Bragasellus oscari, López, 2020

López, Eduardo, 2020, A new species of Bragasellus (Isopoda, Asellidae) from NW Spain, with a key to the known species of the genus, Zootaxa 4861 (2), pp. 257-269: 259-266

publication ID

https://doi.org/10.11646/zootaxa.4861.2.6

publication LSID

lsid:zoobank.org:pub:85C58AE4-5387-41A3-B31A-93F038A8CD9B

DOI

http://doi.org/10.5281/zenodo.4416240

persistent identifier

http://treatment.plazi.org/id/03A5D563-FFE4-FF92-7DF1-FDD5097DFAB3

treatment provided by

Plazi

scientific name

Bragasellus oscari
status

sp. nov.

Bragasellus oscari   sp. nov.

Figs 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7

Material examined. Holotype: male, 4.7 mm long and 1.5 mm wide at level of pereonite VII, Fonteo, Lugo, Galicia, NW Spain; 43°03´43.63´´N, 7°15´47.11´´W, 640 m. a.s.l., shallow artificial pool in the source of the river, bottom covered of coarse gravel and water mosses, 22 August 2019, fixed in 70% etanol ( MNCN 20.04 View Materials /12506). GoogleMaps  

Paratypes: Same collection data as for holotype; one male fixed in 70% ethanol and permanent microscope slides with DMHF as mounting medium containing detached appendages ( MNCN 20.04 View Materials /12507); 11 males fixed in 70% ethanol ( MNCN 20.04 View Materials /12508-12518); 5 gravid females fixed in 70% ethanol ( MNCN 20.04 View Materials /12519-12523); 13 non-gravid females fixed in 70% ethanol ( MNCN 20.04 View Materials /12524-12531); three non-gravid females fixed in absolute ethanol ( MNCN 20.04 View Materials /12532-12534); 3 males fixed in absolute ethanol ( MNCN 20.04 View Materials /12535-12537); 15 males, 4 gravid females and 17 non-gravid females (MHNUSC_10115), largest male 5.5 mm long and 2.0 mm wide, largest female, gravid, 4.1 mm long, 1.2 mm wide GoogleMaps   .

Other material. Same collection data as for holotype; fixed in 70% etanol; 43 male and 47 non gravid female specimens GoogleMaps   .

Diagnosis. Pereopod I dactylus shorter than the palm of propodus; male pleopod I exopod marginal setae smooth; male pleopod II endopod lacking basal process and bearing a short but distinct cylindrical cannula; pleopod III exopod with straight internal side.

Description. Male. Holotype ( Fig. 2A, B View FIGURE 2 ), paratype, MNCN 20.04/12508 ( Fig. 2C View FIGURE 2 ), paratype ( Figs 3–7 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 ). Body flattened, about 2.5 times as long as wide, width increasing progressively towards posterior end ( Fig. 2A, B View FIGURE 2 ), uniformly black in live specimens ( Fig. 2D View FIGURE 2 ), greyish after preservation. Coxae not visible in dorsal view ( Fig. 2A, B View FIGURE 2 ). Dorsal coarse setae absent; each pereonite with 12–15 lateral coarse setae, irregularly alternating short and long ones. Head trapezoidal ( Fig. 2C View FIGURE 2 ), about 1.5 as wide as long, rostrum absent, margins convex and fringed with few setae. Pleotelson semioval ( Fig. 2C View FIGURE 2 ), of similar length and width, slightly longer than preceding pereonite, margin setae similar to those of pereonites; caudomedial lobe blunt, broadly rounded.

Antennula flagellum of five articles ( Figs 3A View FIGURE 3 , 4A View FIGURE 4 ) with aesthetascs on last four ( Fig. 4B View FIGURE 4 ). Antenna flagellum of about 35 articles, with aesthetascs on last three.

Mandibles with robust palps ( Figs 3B View FIGURE 3 , 4C View FIGURE 4 ), distal article with 14 plumose spines, median article with ten; tetracuspate incisors ( Figs 3B View FIGURE 3 , 4C, D View FIGURE 4 ); right mandible with 13 plumose spines proximal to lacinia mobilis in right mandible, 12 in left one ( Figs 3B View FIGURE 3 , 4D View FIGURE 4 ).

