Alpheus songkla Banner & Banner, 1966

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 : 75-81

Alpheus songkla Banner & Banner, 1966 , stat. nov.

( Figs. 41 , 52C )

[see also Fig. 42 for A. cf. songkla ]

Alpheus malabaricus songkla Banner & Banner 1966: 147 , fig. 56; Angsupanich & Kuwabara 1999: 6; Angsupanich et al. 2005: 376; Naiyanetr 2007: 173.

(?) Alpheus malabaricus songkla .— Thomas 1976: 668.

Type material. Holotype, female (cl 6.1 mm), USNM 120407 , Thailand, Thale Sap (Songkhla Lake ), BR44 , commercial shrimp trawl, sandy bottom, depth: approximately 1 m, leg. A.H. Banner, 27.03.1963; paratype, female (cl 6.4 mm), USNM 120408 , same collection data as for previous specimen.

Tentative identification. Alpheus cf. songkla . Singapore: 2 males (cl 8.8, 10.0 mm), 1 female (9.6 mm), ZRC 1992.11117 – 11119 , Pulau Ubin, mudflat, leg. P.K.L. Ng, 08.1987; 1 male (cl 6.8 mm, missing minor cheliped), 2 females (cl 5.6, 7.5 mm), ZRC 2014.0665 , near Sarimbun Scouts Camp (Jalan Bahtera), seining on mud, leg. H.H. Ng, H. Wong & Y.L. Teo, 14.02.2012 [48193–48195].

Malaysia: 3 males (cl 7.4–8.0 mm) , 1 female (cl 9.5 mm), OUMNH. ZC. 2019.06.50 [ex ZRC 2009.0306 ], Terengganu, Telok Tebrau, intertidal mudflats, with gobies, leg. Z. Jaafar, 05.11.2002 .

Thailand: 1 male (cl 9.6 mm), USNM 65561 , “ Sin Gora inland sea [locality not found], leg. H.M. Smith, 20.06.1925 ; 1 male (cl 10.6 mm, missing both chelipeds), USNM 65558 , Paknam, Menam Chao Phraya near Bangkok, Klang Krang, leg. H. Smith, 21.05.1925 ; 1 female (cl 9.0 mm), USNM 65477 /2, Bangpakong River , leg. H. Smith, 01.07.1923 .

Vietnam: 1 male (cl 8.1 mm), MNHN-IU-2018-5655, Duyen-Hai near Ho Chi Minh City, leg. H. Dung, 12.08.1995 ; 1 male (cl 10.4 mm, minor cheliped abnormal, see below), MNHN-IU-2019-2290, same collection data as for previous specimen .

Australia: 1 male (cl 6.5 mm), NTM Cr.015100, Northern Territory, Arnhem Land, Milingimbi, east of Nilpaiwa Islands , 12º03.389’S 134º52.835’E, depth: 2.2 m, leg. S.K. Horner & G.M. Dally, 04.12.2004 .

Comparative material. Alpheus malabaricus ( Fabricius, 1775) sensu lato (sensu Banner & Banner 1982; Chace 1988; but see discussion below). Taiwan: 1 male (cl 7.1 mm), OUMNH. ZC. 2019.06.51, Chang Hua, mudflat, leg. T. Y. Chan et al., 07.1996 .

Thailand: 1 female (cl 12.0 mm), OUMNH. ZC. 2019.06.52, Lake Thale Sap (= Songkhla), leg. S. Hajisamae, 17.08.2013 ; 1 male (cl 11.7 mm), OUMNH. ZC. 2019.06.53, Pattani Bay , Pattani, leg. S. Hajisamae, 01.2013; 1 ov. female (cl 9.5 mm), OUMNH. ZC. 2019.06.54, Phuket, E Chalong Bay , mudflat in front of mangrove, depth: <0.5 m, suction pump, leg. A. Anker, J.C.Y. Lai & M. Ng, 04.03.2008 [ PH 12-08-036].

