Salmoneus Holthuis 1955

Salmoneus spp.

Material examined. 1 non-ovigerous specimen (cl 3.5 mm, missing both chelipeds), FLMNH UF 51908, Panama, Azuero Peninsula, Puerto Cañas, 7°25’53.8”N 80°16’01.6”W, estuarine muddy sandflat, in burrow, suction pump, leg. P.P.G. Pachelle et al., 15.02.2019 [fcn PAN-019]; 1 non-ovigerous specimen (cl 2.4 mm), FLMNH UF 51909, Panama, Coiba Archipelago, Panama, Granito de Oro, north side of the island, depth: 8–10 m, under rocks on sand, leg. M. Leray & B. Figuerola, 20.02.2019 [fcn PAN-186]; 1 non-ovigerous specimen (cl 1.8 mm, missing major cheliped), FLMNH UF 51910, Colombia, Bahía Málaga, Naidizal, 04°02’34.3”N 77°13’48.4”W, intertidal, under rocks on mud/sand near water edge, hand sieve, leg. A. Anker, 23.04.2009 [fcn COL-001].

Remarks. The above-listed three specimens from Panama and Colombia are preliminarily reported as Salmoneus spp. because of their incomplete condition (Azuero specimen, missing both chelipeds), their immaturity (Coiba and Bahía Málaga specimens, with cl <2.5 mm), or both (Bahía Málaga specimen, young and missing the major cheliped).

The Azuero specimen, which appears to be an adult (cl 3.5 mm), was damaged during the sampling process (extraction of infaunal decapods from burrows by means of a suction pump), having lost both chelipeds; the distal region of the tail fan was also damaged. The general shape of the frontal region and the fairly slender third to fifth pereiopods indicate a possible affinity with S. cavicolus Felder & Manning, 1986, a western Atlantic species known to be associated with burrows, but also S. camaroncito Anker, 2010, also from the western Atlantic (Felder & Manning 1986; Anker 2010). Some of the most notable morphological features of this specimen are the somewhat square-shaped eyestalks (in lateral view), with a fairly reduced cornea and very small tubercle; the presence of a small subdistal tooth on the ventral margin of the rostrum, which does not reach the distal margin of the second article of the antennular peduncle; the small but sharp orbital teeth, partly concealing the cornea in lateral view; and the presence of two cuspidate setae on the ischium of the second pereiopod.

The Coiba specimen, which was collected by flipping rocks in deeper water (8–10 m), is complete, but at its very small size (cl 2.4 mm) is likely to be a juvenile or at least a very young adult (Fig. 8). This specimen has very unequal and asymmetrical chelipeds typical for the majority of species currently assigned to Salmoneus, with the major cheliped fairly slender and with serrated cutting edges of the chela fingers. It also has a minute ventral subdistal tooth on the rostrum and a small mesial tubercle on the eyes, while the general shape of the frontal margin of the carapace is similar to that of the Azuero specimen. These and some other morphological characters are reminiscent of S. cavicolus, S. camaroncito, as well as some Indo-West Pacific species, such as S. gracilipes Miya, 1972.

The Bahía Málaga specimen, which was collected by sieving muddy water under intertidal rocks, is clearly an immature (cl 1.8 mm). It cannot be excluded that it belongs to the same species as the Azuero specimen, based on the slightly reduced cornea and main taxonomic features of the frontal region. Noteworthy, this specimen has a very robust minor cheliped armed with a few teeth on the finger cutting edges, a configuration that resembles that of the minor stout cheliped of several burrow-dwelling Atlantic species, such as S. degravei Anker, 2010 and S. caboverdensis Dworschak, Anker & Abed-Navandi, 2000 (Dworschak et al. 2000; Anker 2010).

The above observations strongly suggest that the eastern Pacific harbours at least two further undescribed species of Salmoneus, in addition to another, presumably undescribed species from southern California (Jensen 2014). However, no new species of Salmoneus or alpheid shrimps in general should be described based on specimens missing both chelipeds (especially the major cheliped) or on single immature specimens.