Salmoneus colinorum De Grave, 2004

Anker, Arthur, 2019, On three symbiotic species of the alpheid shrimp genus Salmoneus Holthuis, 1955 from the Indo-West Pacific, including one new to science (Malacostraca: Decapoda: Caridea), Zootaxa 4651 (1), pp. 51-63 : 60-61

Salmoneus colinorum De Grave, 2004

Fig. 6

Salmoneus colinorum De Grave 2004: 41 , figs. 1–4; Anker et al. 2015: 325, fig. 18.

Material examined. 1 non-ovigerous specimen (cl 3.4 mm), MNHN-IU-2013-924, Papua New Guinea, Madang lagoon, Riwo, 5°8’40.30”S 145°48’12.40”E, shallow bay with sea grass, depth: 2–3 m, vacuum suction, coll. B. Faure & R. Ibik, 10.xii.2012 [fcn PS 46-PZD-628G].

Description. See De Grave (2004).

Colouration. Body semitransparent-whitish, with dark purple-red banding as following: carapace with three transverse bands on dorsal surface, second connected to pair of lateral bands, slightly posterior and descending to branchiostegial margin; additional pair of transverse bands descending along anterolateral margin, not connecting dorsally; postrostral area with purple-brown blotch; pleonites each with fairly broad transverse band; telson and uropods with proximal and distal transverse blotches/ major cheliped hyaline generally whitish with red-purple chromatophores forming blotches or longitudinal lines, especially on chela; minor chela, walking legs and pleopods whitish; antennular peduncles and antennal carpocerite with red-purple chromatophores forming blotches and bands, flagella mostly colourless ( Fig. 6 ).

Type locality. Palau .

Distribution. Indo-West Pacific: currently only known from Palau ( De Grave 2004); Lombok, Indonesia (Anker et al. 2015); and Madang, Papua New Guinea (present study).

Ecology. Intertidal sand-mud flats, usually near mangroves; associated with burrows of larger snapping shrimps, typically members of the Alpheus malabaricus (Fabricius, 1775) species complex (Anker et al. 2015; see also below).

Remarks. The specimen from Madang extends the previously known distribution of Salmoneus colinorum from Palau and central Indonesia to western Papua New Guinea. Living individuals of this interesting species can be easily recognised by a striking and diagnostic colour pattern consisting of transverse purple-brown bands across the carapace, pleon and tail fan ( Fig. 6 ; see also Anker et al. 2015: fig. 18, showing a young specimen missing both chelipeds).

As already noted in the original description of the species ( De Grave 2004), S. colinorum associates with larger burrowing snapping shrimps of the genus Alpheus . The type specimens from Palau have been collected from burrows of a snapping shrimp tentatively identified as Alpheus aff. mackayi Banner, 1959 ( De Grave 2004). It must be noted that A. mackayi is currently seen as a junior synonym of A. malabaricus ( Chace 1988; De Grave & Fransen 2011). However, in the present author’s opinion, this synonymy, first proposed by Chace (1988), may have been premature and the entire A. malabaricus species complex is in need of a thorough taxonomic revision. Therefore, all that can be stated now with some certainty is that S. colinorum dwells in burrows of one or several species of the A. malabaricus species complex. The Madang specimen was collected by the scuba-operated “vacuum cleaner”, which, despite its efficiency, can be quite destructive for shrimps and in addition does not allow to track host associations.

Noteworthy, the western Atlantic S. carvachoi Anker, 2010 and its eastern Pacific sister species S. malagensis Anker & Lazarus, 2015 both display a morphology superficially similar to that of S. colinorum , except for some features of the major cheliped, and have similar transverse deep-purple banding ( Anker 2010; Anker & Lazarus 2015; Oliveira et al. 2015). Interestingly, both species are also associated with burrowing snapping shrimps of the genus Alpheus , viz. A. estuariensis Christoffersen, 1984 and A. colombiensis Wicksten, 1988 , respectively ( Anker 2010; Anker & Lazarus 2015; Oliveira et al. 2015; Vera Caripe et al. 2015). Whether this resemblance is a product of an ecology-driven convergence or whether these three taxa are also phylogenetically related, remains to be studied.

Figures

FIGURE 6. Salmoneus colinorum De Grave, 2004: non-ovigerous specimen (cl 3.4 mm) from Madang, Papua New Guinea, MNHN-IU-2013-924; a—living individual, dorsal view; b—same, lateral view (both photographs by the author).