Alpheus euphrosyne De Man, 1897

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 : 12-23

Alpheus euphrosyne De Man, 1897

( Figs. 1 , 4–10 , 51A , 53A , lower row)

Alpheus euphrosyne De Man 1897: 745 , pl. 36, fig. 64; De Man 1898: 317, pl. 4, fig. 2; De Man 1911: 413; Ahmad 1957: 16; Banner & Banner 1966: 130 (part.?, not fig. 49); Thomas 1976: 667; Holthuis, 1980: 119 (part.?); (?) Becker 1996: 95; (?) Becker et al. 2000: 195; Naiyanetr 2007: 173 (part.?, referring to Banner & Banner 1966); Harikrishnan & Kurup 2008: 111, fig. 1 (part., specimen on the left photograph); Paras et al. 2019: 1695 (part., not description), figs. 1–3.

Crangon euphrosyne .— Suvatti 1937: 48 (part.?).

Alpheus euphrosyne euphrosyne . — Li et al. 2008, fig. 2A; Harikrishnan et al. 2010: 195.

Alpheus euphrosyne sensu lato.— Anker & De Grave 2016: 355 [specimen dredged off the eastern Straits of Johor; most Singaporean specimens are A. mangalis sp. nov. and A. eurydactylus ; at least one specimen is A. takla sp. nov., see below].

Not Alpheus euphrosyne . — Johnson 1976: 37 [= Alpheus spp. , most probably A. eurydactylus De Man, 1920 or A. mangalis sp. nov.]; Frith et al. 1976: 18 [= Alpheus spp. , most probably A. eurydactylus De Man, 1920 or A. takla sp. nov.]; Yeo & Ng 1996: 58 [= Alpheus spp. , including A. eurydactylus and A. mangalis sp. nov., fig. 8d = A. mangalis sp. nov.]; Bruce & Coombes 1997: 321 [= Alpheus spp. , most probably A. eurydactylus De Man, 1920 or A. mangalis sp. nov.]; Edgar 1997: 194 (colour photo only) [= Synalpheus sp. ]; Shokita 2004: 82 [= Alpheus spp. , most probably A. eurydactylus De Man, 1920 or A. takla sp. nov.]; Wada 2013: 184, fig. 5 [= Alpheus spp. , most probably A. takla sp. nov.]; Paras et al. 2019: 1695 (part., text, not figs. 1–3) [= A. euphrosyne euphrosyne sensu Banner & Banner (1982) , see below]; Sha et al. 2019: 87, fig. 2.48 [= Alpheus spp. , possibly A. eurydactylus De Man, 1920 , A. nomurai sp. nov. or other taxa, see below].

Not Alpheus euphrosyne euphrosyne .— (?) Banner & Banner 1981: 23, 92; Banner & Banner 1982: 232, fig. 73, tab. 5 (part.?); (?) Banner & Banner 1983: 30; Banner & Banner 1985: 16 (part.); Chace 1988: 27 (part.) [= Alpheus spp. , possibly A. eurydactylus De Man, 1920 , A. takla sp. nov. and A. mangalis sp. nov.].

Not Alpheus euphrosyne langi .— Banner & Banner 1982: 238 [= A. pontederiae de Rochebrune, 1883 ].

Alpheus tirmiziae Kazmi 1974: 170 , figs. 1–4; Banner & Banner 1978: 233, fig. 2i–m; Sha et al. 2019: 122, fig. 2.67.

Alpheus tirmizae (lap. cal.).— Kazmi & Kazmi 1979: 154.

Type material. Neotype: male (cl 16.6 mm, tl 48.5 mm, chl 26.0 mm), RMNH Crus.D. 49669, Indonesia, Java, Surabaya, leg. P. Buitendijk, 02.1929.