Maxillula ( Figs 3C View FIGURE 3 , 4E View FIGURE 4 ) distal lamella with 12 terminal teeth, five distal ones smooth and fang-like, remainder pectinate ( Figs 3C View FIGURE 3 , 4F View FIGURE 4 ); basal lamella with five thick plumose spines ( Figs 3C View FIGURE 3 , 4G View FIGURE 4 ). Maxilla ( Fig. 4H View FIGURE 4 ) with 16 and 22 setae in median and external lobes respectively, short spines pectinate, longer ones smooth; inner lobe with two rows of setae, lower row bearing about 30 smooth and fine setae, upper row with 30–32 plumose and shorter ones. Maxilliped ( Figs 3D View FIGURE 3 , 4 View FIGURE 4 I–K) typical of the genus, with six retinacula.

Pereopod I ( Figs 5A View FIGURE 5 , 7A View FIGURE 7 ) with ellipsoid propodus, 1.8 times as long as wide, palmar margin with four coarse conical setae and several thinner marginal ones ( Figs 5A View FIGURE 5 , 7B View FIGURE 7 ); dactylus curved, 2/3 as long as propodus and shorter than palm of latter, flexor margin bearing six conical coarse seate ( Figs 5A View FIGURE 5 , 7B View FIGURE 7 ); carpus triangular, similar length and width, with 4–5 coarse setae on sternal margin, without tergal setae; merus triangular, longer than wide, with three coarse tergal setae in distal end and several thinner sternal ones; ischium twice as long as wide, with three coarse tergal setae; basis 2 times longer than wide, bearing a few fine sternal setae ( Fig. 5A View FIGURE 5 ).

Pereopods II–VII with basis 2.5 times longer than wide; ischium 2.3 times longer than wide, ten coarse tergal setae, two small sternal ones on distal end; merus triangular, twice as long as wide, three pairs of sternal setae, one long and three shorter tergal setae in distal end; carpus four times as long as wide, three pairs of coarse sternal setae, three tergal ones in distal end; propodus slightly longer than carpus, six times as long as wide, two pairs of coarse sternal setae and a distal projection; dactylus slightly curved, bearing four setae on flexor margin ( Fig. 5D View FIGURE 5 ).

Pleopod I ( Figs 6A View FIGURE 6 , 7E View FIGURE 7 ) slightly longer than pleopod II, exopod oval bearing 15–16 long and smooth distolateral setae. Pleopod II protopod quadrangular, slightly longer than wide, bearing a smooth seta on inner margin; exopod proximal article cup-like bearing two setae on external side, distal article semioval and clearly longer, five smooth lateral setae and four plumose ones on distal position ( Figs 6B View FIGURE 6 , 7F View FIGURE 7 ); endopod (appendix masculina) larger than exopod, subconical, without basal processes, bearing a cylindrical cannula with slightly projecting opening, setation absent ( Fig. 6B View FIGURE 6 ). Pleopod III exopod ( Figs 6D View FIGURE 6 , 7H View FIGURE 7 ) with transverse suture, distal area shorter than proximal one, with smooth setae along distal and lateral margins, internal margin distinctly straight and bearing a short triangular basal process ( Fig. 7H View FIGURE 7 ); endopod reaching transverse suture, distally rounded. Pleopod IV exopod ( Fig. 7I View FIGURE 7 ) nearly as long as wide, with suture only noticeable on external margin, external margin densely ciliated without setae ( Fig. 7J View FIGURE 7 ); endopod similar in length to exopod, rounded distally.

Uropods three quarter as long as pleotelson ( Figs 2C View FIGURE 2 , 5D View FIGURE 5 ); rami tubular, endopod slightly shorter than exopod and half as long as protopod; exopod bearing long apical setae.

