Sphaerodoridium claparedii (Greeff, 1866)

Capa, Maria, Nygren, Arne, Parapar, Julio, Bakken, Torkild, Meissner, Karin & Moreira, Juan, 2019, Systematic re-structure and new species of Sphaerodoridae (Annelida) after morphological revision and molecular phylogenetic analyses of the North East Atlantic fauna, ZooKeys 845, pp. 1-97 : 71-73

Sphaerodoridium claparedii (Greeff, 1866) Fig. 5V, 23G, H, 28

Sphaerodorum claparedii Greeff, 1866: 338-350, Taf 6. figs 1-14. Southern 1914: 89-90; Fauvel 1923: 379-380; Amoureux et al. 1978: 88.

Sphaerodoridium claparedii Lützen, 1961: 415; Fauchald 1974: 270.? Campoy 1982: 464-465;? Moreira 2012: 26-28, Fig. 5;? Wehe and Fiege 2002: 138.

Type locality.

Dieppe, France, English Channel.

Material examined.

(3 specs). Ireland: NMINH: 1908.77 (1 spec.), St. Ballynakill xxviii, 0.2 m, 10 Apr 1899; NMINH:1914.313 (1 spec.), St. W236, Blacksod Bay, Co. Mayo, 1.8 m, on 25 Sept 1911; NMINH:1914.313, (1 spec.) Station W181, Blacksod Bay, Co. Mayo, 5.5 m, on 15 Mar 1911.

Diagnosis.

Body ellipsoid. Prostomial appendages digitiform, elongated. Median antenna smooth, shorter than lateral antennae. Lateral antennae similar in length to palps, with 3-4 basal papillae (spurs). Tentacular cirri digitiform, smooth, slightly shorter than lateral appendages. Dorsal macrotubercles stalked, smooth, arranged in eight longitudinal rows in mid-body chaetigers; stalk as long as or shorter than tuber cle. Dorsum with additional 10-12 rounded papillae between transverse rows of macrotubercles somewhat arranged in a zig-zag pattern. Ventrum with 3-4 transverse rows of papillae per segment. Parapodia with digitiform, large ventral cirri, and acicular lobe; parapodia without papillae, or with a spherical papilla in anterior surface. Approximately six chaetae per parapodium, with short blades (ca. four times as long as wide).

Description of Irish material.

Measurements and general morphology. Body ellipsoid, with rounded anterior and posterior ends, with convex dorsal surface and flat ventrum. Segmentation inconspicuous and pigmentation absent (Fig. 28A, B).

Head. Prostomium fused to first segment (Fig. 28A, B). Prostomial appendages including palps and lateral antennae similar in shape and size, digitiform and longer than wide, except for median antenna that is shorter and similar to other rounded prostomial papillae. Lateral antennae with 3-4 basal papillae or spurs (Fig. 28C). Tentacular cirri, similar in size and shape to prostomial appendages (Fig. 28B).

Tubercles. Dorsal macrotubercles, spherical, smooth, and with a short stalk, arranged in eight longitudinal rows from second chaetiger (six in first chaetiger), and one transverse dorsal row per chaetiger (Figs 23H, 28A, C, D). All macrotubercles similar in size. Approximately 10-12 spherical papillae per segment over dorsum (less in anterior and posterior segments), arranged in three irregular transverse rows (Fig. 28A, D). Ventral papillae hemispherical, arranged in four longitudinal rows (Fig. 28B).

Parapodia. Parapodia conical, slightly longer than wide (Fig. 28 G–J). Ventral cirri digitiform, similar on shape and size to the acicular lobe (Fig. 28 G–J). Parapodial papillae absent or in some parapodia, one spherical papilla in anterior surface, close to the base of parapodium (Figs 5V, 28 G–J).

Chaetae. Four to six compound chaetae on each parapodium, with short and wide blades (ca. four times as long as wide), unidentate, finely serrated; all similar in size and shape. A single straight acicula per parapodium.

Pygidium. Pygidium with paired anal cirri resembling macrotubercles and medio-ventral digitiform anal papilla.

Internal features. Two dark eyes visible dorsally inside the head of holotype. Pharynx extending over two chaetigers.

Reproductive features. Not described. Sexual structures not observed in Irish material.

Variation.

The species was described as bearing six rows of longitudinal and stalked macrotubercles (Fig. 23G). The number of longitudinal rows of macrotubercles counted in the Irish material is eight (Fig. 23H), but two of the lateralmost rows were difficult to assess given the strongly convex dorsum of specimens, that hide them below the animal, in specimens flattened by the microscopy slides (Fig. 28A, C). This could also be the case in the holotype. Some features were not addressed in the original description but found in the Irish specimens ( Southern 1914). These are the presence of a short median antenna, and a pygidial median papilla. These attributes seem to be the norm in other sphaerodorids and therefore considered as present in S. claparedii comb. n. Irish specimens were smaller than the holotype, all (including mature adults) with less than 18 chaetigers and measuring up to 1.8 mm long. An important note on the variation observed among the studies reported in the literature concerns the number of ventral papillae. While the species was described with four transverse rows of papillae in the ventrum ( Greeff 1866), the material collected in Claire Island has small papillae scattered in the ventrum, resembling the dorsal papillae ( Southern 1914). Parapodia were described without papillae but in the Irish specimens, a spherical papilla is present in the anterior side of some parapodia.

Remarks.

This species has only been reported twice, from Dieppe, France ( Greeff 1866, original description), and Claire Island, Ireland ( Southern 1914, complementary morphological features). There are reports of this species across European coasts (Atlantic and Mediterranean) and the Red Sea but no description was provided (e.g., Saldanha 1974, Amoureux et al. 1978, Méndez and Cardell 1996). For instance, Mòllica (1995) considers the presence of this species in Italy as doubtful.

Sphaerodoridium claparedii is distinguished from other congeners by the presence of only eight rows of stalked macrotubercles, a feature that is shared by S. amoureuxi comb. n. (if macrotubercles are considered with a short stalk), S. campanulata comb. n. and S. guerritai . Sphaerodoridium guerritai is clearly distinguished from S. claparedii in the presence of stalked macrotubercles with papillae prostomial appendages also with spurs, and 5-6 parapodial papillae. Sphaerodoridium campanulata comb. n. was described as bearing different sized bell-shaped macrotubercles, not arranged in clear longitudinal or transverse rows ( Borowski 1994), unlike the turgid and in line dorsal tubercles of S. claparedii .

Distribution.

English Channel and western coast UK.? Atlantic coast of Iberian Peninsula,? Mediterranean,? Red Sea ( Campoy 1982, Wehe and Fiege 2002).

Habitat.

Among algae and shallow sediments (1-5 m). Also collected in planktonic samples (Southern, 1914).