Additional material examined. Indonesia: 1 female (cl indet., missing both chelipeds), ZMA Crus.D. 202727, Siboga-Expeditie, Postillon Islands (Sulawesi Selatan), leg. Jacquin, no date ; 1 male (cl indet.), 1 ov. female (cl indet., missing both chelipeds), ZMA Crus.D. 202726, Sumatra, Bagansi Api-Api, leg. J.D.F. Hardenberg, 01.1929, det. H. Balss ; 1 female (cl 15.5 mm, missing both chelipeds), 1 ov. female (cl 16.2 mm, missing major cheliped, identification somewhat tentative), ZMA Crus.D. 202793, Nias, leg. Kleiweg de Zwaan , no date .

China: 1 male (cl 14.3 mm), ZRC 2014.0677 , Guangdong, Nanao County, Houzhai , fish market, leg. Y. Cai & N.K. Ng, 12.11.1998 ; 1 male (cl 23.0 mm), USNM 62106 , locality not specified, don. S.F. Light ; 1 male (cl 20.5 mm), USNM 62107 , Fujian, “Santu north of Foochow” (possibly Shantou, south of Fuzhou ), no date, don. S.F. Light ; 1 female (cl 13.7 mm), USNM 62109 , Fujian, Xiamen, Amoy , outer harbour, net trap, leg. & don. S.F. Light, 16.04.1923 ; 1 male (cl 17.5 mm), MCZ 1743 , Hong Kong, leg. Capt. Putnam, 03.1861.

Taiwan: 1 female (cl 10.0 mm), ZRC 1999.0723 , Kaohsiung County, Tungkang , fish port, leg. P.K.L. Ng & K. Lim , 05.1999; 1 female (cl 13.8 mm), USNM 59044 , Yensui River , leg. M. Maki , don. M. Oshima, 01.1923.

Vietnam: 4 males (cl 12.5–18.0 mm), MNHN-IU-2018-5730, Ha Tien, Sau, depth: 20–30 m, leg. H. Duy, 21.08.1995 .

Cambodia: 1 male (cl 18.9 mm), ZRC 2013.0458 , Kampot and Prek Romeas fish landings, leg. T. R. Roberts, 29.03.2006 – 03.04.2006 .

Thailand: 5 specimens, including 3 males (cl 16.0–16.9 mm), ZRC 2000.2150 , Gulf of Thailand, off Khanom, trawl, fish port, leg. P.K.L. Ng, 12.1984; 1 male (cl 19.3 mm), MNHN-IU-2018-5752, same collection data as for previous specimens; 1 male (cl 14.0 mm), ZRC 2003.0619 , Songkhla Lake (Thale Sap), Sakom crab landing, leg. P.K.L. Ng et al., 15– 17.10.2003; 1 male (cl indet.), ZRC 2000.2137 , Gulf of Thailand, Siracha, fish market, leg. P.K.L. Ng, 02.2000; 3 males (cl 20.2–21.7 mm), 1 ov. female (cl 21.9 mm), ZRC 2000.0957 , Gulf of Thailand, Chonburi, Angsila and Siracha, fish ports, leg. P.K.L. Ng et al., 20.02.2000; 3 males (cl 15.0–16.9 mm), OUMNH. ZC. 2019.06.42 [ex-ZRC 2000.0956], Gulf of Thailand, Chonburi, Angsila and Siracha, fish ports, leg. P.K.L. Ng et al., 20.02.2000; > 20 specimens of both sexes (cl indet.), ZRC 1998.1066 , Gulf of Thailand, Chonburi, Angsila, fish port, leg. P.K.L. Ng, 25.09.1998; 1 male (cl 16.4 mm), 1 female (cl 18.0 mm), MNHN-IU-2018-5593 (ex-ZRC 1998.1066), same collection data as for previous specimens; 2 males, 1 female (cl indet.), RMNH Crus.D.42009, Gulf of Thailand, Chonburi, ca. 100 km SE of Bangkok, between Si Racha and Naklua, fishermen, 14.03.1985, leg. A.C.J. Burgers & L.B. Holthuis; 1 male, 1 female (cl indet.), RMNH Crus.D.42426, Gulf of Thailand, Surat Thani, off river mouth of Don Sak, depth: 4 m, 20.10.1992, leg. S. Chaitiamvong; 1 male (cl 21.9 mm), 1 female (cl 13.2 mm), MNHN-IU-2018-5751 (ex ZRC 1999.2006 ), Gulf of Thailand, Siracha, fish port, leg. P.K.L. Ng et al., 10.11.1999; 1 male (cl 16.1 mm), 1 female (cl 14.5 mm), ZRC 1999.2005 , Gulf of Thailand, Angsila, fish port, leg. P.K.L. Ng et al., 10.11.1999; 2 males (cl 15.5 mm, 17.5 mm), 1 female (cl 16.0 mm), USNM 95528 , Gulf of Thailand, off Lem Sing, 14.06.1926; 1 male (cl 21.5 mm), ZRC 2008.0600 , Andaman Sea off Phuket, Phuket fish port, leg. P.K.L. Ng et al., 17.02.2001; 1 male (cl 20.2 mm), OUMNH. ZC. 2019.06.43 [ex-ZRC 1998.1152], Andaman Sea off Phuket, Phuket fish port, leg. S. Chiatiamuong et al., 12.1998.

