Schizomavella halimedae ( Gautier, 1955 ) López De La Cuadra Car Los G Ar Cía Góm Ez, Los M., 2001

López De La Cuadra Car Los G Ar Cía Góm Ez, Los M., 2001, Mediterranean, collected by`Fauna IbeÂrica’ expeditions, Journal of Natural History 35 (11), pp. 1717-1732 : 1720-1724

Schizomavella halimedae ( Gautier, 1955) n. comb.

(gure 2A, B, table 2)

Smittina halimedae G autier, 1955: 252, pl. 3, gure 18, 19.

Schizomavella discoidea : G autier, 1962: 138 (part), gure 13; H ayward and R yland, 1979 (part): 182, gure 75D; H ayward and R yland, 1999 (part): 280, gure 126D; Zabala, 1986: 470, text- gure 159, pl. 12, gure E, F; Zabala and Maluquer, 1988: 130,

text- gure 296, pl. 16, gure F.

Material

Schizomavella halimedae . Numerous colonies from Balearic and Columbretes Islands , on algae at less than 40 m depth . Fauna III and Fauna IV expeditions. F igured and measured for this work: MNCN 25.03 /1248. Three well-developed colonies on algae. Fauna III sta. 259 B, 38ss58.68¾N, 1ss13.20¾ E. Western coast of Ibiza Island (Baleares), 35 m, 9 July 1994 .

Schizomavella discoidea . MNCN 25.03 /1214: One colony on stone. Fauna III sta. 213 A. Trawling from 40ss4.23¾N, 4ss11.38¾E to 40ss5.20¾N, 4ss8¾E. ‘P unta de’s Murté’ , northern coast of Menorca (Balearic Islands), 55–60 m, 29 June 1994 . MNCN 25.03 /1215: One colony with ovicells on a piece of a broken Pinna shell. F auna III sta. 200 A. Trawling from 39ss52.30¾N, 3ss36.65¾E to 39ss55.24¾N, 3ss37.02¾E. Menorca Channel (Baleares), 85–92 m depth, 28 June 1994 (gure 2C, D, table 2) . M N CN 25.03 /2731: On stone. F auna IV sta. 295 B. 39ss54.02¾N, 0ss41.08¾E, Columbrete Grande Island, Columbretes , 40 m depth . Collection of the authors, LBM.BRI-1984-131: One colony with ovicells on stone. Tarifa Island , 25 m , D ecember 1984.

Description

Colony discoid, mostly unilaminar, although frontal budding may be observed in the centre of well-developed colonies, where the ancestrula is usually overgrown. Autozooids hexagonal or rectangular, radially arranged. F rontal wall rugose, evenly perforated by pseudopores, with marginal areolae. Ori ce D -shaped, parallel-sided, with straight poster and a small drop-shaped sinus. F ive oral spines. The spines of the ovicellate zooids are not visible because they are overgrown by the ovicell. Peristome present only in ovicellate zooids, well developed at both sides of the ori ce, but not proximally. Two types of avicularia are present, both situated close to the ori ce, centrally placed and proximally directed. The most common type is small, shorter than the ori ce, elliptical, with crossbar, small columella, narrow palate and wide semi-elliptic palatal foramen; the gigantic type is less common but frequent, and occupies the central part of the frontal wall up to the proximal end. These gigantic avicularia are spatulate and have a well-developed palate covering most of the surface under the mandible, leaving a comparatively small, transversely elongate palatal foramen. As in the small type, the gigantic avicularia have a crossbar and a small columella. Ovicell prominent, recumbent on the frontal wall of the succeeding zooid, but not immersed, with a semilunar perforated proximal area. Interzooidal communication by numerous small basal pore chambers.

