus sp. — Kirihara et al. 2021: 99, fig. 1B.

Type material. Holotype, male (cl 8.8 mm, tl 23.0 mm, chl 13.0 mm), MNHN-IU-2018-5590, Japan, Wakayama, Tanabe, intertidal, leg. I. Sakamaki, 27.11.1993 [SMP-940] . Paratypes: 1 male (cl 8.5 mm), MNHN-IU-2018-5588, Japan, Wakayama, Tanabe, intertidal, leg. K. Nomura, 25.08.1995 [SMP-1220]; 1 ov. female (cl 8.8 mm), MNHN-IU-2018-5744, same collection data as for previous paratype [SMP-1220a] ; 1 male (cl 9.6 mm), OUMNH. ZC. 2011.06.6, same collection data as for previous paratypes [SMP-1220b]; 1 ov. female (cl 11.9 mm), MNHN-IU-2018-5589, Japan, Kochi, Shimanto River , intertidal, leg. K. Nomura, 12.07.2002 [SMP-1748] .

Additional material. Japan: 1 ov. female (cl 9.6 mm, tl 27.5 mm, chl 12.7), MNHN-IU-2018-5748, OkinawaJima, Sajiki, intertidal, leg. K. Nomura, 17.10.1994 [SMP-1334]; 1 male (cl 6.5 mm), 1 ov. female (7.7 mm), OUMNH. ZC. 2019.06.58, Okinawa, Sajiki, intertidal, leg. A. Kikukawa, 08.08.1994 [SMP-1332] .

South Korea: 1 male (8.7 mm), 1 ov. female (cl 8.2 mm), MNHN-IU-2018-5587 (ex-SNU-220610-012), Garorim Bay, Yecheon-dong, Seosan-si , Chungcheongnam-do, 36°53’5.74”N – 126°23’23.46”E, collector unknown (probably H.J. Yang), 22.06.2002 .

Taiwan: 1 male (cl 11.8 mm) , 2 females (cl 5.5, 8.5 mm), OUMNH. ZC. 2019.06.59, Chang Hua, mudflat, leg. T. Y. Chan et al., 12.1996 ; 1 juv. male (cl 4.7 mm), ZRC 2014.0676 , Shinzhu, mangrove, leg. Y. Cai & C.W. Lin, 28.11.1997 .

Description. See Figs. 25–27 . Medium-sized species of Alpheus (maximal cl 12.1 mm, tl ~ 36.3 mm; present study; Miya 1995). Carapace glabrous, finely pitted, without pubescence, with slight grooves. Rostrum short, triangular, distally acute, typically reaching 0.3 length of first article of antennular peduncle, sometimes its mid-length; rostral carina present as low elevation, fading posterior to eye level; rostro-orbital furrows poorly demarcated or indistinct. Pterygostomial angle broadly rounded; cardiac notch deep.

Pleon smooth, scarcely pitted, without pubescence. Telson moderately broad, ovate-rectangular, gently tapering towards posterior margin, about 1.7–1.8 times as long as maximal width near proximal margin; lateral margins with broad concavity on proximal half; dorsal surface finely pitted, without trace of median depression, with two pairs of short spiniform setae inserted in deep pits at considerable distance from lateral margins, first pair near telson mid-length, second pair between 0.7 and 0.8 of telson length; posterior margin broadly rounded, with two pairs of spiniform setae at posterolateral angles, lateral shorter than mesial.

Antennular peduncle with stylocerite broad, markedly convex laterally, with acute tip, latter reaching, but not overreaching distal margin of first article; ventromesial carina with anteriorly directed, distally subacute tooth; second article about 2.3–2.4 times as long as wide. Antennal peduncle with basicerite armed with small, sharp tooth; carpocerite reaching far beyond scaphocerite; scaphocerite with lateral margin nearly straight to very shallowly concave; blade moderately broad, separated from broad distolateral tooth by deep cleft; anterior margin of blade broadly rounded, exceeded by stout distolateral tooth.

Third maxilliped with antepenultimate article not particularly broadened; penultimate article elongate, about four times as long as wide, with long setae on ventral margin; ultimate article with dense transverse rows of short serrulate setae on mesial surface and longer setae on dorsal and lateral surfaces, especially near or on apex; coxal lateral plate acutely protruding dorsally; exopod reaching end of antepenultimate article.