Malaysia: 1 male (cl indet., missing major cheliped), RMNH Crus.D. 49740, Penang, Kuala Jalan Baru, 02.06.1961, leg. E. R. Alfred ; 1 female (cl 21.5 mm), MNHN-IU-2018-5594, Lumut, no further data, don. V. C. Chong, 1999 .

Singapore: 1 male (cl 23.6 mm), ZRC 2008.0632 , Siglap ( Bedok area ), 06.1933 ; 1 male (cl 6.7 mm, missing both chelipeds), ZRC 2014.0671 , south of Pulau Tekong , MPA grid 0422, depth: 11.9–12 m, mud, clay, rectangular dredge, leg. S.C. Lim, A. Anker & C.K. Chim, 25.03.2014 .

India: 1 male (cl indet.), RMNH Crus.D.49747, Kochi (Cochin), 28.03.1979, leg. J.C. Miquel; 1 female (cl indet.), RMNH Crus.D.49748, same collection data as for previous specimen .

Pakistan. 1 female (cl 11.4 mm), USNM 63515 , Pakistan, Kurrachee Bay (= Karachi), no further data [identified by H. Coutière as A. euphrosyne ] .

Redescription. See Figs. 4–7 . Large-sized species of Alpheus (maximal cl 23.6 mm, tl ~72.0 mm). Carapace glabrous, finely pitted, especially around cardiac region, without pubescence, with slight grooves. Rostrum short, triangular, distally acute, reaching at most to mid-length of first article of antennular peduncle; rostral carina absent or present as low broad elevation; rostro-orbital furrows indistinct or extremely shallow. Pterygostomial angle broadly rounded; cardiac notch deep.

Pleon smooth, finely and scarcely pitted, without pubescence. Telson very broad, ovate-rectangular, slightly tapering towards posterior margin, about 1.3–1.4 times as long as maximal width near proximal margin; lateral margins with shallow concavity on proximal half; dorsal surface finely pitted, with longitudinal median depression densely furnished with setae along its margins, and 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, and with numerous erect simple setae; posterior margin broadly rounded, with two pairs of small spiniform setae at posterolateral angles, lateral shorter than mesial (often broken or missing).

Antennular peduncle with stylocerite broad, markedly convex laterally, with acute tip, latter not overreaching distal margin of first article; ventromesial carina with small, anteriorly directed, sharp tooth; second article about 2.2–2.5 times as long as wide. Antennal peduncle with distoventral margin of basicerite unarmed or with minute, blunt or subacute tooth; carpocerite not reaching beyond scaphocerite; scaphocerite with lateral margin almost straight; blade very broad, separated from broad distolateral tooth by deep cleft; anterior margin of blade broadly rounded and reaching somewhat beyond distolateral tooth.

