Salmoneus depressus Anker, 2011

Anker, Arthur, Mendonça, Oel B., Pachelle, Paulo P. G. & Tavares, Marcos, 2013, New And Additional Records Of Salmoneus Holthuis, 1955 (Decapoda, Caridea, Alpheidae) From Brazil, With A Key To The Southern Atlantic Species, Papéis Avulsos de Zoologia (São Paulo) 53 (33), pp. 451-458 : 451-458

Salmoneus depressus Anker, 2011

Figs. 1 , 2

Salmoneus depressus Anker, 2011: 44 , figs. 4-6.

Material examined: Brazil, São Paulo: 1 ovigerous specimen (cl 5.2 mm), MZUSP 30934 , São Sebastião, Praia do Segredo , near CEBIMar, 23°49’43.53”S, 45°25’24.68”W, rocky intertidal, low tide (0.2 m tide), near low tide mark, under very large rock on mixed gravel-sand substrate, sieving muddy water with dip-net, P.P.G. Pachelle, A. Anker, J.B. Mendonça coll., 31 October 2013 ; 1 non-ovigerous specimen, missing minor cheliped (cl 3.8 mm), MZUSP 28412 , São Sebastião channel, off CEBIMar, near tide-gauge, mud-rock bottom, depth 3-4 m, from ARS (retrieved after 14 months), M. Tavares and J.B. Mendonça coll., 17 April 2013 .

Comparative material: Caribbean Sea , St. Martin: 1 non-ovigerous specimen, missing major cheliped (cl 5.4 mm), FLMNH UF 31907 , Tintamarre Island , near Remorqueur wreck, coral rubble brushing under rocks, depth 10-15 m, A. Bemis et al., 10 April 2012 [field collection number BSTM 0227 ] .

Description: See detailed description in Anker (2011); some additional drawings of the Brazilian specimens are provided in Fig. 1 .

Colour in life: Semitransparent beige to pale strawyellow; eggs and ovary pale rusty-orange ( Fig. 2 ).

Distribution: Caribbean Sea ( Panama, Venezuela, Barbados, St. Martin) ( Anker, 2011; present study); Brazil (São Paulo) (present study).

Remarks: The material from São Sebastião agrees reasonably well with the description of S. depressus in Anker (2011) based mainly on material from the Caribbean coast of Panama. In addition, the two Brazilian specimens were directly contrasted to a more recently collected specimen from St. Martin, eastern Caribbean Sea. The differences observed between the Brazilian and Caribbean specimens include the shape and size of the orbital teeth, development of the rostral carina, armature of the major chela, fifth and sixth pleonite, and ischium of the fifth pereiopod.

The two Brazilian specimens of S. depressus markedly differ from each other in the development of the orbital teeth ( Fig. 1A, E ). In the larger ovigerous specimen ( Fig. 1E ), the orbital teeth are distinctly smaller than in the smaller non-ovigerous specimen ( Fig. 1A ), in which they are similar to those of the non-ovigerous specimen from St. Martin ( Fig. 1G ) and the type specimens from Panama ( Anker, 2011: Fig. 4A, M). In fact, in the development of the orbital teeth, the ovigerous specimen from São Sebastião ( Fig. 1E ) approaches S. excavatus Anker, 2011 , the presumed eastern Pacific sister species of S. depressus ( Anker, 2011: fig. 1A). However, the two species can still be separated from each other by the presence (in S. depressus ) and absence (in S. excavatus ) of a stout spiniform seta on the ischium of the minor cheliped, as well as the comparatively longer second article of the antennular peduncle in S. excavatus ( Anker, 2011) .