Major cheliped of A. edwardsii - type. Merus stout, about twice as long as wide; ventromesial margin unarmed distally. Carpus very short, cup-shaped. Chela large, massive, with fingers about 0.7 length of palm. Mesial face of palm largely smooth, except for small field of minute granules dorsal to ventral shoulder, and with weak mesial transverse ridge in proximal half, extending from proximal edge of subtriangular mesial longitudinal groove to ventral surface of palm. Lateral face of palm smooth; lateral longitudinal groove deep, subrectangular; proximal half without distinct transverse ridge. Dorsal shoulder smooth, gently sloping into broad transverse groove with angle of about 45°. Ventral shoulder pronounced, slightly protruding in lateral view, broadly rounded, smooth. Pollex with mesial face finely granulated over most of its surface, with short subdistal mesial ridge near margin, without proximal protuberance; area ventral to mesial subdistal ridge not grooved; distomesial angle distinctly superior to 90°, blunt; lateral face smooth; distolateral angle superior to 90°. Dactylus with weak dorsal ridge, latter slightly twisted mesially, not protruding proximally; mesial and lateral surfaces smooth; dactylar plunger very stout, large, with anterior margin well delineated, clearly separated from ventral margin of dactylus; distal surface of plunger somewhat truncate. Adhesive discs small.

Male minor cheliped with chela strongly balaeniceps. Merus slightly slenderer than that of major cheliped, about 2.5 times as long as wide; ventral margin with distomesial angle unarmed; distomesial margin slightly rugose. Chela not particularly swollen, slender in lateral view, with fingers about as long as palm; all surfaces smooth, without granulation. Palm subcylindrical, compressed, feebly swollen; both mesial and lateral longitudinal grooves well marked, deep; dorsal shoulder distinct, rounded, sloping almost perpendicularly into dorsal transverse groove; ventral transverse groove present, relatively deep, marked by distinct ventral shoulder on lateral surface. Pollex with mesial surface bearing row of balaeniceps setae on low crest extending from base to about mid-length of pollex; lateral surface with similar row of balaeniceps setae as on mesial surface. Dactylus with conspicuous lateral expansion (balaeniceps expansion) in proximal half, about 1.7 as long as maximal width; lateral and mesial dactylar ridges each with dense rows of balaeniceps setae. Cutting edges of both fingers shallowly excavated on each side of sharp, blade-like ridge.

Female minor cheliped simple, not balaeniceps. Chela slender, not particularly swollen, with fingers subequal to, or slightly longer than palm. Palm with surface smooth, not granulated; mesial longitudinal groove feebly developed; lateral longitudinal groove distinct, but shallow; dorsal transverse groove usually distinct, but dorsal shoulder poorly demarcated; ventral transverse groove present in form of deep sinus bordered by feebly developed ventral shoulder, latter sometimes not distinct (especially in younger females or regenerated chelipeds). Fingers simple, with sharp cutting edges, slightly gaping when closed; fingertips strongly curved and crossing.

Second pereiopod with ratio of carpal subarticles approximately equal to 4: 2.3: 1: 1: 1.7. Third pereiopod moderately robust; ischium armed with short, stout spiniform seta on ventrolateral surface; merus about 5.2 times as long as maximal width, unarmed; propodus with three or four short spiniform setae on ventral margin and one spiniform seta on distoventral margin adjacent to dactylus; dactylus about half-length of propodus, distinctly spatulate, expanded, wider than propodus in dorsal view, with two rows of setae along ridges. Fourth pereiopod generally similar to third pereiopod, shorter and slenderer; dactylus comparatively shorter, about 0.4 length of propodus. Fifth pereiopod much slenderer than third and fourth pereiopods; ischium unarmed; propodus apparently without spiniform setae, with well-developed setal brush; dactylus subspatulate, much less expanded compared to that of third or fourth pereiopod, about half-length of propodus.

Male second pleopod with appendix masculina 0.8 length of appendix interna. Uropod with each protopodal lobe ending in subacute tooth distally; exopod and endopod broad, ovate; diaeresis of exopod complete, almost straight, with broadly subtriangular lobe near small distolateral spiniform seta and adjacent distolateral tooth; lateral margin of exopod broadly convex.

Eggs numerous (> 100 in larger females), small; egg diameter about 0.65 mm.

Colour pattern. Carapace greyish, semi-opaque, with two complete transverse bands of dark brown to dark grey-blue colour, one broad complete band near posterior margin and one narrower, laterally broken band at about carapace mid-length; two smaller, incomplete (dorsally not closing) and more diffuse bands present in anterior half of carapace, one along its anterolateral margin and one lateral to cardiac area; pleon with six moderately broad, dark blue-grey, blue-green or red-brown transverse bands, one across each pleonite and near its posterior margin; broad white spaces between dark bands with small but conspicuous neon-yellow spots, most of them fringing dark bands on carapace and pleon; antennular peduncles and scaphocerite patchily marbled with brown and yellow; antennular and antennal flagella pale yellow or pale greenish; mesial face of major chela olive-green, with paler greenish or orange-yellowish areas, especially on dorsal and ventral transverse grooves; dactylus dark olive-green; distal portion of both fingers pale orange; minor chela olive-green mottled with brown, fingers darker; second to fifth pereiopods pale yellowish; telson and uropods with patchy brown mottling and yellow spots, darker distally; posterior half of uropodal exopod dark blue ( Fig. 28 ; see also Jeng & Chang 1985: fig. 23; Yoshigou 2009: pl. III, figs. 1–4).