Indonesia: 1 male (cl 11.7 mm), OUMNH. ZC. 2019.06.55, Papua, Ajkwa Island, mangrove, leg. A. Darmawan et al., 20.07.2012; 1 ov. female (cl 12.4 mm), QM W25803-1, Papua, Ajkwa River estuary, 4°50’S 136°50’E, Environmental Laboratory, PT Freeport, Sta. Ajk-36, estuarine habitat, 30.03.2000; 3 males (cl 10.2–14.6 mm), 1 female (cl 11.0 mm), QM W25802, Papua, West Ajkwa River, river mouth at Lanal Base, 4°50’S 136°50’E, Environmental Laboratory, PT Freeport, Sta. Ajk-36, estuarine habitat, 29.07.1999; 1 ov. female (cl 11.6 mm), 1 male major cheliped, OUMNH. ZC. 2019.06.56, Lombok, Lembar, prawn ponds, muddy banks of brackish stream, low tide, suction pump, leg. A. Anker, I.S. Pratama, M. Firdaus & D.L. Rahayu, 14.05.2014 [St5-14]; 1 male (cl 9.4 mm), 1 ov. female (cl 7.8 mm), OUMNH. ZC. 2019.06.57, Lombok, Teluk Sekotong, near mangrove, 0.1–0.3 m at low tide, suction pump, leg. A. Anker, I.S. Pratama, M. Firdaus & D.L. Rahayu, 14.05.2014 [St6-03]; 1 ov. female (cl indet.), ZRC 2014.0682, Anambas, sta. EAJL 03, Pulau Jemaja Teluk, deep sheltered sandy bay, northern and eastern sides with fringing Rhizophora and Bruguiera mangrove inlets, leg. J.C.Y. Lai et al., 13.03.2002.

Singapore: 2 males (cl 15.4, 15.9 mm), 1 ov. female (cl 16.7 mm), ZRC 1992.11124 – 11126 , Pulau Ubin, mudflat, leg. P.K.L. Ng , 08.1987; 2 males (cl 12.4, 12.5 mm), ZRC 1992.11122 – 11123 , same collection data as for previous specimens ; 1 male (cl 9.0 mm), ZRC 1994.4392 , Kallang Basin , sta. 5, dredge, leg. Reef Ecology Study Team, 16.12.1994 .

Australia: 1 male (cl indet.), QM W25812 , SE Queensland, Innes Park, creek, 300 m from mouth, mangroves, sand, leg. J. Johnson & A. Gill, 12.05.2000 ; 1 male (cl 13.4 mm), 1 ov. female (cl 14.9 mm), NTM Cr. 008307, Northern Territory, Darwin, Ludmilla Creek mouth, 12º24.8’S, 130º50.7’ E, undisturbed mangrove, low tide, leg. M. Burke, 04.06.1991 .

Description. See Banner & Banner (1966) for original description and illustrations, as A. malabaricus songkla ; see also discussion below.

Colour pattern. The colour pattern of the type specimens from Songkhla Lake is unknown. The colour pattern of the Indian specimens identified by Thomas (1976) as A. malabaricus songkla was described as following: general body colour cream with dark brown cross bands along posterior margins of pleonites and carapace; tips of uropods and anterior border of carapace between orbital hood and lateral angle dark brown; antennal flagella bluish violet, antennular flagella with brownish tinge; chelipeds grey with violet inner [mesial?] depression of large chela; remaining portion of chela and legs pinkish; exopods and endopods of pleopods [erroneously called chelipeds] bright red with paler bases; underside of pleon and chela white (adapted from Thomas 1976; however, see below).

Type locality. Thale Sap (Songkhla Lake), Thailand .

Distribution. Indo-West Pacific: with certainty known only from the type locality in Thailand, Thale Sap = Songkhla Lake ( Banner & Banner 1966); record from India ( Thomas 1976) requires confirmation; additional records of A. cf. songkla from Thailand, Vietnam, Malaysia, Singapore and Northern Territory, Australia ( Fig. 52C ) (see discussion below).

Common name proposed. Songhkla snapping shrimp.

Ecology and biology. Shallow subtidal species found on mud and sand bottoms usually off mangroves or inside brackish and saltwater lagoons; the South-East Asian and Australian specimens were collected in 1–3 m deep water ( Banner & Banner 1966; present study), whereas the Indian specimens (which may or may not be A. songkla ) came from a depth range of 3–10 m ( Thomas 1976).

Taxonomic remarks. Banner & Banner (1966) separated their new subspecies A. malabaricus songkla from A. malabaricus , including the forms known as A. malabaricus dolichodactylus Ortmann, 1890 and A. malabaricus leptopus De Man, 1910 (both now in the synonymy of A. malabaricus , see below), by the relative length of the fingers of the minor chela, which are 1.5 times as long as the palm (vs. at least three times as long as the palm in the other three forms). In addition, in A. malabaricus songkla , the distal parts of the fingers are strongly crossing, which is not the case of A. malabaricus dolichodactylus and A. malabaricus leptopus .

