Salmoneus auroculatus, Marin, 2006

Marin, Arthur Anker Ivan N., 2006, New Records And Species Of Alpheidae (Crustacea: Decapoda) From Vietnam. Part I. Genus Salmoneus Holthuis, 1955, Raffles Bulletin of Zoology 54 (2), pp. 295-319 : 300-304

publication ID	https://doi.org/ 10.5281/zenodo.13245424
persistent identifier	https://treatment.plazi.org/id/03AB572D-FFE1-FFBF-FF66-F950FEFED9A6
treatment provided by	Felipe
scientific name	Salmoneus auroculatus
status	sp. nov.

Treatment

Salmoneus auroculatus View in CoL , new species

( Figs. 4-6 View Fig , 7a View Fig )

Material examined. – Holotype, ovigerous female (CL 3.4, TL 10.6)( ZMMU Ma 5440), South China Sea , Vietnam, Nhatrang Bay, Tre Island, depth 6-8 m, SCUBA, with suction pump, coll. I. Marin, 24 Oct.2003.

Description. – Carapace slightly setose, with inconspicuous rounded depressions or pits, appearing finely granular, laterally with shallow oblique depression and slight suture starting from lateral margin proximal to base of antenna ( Figs. 4 View Fig , 5b). Rostrum moderately long, overreaching distal margin of first segment of antennular peduncle ( Fig. 5a), longer than broad at base; lateral margins slightly concave ( Fig. 5a); rostral carina well developed, reaching beyond 3/4 of carapace length ( Figs. 4 View Fig , 5a). Extra-corneal teeth acute, directed anteriorly; margin between rostrum base and extra-corneal teeth broadly concave ( Fig. 5a). Pterygostomial angle rounded. Eyes without tubercle, completely covered by carapace, not visible in dorsal and lateral view ( Fig. 5b). Epistomial sclerite with small, rounded process. Ocellar beak slightly protruding between eyes.

Antennular peduncle stout, second segment approximately equal to first and third segments; ventromesial carina of first segment with acute tooth; stylocerite reaching to, but not exceeding distal margin of second segment, distally acute ( Fig. 5a); lateral flagellum biramous, with shorter ramus situated at second segment. Antenna with basicerite bearing strong ventrolateral tooth ( Fig. 5b); scaphocerite relatively broad, anterior margin of blade convex, only slightly exceeding distolateral tooth; carpocerite short, reaching to about 3/4 length of scaphocerite ( Fig. 5b).

Mouthparts typical for genus. Mandible with incisor process bearing eight teeth, with third and fourth largest. Maxillule with bilobed palp, lower lobe with one seta, upper lobe non-setose. Second maxilliped with rounded epipod. Third maxilliped slender ( Fig. 5c); lateral plate oval, ear-shaped ( Fig. 5e); ultimate segment distally with one apical and one subapical spines ( Fig. 5d); arthrobranch normally developed.

First pereiopods (chelipeds) very asymmetrical, unequal ( Fig. 6 View Fig ), carried flexed ventrally in life, mesially when preserved ( Fig. 4 View Fig ); major cheliped robust (cf. Fig 7a View Fig ); ischium slightly elongate, without spines; merus slender, elongate, distally not widening, with feebly marked rounded lobes, ventrally flattened; carpus somewhat elongate, vase-shaped, ventrally depressed, distally with two pronounced lobes ( Fig. 6b View Fig ); chela subcylindrical, with palm slightly longer than fingers; palm proximoventrally with deep groove, continuing by oblique groove across lateral to dorsal surface ( Fig. 6b View Fig ), dorsal surface with slight, elongate depression ( Fig. 6a View Fig ), distolateral surface with feeble groove, extending to pollex; pollex with cutting edge bearing 11 rounded-triangular, regularly spaced teeth, tip curved; dactylus with cutting edge bearing nine teeth, distal 1/6 unarmed, tip curved ( Fig. 6c View Fig ). Minor cheliped slender; ischium elongate, equal in length to merus; carpus equal in length to merus, subcylindrical, ventrally flattened, distally widening; chela simple, not particularly enlarged, fingers slightly shorter than palm, cutting edges unarmed ( Fig. 6d View Fig ).

Second pereiopod slender; ischium about 5/6 length of merus; carpus with five segments having ratio of approximately 4.5/ 1/0.6/0.6/1.2; chela simple, fingers equal to palm ( Fig. 5f). Third pereiopod slender; ischium with three spines; merus about 1.4 length of ischium, about 5.5 times as long as wide at base; carpus slender, shorter than merus, with small distoventral spinule (broken); propodus slightly longer than carpus, ventrally with four small spines and one slender distoventral spine proximal to dactylus; dactylus simple, slender, less than half length of propodus, slightly curved ( Fig. 5g). Fourth pereiopod similar to third. Fifth pereiopod slender; ischium unarmed; merus 2.5 times length of ischium, about five times as long as wide at base; carpus slender, slightly longer than merus, with small distal spinule; propodus about 1.3 length of carpus, ventrally with numerous rows of small setae, five small ventral spines and one inconspicuous distoventral spine proximal to dactylus; dactylus simple, slender, less than 1/3 length of propodus, slightly curved ( Fig. 5h).

Abdominal segments I-III with posteroventral margins rounded or rounded-angular; segments IV and V with posteroventral angle acutely projecting ( Fig. 4 View Fig ); segment VI with acute posterior projection, without articulated plate ( Fig. 4 View Fig ); preanal plate rounded posteriorly ( Fig. 5k). Second pleopod with appendix masculina longer than appendix interna, with slender spines along mesial margin ( Fig. 5i, j). Telson about twice as long as wide proximally; basal width about 2.3 times width of posterior margin; dorsal surface with two pairs of spines situated at some distance from lateral margin, at mid-length and 3/4 length of telson, respectively ( Fig. 5l); posterior margin with deep, U-shaped median notch bearing two very long, fine setae and two pairs of spines, lateral shorter than mesial ( Fig. 5m); anal tubercles absent. Uropods slightly longer than telson; sympodite with acute tooth; diaeresis slightly sinuous; lateral spine well developed ( Fig. 5l). Gill formula typical for genus: see under S. nhatrangensis , new species.