Discussion

Schizomavella halimedae is a common species which has been frequently found but reported as Schizomavella discoidea ( Busk, 1859) . Gautier (1955) described it as Smittina halimedae n. sp. from Algerian material. Later, the same author (G autier, 1962) correctly transferred it to Schizomavella but considered that it was conspeci c with S. discoidea ( Busk, 1859) . Subsequent authors followed this opinion (H ayward and Ryland, 1979, 1999; Zabala, 1986; Zabala and Maluquer, 1988). The general shape of the colony and of the ovicellate zooids (particularly their peristome) are similar in the two species (gure 2A, C), and the clear diOEerences in the avicularia have been considered intraspeci c variation. Observation by SEM reveals the diOEerences in the ori ce and avicularia between the two species. Both species share a straight poster and a small sinus, and the diOEerences are little apparent with optical microscopy. The ori ce of S. discoidea is horseshoe-shaped with a deep, U-shaped, parallel-sided sinus (gure 2D). In contrast, S. halimedae has a D-shaped parallelsided ori ce and a drop-shaped sinus (gure 2 B). S. halimedae has usually ve spines while S. discoidea commonly has six. Other diOEerences occur in the frontal wall, the ovicell, the avicularia and in substratum preference. The frontal pseudopo res are fewer and smaller in S. discoidea than in S. halimedae (gure 2A, C). As in most species of Schizomavella , the ovicell of S. halimedae has a proximal crescentic porous area and the surface outside of this area is very rugose. In contrast, the porous area of the ovicell of S. discoidea occupies most of its surface, leaving only a narrow marginal imperforate rim. The avicularia of S. halimedae are usually centrally situated, only occasionally slightly oblique, and the palate of the gigantic avicularium is a well-developed continuous sheet which occupies most of the surface below the mandible. The palate of the small avicularium is little developed, and its palatal foramen is wide and semi-elliptic (gure 2B). In contrast, the avicularia of S. discoidea are often more or less proximolaterally directed, even the small ones. The small avicularia have a laterally developed palate, which leaves a Y-shaped palatal foramen (gure 2D). The large avicularia, often paired, are elongate, narrow and parallel-sided. They are placed near and parallel to one or both distolateral zooidal margins. The palate is continuous at the distal half of its length, but at the proximal half it grows from the sides to contact at the midline, producing a longitudinal suture and a drop-shaped central foramen. Habitat preference also diOEers between the two species. Schizomavella halimedae , as stated in previous reports ( Gautier, 1955, 1962; Zabala, 1986; Zabala and Maluquer, 1988) and observed in material from the Fauna cruises, is usually an epiphytic species, commonly found on algae between 20 and 80 m depth. Less frequently (only one of many Fauna colonies), it may grow on biogenic concretions. M ost samples found in F auna cruises were collected by diving in less than 40 m depth. In contrast, S. discoidea occurs oOEshore on shell, stone and concretions ( Hayward and Ryland, 1979) but not commonly on algae. In accordance with this, the three colonies found by Fauna III and Fauna IV expeditions, near Menorca (Fauna III) and Columbretes (Fauna IV), were collected on shells and biogenic concretions. Some colonies were found by the authors at the Straits of Gibraltar between 25 and 50 m on shells and concretions, and were cited without description in a previous work (López de la Cuadra and G arcóa-G ómez, 1994).

Schizomavella halimedae ts the characters of the ‘G roup I’ of Schizomavella , as described by R everter-Gil and Fernández Pulpeiro (1995), especially in the features of the ovicell, frontal wall and avicularia, although a well-developed peristome and a horseshoe-shaped sinus are not usual characteristics of the genus. Schizomavella discoidea shows a number of peculiarities which make this species a very distinctive representative of Schizomavella . These unusual features may be summarized as: the very large porous area of the ovicell, the comparatively numerous oral spines, the lateral avicularia parallel to the proximolateral walls and the few frontal pseudopo res (gure 2C, D). These general features are shared by the deep-water species Schizomavella neptuni ( Jullien, 1882) (see Zabala et al., 1993 for an updated description and SEM pictures), which has a very similar ori ce and ovicell, eight oral spines, very few frontal pseudopores (even less than S. discoidea ) and, very remarkably, the same pattern of location of avicularia, which may be either a suboral one, proximally directed, or one or two in lateral position, parallel to the distolateral margins. In contrast, S. neptuni lacks a peristome and the avicularia are never elongate, but the similarities suggest a close relationship between both species, which could constitute a clade within Schizomavella .

Due to the peculiarity of S. discoidea, Reverter-Gil and Fernández Pulpeiro (1995) preferred not to include this species in any of the two groups which they distinguished within Schizomavella , and even expressed some doubt about the correct assignation of S. discoidea to this genus. This doubt can be extended to S. neptuni , although both species show a reasonable coincidence with the current diagnosis of the genus, updated by Hayward and Thorpe (1995).

Schizomavella W scheri ( Jullien, 1882) and S. linearis profunda Harmelin and d’Hondt, 1992 are also present in deep water of the Atlanto-mediterranean region (Harmelin and d’Hondt, 1992). Both species share with S. discoidea and S. neptuni a quite high number of spines (up to seven), but they are otherwise unambiguous members of the ‘G roup I’. Schizomavella W scheri has a single medial and pointed suboral avicularium (see Harmelin and d’Hondt, 1992, for an updated description and gures) and S. linearis profunda is a subspecies of S. linearis , an unequivocal representative of the ‘G roup I’.

Many previous records of S. discoidea in the Mediterranean are probably referable to S. halimedae , as is evident from their descriptions and gures (G autier, 1955, 1962; Zabala, 1986; Zabala and Maluquer, 1988). Two previous citations without description are likely to correspond, at least in part, to S. discoidea: Saguar and Boronat (1987) report this species from biodetritic habitats in the Columbretes Islands at 80–95 m depth, a typical habitat for S. discoidea but unlikely for S. halimedae . Harmelin et al. (1989) found S. discoidea in the Gulf of Tripolitania (Lybian coast) from the shallow sublittoral to the limits of the shelf. At least the deepest examples found are probably of S. discoidea . Some photographs sent to the authors by D r J.-G. H armelin clearly represent S. discoidea , collected in a cave 13 m deep at Trémies (French coast). The usually supposed geographical range of S. discoidea , as has been given, for instance, by Hayward and Ryland (1979, 1999), and which includes the western Mediterranean, is still valid, despite the distinction between S. discoidea and S. halimedae . Schizomavella halimedae has not been found in the Alborán Sea or the Straits of Gibraltar and it seems to be restricted to the inner Mediterranean.