In the general shape and proportions of the minor chela, A. malabaricus songkla approaches A. malabaricus mackayi Banner, 1959 , which was elevated to species rank, as A. mackayi ( Banner 1959; Banner & Banner 1974). However, Chace (1988) placed all the above-mentioned species and varieties, including A. malabaricus songkla and A. mackayi , as well as A. macrodactylus Ortmann, 1890 , A. malabaricus trefzae Banner & Banner, 1982 and A. mazatlanicus Wicksten, 1983 , in the synonymy of A. malabaricus . The clearly premature synonymisations of Chace (1988) resulted in the morphologically and ecologically highly variable A. malabaricus sensu lato, a “species” with a vast geographic range, intertidal and deep-water populations, specimens with relatively short to extremely elongated fingers of the minor cheliped, specimens with the dactylar plunger of the major cheliped ranging from very large and stout to greatly reduced, and a great deal of other “intraspecific variation”. Although the revision of the entire A. malabaricus complex ( A. malabaricus sensu Chace 1988 ) is well beyond the scope of the present study, the author sees no reason for treating A. macrodactylus , A. mackayi , A. mazatlanicus and A. malabaricus songkla as junior synonyms of A. malabaricus (cf. Banner & Banner 1966, 1974, 1982, 1983; Kim & Abele 1988), whilst the taxonomic status of A. malabaricus dolichodactylus , A. malabaricus leptopus and A. malabaricus trefzae (cf. De Man 1911; Banner & Banner 1982) will need further clarification. Nevertheless, awaiting a long-needed revision of A. malabaricus , the comparative material examined in this study is listed under A. malabaricus sensu lato, even though it certainly contains more than one species.

Banner & Banner (1966) noted that A. malabaricus songkla differs from A. mackayi by the longer rostrum; the lack of rostro-orbital furrows; and the fingers of the minor chela slenderer and with longer, distally stronger crossing tips. In A. malabaricus songkla , the orbital hoods seem to be less projecting than in A. mackayi , whereas the second article of the antennular peduncle is noticeably shorter than in A. mackayi (cf. Banner & Banner 1966: fig. 56A; Banner 1959: fig. 12a, b). Furthermore, the telson of A. malabaricus songkla has straight lateral margins; these are strongly convex in A. mackayi (cf. idem: fig. 56H; fig. 12m). The main differences between A. malabaricus songkla and A. macrodactylus consist in the less projecting orbital hoods (cf. Banner & Banner 1966: fig. 56A; Banner & Banner 1982: fig. 65a); the ratio of the fingers to the palm in the major chela being around 0.7 in A. malabaricus songkla vs. closer to 1.0 in A. macrodactylus (cf. idem: fig. 56B, C; fig. 65b, c); and the minor cheliped fingers somewhat shorter relative to the palm (1.5 times as long as the palm), without armature on the cutting edges and with the fingertips strongly crossing in A. malabaricus songkla vs. noticeably longer (1.8 times as long as the palm), with small teeth in the proximal portion of the cutting edges and with the fingertips not strongly crossing in A. macrodactylus (cf. idem: fig. 56D, E; fig. 65e, f). Finally, A. malabaricus songkla can be easily separated from the eastern Pacific A. mazatlanicus , for instance, by the shape of the rostro-orbital area; the length of the second article of the antennular peduncle; the shape of the major chela dactylus; and the relative proportions of the carpal subarticles in the second pereiopod (cf. Banner & Banner 1966: fig. 56; Kim & Abele 1988: fig. 36). Therefore, A. malabaricus songkla is herein elevated to full species rank, as A. songkla stat. nov.

Despite the fact that A. songkla is morphologically different from all species and subspecies (or varieties) currently assigned to the A. malabaricus complex, it remains a problematic taxon. The description by Banner & Banner (1966) was based exclusively on females, i.e., the morphology of the male minor chela, of critical importance for taxonomy of Alpheus , currently remains unknown. Therefore, at this stage, a redescription or a new diagnosis for A. songkla would not be very useful. However, an opportunity is taken to correct a number of small errors and inaccuracies in the original description of A. songkla by Banner & Banner (1966), based on re-examination of the type material ( Fig. 41 ).

