Macrobrachium luscus (Holthuis, 1973) Mantelatto & Pileggi & Pantaleão & Magalhães & Villalobos & Álvarez, 2021

Mantelatto, Fernando L., Pileggi, Leonardo G., Pantaleao, Joao A. F., Magalhaes, Celio, Villalobos, Jose Luis & Alvarez, Fernando, 2021, Multigene phylogeny and taxonomic revision of American shrimps of the genus Cryphiops Dana, 1852 (Decapoda, Palaemonidae) implies a proposal for reversal of precedence with Macrobrachium Spence Bate, 1868, ZooKeys 1047, pp. 155-198 : 155

Macrobrachium luscus (Holthuis, 1973) comb. nov.

Bythinops luscus Sbordoni, Argano & Zullini, 1973: 24 (nomen nudum).

Bithynops luscus Holthuis, 1973: 136, figs 1, 2. - Holthuis 1977: 181. - Hobbs, Hobbs and Daniel 1977: 25 (key), 46, fig. 17. - Reddell 1981: 108, fig. 15 (map), 319 (in list), 323 (list). - Villalobos 1982: 217 (in list). - Fitzpatrick 1983: 217. - Holthuis 1986: 606 (list). - Holthuis 1993: 103, fig. 89. - Hobbs III 1993: 20 (list). - Álvarez et al. 1996: 110, chart 12.2 (list). - Pereira 1997: 47, table 6 (list). - Fransen et al. 1997: 15 (catalog). - Jayachandran 2001: 17, fig. 1. - Palacios-Vargas 2006: 7 (list). - Mejía-Ortiz et al. 2013: 32, table 1. - Lamoreux et al. 2015: 306, Appendix 2 (list). - De Grave et al. 2015b: 7, table 3.

Cryphiops (Bithynops) luscus . - Villalobos Hiriart et al. 1989: 163, figs 1, 6a, c, 8a. - Villalobos-Hiriart et al. 1993: 281, table 5 (list). - Hobbs III 1994: 98 (list). - Fransen et al. 2010: 30, Appendix III (list). - De Grave and Fransen 2011: 316 (catalog). - Álvarez et al. 2011: 258, fig. 4a. - Palacios-Vargas and Reddell 2013: 43 (list). - Palacios-Vargas et al. 2014-2015: 22. - Quiroz-Martínez et al. 2014: table S1 (list). - Alvarez and Villalobos 2016: 250, table 8.1 (list).

Cryphiops luscus . - Palacios-Vargas 2006: 7 (list). - Baldari et al. 2010: 48, fig. 1 (map), 52, table 1. - Botello and Alvarez 2013: table 1 (list). - Mantelatto et al. 2020: 915 (key).

Material examined.

Mexico - Chiapas • 8 males, tl 30.5-49.4 mm, 15 ovigerous females, tl 30.8-46.3 mm; Municipality of La Trinitaria, Rancho de San Rafael del Arco, Gruta del Arco ; 07 Apr. 1986; J.L. Villalobos leg.; CNCR 5759 .

Description.

Rostrum. Short, directed slightly downwards, tip directed slightly upwards, reaching or slightly overreaching joint between second and third article of antennular peduncle, and at level of distal third of scaphocerite; upper margin convex over orbit, with 5-8 teeth regularly spaced, first over or slightly behind posterior edge of orbit; lower margin with none or one tooth.

Cephalon. Scaphocerite 2.5 × as long as wide; outer margin straight.

Carapace. Smooth, with minute punctuations; antennal spine small, slightly overreaching lower portion of orbit; hepatic spine absent. Lower orbital angle obtuse, moderately pronounced.

Pereiopods . P1 slender, reaching with nearly entire chelae beyond scaphocerite; fingers slightly longer than palm; chelae 2/3 length of carpus. P2 moderately robust, with several spines, equal in form and size, reaching with proximal third of carpus beyond scaphocerite; ischium evidently shorter than merus; merus as long as carpus; carpus as long as palm, with basal constriction; propodus 2 × as long as dactylus, 2 × as long as carpus; palm inflated, nearly 3 × as long as high; fingers as long as palm, with numerous small spinules; cutting edge with two denticles of same size in both teeth. P3-P5 with all joints covered with row of small spinules on the lower margin; P3 reaching with entire dactylus beyond scaphocerite, propodus 2 × as long as dactylus, propodus slightly longer than merus; P4 reaching with tip of dactylus end of scaphocerite, propodus 3 × as long as dactylus, propodus slightly longer than merus; P5 reaching with tip of dactylus half-length of scaphocerite, propodus 3 × as long as dactylus, propodus slightly longer than merus.

Pleon. Smooth. Somite 5 with posteroventral angle of pleuron acute; somite 6 nearly 2 × as long as somite 5. Inter-uropodal sclerite without, keel-shaped pre-anal carinae.

Pleopods. PL2 with appendix masculina 2 × as long as appendix interna.

Uropods. Exopodite with mobile spines as long as spiniform projection of outer margin.

Telson. Broad, smooth, slightly longer than abdominal somite 6, bearing two pairs of dorsal spinules closer to posterior margin of telson. Posterior margin ending in moderately acute triangular point, with several plumose setae and two pairs of posterior spinules, inner pair overreaching end of telson.

Size.

See in material examined.

Color.

Whitish to transparent.

Type locality.

México, Chiapas, Municipality of La Trinitaria, Gruta del Arco, El Rancho de San Rafael Del Arco, Lagunas de Montebello, altitude 1,470 m. Recent visits to the type locality showed an increasing contamination in the lakes that supply water to the underground stream of the Gruta del Arco, and the collections of specimens were not successful, at least in the closest access to the water pools. Possibly, M. luscus comb. nov. is seriously threatened.

Distribution.

Only known from the type locality ( Holthuis 1973; present paper).

Life cycle.

This is a cave species exclusive of inland waters, therefore independent of brackish to complete its life cycle. The eggs are few and large: 1.8-2.4 mm ( Villalobos Hiriart et al. 1989). The duration of the embryonic development is probably long and with few larval stages following the pattern of other inland species.

Remarks.

This species is similar to Macrobrachium valdonii nom. nov., comb. nov., which is the other hypogean species with abbreviated development and without hepatic spine. The most remarkable differences between them concerns the length of the rostrum, and the proportion of the articles of second pereiopod (Table 2 ). In M. luscus comb. nov., the rostrum is short, reaching or slightly overreaching joint between second and third article of antennular peduncle, and at level of distal third of scaphocerite. The ischium of the second pereiopod is evidently shorter than the merus, and the dactyl is little longer or as long as palm. In M. valdonii nom. nov., comb. nov., the rostrum is longer, reaching the third article of antennular peduncle and the distal border of scaphocerite; the ischium of the second pereiopod is slightly shorter than the merus, and the dactyl is slightly shorter than the palm.