Periclimenaeus maxillulidens ( Schmitt, 1936 )

Periclimenaeus maxillulidens ( Schmitt, 1936) View in CoL

( Figs. 5–7)

Periclimenes maxillulidens Schmitt, 1936: 371 View in CoL , pl. 13, fig. 3a–o.

Periclimenaeus maxillulidens View in CoL .— Holthuis, 1951: 87, pl. 26.— Abele and Kim, 1986: 11, 90.— Chace, 1972: 28.— Cardoso and Young, 2007: 295 (key), 296.— Santana-Moreno et al., 2013:231, fig.2G.— Ramos-Tafur and Lemaitre, 2017: 505 (key).— Pachelle et al., 2018: 132 View Cited Treatment .

Material examined. Brazil, Espírito Santo, off Vitória, Escalvada Island , 20°41’55.3”S 40°24’20.8”W, scuba dive, 15 m depth, coral rubble, inside Diplosoma sp. ( Fig. 4), coll. Sandra Vieira Paiva, 29 March 2017: 1 ovigerous female, 3.7 mm CL, MZUSP 39108 View Materials GoogleMaps .

Distribution. Western Atlantic: USA (Florida), Mexico (Yucatan), Bonaire, Panama (Bocas del Toro) and Brazil (Espírito Santo) ( Schmitt, 1936; Holthuis,

1951; Santana-Moreno et al., 2013; Pachelle et al., 2018; present study).

Remarks. Schmitt (1936) described P. maxillulidens (as Periclimenes maxillulidens ) based on one male collected in Bonaire. Afterwards, the species was only reported from USA (Florida), Mexico (Yucatan) and Panama (Bocas del Toro) ( Holthuis, 1951; Santana-Moreno et al., 2013; Pachelle et al., 2018). The present female from Escalvada Island represents the fourth record of this rare species and its first record in Brazil and the southwestern Atlantic Ocean.

Our specimen agrees well with the specimens described and illustrated in Schmitt (1936: pl. 13) and Holthuis(1951:pl.26),including(i)shape and armature of the rostrum ( Fig. 5A), (ii) first article of antennular peduncle with distolateral angle blunt, lacking a tooth ( Fig. 5C), (iii) scaphocerite wider distally, with a small lateral tooth ( Fig. 5D), (iv) proportions of the first pereopod ( Fig. 5E), (v) overall shape and armature of the major second pereopod ( Fig. 6A–C), and (vi) pereopods 3–5 with dactyli simple, lacking both subdistal and proximoventral teeth ( Fig. 7B, D, F). The minor second pereopod, herein illustrated for the first time for the species ( Fig. 6D–F), lacks granules on its surface, but is furnished with setae, which are more abundant on the chela fingers. The fingers are slightly curved inwards; the cutting edge of the fixed finger has a small triangular tooth on its proximal half and a series of tiny teeth on the distal half; the dactylus has a wide, laterally excavated process proximally, separated from the rest of the cutting edge by a sinus; cutting edge distally serrated ( Fig. 6F).

According to Holthuis (1951), P. maxillulidens is morphologically very similar to two other Atlantic species, P. atlanticus and P. schmitti Holthuis, 1951 . Periclimenaeus maxillulidens , however, can be readily separated from both species by the combination of three morphological characters:(i)shape and armature of rostrum (1–2 dorsal teeth in P. maxillulidens and P. schmitti , 4 teeth in P.atlanticus ; cf. Holthuis, 1951: pl. 24, fig. b; Fig. 5A), (ii) armature of the scaphocerite (blunt in P.schmitti , with small tooth in P.maxillulidens , with distinct tooth in P.atlanticus ; cf. Holthuis, 1951: pl. 24, fig. e; pl. 27, fig.c; Fig. 5D), and (iii) the shape of pereopods 3–5 dactyli (simple in P. maxillulidens and P.atlanticus , biunguiculate in P. schmitti ; cf. Holthuis, 1951: pl. 24, fig. o; pl. 27, fig. m; Fig. 7B, D, F).

Although most species of Periclimenaeus are known to associate with sponges and ascidians, the hosts for several species are either unknown or reported as unidentified sponges or ascidians ( Holthuis, 1951; Bruce, 2006; Fransen, 2006; Dobson et al., 2016). Periclimenaeus maxillulidens has been reported from sandy debris ( Schmitt, 1936), broken shells, gravel, sand and coral ( Holthuis, 1951; Santana-Moreno et al., 2013). Pachelle et al. (2018) reported a single ovigerous female of P. maxillulidens in epibiotic growth on mangrove roots, but without specifying whether the specimen was collected inside sponges or ascidians. Therefore, the present study confirms that the species is, at least, associated with colonial ascidians of the genus Diplosoma ( Fig. 4).

Identification key for the species of Periclimenaeus from the southwestern Atlantic

1a. Pereopods 3–5 with dactyli simple 2

1b. Pereopods 3–5 with dactyli biunguiculate 3

2a. Rostrum straight, dorsal margin with 4 teeth; scaphocerite with lateral tooth distinct, strong

P. atlanticus [ Brazil: Paraíba]

2b. Rostrum sinuous, dorsal margin with 2–3 teeth; scaphocerite with lateral tooth subtle, weak

P. maxillulidens

[ Brazil: Espírito Santo (Escalvada Island)]

3a. Rostrum with a ventral tooth; carapace with small supraorbital tooth or acute tubercle; scaphocerite with lateral tooth distinct, clearly overreaching blade; dactyli of pereopods 3–5 with unguis ventrally serrulate P. caraibicus [ Brazil: Rio Grande do Norte (Atol das Rocas)]

3b. Rostrum with ventral margin unarmed; orbital region of carapace smooth; scaphocerite with lateral tooth not as distinct, at most reaching the distal margin of the blade; dactyli of pereopods 3–5 with unguis ventrally smooth 4

4a. Telson with both pairs of dorsal spines inserted in the anterior half of telson; outer pair of distal spines of telson removed from the distal margin, inserted more proximally than the remaining two distal pairs of spines 5

4b. Telson with posterior pair of dorsal spines inserted in the posterior half of telson; outer pair of distal spines of telson placed in the distal margin, in line with the remaining two distal pairs of spines 7

5a. Rostrum very high, dorsal teeth large; pereopod 1 carpus long, almost twice as long as chela

P. perlatus

[ Brazil: Ceará, Paraíba, Pernambuco] 5b. Rostrum not very high, dorsal teeth mediumsized; pereopod 1 carpus short, slightly longer than chela 6

6a. Carapace not inflated; second pereopods with palm furnished with numerous granules P. brucei [ Brazil: Rio Grande do Norte (Atol das Rocas)]

6b. Carapace inf lated; second pereopods chelae smooth, without granules P. crosnieri

[ Brazil: Rio Grande do Norte (Atol das Rocas)]

7a. Rostrum long, distinctly overreaching the corneas; stylocerite slender, tip acute; dactylus of both second pereopods with cutting edge serrated near apex; minor second pereopod fingers serrated near apex; propodus of pereopod 3 with ventral spines restricted to the distoventral angle P. ascidiarum

[ Brazil: Maranhão, Ceará, Pernambuco, Espírito Santo ( Escalvada Island )]

7b. Rostrum short, not reaching the distal margin of the corneas; stylocerite broad, tip triangular; dactylus of both second pereopods with cutting edge smooth near apex; minor second pereopod fingers smooth near apex; propodus of pereopod 3 with ventral spines distributed along the margin P. pearsei

[ Brazil: Maranhão]