Third maxilliped with antepenultimate article somewhat broadened; penultimate article elongate, about three times as long as wide, with long setae on ventrolateral margin, some surpassing ultimate article; ultimate article with dense transverse rows of short serrulate setae on mesial surface and much longer setae on dorsal and lateral surfaces, especially near or on apex; coxal lateral plate bluntly protruding dorsally; exopod fleshy, broad, 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 0.6–0.7 length of palm; surface partly heavily granulated. Mesial face of palm with distinct mesial transverse ridge in proximal half, extending from proximal edge of subtriangular mesial longitudinal groove to ventral surface of palm, although not reaching it; large areas of mesial surface, including mesial longitudinal groove and part of mesial transverse ridge, densely covered with granules. Lateral face of palm mostly smooth, with relatively small field of granules present on low ridge between lateral longitudinal groove and dorsal edge of ventral shoulder; lateral longitudinal groove deep, subrectangular; proximal half with low transverse ridge. Dorsal shoulder overhanging transverse groove, i.e., distinctly protruding above groove in form of blunt tooth. Ventral shoulder pronounced, slightly protruding in lateral view, broadly rounded; surface covered with granules. Pollex with mesial face distinctly granulated over most of its surface; both mesial subdistal ridge and adjacent proximal protuberance prominent, extending subdistal angle of pollex; area ventral to mesial subdistal ridge conspicuously grooved; distomesial angle distinctly superior to 90°, blunt; lateral face distinctly granulated, except close to ventral edge; distolateral angle about 90°, broadly rounded. Dactylus with prominent dorsal ridge, latter distinctly twisted mesially and protruding proximally; mesial surface strongly granulated; lateral surface moderately granulated, mostly proximally so, with deep depression above plunger; dactylar plunger relatively short, with anterior margin gently sloping and merging into (i.e., almost in continuation with) ventral margin of dactylus; distal surface of plunger obliquely flattened, its mesial surface with deep transverse channel. Adhesive discs small.

Male minor cheliped with chela strongly balaeniceps. Merus noticeably slenderer than that of major cheliped, about three times as long as wide; ventral margin with distomesial angle unarmed. Chela moderately swollen, slender in lateral view, with fingers about as long as palm. Palm subcylindrical, slightly compressed, feebly swollen; mesial face smooth proximally, distinctly granulated distally, with low bump-like elevation subdistally; mesial longitudinal groove well marked, deep; lateral face of palm with small field of granules distally, below lateral longitudinal groove; lateral longitudinal groove well marked, deep, with lower margin slightly elevated; dorsal shoulder pronounced, rounded, in form of blunt tooth slightly overhanging deep, broad dorsal transverse groove; ventral transverse groove moderately deep, bordered by distinct ventral shoulder on lateral surface. Pollex with mesial surfaces granulated proximally and with row of balaeniceps setae on low crest extending from base to mid-length of pollex; lateral surface mostly smooth, with similar row of balaeniceps setae as on mesial surface. Dactylus with well-developed proximal balaeniceps expansion, about 1.7–1.8 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 1.5–2.0 times as long as palm. Palm granulated, more on mesial than on lateral side, without mesial or lateral longitudinal grooves. 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: 3: 1: 1: 1.5. Third pereiopod moderately robust; ischium armed with short, stout spiniform seta on ventrolateral surface near proximal margin, sometimes unarmed; merus about 4.5 times as long as maximal width, unarmed; propodus with two to four more or less stout spiniform setae on ventral margin and one pair of spiniform setae on distoventral margin adjacent to dactylus; dactylus about 0.3 length of propodus, spatulate, conspicuously expanded, slightly wider than propodus in dorsal view, with dense row of setae and tufts of setae along median ridge. Fourth pereiopod generally similar to third pereiopod, slightly slenderer; merus about 5.0 times as long as maximal width; dactylus about 0.3 length of propodus. Fifth pereiopod much slenderer than third and fourth pereiopods; ischium unarmed; propodus with four slender spiniform setae and well-developed setal brush; dactylus spatulate, less expanded compared to that of third or fourth pereiopod, about 0.4 length of propodus.

Male second pleopod with appendix masculina 0.6–0.8 length of appendix interna. Uropod with each protopodal lobe ending in sharp tooth distally; exopod and endopod broad, ovate; diaeresis of exopod complete, straight for most part, with small subacute or blunt tooth near small distolateral spiniform seta and adjacent distolateral tooth; lateral margin of exopod broadly convex.

