European species of Haustorius (Crustacea: Amphipoda: Haustoriidae), with description of a new Mediterranean species

The genus Haustorius is represented by six species in the world; three are described as American species, three European including a new species described from the Mediterranean. This new species, H. orientalis, is similar to H. algeriensis Mulot, 1967 from the Algerian coast but differs in rostrum slightly exceeding in length the antennal lobes, merus of pereiopod 7 with posterior margin lacking spines, and uropod 1 with two separate rows of spines.


Introduction
The genus Haustorius Mü ller, 1775 is now represented by five valid described species: Haustorius arenarius (Slabber, 1769), H. canadensis Bousfield, 1962, H. algeriensis Mulot, 1967, H. jayneae Foster and Lecroy, 1991, and H. mexicanus Ortiz, Chazaro-Olvera and Winfield, 2001 When in 1967, Mulot described H. algeriensis from the Algerian coast, he indicated that this species was the first Haustorius found in the Mediterranean sea and it remains unique (Bellan-Santini et al. 1989) and has never been sampled beyond its type locality of Sidi Fredj region: Bou Ismail Bay, Djinet Cape (Bakalem and Dauvin 1995). A new species collected on a beach at Michmoret (Israel coast) presents significant differences with the other species, and in particular with H. algeriensis. It brings the number of Haustorius to six species with three of them European.

Type locality
Michmoret beach (Israel coast), in the sand in the upper part of infralittoral zone.

Description
Female, 6 mm. Body broad, eyes not visible in the animal preserved in alcohol. Last segment of pereon produced distally and overhanging reduced urosome. Rostrum exceeding in length slightly the antennal lobes. Antenna 1 with flagellum seven-articulate, accessory flagellum three-articulate. Antenna 2 little longer than A1, flagellum eightarticulate. Mouthparts normal. Mandible with incisor and a triarticulate palp, article 3 with lateral edge bearing 17 small setae in comb row. Maxilla 1 inner plate with 10 marginal setae. Maxilla 2 with inner plate linguiform, outer plate enlarged, lunate, both lined with long fine setae. Maxilliped with triarticulate palp, article 2 enlarged distally, article 3 geniculate. Coxa 1 long and deep, fringed at the posterior part with long plumose setae. Gnathopod 1 simple, carpus enlarged, propodus ovate, dactylus with a distal spine. Coxa 2 ovate. Gnathopod 2 little different from gnathopod 1 but minutely chelate. Coxa 4 larger than coxa 3. Pereiopods 3 and 4 similar, typical for the genus. Pereiopods 5-7 broad. Pereiopod 5 with rounded basis, fringed with long setae, ischium short, merus enlarged, spinose on the surface, fringed with spines and plumose setae, carpus less enlarged than merus, very spinose, propodus very spinose on the anterior margin and with five distal spines. Pereiopod 6, basis rounded, fringed with long setae, ischium short, merus expanded    with numerous spines on the surface and on the margins, long plumose setae on the anterior and distal margins, carpus subquadrate covered and fringed with spines, propodus fringed at the posterior margin with spines, seven distal spines. Pereiopod 7, basis large, anteriorly fringed with plumose setae, ischium short, merus produced posteroventrally, anterior margin spinose on the distal half, distal margin spinose, posterior margin without spines, fringed with long plumose setae, carpus and propodus fringed with many spines, short setae on the surface of the carpus. Epimeron 2 with the distal posterior corner quadrate. Epimeron 3 rounded posteriorly, without process, with long plumose setae on the surface. Uropod 1 rami unequal, peduncle and rami armed with strong spines, peduncle with two rows of four spines. Uropod 2, rami unequal, outer ramus longer than inner, peduncle and rami fringed with long setae. Uropd 3, peduncle shorter than rami, outer ramus longer than inner biarticulate, long setae on the distal margin. Telson cleft to the base, consisting of two widely separated lobes with two lateral and 12 distal long setae, two plumose setae on each lobe.

Etymology
The specific name refers to the region of the type locality, in the oriental basin of the Mediterranean.

Relationship
The different species of Haustorius differ from each other in the shape of the rostrum, uropod 1 and pereiopod 7 (denoted 5 by Bousfield 1965 andMulot 1967). The three European species differ from the American ones essentially in the merus of P7, which has the proximal margin continuous with the posterior margin. It is sharply set off from posterior margin in American species (Barnard and Karaman 1991; Foster and Lecroy 1991) ( Figure 5). Among the three European species, the Atlantic H. arenarius has a five-articulate accessory flagellum and the merus of P7 with three to four stiff spines groups at the posterior margin. The two other European species are Mediterranean. Haustorius orientalis differs from H. algeriensis in the rostrum exceeding slightly the antennal lobes (equal in length in H. algeriensis), the flagellum of A2 eight-articulate (nine-articulate in H. algeriensis), the third article of the mandibular palp with a comb of 17 small setae (14 in H. algeriensis), the merus posterior margin of P7 not spinose (three spines in H. algeriensis), and the peduncle of U1 with two clusters of four spines on the ventral margin (a row of spines in H. algeriensis).

Comments
There are two groups of described Haustorius: the American and the European groups. The American has three species H. canadensis, H. jayneae and H. mexicanus. They have in common a strong character concerning the merus of pereiopod 7 with the proximal margin sharply set off from posterior margin (Figure 6: 3, 4, 5). Foster and Lecroy (1991) report also a great number of undescribed haustoriid species as pointed out by Bousfield (1970), Fox and Bynum (1975) and Thomas (1976).
The three European species are close with a merus of the pereiopod 7 with proximal margin rounded, continuous with posterior margin (Figure 6: 1, 2, 6).
On the ecology of these species little is known for H. algeriensis and H. orientalis. The two species live in sandy beaches as other Haustorius, at the upper infralittoral level, between 0 and 25 m for H. algeriensis (Bakalem and Dauvin 1995) and with another peracarid species, a Mysidea, probably Gastrosaccus for H. orientalis (P. Chevaldonné, personal communication). For H. arenarius interesting data are believed by different authors. Vader (1965), on the Elbe estuary populations, considers that this species is euryhaline, it lives on exposed shores at the intermediate zone and shows a preference for coarse sand with 50% or less of sediment finer than 210 mm. For Moore (1984), in the Clyde sea area, it ''is confined to upper half of intertidal area and prefers rather loose sand' '. Dennell (1933) considers this species to be a burrowing and filter feeder. Cherkaoui et al. (2003) give more complete information on the population of the Bou Regreg estuary (Morocco). H. arenarius was sampled in stations between 0.5 and 6 m; with fine sand with 0.2-10.2% of silt ,63 mm and 2.58-2.68% of organic matter, the salinity is normal at 34.7 PSU. The H. arenarius community is composed of two assemblages dominated, respectively, by Gastrosaccus spinifer and Solen marginatus.