Bathyporeiidae

D'Acoz, Cedric D'Udekem, 2011, Validation of the family Bathyporeiidae (Crustacea, Amphipoda), Zootaxa 2791, pp. 54-62 : 54-60

Bathyporeiidae fam. nov.

Bathyporeid [sic] Lincoln & Hurley, 1981: 106 (vernacular name)

Bathyporeiidae Bousfield & Shih, 1994: 92 , 94, 114, 128 (invalid: no description). —d'Udekem d'Acoz, 2007: 63 (invalid: not considered as new)

Diagnostic description. Gammaromorphic facies. Appendages with more spines than setae, modified for endopsammic life. Head with anterior lobe rounded to bluntly angula r and posterior lobe very weakly rounded, the two lobes being separated by a wide and very weak concavity; rostrum obsolete; eye somewhat elongate, in normal or slightly lower position, with ommatidia usually very distinct. Calceoli on flagellum of antenna 2 and usually of antenna 1 in mature males (no more than one calceolus per article); no calceoli on peduncle of antenna 1 and antenna 2; calceoli absent in females and immature males; calceoli of 'bathyporeiid type', being very similar to 'gammarid type' ( Lincoln & Hurley, 1981): nearly circular, with proximal element reduced, forming a weakly concave crescentic plate, closely applied along its inner margin to the distal element and with short but narrow projections along its posterior margin; distal element with curved transverse banding. Antenna 1 with article 1 of peduncle massive, geniculate, forming a pseudorostrum, much longer than articles 2 and 3; article 2 and 3 of peduncle subequal, each with a transverse row of spines; accessory flagellum biarticulated; article 2 much shorter than article 1. Antenna 2 of males with flagellum increasing in size at maturity or not. Mouthparts of gammaroid type. Upper lip without median notch. Lower lip with inner lobes. Mandible variable (especially as concerns the shape of the lacinia mobilis) but always with well-developed molar and incisor process and welldeveloped 3-articulate palp (article 1 very short); setation of article 3 of palp variable. Maxilla 1: article 2 of palp with ornamentation variable; outer plate with 9–11 spines; inner plate well developed, triangular, with row of strong setae. Maxilla 2 with broad and apically densely setose plates; inner plate with oblique facial row of strong setae. Maxilliped with plates and palp normally developed; each inner plate with 3 anterior spines, and 1 curved posterofacial spine terminated by a row of denticles and interlocking with the posterofacial spine of the opposite inner plate; outer plate with marginal posterior and distal spines and marginofacial strong setae; article 2 of palp with posterior longitudinal row of long and strong setae on medial surface. Setae and spines of maxilla 1, maxilla 2 and maxilliped not degenerating at maturity. Gills simple, present from gnathopod 2 to pereiopod 6. Oostegites on pereiopods 3–5. Coxae of pereiopods ventrally setose; coxae 1 – 4 long; coxae 1 – 3 without anterior tooth/notch, with or without posterior tooth/notch; coxa 4 without tooth/notch, with posteroproximal concavity; coxae 5 – 6 bilobate; coxa 7 non lobate or scarcely lobed. Gnathopods 1 – 2 not or scarcely sexually dimorphic. Gnathopod 1 subchelate, normally developed and scarcely smaller than gnathopod 2 ( Amphiporeia ), or very small and much smaller than gnathopod 2 ( Bathyporeia ). Gnathopod 2 either subchelate ( Amphiporeia ), or highly transformed ( Bathyporeia ): with dactylus vestigial, and elongate propodus with very long strong setae on posterior border. Pereiopods 3 – 4 with merus and carpus very stout; propodus narrow; dactylus normally developed to rather short; merus, carpus andpropodus with long spines/setae on posterior border; carpus with one long posterodistal spine distinctly stronger than others; propodus without setae on anterior border; posterior spines and setae of propodus not forming two distinct rows; dactylus with terminal unguis, sometimes with a short posterodistal seta (otherwise without ornamentation). Pereiopod 5 highly transformed: basis broadly elliptic with anterior transverse combs of spines; merus broadly elliptic, posterior border with 2 well-developed groups of setae (one at 0.6 and one distal), rarely with a third group in a more proximal position (in teratological specimens only), anterior border with a lateral longitudinal comb of spines and a medial longitudinal comb of long setae; carpus and propodus small, subequal in size, cylindrical and narrow; dactylus very short to vestigial. Pereiopod 6 with basis subcircular; merus, carpus and propodus with transverse groups of strong spines; dactylus very short. Pereiopod 7 with basis broad, with strong pappose setae on medial surface; ischium quadrate or pentagonal; merus, carpus and propodus with transverse groups of strong spines; dactylus very short. Pleonites dorsally smooth. Third epimeral plate with or without posteroventral tooth, with ventrofacial spines, which are often placed in transverse groups. Pleopods with peduncle elongate, with well-developed rami. Urosomite 1 with or without ventrofacial spines, with or without dorsal spines and setae; peduncle of uropod 1 usually with more than 1 ventrofacial spiniform seta; long distolateral spine of peduncle of uropod 1 paired with a smaller one in a slightly more proximal position. Rami of uropods 1 – 2 broad along their entire length, distally truncated (not tapering); tip with 5 spines: a pair of long spines flanking a pair of short spines flanking a distal long spine; inner ramus often with ventral setae. Uropod 3 weakly attached to urosome. Outer ramus of uropod 3 long and narrow with well-developed article 2; outer border with groups of spines; inner border with long plumose setae at least in mature males, sometimes associated with spines. Inner ramus of uropod 3 much shorter than outer ramus. Telson almost entirely cleft; lobes not acute-tipped; group of terminal spines and 1 or 2 groups of lateral spines present; each lobe with 2 to 3 large dorsal transparent pappose blunt-tipped setae.