Eggs numerous (> 200 in large females), small; egg diameter less than 0.6 mm.

Colour pattern. Body pale beige to greyish yellow; carapace with dark grey-blue anterolateral margin and two diffuse, dark brown, transverse bands, one across mid-length and one near posterior margin; each pleonite with dark brown to grey-brown band running transversely near posterior margin; antennular flagella bright blue (lateral) or reddish purple (mesial); antennal flagella bright blue; mesial face of major chela olive-green with large pale yellow or pale brown-orange areas, and two large, more or less conspicuous, violet-blue patches on palm; fingers distally pale orange-pink; dactylar plunger with whitish blue area; minor chela pale olive-green, darker and with purplish tinge on fingers; walking legs pink to reddish; pleopods reddish; telson pale greenish yellow, darker posteriorly; uropods pale yellow proximally, dark blue distally ( Figs. 8–10 ; see also black-and-white photograph in Li et al. 2008: fig. 2A, and colour photographs in Harikrishnan & Kurup 2008: fig. 1 and Paras et al. 2019: figs. 1–3, specimen with faded colours).

Type locality. Java Sea ( De Man 1897). Neotype from Surabaya , Java, Indonesia.

Distribution. Tropical Indo-West Pacific from the northern Arabian Sea to South China Sea and Java Sea ( Fig. 51A ), including Pakistan (Karachi), India ( Kochi, Vembanad Lake, Gulf of Mannar, Palk Bay), Bangladesh, Thailand (Andaman Sea: Phuket; Gulf of Thailand: Pattani, Angsila, Khanom, Surat Thani, Satun, Songkhla Lake), Cambodia (Kampot), Vietnam (Nhatrang Bay), Malaysia (Andaman Sea: Penang), Indonesia (Java, Sulawesi, Sumatra, Nias?), Singapore (Bedok, Pulau Tekong), southern China (Guangdong, Zhejiang, Hong Kong), and Taiwan (Yensui, Kaohsiung) ( De Man 1897; Kazmi 1974; Banner & Banner 1978; Li et al. 2008; Harikrishnan et al. 2010; Paras et al. 2019; present study).

Common names proposed. Euphrosyne snapping shrimp; De Man’s estuarine snapping shrimp.

Ecology and biology. Alpheus euphrosyne appears to be mainly a marine / estuarine snapping shrimp associated with subtidal sandy, sandy-muddy and muddy bottoms.Therefore, it can be considered as a polyhaline and mesohaline species, typically encountered within or near large estuarine areas. However, A. euphrosyne is capable of tolerating very low salinities and even freshwater conditions, at least in laboratory experiments ( Harikrishnan & Kurup 2008; Harikrishnan et al. 2010). The exact depth range of A. euphrosyne is unknown as most specimens examined herein came from crab/prawn/fish landings or fish markets. Others were dredged from a depth of 8.5–27 m ( Thomas 1976; Banner & Banner 1978; Paras et al. 2019; present study) or collected with indigenous stake nets ( Harikrishnan et al. 2010). However, the identity of A. euphrosyne in Harikrishnan & Kurup (2008) and Harikrishnan et al. (2010) needs confirmation (see below).

In the lower Kochi ( Cochin) estuary in southern India, Harikrishnan et al. (2010) observed a high preponderance of A. euphrosyne in post- and pre-monsoon months, i.e., in salinity conditions varying from polyhaline in pre-monsoon months to mesohaline (5–18 0 / 00) in post-monsoon months, suggesting an inward migration of primarily marine species to highly fertile estuarine areas for feeding and breeding. These authors also studied some aspects of the reproductive biology of A. euphrosyne , examining 1309 females with cl 8.5–21.5 mm. The large number of eggs (141–1553 eggs per brood, mean fecundity 480 272) and their small size (diameter range: 0.12–0.53 mm) suggest an extended larval development in this species.

