Microprosthema looensis Goy & Felder, 1988

Ferreira, Luciane Augusto De Azevedo, Leray, Matthieu & Anker, Arthur, 2020, New findings of the stenopodidean shrimp Microprosthema looensis Goy & Felder 1988 (Decapoda: Stenopodidea: Spongicolidae), Zootaxa 4729 (3), pp. 445-450 : 445-449

Microprosthema looensis Goy & Felder, 1988

( Figs. 1–3 )

Material examined. 1 male (cl 5.2 mm), FLMNH UF 53415 , Panama, Bocas del Toro, east of Isla Bastimentos, near Cayo Coral (Coral Key), shallow sand flat with abundance of coral rubble and sponges, depth: 3 m, in crevice of large dead coral block, leg. M. Leray, A. Anker & E.C. Rodriguez Guerra, 23 July 2018 [fcn 18-002] ; 1 female (cl 4.7 mm), FLMNH UF 53416 , Panama, Isla Mamey near Isla Grande , shallow reef flat with strong current, depth: 1.5 m, under large flat piece of coral rubble, leg. A. Anker, 1 August 2018 [fcn 18-007] .

Distribution. USA: Florida Keys ( Goy & Felder, 1988); Panama: Bocas del Toro and Isla Mamey near Isla Grande (present study).

Remarks. The morphological characters of the two Panamanian specimens agree well with those described by Goy & Felder (1988) for M. looensis : (i) carapace covered with numerous blunt to subacute teeth ( Fig. 1A, B ); (ii) cervical groove distinct ( Fig. 1B ); (iii) third pereopod with teeth on both carpus and merus ( Fig. 1G ); (iv) most of the third pereopod surface pubescent, i.e. covered with fine, hair-like setae ( Figs. 1G , 2B ; see also Goy & Felder 1988: fig. 7D); and (v) pleonites sculptured and armed with blunt teeth ( Fig. 1E ). Goy & Felder (1988) described and illustrated the rostrum of the holotype, which has two distal (= pre-orbital) teeth on the dorsal margin and no teeth on the ventral margin. However, in the Panamanian specimens, the rostrum is rather variable: the male has three pre-orbital teeth on the dorsal margin and one tooth on the ventral margin ( Fig. 1A, C ), whilst the female possesses two small pre-orbital teeth and one small subapical tooth dorsally and two small subapical teeth ventrally ( Fig. 1H ). According to Goy & Felder’s (1988) illustrations of the holotype, none of the teeth on carapace attains the post-orbital margin, whereas the Panamanian male has two particularly large teeth that reach slightly beyond the post-orbital margin in dorsal view ( Fig. 1B ).

The previously unknown male thoracic sternum ( Fig. 1D ), pleon ( Fig. 1E ) and third pereopod ( Fig. 1G ) are shown to complete the original description of M. looensis . The third pereopod is noticeably stouter in the Panamanian male than in the Panamanian female ( Figs. 2A , 3 ), but not significantly stouter than in the ovigerous female from Florida (holotype, cf. Goy & Feder 1988: fig. 7D). We also noted some rather minor differences in the armature of the third pereopod, for example, between the Panamanian male and the holotype. For instance, in the holotype, the dorsal surface of the merus of the third pereopod bears two adjacent teeth subdistally, whilst in the Panamanian male, it has only one tooth (cf. Fig. 1G and Goy & Felder 1988: fig. 7D). The ventral surface of the merus in both the holotype and the Panamanian male has two large widely spaced teeth, however, in a slight different positions (cf. ibid.). Similarly, in the holotype, the dorsal surface of the third pereopod carpus is armed with a series of small teeth in its proximal half and one larger tooth at about its 0.7 length ( Goy & Felder 1988: fig. 7D). In contrast, in the Panamanian male, the configuration of the dorsal carpal dentition is fairly different, with two larger and several smaller teeth, in addition to a stout distal tooth ( Fig. 1G ). However, all these differences can be interpreted as intraspecific variation, which indeed seems to be common in the genus Microprosthema ( Goy & Martin 2013) .