Type locality. Tanabe , Wakayama Prefecture, Honshu, Japan (collection locality of the holotype) .

Distribution. Temperate and subtropical north-western Pacific ( Fig. 51F ): Japan (Honshu, Kyushu, Shikoku, Okinawa), South Korea (Garorim Bay, Byeonsan = Pyonsan) and Taiwan (Chang Hua, Shinzhu, Tamsui River).

Etymology. This species is named after the author’s dear colleague, Keiichi Nomura (Sabiura Marine Park Research Station, Japan), who contributed to alpheid taxonomy early in his career and made important material available for the present study.

Common name proposed. Nomura’s snapping shrimp.

Ecology and biology. Alpheus nomurai sp. nov. is a marine / estuarine snapping shrimp largely confined to intertidal mudflats, especially those situated inside or close to estuaries. The shrimps usually live in pairs (rarely as singles) in complex tridimensional burrows made in soft mud, with side branches extending from the burrow entrance in a radius of about 25 cm and penetrating about 10–20 cm deep into the mud ( Miya 1995, as A. euphrosyne richardsoni , based on Dôtu 1961: fig. 1). The burrows of A. nomurai sp. nov. are typically composed of a main tunnel with one or two or three openings and multiple branches, either interconnected or ending blindly (see Kirihara et al. 2021: figs. 2, 3, as Alpheus sp. ). They often serve as shelter for small gobies, such as Apocryptodon punctatus Tomiyama, 1934 , Gymnogobius cylindricus ( Tomiyama, 1936) and Acentrogobius sp. ( Miya 1995; Suzuki & Wada 1999; Yoshigou 2009; Koyama et al. 2017; Kirihara et al. 2021, as Alpheus sp. , A. euphrosyne richardsoni or A. richardsoni ). It must be noted that the association between the snapping shrimp identified as A. richardsoni and the goby Drombus ocyurus ( Jordan & Seale, 1907) in Kunishima et al. (2022, as Acentrogobius ocyurus ) involves a species from the A. malabaricus complex, possibly A. dolichodactylus Ortmann, 1890 (see under the synonymy of A. richardsoni ). Whether or not A. ocyurus also associates with A. nomurai sp. nov. remains to be shown. Some shrimps were found in burrows made under large intertidal rocks partly embedded in mud ( Jeng & Chang 1985, as A. euphrosyne ). The large number of eggs and their small size suggest an extended larval development in A. nomurai sp. nov. ( Yang & Kim 1996, as A. euphrosyne richardsoni ).

Taxonomic remarks. Alpheus nomurai sp. nov. was previously confused with two other species of Alpheus , viz. the distantly related A. bisincisus De Haan, 1844 ( Dôtu 1961) and the presumably more closely related A. richardsoni ( Miya 1995, as A. euphrosyne richardsoni ). The morphological differences between A. nomurai sp. nov. and A. richardsoni are relatively subtle, which explains Miya’s (1995) identification of the Japanese and Korean material as A. euphrosyne richardsoni , despite the resulting disjunct, antitropical distribution for A. richardsoni . Nevertheless, A. nomurai sp. nov. and A. richardsoni can be separated from each other by the shape of the dactylar plunger of the major chela, which appears to broader and stouter in A. nomurai sp. nov. (cf. Fig. 27D ; Miya 1995: fig. 2C; Banner & Banner 1982: fig. 74e); the presence of a small subdistal mesial ridge in A. nomurai sp. nov., which is not distinct in A. richardsoni (cf. Fig. 27C ; Banner & Banner 1982: fig. 74c); the size and position of the tooth on the distolateral margin of the antennal basicerite, which is more developed and more ventral in A. nomurai sp. nov. (cf. Fig. 26D ; Miya 1996: fig. 2A; Banner & Banner 1982: fig. 74b); and the armature of the third pereiopod propodus, which has only three to four spiniform setae in A. nomurai sp. nov. vs. at least six in A. richardsoni (cf. Fig. 26G ; Miya 1995: fig. 2F; Banner & Banner 1982: fig. 74n). In addition, A. nomurai sp. nov. with the maximal total length not exceeding 36.5 mm is a much smaller species compared to A. richardsoni , which may reach 65 mm. The most obvious and reliable distinguishing feature between these two species involves the banding pattern of the pleon: in A. nomurai sp. nov., each pleonite has a simple dark transverse band ( Fig. 28 , disregarding diffuse bands formed by neon-yellow spots), whereas in A. richardsoni , each pleonite has a double or even triple band ( Figs. 17 , 18 ). Of course, the two species are also geographically widely separated, with A. nomurai sp. nov. and A. richardsoni each restricted to temperate and subtropical north-eastern Asia and Australia / New Zealand, respectively ( Fig. 51C, F ).