Type genus. Bathyporeia Lindström, 1855 .

Composition. Bathyporeia Lindström, 1855 and Amphiporeia Shoemaker, 1929 .

Illustrations and references. The systematic literature on Bathyporeia and Amphiporeia has been reviewed by d'Udekem d'Acoz (2007), who lists papers with good descriptions and figures of all known species. As a supplement to this, a live picture and SEM photographs of representatives of Bathyporeia (the type genus of the family) are given herein ( Figures 1 – 4 ).

Distribution and biology. Northwestern, Northeastern and Southeastern Atlantic, Mediterranean, Black Sea; intertidal to 106 m depth; on sandy bottoms (d'Udekem d'Acoz, 2007). An enigmatic record of Bathyporeia sp. from the equatorial Eastern Pacific ( Aerts et al. 2004) needs confirmation. Endopsammic amphipods swimming at night in the water column. Females interoparous (AT least in Bathyporeia ).

Putative synapomorphies. Antenna 1: article 1 of peduncle massive and geniculate; article 2 and 3 of peduncle very short and equal in length; accessory flagellum biarticulated with article 2 much shorter than article 1. Pereiopod 5: basis broadly elliptic; merus broadly elliptic, anterior border with lateral longitudinal comb of spines and medial longitudinal comb of long setae; carpus and propodus short and narrow, subequal in size; dactylus very short to vestigial. Pereiopod 6: basis broadly elliptic to circular; dactylus very short. Pereiopod 7: dactylus very short.

Systematic position of the Bathyporeiidae . In the literature, Bathyporeia and Amphiporeia are traditionally assigned to the Pontoporeiidae Dana, 1853 sensu lato (= Haustoriidae Stebbing, 1906 , s.l.). This view is questionable because the Haustoriidae / Pontoporeiidae s.l. appears as a heterogeneous assemblage of taxa linked by the sole occurrence of morphological adaptations to a fossorial way of life, such as the transformation of legs into shovels and an increase in the number and strength of spines and setae. The morphology of the shovel-like appendages is so disparate and the disposition of spines and setae is so diverse across the family that, in most cases, no potential synapomorphies can be inferred from those characters. Therefore, successive fragmentations of the Haustoriidae / Pontoporeiidae s.l. have been proposed ( Bousfield 1978; Bousfield & Shih 1994; d'Udekem d'Acoz 2007) and the following nomenclaturally valid families have been recognized in the North Atlantic: Haustoriidae senu stricto (see drawings by Bousfield 1965), Urothoidae Bousfield 1978 (see drawing by e.g. Bellan-Santini 1989; Jaume & Sorbe 2001), Pontoporeiidae (see drawings by Bousfield 1989; d'Udekem d'Acoz 2007) and Priscillinidae d'Udekem d'Acoz, 2007 (see drawings by d'Udekem d'Acoz 2007). Bathyporeia and Amphiporeia exhibit very few similarities in the morphology of legs and the arrangement of spines and setae with these families, but in many respects, look similar to the Gammaroidea Leach, 1814 as defined by Bousfield (1977, 1979). Actually, the geniculate article 1 of the peduncle of antenna 1, the highly transformed pereiopod 5 (and also pereiopod 2 in Bathyporeia ) can be considered as mere adaptations to endopsammic life superimposed on a typical gammaroid body plan, or better, on the body plan of already fossorial gammaroids like some pontogammarid species (see Cäräuşu 1943 for illustrations). However it must be pointed out that a downwards flexibility of the articulation between article 1 and 2 of antenna 1 is a character state frequent in the Phoxocephalidae G. O. Sars, 1891 and Haustoriidae , and this condition could be interpreted as a possible predecessor of the true geniculate articulation of the Bathyporeiidae . In a cladistic analysis of morphological characters carried out by d'Udekem d'Acoz (2007), Bathyporeia and Amphiporeia cluster with the Gammaridae Leach, 1814 and the Pontogammaridae Bousfield, 1977 and not with other Haustoriidae / Pontoporeiidae s.l. The structure of calceoli in Bathyporeia and Amphiporeia is also very similar to that of the Gammaridae (especially for the strong curvature in the transverse banding of the distal element), but is different from that of the Pontoporeiidae , Urothoidae and Phoxocephalidae , which have straight or nearly straight transverse banding ( Lincoln & Hurley 1981; Bousfield & Shih 1994). The Haustoriidae have no calceoli and nothing is known concerning the condition occurring in the Priscillinidae , since no adult male has ever been recorded. However, the elongation of antenna 2 frequently observed in adult male Bathyporeia (e.g. d'Udekem d'Acoz 2004) is a character state unrecorded in the Gammaroidea and the Haustoriidae s.s., but often present in the Phoxocephalidae , Urothoidae , Pontoporeiidae and Priscillinidae . The absence of gill on pereiopod 7 observed in Bathyporeia and Amphiporeia is also a condition unusual for the Gammaroidea ( Bousfield 1977), but is the rule in the Haustoriidae s.s., the Pontoporeiidae s.s., the Priscillinidae ( Bousfield, 1978) and the Urothoidae ( Barnard & Karaman 1991) .

