Periclimenes tenellus ( Smith, 1882 )

Anker, Arthur, Pachelle, Paulo P. G. & Tavares, Marcos, 2014, Two new species and two new records of deep-water caridean shrimps from Brazil (Decapoda: Pandalidae, Palaemonidae, Crangonidae), Zootaxa 3815 (2), pp. 263-278 : 264-269

Periclimenes tenellus ( Smith, 1882)

( Figs. 3 , 4 )

Anchistia tenella Smith 1882: 55 , pl. 9, figs. 1–1b.

Periclimenes tenellus — Borradaile 1898: 383; Chace 1972: 38. Periclimenes (Cristiger) tenellus — Borradaile 1917: 363.

Periclimenes (Ancylocaris) tenellus — Kemp 1922: 179.

Periclimenes (Periclimenes) tenellus — Holthuis 1951: 32, pl. 8, figs. a–l.

Material examined. Southwestern Atlantic Ocean off Brazil: 1 female (?) [two first pairs of pleopods missing, sex determined tentatively based on gonopore and presence of oviferous setae] (pocl 4.7 mm, rl 2.8 mm), TAAF MD 55 / BRÉSIL 1987, station 53 CB 92, depth: 360 m, 19º34’S 38º55’W, 29.V.1987 ( MZUSP 31496); 1 male (pocl 2.7 mm, rl 2.2 mm), TAAF MD 55 / BRÉSIL 1987, station 54 CB 93, depth: 707–733 m, 19º36’S 38º53’W, 30.V.1987 ( MZUSP 31497); 1 male (pocl 3.4 mm, rl 3.1 mm), REVIZEE, Transecto II, station 4, depth: 500 m, 01.VIII.2003 ( MZUSP 17640); 1 female (pocl 4.1 mm, rl 3.5 mm), REVIZEE, Transecto II, station 4, depth: 500 m, 01.VIII.2003 ( MZUSP 24982).

Description. For original description and illustrations of Periclimenes tenellus see Smith (1882, as Anchistia tenella ); Holthuis (1951) provided a detailed redescription and additional figures of the species; the Brazilian material is illustrated in Figs. 3–4 .

Distribution. Western Atlantic: off South Carolina and New Jersey, U.S.A., 267–419 m ( Smith 1882; Holthuis 1951; Chace 1972); Brazil, off Espírito Santo, 360–733 m (present study).

Remarks. Periclimenes tenellus was hitherto known only from specimens collected by U.S. S. Blake and Fish Hawk in 1880 and 1881, respectively, off the eastern coast of the U.S.A. ( Smith 1882; Holthuis 1951). The holotype of P. tenellus is a heavily damaged ovigerous female from off South Carolina (MCZ CRU-3244), with several appendages regenerating and taxonomically non-informative ( Holthuis 1951). The redescription of P. tenellus by Holthuis (1951) was based partly on a series of USNM specimens of both sexes, some of them complete, dredged off New Jersey. The present material thus represents the first record of P. tenellus in the southwestern Atlantic and Brazilian territorial waters.

The Brazilian specimens ( Figs. 3 , 4 ) agree well with Holthuis’ (1951) redescription of the species, with the exception of the proportionally longer and slightly more curved chela of the major second cheliped (cf. Fig. 4 b, c and Holthuis 1951: pl. 8, fig. g). The number of dorsal teeth on the carapace and rostrum in the Brazilian specimens ranges from eight to ten; the number of ventral rostral teeth from three to four ( Fig. 3 b, j, k, l); this is very similar to the rostral formula (10/3) of the New Jersey specimen illustrated by Holthuis (1951).

Periclimenes tenellus is one of the deepest-known pontoniine shrimps in the Atlantic Ocean, with most known specimens ranging between 267 and 500 m. However, one Brazilian specimen was found at a depth exceeding 700 m together with the more typical deepwater shrimps, Parapontophilus gracilis ( Smith, 1882) and Prionocrangon brasiliensis sp. nov. (see below). It presently remains unknown whether P. tenellus is a free-living shrimp or associated with a sessile (e.g., sponge, octocoral) or slowly moving (e.g., echinoderm) marine invertebrate host.

Figures

FIGURE 3. Periclimenes tenellus (Smith, 1882): female from REVIZEE, Transecto II, station 4, Brazil (MZUSP 24982) (a – i); female and male from TAAF stations 53, 54, off Espírito Santo, Brazil (MZUSP 31496, 31497) (j, k); male from REVIZEE, Transecto II, station 4, Brazil (MZUSP 17640) (l); a, frontal region, dorsal; b, same, lateral; c, abdomen, lateral; d, telson, dorsal; e, same, posterior margin; f, third maxilliped, lateral; g, third pereiopod, lateral; h, same, distal propodus and dactylus, lateral; i, uropod, dorsal; j, k, l, rostrum, lateral.

FIGURE 4. Periclimenes tenellus (Smith, 1882): female from REVIZEE, Transecto II, station 4, Brazil (MZUSP 24982); a, first pereiopod, lateral; b, second (major) pereiopod, mesial; c, same, carpus and chela, mesial; d, same, distal chela, lateral; e, second (minor) pereiopod, lateral; f, same, carpus and chela, mesial.