Alpheus euphosyne is one of the largest snapping shrimps known to date, with the carapace length (cl) reaching 22.6 mm and total body length (tl) up to 71 mm ( Thomas 1976). The largest specimen in the present material is a female from Thailand (ZRC 2000.0957) with cl 22 mm and tl 66 mm, with several other adults exceeding cl 20 mm and tl 60 mm; in the largest specimens ( Fig. 8 ), the major chela length (chl) overreaches 35 mm. Due to its large size, A. euphrosyne is occasionally sold on fish / crab landings and seafood markets, mainly in Thailand (Angsila, Siracha, Songkhla Lake, Phuket; see also Fig. 10D ), but also in China (Houzhai), Vietnam (Nha Trang), Cambodia (Kampot) and India (Pamban, Mandapam) ( Thomas 1976; present study).

Taxonomic remarks. Alpheus euphrosyne can be most easily recognised by several features on the major cheliped ( Figs. 5C, D , 7A–D ) and telson ( Fig. 6B ) and, when alive or fresh, by its unmistakable and therefore diagnostic colour pattern ( Figs. 8–10 ). The most important distinguishing features of the major cheliped of A. euphrosyne are the absence of a sharp tooth on the mesioventral margin of the merus; the presence of a prominent sharp ridge preceded by a conspicuous bump-like elevation on the mesial face of the pollex; the dorsal shoulder forming a blunt tooth overhanging the adjacent transverse groove; the mesial palmar face with large areas covered by numerous, very conspicuous granules; and the dactylus with a very short, distally truncate plunger and prominent, mesially protruding, proximal ridge ( Figs. 5C, D , 7A–D ). The male minor cheliped is fully balaeniceps, i.e., with a strongly expanded dactylus and well-developed rows of balaeniceps setae, and with a pronounced sculpture on the palm, consisting of a deep dorsal groove and shallower ventral transversal groove (the former usually being slightly overhung by dorsal shoulder), and well-marked longitudinal grooves on both sides ( Figs. 5E , 7E–G ). Other important features of A. euphrosyne are the absence of a rostral carina; the extremely shallow, barely noticeable rostro-orbital furrows; the very broad scaphocerite; the antennal basicerite unarmed or armed with a minute subacute tooth; the ischium of the third pereiopod typically armed with a small spiniform seta (not illustrated by De Man 1897, see Fig. 1D ); the third and fourth pereiopods with dactyli expanded, spatulate; and the dorsal surface of the telson with a longitudinal median depression, with its lateral edges densely furnished with setae ( Fig. 6A, B, D, G, I ). For separation of A. euphrosyne from closely related species see below and refer to Table 1 .

All material reported as A. tirmiziae ( Kazmi 1974; Kazmi & Kazmi 1979; Banner & Banner 1978; Sha et al. 2019) is herein referred to A. euphrosyne . The female holotype of A. tirmiziae dredged in the Bay of Bengal off Bangladesh has a somewhat aberrant, most probably damaged rostro-orbital area ( Banner & Banner 1978), but in most other characters agrees very well with female specimens of A. euphrosyne from Thailand and Taiwan. The main difference between A. tirmiziae and A. euphrosyne lies in the relative length of the minor cheliped fingers, which are about twice as long as the palm in the holotype of A. tirmiziae ( Kazmi 1974: fig. 4B) vs. at most 1.6 times as long as the palm in De Man’s type specimen from Java and three females from Thailand ( Figs. 1B , 7H ). Banner & Banner (1978) noted some other differences between the holotype of A. tirmiziae and their material from Hong Kong. However, the most important difference that these authors found is directly related to sexual dimorphism of the minor cheliped, which in A. euphrosyne and all related species is strongly balaeniceps in males and simple in females. The minute pits present on the carapace and pleon of the holotype of A. tirmiziae were overlooked by Banner & Banner (1978); these pits are clearly present in the neotype of A. euphrosyne and several other specimens from Thailand and Singapore. The above presented evidence justifies the placement of A. tirmiziae in the synonymy of A. euphrosyne .