Goy & Felder (1988) described and illustrated the mandible of the holotype of M. looensis . The mandibular palp of the holotype is subdivided, according to the authors, into two distinct articles, the peduncular article and the expanded terminal article ( Goy & Felder 1988: fig. 6B, C). However, the presence of a two-articulated palp in the mandible of M. looensis contradicts previous observations made in various other stenopodidean taxa, the vast majority of which are characterised by the presence of a three-articulated palp ( Goy 2010: fig. 65.6; but see Quintal & Goy 2019: fig. 2F). Therefore, one of the mandibles of the Panamanian male was dissected and its palp illustrated ( Fig. 1F ) for comparison with that of the holotype. Interestingly, the mandibular palp of the male shows the typical three-articulated condition, as described for most other species of Microprosthema and Stenopodidea in general. Thus the biarticulated mandibular palp of the holotype of M. looensis may be an aberrant condition of that specimen or at least may be viewed as untypical for the species.

The colouration of M. looensis was briefly described by Goy & Felder (1988) as “Carapace and abdomen [= pleon] whitish tan; antennae, telson, uropods, and all appendages white. Eggs are pale green”. This description was possibly based on a superficial observation of the living shrimp against a solid black background. The carapace, pleon and third pereopods of both Panamanian specimens are pale pink with a slight yellowish tinge ( Figs. 2 , 3 ), which is due to the presence of numerous, scattered, small, red chromatophores, visible only under a dissecting microscope or with a digital camera zoom. The tail fan, antennular and antennal flagella, and all other appendages (first and second pereopods, ambulatory pereiopods) are white to semi-translucent with a pale yellow tinge ( Figs. 2 , 3 ).

Microprosthema is represented by five other species in the western Atlantic, in addition to M. looensis . These species are: M. granatense Criales, 1997 , M. inornatum Manning & Chace, 1990 , M. manningi Goy & Felder, 1988 , M. semilaeve (von Martens, 1872) and M. tortugasensis Goy & Martin, 2013 ( Goy & Felder 1988; Criales 1997; Goy & Martin 2013). Although De Grave et al. (2016) questioned the presence of M. inornatum in the western Atlantic, based on a single record from a deep-water locality (63–110 m) in the Gulf of Mexico ( Goy & Martin 2013), Dr. Joseph W. Goy (pers. comm.) confirmed the identity of the specimen in question (USNM 1541992) as M. inornatum . Microprosthema looensis is the only western Atlantic species with the carapace densely covered with spines, the third pereopods pubescent, and the pleon sculptured and armed with small scattered spines (see also key in Goy & Martin 2013). It is also the second species reported from Panama, together with M. semilaeve , which is much more common on shallow sand flats with abundant coral rubble ( De Grave & Anker 2017).

Figures

FIGURE 1. Microprosthema looensis Goy & Felder, 1988. (A–G) Male (cl 5.2 mm) from Bocas del Toro, Panama (FLMNH UF 53415). (H) Female (cl 4.7 mm) from Isla Mamey, Panama (FLMNH UF 53416). (A) Carapace and cephalic appendages, lateral view. (B) Carapace, dorsal view. (C) Detail of rostrum of male, lateral view. (D) Sixth to eighth thoracic sternites, ventral view. (E) Pleon, lateral view. (F) Mandibular palp, mesial view. (G) Left third pereopod, lateral view. (H) Detail of rostrum of female, lateral view. Scale bars = 1 mm.

FIGURE 2. Microprosthema looensis Goy & Felder, 1988. Male (cl 5.2 mm) from Bocas del Toro, Panama (FLMNH UF 53415). (A) shrimp alive, dorsal view (specimen missing right first and second pereopods). (B) same, detail of left third pereopod, lateral view.

FIGURE 3. Microprosthema looensis Goy & Felder, 1988. Female (cl 4.7 mm) from Isla Mamey, Panama (FLMNH UF 53416), shrimp alive, dorsal view.