Female. Similar in body shape to male but distinctly smaller. Pereopod I ( Figs 5B View FIGURE 5 , 7C View FIGURE 7 ) with clearly more gracile propodus than male, 2.8 times as long as wide, palmar margin with three conical coarse setae and several marginal thinner ones ( Figs 5B View FIGURE 5 , 7D View FIGURE 7 ); dactylus similar to that of male, but bearing four conical coarse setae on flexor margin ( Figs 5B View FIGURE 5 , 7D View FIGURE 7 ). Pleopod II ( Figs 6C View FIGURE 6 , 7G View FIGURE 7 ) triangular, about 2.5 as long as wide, with four very short and smooth setae on external margin. Uropod similar to male, but shorter ( Fig. 5E View FIGURE 5 ).

Remarks. The new species is referred to genus Bragasellus Henry & Magniez, 1968   for the shape of the endopod of pleopod 2 in males, in which the distal article lacks any kind of process. The equivalent sexual structure bears an elongated basal process supported by a sclerotized rod in the genus Asellus Geoffroy, 1762   , which is absent in the species of Bragasellus   ; although a number of species in the former genus bear one or two basal processes they are proportionally shorter and are never supported by a rod ( Henry & Magniez 1974). The numerous species of Proasellus Dudich, 1925   possess a subapical tergal process in the appendix masculina, a trait totally absent in Bragasellus   species ( Henry & Magniez 1974), except for B. afonsae Henry & Magniez, 1988   . The rest of genera reported from Western Europe encompass only hipogean species thus far. Gallasellus Henry & Magniez, 1977   , a monotypic genus from Southern France, and Chthonasellus Argano & Messana, 1991   , a genus endemic from central Italy and also monotypic, present a cannula protruding from a terminal depression partially covered by a curved caudal process ( Henry & Magniez 1977; Argano & Messana 1991), which is very different to the appendix masculina of the rest of west European genera. Finally, the Iberian endemic genus Synasellus   Braga, 1944 is characterized by the lack of mandibular palp, whereas this structure is well developed in all Bragasellus   species, and its appendix masculina bears a markedly tapering cannula ( Henry & Magniez 1995), very different to that of B. oscari   , in which it appears as a cylindrical tube.

To date, genus Bragasellus   contained 20 valid species, all of them endemic of the Iberian Peninsula ( Braga 1943, 1944, 1946, 1958, 1964; Henry & Magniez 1973, 1976, 1978, 1980, 1988; Afonso 1984, 1989; Afonso et al. 1996; Magniez & Bréhier 2004). Most of them are cave-dwelling, unpigmented taxa and only two are epigean and were described as having conspicuous body pigmentation: B. peltatus   ( Braga, 1944) and B. cortesi Afonso, 1989   . The new species is also epigean, but differs from them by the proportionately shorter pereopod I dactylus, which is shorter than the palm of propodus, by the pleopod I exopod marginal setae, which are smooth instead of plumose, and by the shape of the pleopod III exopod, which has a straight internal side instead of more or less rounded one ( Braga 1944; Afonso 1989). Bragasellus oscari   sp. nov. and B. cortesi   have very similar male pleopod II, with exopod shorter than endopod, and with the latter lacking basal process and bearing a developed cannula, contrary to B. peltatus   , which posseses a basal process and lacks a cannula in its appendix masculina. However, the male pleopod II of B. oscari   sp. nov. and B. cortesi   differ in the setal arrangement of the exopod, which shows a clear gap between marginal and distal setae in the former species.

Some publications recorded abundant populations of the epigean asellids Proasellus coxalis (Dolfuss, 1982)   , P. meridianus (Racovitza, 1919)   and P. ibericus   ( Braga, 1946) near the type locality of the new species ( González & Cobo 2006; Cobo 2017). Apart of a distinct colour pattern with yellowish speckles over their head and body, these three species possess conspicuous subapical process in their appendix masculina, which are clearly shorter than corresponding exopodites ( Braga 1946; Henry & Magniez 1992), so they may be easily separated from B. oscari   n. sp.

Etymology. The new species is named after Óscar, youngest child of first author.