One of the most important features of A. songkla setting it clearly apart from the A. malabaricus complex is the relatively weak anterior projection of the orbital hoods ( Banner & Banner 1966: fig. 56A; see also Figs. 41A , 42A ; cf. Banner & Banner 1974: fig. 12a; Banner & Banner 1982: fig. 64a, 65a; Kim & Abele 1988: fig. 36a, b; Chace 1988: fig. 9a). The antennal basicerite of the holotype (USNM 120407) has a small, curved tooth in the middle of the distolateral margin (apparently broken on the right side), which seems to correspond to “minute lateral spine” in the description of Banner & Banner (1966). However, the antennal basicerite of the examined paratype (USNM 120408) has a similar curved tooth only on the right side, being unarmed on the left side. The ischium of the third pereiopod has a small spiniform seta, as correctly figured by Banner & Banner (1966: fig. 56G). The propodus of the third pereiopod has a row of tightly appressed spiniform setae between the long stiff setae; only the latter were shown by Banner & Banner (1966: fig. 56G), who stated that the propodus is “bearing strong setae but no spinules”, which is incorrect. Furthermore, the mesial face of the major chela is not perfectly smooth, but has a large field of fine granules distally, i.e., on the distal portion of the palm and most of the pollex, reminiscent of the granulation of A. eurydactylus (although weaker). The mesial subdistal ridge of the pollex is long and sharp, and departs from a conspicuous proximal bump, as in A. euphrosyne , A. eurydactylus , A. takla sp. nov., etc. The last two taxonomically important features of the major chela (granulation and mesial subdistal ridge) were not mentioned nor illustrated by Banner & Banner (1966). In addition, the minor chela fingers of both examined type specimens are quite setose, covered by tufts of numerous stiff setae; these setae were omitted in the original illustrations of the minor cheliped by Banner & Banner (1966: fig. 56D, E). The ventromesial carina of the first article of the antennular peduncle (not illustrated in the original description) is broadly rounded-triangular and without an acute point.

The taxonomic identity of two males and four females from southern India (Korapuzha estuary north of Kozhikode on the Malabar Coast) reported as Alpheus malabaricus songkla by Thomas (1976) remains uncertain. According to Thomas (1976), both male and female specimens had “dense setae” on the lateral margins of the minor chela fingers, which were not referred to as “balaeniceps setae” (the same author reported a balaeniceps minor chela in A. euphrosyne ). Banner & Banner (1966) did not mention nor illustrated dense setae on the female minor cheliped of A. songkla , but the re-examination of the type material confirmed that the minor chela is indeed quite setose (see above). Noteworhy is that Thomas’ (1976) descriptions of the colour patterns of A. m. songkla and A. euphrosyne are almost identical.

The material from Singapore, Malaysia, Vietnam, Thailand and Australia herein tentatively identified as A. cf. songkla is morphologically somewhat heterogeneous and needs further study. The material from Singapore, Thailand and Vietnam is discussed in more detail below.

(1) The specimens from Pulau Ubin and Sarimbun, Singapore (ZRC 1992.11117–11119, ZRC 2014.0665), are morphologically most similar to A. songkla , e.g., in the configuration of the rostro-orbital area and antennules; the presence of a small tooth on the antennal basicerite; the relatively slender major chela, with a moderately developed plunger on the dactylus; and the general proportions of the female chela. The general characteristics of the male minor cheliped place these specimens close to A. eurydactylus . However, they differ from A. eurydactylus in the longer distolateral tooth of the scaphocerite, exceeding the distal margin of the blade (vs. not exceeding it in A. eurydactylus ), and in the dorsal surface of the telson without longitudinal depression (present in A. eurydactylus ). In addition, the Singaporean specimens have slenderer chelipeds compared to those of similarly sized specimens of A. eurydactylus .

(2) The male from “Sin Gora inland sea” in Thailand (USNM 65561) generally agrees with A. songkla , for instance, in the similar frontal area; the third pereiopod ischium armed with a spiniform seta; the third pereiopod propodus bearing stout appressed spines and long stiff setae; and the spatulate third pereiopod dactylus. However, the distolateral margin of the antennal basicerite of this specimen has no trace of tooth on both sides. The minor chela of this male specimen, which cannot be directly compared with that of the females of A. songkla , is very similar to that of A. eurydactylus .