Alpheus nomurai sp. nov. can be separated from A. euphrosyne and A. eurydactylus essentially by the same criteria as A. richardsoni (see above), and from A. microrhynchus and A. cyanoteles by the conspicuously broadened, spatulate dactylus of the third to fifth pereiopods, which in the other two species is trigonal-subspatulate in shape (cf. Miya 1995: fig. 2F; Yeo & Ng 1996: fig. 6b, d). For separation of A. nomurai sp. nov. from other morphologically similar species see below and refer to Table 1 .

Figures

FIGURE 17. Alpheus richardsoni Yaldwyn, 1971: male (cl 8.3 mm) from Loders Creek, Moreton Bay, Queensland, Australia (FLMNH UF 18694) [A]; male (cl 9.3 mm) from Cleveland, Queensland, Australia (OUMNH.ZC 2009-09-0015); A, B— habitus, dorsal view; C—same, lateral view. Photographs by the author.

FIGURE 18. Alpheus richardsoni Yaldwyn, 1971: male (cl indet.) from Brunswisk River, New South Wales, Australia [A, B]; male from Parengarenga (Paua), New Zealand [C]; male from Whangarei, New Zealand [D]; A, C—habitus, dorsal view; B—same, lateral view; D—tail fan, dorsal view. Specimens not deposited / deposition unknown. Photographs courtesy of Denis Riek (A, B) and Richard B. Taylor (C, D).

FIGURE 25. Alpheus nomurai sp. nov.: holotype, male (cl 8.8 mm) from Tanabe, Wakayama, Japan (MNHN-IU-2018-5590); A—habitus, dorsal view; B—frontal region, dorsal view; C—major (left) cheliped, lateral view; D—same, mesial view; E— minor (right) cheliped, mesial view; F—same, dorsolateral view; G—same, lateral view. Refer to A for scale.

FIGURE 26. Alpheus nomurai sp. nov.: paratype, male (cl 8.5 mm) from Tanabe, Japan (MNHN-IU-2018-5588); A—frontal region, dorsal view; B—telson, dorsal view; C—ventromesial carina of first article of antennular peduncle, lateral view; D— antennal basicerite, lateral view; E—third maxilliped, lateral view; F—second pereiopod, lateral view; G—third pereiopod, lateral view; H—same, dactylus, dorsal view; I—fifth pereiopod, lateral view; J—same, propodus and dactylus, mesial view; K—second pleopod, appendices masculina and interna, anterior view; L—left uropod, dorsal view.

FIGURE 27. Alpheus nomurai sp. nov.: paratype, male (cl 8.5 mm) from Tanabe, Japan (MNHN-IU-2018-5588) [A–G]; paratype, ovigerous female (cl 8.8 mm) from the same locality (MNHN-IU-2018-5744) [H]; paratype, ovigerous female (cl 11.9 mm) from Shimanto River, Japan (MNHN-IU-2018-5589) [I]; A—major (right) cheliped, chela, lateral view; B—same, ischium to carpus, lateral view; C—same, chela and carpus, mesial view; D—same, dactylus, lateral view; E—male minor (left) cheliped, chela and carpus, mesial view; F—same, chela, lateral view; G—same, ischium to carpus, lateral view; H—female minor cheliped, lateral view; same, carpus and chela, lateral view.

FIGURE 28. Alpheus nomurai sp. nov.: male (cl not determined) from Yabu River, Nago, Okinawa-jima, Japan (not deposited) [A, B]; male paratype (cl 9.6 mm) from Tanabe, Wakayama, Japan (OUMNH.ZC. 2011.06-006) [C]; four specimens, including male holotype (cl 8.8 mm), from Tanabe, Wakayama, Japan (holotype: MNHN-IU-2018-5590) [D]; A—habitus, lateral view; B–D, same, dorsal view. Photographs courtesy of Tadafumi Maenosono (A, B) and Keiichi Nomura (C, D).

FIGURE 51. Distributional maps for species of Alpheus treated in this study: A—A. eurphrosyne De Man, 1897; B—A. eurydactylus De Man, 1920; C—A. richardsoni Yaldwyn, 1971; D—A. microrhynchus De Man, 1897; E—A. cyanoteles Yeo & Ng, 1996; F—A. nomurai sp. nov.