Colour. – Semitransparent white, corneas conspicuously golden-yellow ( Fig. 7a View Fig ).

Habitat. – The specimen was collected with a suction pump beneath a boulder in a transition zone between coral reef and sand plain. The biotope is characterized by dead fungiid and branching corals, coral rubble and stones partly covered by sand and mud. Other alpheids collected at this location were S. nhatrangensis , new species, and Athanas parvus .

Etymology. – Salmoneus auroculatus , new species, received its name (aurum – gold, oculus – eye) from the strikingly golden colour of the cornea ( Fig. 7a View Fig ).

Remarks. – Salmoneus auroculatus , new species, must first be first contrasted to species with a well-marked mediodorsal carina, extending to or beyond the mid-length of the carapace: S. tricristatus Banner, 1959 , S. cristatus ( Coutière, 1897) and S. brevirostris . Salmoneus auroculatus , new species, can be easily separated from S. tricristatus by the absence of the two strong dorsolateral carinae on the carapace (cf. Banner, 1959; Miya, 1972; Banner & Banner, 1973). It also differs markedly from S. cristatus by the shape of the rostrum and extra-corneal teeth, and the much deeper posteromedian notch on the telson (cf. Coutière, 1897, 1899; Holthuis, 1958; Banner & Banner, 1966b; Anker, 2003b). This new species can be distinguished from S. brevirostris by the absence of a slight carina on each orbital hood, posterior to the extra-corneal tooth, and the presence of three spines on the ischium of the third pereiopod (vs. unarmed ischium in S. brevirostris , cf. Banner, 1953). Furthermore, these three species have different colour patterns: S. tricristatus is semitransparent, with posterior portion of the carapace appearing reddish due to the presence of numerous red chromatophores (A. Anker, pers. obs.); S. cristatus is semitransparent, with bright transverse red bands across the carapace and the abdomen ( Coutière, 1899; Banner & Banner, 1981); S. brevirostris is uniformly bright yellow-orange ( Edmondson, 1930; Banner & Banner, 1983).

The other closely related Indo-Pacific and Atlantic species, characterized by the fingers of the major cheliped armed with numerous small teeth, the merus of the major cheliped not inflated and ventrally not excavated, the eyes dorsally concealed by the orbital hoods and the carapace lacking strong mediodorsal carina, are S. serratidigitus , S. sibogae , S. hilarulus , S. brevirostris , S. mauiensis , S. babai and S. nhatrangensis , new species, in the Indo-Pacific, and S. teres , S. setosus and S. arubae in the Atlantic. However, in none of these species, the mediodorsal carina, if present, extends far beyond the eyes (cf. Coutière, 1896, 1899; De Man, 1911, 1915; Edmondson, 1930; Schmitt, 1936; Banner, 1953; Banner & Banner, 1981, 1982; Manning & Chace, 1990).

Among the above-mentioned species, S. serratidigitus , S. sibogae , S. hilarulus , S. brevirostris and S. mauiensis appear to be particularly close to S. auroculatus , new species, especially in the configuration of the frontal margin and most features of the major cheliped. As already mentioned, S. auroculatus , new species, can be separated from these species by the presence of a well marked rostral carina continued by a mediodorsal carina, the latter reaching beyond the 3/4 length of the carapace ( Figs. 4 View Fig , 5a). Salmoneus auroculatus , new species, differs more specifically from S. serratidigitus and S. sibogae (cf. Coutière, 1899; De Man, 1911, 1915; Banner & Banner, 1981) by the shorter rostrum; the shorter stylocerite (not reaching distal margin of the second segment of the antennular peduncle in S. auroculatus , new species, vs. exceeding this margin in S. serratidigitus ); and the longer carpus of the major cheliped. It differs from S. hilarulus by the shorter rostrum and more slender minor cheliped; and from S. mauiensis by the shorter rostrum; the shape and extension of the posteromedian notch on the telson; and the presence of spine on the ischium of the third pereiopod.

Salmoneus auroculatus , new species, differs from the above-described S. nhatrangensis , new species, by the presence of a strong mediodorsal carina; the shape of the orbital teeth and the rostrum; the more elongated, vase-shaped carpus of the major cheliped; the much more developed posteromedian notch on the telson; and the proportions of the articles of the minor cheliped. Salmoneus babai is more distantly related to S. auroculatus , new species, and can be distinguished from it by the same features as from S. nhatrangensis , new species (see above), and also by the much less pronounced rostromediodorsal carina.

Salmoneus auroculatus , new species, differs in several important characters from the above-mentioned Atlantic species, for instance, from S. arubae by the presence of a deep posteromedian notch on the telson and the shape of the major chela; from S. setosus by the absence of thick, erect setae on the carapace and abdomen and the presence of a deep posteromedian notch on the telson; and from S. teres by the shape of the frontal margin and the much less developed posteromedian notch on the telson (cf. Schmitt, 1936; Holthuis, 1990; Manning & Chace, 1990). Noteworthy, like the above-described S. nhatrangensis , new species, S. auroculatus , new species, possesses small, inconspicuous pits on the carapace, a character shared with S. arubae , S. teres and an undescribed species from the western Atlantic (Anker, in prep.).

Distribution. – Presently known only from the type locality, Nhatrang Bay, Vietnam.