(3) The incomplete male from Menam Chao Phraya near Bangkok, Thailand (USNM 65558), matches A. songkla in most characters, including the very similar rostro-orbital area; the presence of a small, sharp tooth on the distolateral margin of the antennal basicerite (on both sides); the major chela with a gently sloping dorsal shoulder and granulated distomesially (with minute granules on the distal portion of the palm, pollex and dactylus); the major chela pollex with a distinct mesial subdistal ridge; the second pereiopod with the first carpal article much longer than the second; and the propodus of the third and fourth pereiopods furnished with stout appressed spines and long stiff setae. However, the ischium of the third and fourth pereiopods of this specimen is unarmed (vs. armed with a spiniform seta in A. songkla ), and the third pereiopod merus appears to be somewhat broader than in A. songkla , as illustrated by Banner & Banner (1966: fig. 56G). The female from Bangpakong River, Thailand (USNM 65477/2), has essentially the same characterstics as the male from Menam Chao Phraya and seems to belong to the same species.

(4) The two males from Duyen-Hai near Ho Chi Minh City, Vietnam (MNHN-IU-2018-5655, MNHN-IU-2019- 2290, see Fig. 42 ), were initially identified by the author as A. cf. eurydactylus . They differ from the typical A. eurydactylus , however, by the slenderer second pereiopod, with the first article much longer than the second; the third pereiopod ischium armed with a spiniform seta (as in A. songkla ); and the slightly different proportions of the minor chela fingers to the palm in the male with the normally developed minor cheliped (MNHN-IU-2018-5655). In the male with a somewhat abnormal minor cheliped (MNHN-IU-2019-2290), the palm has a distinct dorsal notch, whilst the fingers possess a weak balaeniceps crest. On the other hand, they appear to be more similar to the afore-mentioned specimens of A. cf. songkla from Singapore.

Thus, the above character combinations do not allow identifying the material from Singapore, Vietnam and Thailand reliably as A. songkla (or as A. eurydactylus ) and the situation is further complicated by the variation in the armature of the antennal basicerite in the type material of A. songkla and of the ischium of the third pereiopod in A. eurydactylus . Since A. songkla is presently known only from females, there is at least a possibility that some of the above-listed material of A. cf. songkla material may indeed represent A. songkla sensu Banner & Banner (1966) . Whatever the case might be, it seems most reasonable to treat A. songkla as a species distinct from A. malabaricus and allied forms, as well as from A. eurydactylus , although its taxonomic identity remains problematic due to the lack of males from the type locality.

The presence of a mesial subdistal ridge on the major chela pollex in A. songkla and A. malabaricus sensu lato (based on comparative material) may represent a phylogenetic link between the A. malabaricus complex and some species of the A. euphrosyne — A. microrhynchus complex. However, this hypothesis, and the phylogenetic affinities of A. songkla , can be tested only by a recollection of both male and female specimens of A. songkla at or near its type locality; a full redescription of A. songkla , including taxonomically important features of the male minor chela (balaeniceps or not) and colour pattern; and a comprehensive molecular analysis of the A. edwardsii group, including numerous specimens from as many localities as possible from both complexes.

Figures

FIGURE 41. Alpheus songkla Banner & Banner, 1966 stat. nov.: holotype, female (cl 6.1 mm) from Thale Sap (= Songkhla Lake), Thailand (USNM 120407); A—habitus (most appendages detached), dorsal view; B—major (left) cheliped, lateral view; C—same, mesial view; D—minor (right) cheliped, lateral view; E—third pereiopod, lateral view. Photographs by Robert M. Lasley Jr.

FIGURE 42. Alpheus cf. songkla stat. nov.: male (cl 8.1 mm) [A–I], male (cl 10.4 mm) [J–M], both from near Ho Chi Minh City, Vietnam (MNHN-IU-2018-5655); 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—major (left) cheliped, chela, mesial; F—same, chela, carpus and distal part of merus, lateral; G—same, dactylus; H—minor (right) cheliped, chela, carpus and distal part of merus, lateral view; I—second pereiopod, lateral view; J—third pereiopod, lateral view; K—same, dactylus, dorsal view; L—fourth pereiopod, ischium, lateral view; M—possibly abnormal minor (right) cheliped, chela, lateral view.

FIGURE 52. Distributional maps for species of Alpheus treated in this study:A—A. takla sp. nov.; B—A. mangalis sp. nov. and A. cf. mangalis sp. nov.; C—A. songkla Banner & Banner, 1966 and A. cf. songkla (see text); D—A. paludicola Kemp, 1915, A. nipa Banner & Banner, 1985 and A. bunburius Banner & Banner, 1982; E—A. pontederiae de Rochebrune, 1883; F—A. firmus Kim & Abele, 1988 and A. cf. firmus (see text).