Molecular studies ( Englisch 2001) suggest a close relationship between the marquedly distinct genera Bathyporeia and Haustorius . If the Bathyporeia / Amphiporeia group is indeed phylogenetically close to the Haustoriidae s.s. (which is a morphologically very homogeneous family), their morphological transformations to a fossorial way of life are so divergent that they must be the outcome of entirely, or almost entirely, independent evolutionary pathways. In such conditions, it seems appropriate to create a separate family for the clade consisting of Bathyporeia and Amphiporeia .

Nomenclatural acts. Lincoln & Hurley (1981) introduced the informal 'bathyporeid' concept as a vernacular name only. Later on, Bousfield & Shih (1994) introduced the family name 'Bathyporeiidae', but this name has to be considered as invalid, because no formal description, as required by Art. 13 of ICZN (1999), was provided.

D'Udekem d'Acoz (2007: 63) used the family Bathyporeiidae Bousfield & Shih, 1994 , but despite the description provided in that paper, authorship of the family cannot be attributed to d'Udekem d'Acoz (2007), as Art. 16 ( ICZN 1999) was not satisfied, in that no explicit intention was stated that the family was to be considered as new. The family Bathyporeiidae fam. nov. is now finally validated herein, as all relevant Articles of ICZN (1999) have been fulfilled.

Figures

FIGURE 1. Bathyporeia elegans Watkin, 1938, adult female, 4 mm, with full ovaries, Norway, Tromsø area, Kvaløya, Sandvika, 62 ° 36 ' 51 " N 018 ° 05 ' 27 " E, 0.5 m depth at low tide, fine sand, July 2004 (specimen not preserved).

FIGURE 2. Bathyporeia spp. A, C, E, B. pilosa Lindström, 1855, adult female, 4 mm Northwestern Europe; B, D, F, B. guilliamsoniana (Bate, 1857), The Netherlands, adult male, 6 mm (specimens not preserved). A, B, habitus; C, D, anterior part of body; E, F, posterior part of body.

FIGURE 3. Bathyporeia spp. A, B. pilosa Lindström, 1855, adult female, 4 mm Northwestern Europe; B – G, B. guilliamsoniana (Bate, 1857), The Netherlands, B, D, E, adult male, 6 mm C, F, G, H, adult female, 6 mm (specimens not preserved). A, peduncle of A 1; B, calceolus; C, mandibular palp (female); D, mandibular palp (adult male); E, D 3 - setae of article 3 of mandibular palp (adult male); F, Mxp; G, posterofacial spine of inner plate of Mxp; H, tip of posterofacial spine of inner plate of Mxp (note the distal row of denticles).

FIGURE 4. Bathyporeia spp. D, B. pilosa Lindström, 1855, adult female, 4 mm Northwestern Europe; A – C, E – I, B. guilliamsoniana (Bate, 1857), The Netherlands: A – C, F – I, adult male; 6 mm, E, adult female, 6 mm (specimens not preserved). A, propodus of Gn 2; B, tip of propodus of Gn 2 and vestigial dactylus; C, tip of carpus, propodus and dactylus of left P 3 (note the enlarged distal carpal spine); D, right P 5; E, distal half of merus, carpus and propodus of left P 5; F, tip of propodus and vestigial dactylus of P 5; G, left P 6; H, left P 7; I, coxa, basis, ischium and proximal part of merus of left P 7.