In both specimens of S. depressus from São Sebastião, the rostral carina is rather poorly marked, relatively short, and does not extend posterior to the level of the eyes ( Fig. 1A, E ). In the specimen from St. Martin, the rostral carina is more conspicuous, extending into the dorsal depression ( Fig. 1G ). In addition, in all three specimens examined, the rostral carina bears a low elevation, sometimes in the form of a tubercle, near the anterior edge of the dorsal depression of the carapace ( Fig. 1A, B, E, G, H ). This feature was not mentioned in the original description of S. depressus , although a low broad elevation can be seen in Anker’s (2011: fig. 4E). This elevation is rather inconspicuous in the larger ovigerous specimen from São Sebastião ( Fig. 1E ) and is most developed in the non-ovigerous specimen ( Fig. 1A, B ) and in the specimen from St. Martin ( Fig. 1G, H ). A similar, minor elevation on the mid-dorsal line of the carapace, at the anterior edge of the dorsal depression, is present in S. excavatus ( Anker, 2011: fig. 1D, F).

In the Brazilian specimens of S. depressus , the major chela fingers are armed with 12-13 teeth, i.e., one or two teeth more than in the type series from Panama (11-12 teeth, cf. Anker, 2011). In the general shape of the major chela, including the characteristic depressions on the palm, the Brazilian specimens closely resemble the type series.

In both specimens from São Sebastião, the posteroventral margin of the fifth pleuron ends in a small, blunt tooth, whilst the posterior margin of the sixth pleonite is produced into a moderately long, sharp tooth ( Fig. 1D, F ). In the specimen from St. Martin, the posteroventral margin of the fifth pleuron is produced into a much larger, subacute tooth, whilst the sixth pleonite is produced into a much stouter, sharp tooth ( Fig. 1I ), which is distinctly longer than the tooth illustrated for a type specimen from Panama ( Anker, 2011: fig. 4G).

Anker (2011) stated that the ischium of the fifth pereiopod is unarmed in S. depressus , see Anker (2011: fig. 5I). The ovigerous specimen from São Sebastião also has no trace of a spiniform seta on the ischium of the fifth pereiopod. However, in the smaller non-ovigerous specimen, a very conspicuous spiniform seta is present on the ischia of both fifth pereiopods ( Fig. 1C ). Thus, the presence or absence of a spiniform seta on the ischium of the fifth pereiopod is now considered to be a variable feature in S. depressus .

The morphological variation shown herein for S. depressus , especially in the rostro-orbital region ( Fig. 1A, E, G ; see also Anker, 2011: fig. 4A, M) and in the configuration of the posterior abdominal somites ( Fig. 1D, F, I ; see also Anker, 2011: fig. 4G), is rather significant. However, with the presently available material (type series from Panama, two heavily damaged specimens from Venezuela and Barbados, one incomplete specimen from St. Martin, one complete and one incomplete specimens from Brazil), it is not possible to make more conclusive statements. The apparently disjunct, Caribbean – southern Brazil distribution of S. depressus may be simply due to insufficient collecting of this cryptically living shrimp along the eastern- and north-eastern Brazilian coast.

Figures

FIGURE 1: A-I, Salmoneus depressus Anker, 2011. A-D, non-ovigerous specimen from São Sebastião, Brazil, MZUSP 28412. E-F, ovigerous specimen from São Sebastião, Brazil, MZUSP 30934; G-I, non-ovigerous specimen from St. Martin, Caribbean Sea, FLMNH UF 31907. A, E, G – anterior region of carapace, dorsal view. B, H – anterior region of carapace, lateral view. C – right fifth pereiopod, lateral view. D, F, I – distal fifth pleuron and sixth pleonite, lateral view. Scale bars = 1 mm. Note in 1A, E, G differences in the development of the orbital teeth; in 1A-B, E, G, H (arrow in A and B) low elevation near the anterior edge of the dorsal depression of the carapace; and in 1C (arrow) a spiniform seta on the ischium of the fifth pereiopod.

FIGURE 2: Salmoneus depressus Anker, 2011, ovigerous specimen from São Sebastião, Brazil, MZUSP 30934, dorsal (A) and lateral (B) views.