As already mentioned, many previous records of A. euphrosyne do not correspond to A. euphrosyne as redefined in the present study. For instance, material from Thailand reported as A. euphrosyne by Banner & Banner (1966) is most likely A. eurydactylus or A. takla sp. nov. (see below). Some Australian specimens reported by Banner & Banner (1982) as A. euphrosyne euphrosyne were reexamined and assigned to one of the below described new species. Most records of A. euphrosyne (sometimes as A. euphrosyne euphrosyne ) from India appear to be correct, especially those accompanied by a description of the colour pattern or colour photographs ( Thomas 1976; Harikrishnan & Kurup 2008; Harikrishnan et al. 2010; Paras et al. 2019). The “new record” of A. euphrosyne from Kochi by Paras et al. (2019) was not new as the species was previously reported from this area by Harikrishnan & Kurup (2008) and Harikrishnan et al. (2010). In addition, the description of the Kochi material was largely adapted, in a simplified form, from Banner & Banner (1982) and therefore does not refer to A. euphrosyne sensu De Man (1897) . However, the photographs provided by Paras et al. (2019) indeed show male and female specimens of A. euphrosyne , as redefined here. Nevertheless, since the presence of other species from the A. euphrosyne — A. microrhynchus complex in India, possibly A. eurydactylus and/or A. mangalis sp. nov. is extremely likely (see below and Fig. 53 ), all biological and ecological data on A. euphrosyne in Harikrishnan & Kurup (2008) and Harikrishnan et al. (2010) must be treated with some caution.

The identity of material from the Red Sea, Persian Gulf and East Africa reported as A. euphrosyne euphrosyne by Banner & Banner (1981, 1983), without illustrations or morphological details, remains unknown. Based on the collection data for the Kenyan specimen in Banner & Banner (1983) and the concept of A. euphrosyne adopted by Banner & Banner (1966, 1978, 1982), the material from the western Indian Ocean is not A. euphrosyne sensu De Man (1897) . The same is true for the material from China reported as A. euphrosyne by Sha et al. (2019); their material ranged from Hainan to Qingdao and included Xisha Islands in the South-China Sea. However, the superficial description and crude illustrations accompanying the Chinese records are unusable for identification of (possibly more than one) species involved. The possibility that some of the Chinese material reported as A. euphrosyne may represent A. eurydactylus is discussed below.

Figures

FIGURE 1. Alpheus euphrosyne De Man, 1897: syntype, female (cl 46.0 mm) from Java Sea, Indonesia (after De Man 1897, specimen lost) [A–E]; male (cl indet., tl 34.0 mm) from Bangkok, Thailand (after De Man 1898) [F, G]; A—frontal region, dorsal view; B—female minor (left) cheliped, lateral view; C—second pereiopod, lateral view; D—third pereiopod, lateral view; E—sixth pleonite, telson and uropods, dorsal view; F—male minor (right) cheliped, dorsolateral view; G—same, minor chela, lateral view. Not to scale.

FIGURE 4. Alpheus euphrosyne De Man, 1897: chelipeds of male (cl indet.) from Sumatra, Indonesia (ZMA Crus.D.202726) showing main features and terminology used in the present study; A—major (right) cheliped, lateral view; B—same, mesial view; C—minor (left) cheliped, mesial view; D—same, lateral view. Abbreviations (in alphabetical order): ad—adhesive disks (plaques) on dactylus and palm (small on major chela, highly reduced in minor chela); be—balaeniceps expansion of minor chela dactylus; ddr—dorsal ridge of major chela dactylus (dactylar dorsal ridge); dla—dorsolateral angle of major chela pollex; dlt—dorsolateral tooth of major / minor chela palm; dma—dorsomesial angle of major chela pollex; dmt—distomesial tooth of major / minor chela palm; dp—plunger of major chela dactylus (dactylar plunger); ds—dorsal shoulder of major / minor chela palm; dtg—dorsal transverse groove of major / minor chela palm (also known as dorsal notch); lbd—lateral balaeniceps ridge of minor chela dactylus; lbp—lateral balaeniceps ridge of minor chela pollex; li—linea impressa of major / minor chela palm; lld—lateral longitudinal depression (groove) of major / minor chela palm; ltr—smooth lateral transverse ridge of major chela palm (often poorly developed); mbd—mesial balaeniceps ridge of minor chela dactylus; mbp—mesial balaeniceps ridge of minor chela pollex; mld—mesial longitudinal depression (groove) of major / minor chela palm; msr—mesial subdistal ridge on major chela pollex; mtr—smooth mesial transverse ridge of major chela palm (often poorly developed); pf—fossa (socket) of major chela pollex; vs—ventral shoulder of major / minor chela palm; vtg—ventral transverse groove of major / minor chela palm (also known as ventral notch).

FIGURE 5. Alpheus euphrosyne De Man, 1897: neotype, male (cl 16.6 mm) from Surabaya, Java, Indonesia (RMNH Crus. D.49669); A—habitus, dorsal view; B—frontal region, dorsal view; C—major (left) chela in situ, mesial view; D—same, lateral view; E—minor (right) chela in situ, dorsal view. Refer to A for scale.

FIGURE 6. Alpheus euphrosyne De Man, 1897: male (cl 16.4 mm) from Angsila, Thailand (MNHN-IU-2018-5593); 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, I—same, dactylus, mesial (H) and dorsal (I) views; J—fifth pereiopod, lateral view; K—same, propodus and dactylus, mesial view; L—second pleopod, appendices masculina and interna, anterior view; M—left uropod, dorsal view; N—right uropod, detail of distolateral angle.

FIGURE 7. Alpheus euphrosyne De Man, 1897: male (cl 16.4 mm) [A–G] and female (cl 18.0 mm) [H] from Angsila, Thailand (MNHN-IU-2018-5593); A—major (right) cheliped, chela, carpus and distal part of merus, mesial view; B—same, chela, lateral view; C—same, coxa to carpus, lateral view; D—same, dactylus, lateral view; E—male minor (left) cheliped, chela, carpus and distal part of merus, mesial view; F—same, chela, lateral view; G—same, coxa to carpus, lateral view; H—female minor chela, lateral view.

FIGURE 8. Alpheus euphrosyne De Man, 1897: male (cl indet.) from Satun, Thailand, in lateral (A) and dorsal (B) views (deposition unknown). Photographs courtesy of Rueangrit Promdam.

FIGURE 9. Alpheus euphrosyne De Man, 1897: male (cl 16.8 mm) from Pattani, Thailand (ZRC 2014.0672), in dorsal view (A), with details of the frontal area and chelipeds (B). Photographs courtesy of Sukree Hajisamae.

FIGURE 10. Alpheus euphrosyne De Man, 1897: male (cl indet.) from Nha Trang Bay, Vietnam (ZMMU) [A]; male (cl indet.) from unknown locality in Taiwan (AST) [B]; male from Dongtou Island, Zhejiang, China (IOCAS-MBM188857) [C]; male (cl indet.) from Siracha, Thailand (ZRC 2000.2137) [D]; male (cl indet.) from Kochi, India (RMNH Crus.D.49747) [E, F]; A, B, C—habitus, dorsal view; D, E—same, lateral view; F—posterior pleon and tail fan, dorsal view. Photographs courtesy of Oleg Savinkin (A), Ming-Shiou Jeng (B), Xinzheng Li (C), Peter K.L. Ng (D) and Juan C.E. Miquel (E, F).

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.

FIGURE 53. Alpheus euphrosyne De Man, 1897 complex in the northern and western Indian Ocean: A—Alpheus cf. mangalis sp. nov. (upper row) and A. euphrosyne (lower row) from an estuary near Kochi, India; B, C—Alpheus cf. eurydactylus De Man, 1920, ovigerious female (cl indet.) from Kochi, India (RMNH.Crus.D.49749), lateral view (B) and pleon and tail fan, dorsal view; D, E—Alpheus sp. euphrosyne complex (?), female photographed in situ in a mangrove at Watamu, Kenya. Photographs courtesy of Mahadevan Harikrishnan (A), Juan C. Miquel (B, C) and Dawn Goebbels (D, E).