Parotoplana crassispina sp. n.
Holotype: one whole mount (SMNH 7568).
Type locality: Castiglione della Pescaia, Capo Capezzolo (Tuscany, Italy) (42°45’55.29”N, long. 10°51’46.11”E); lower intertidal, medium sand, March 2007.
Paratype: one specimen from the type locality sagittally sectioned (SMNH 7569).
Additional material: Tuscany: Castiglione della Pescaia,CapoCapezzolo. Six specimens sagittally sectioned (CZM 121-126) and four karyological slides made permanent with lactophenol (CZM 127-130), March 2007. Punta Ala, Torre Civette (lat. 42°50’41.70”N, long. 10°46’30.34”E), lower intertidal, medium to coarse sand. 14 specimens sagittally sectioned (CZM 131-144) and eight karyological slides made permanent with lactophenol (CZM 145-152), March 2007. Sardinia: Le Bombarde beach, Alghero (lat. 40°35’2.59”N, long. 8°15’37.36”E), in medium to coarse sand, from the lower intertidal to about 2 m deep. One specimen sagittally sectioned (CZM 153) and five karyological slides made permanent with lactophenol (CZM 154-158). Several specimens observed alive, July 2006. Archi Cave, Capo Caccia (lat. 40°34’10.71”N, long. 8°13’43.93”E), medium sand, about 10 m deep. One specimen made as whole mounth (CZM 159), July 2006. Girin beach, Carloforte Is. (lat. 39°6’56.68”N, long. 8°18’33.33”E), about 50 cm deep, medium sand. Three specimens made as whole mount (CZM 160-162), June 2008. France: Canet, city beach (lat. 42°41’41.36”N, long. 3°2’14.98”E), about 2 m deep, medium sand. Five specimens made as whole mounts (CZM 163-167), August 2008.
Etymology: from latin crassus, fat – with reference to the peculiar, broad spines of the new species.
Description: With 14 copulatory spines, arranged as follows:
- Dorsal pairs: D1 : thin, straight, needle-shaped spines, ranging 45-58 μm long in specimens from Tuscany (holotype: 56-58 μm) with maximum width at the basis of about 2.5 μm; and 42-48 μm and 51-53 μm long in specimens from Sardinia (Le Bombarde) and Canet, respectively; D2 : broad, straight spines, ranging 47-64 μm long (holotype: 59 µm) and 6-7 μm broad at their basis (Tuscany); 42-50 μm long, 4.5 μm broad (Sardinia); 53-56 μm long, 6 μm broad (Canet).
- Girdle: G1 : short, straigth spines with slightly falcate, conical apices, provided with very small apophyses, ranging 37-44 μm long, 5-6 μm wide (Tuscany) (Holotype: 41-44 µm; distance between apophysis and tip about 8.5 µm; stem 5.5 µm wide); 37-43 μm long, 4.5 μm wide (Sardinia); 41-46 μm long, 4.5 μm wide (Canet). Sardinian specimens have a comparatively longer (about 1/3 of the whole length of the spine) distal tip; G2 -G4 : three pairs of broad spines, with characteristic flat and broad apophyses, falcate distal tips and blunt apices. Stems become progressively longer from G2 to G4 , and spines gradually assume a more slender shape. Lengths range 32-52 μm long (Holotype: 42-50 µm), stem 3.5-6.5 μm broad, length of apex 11-13 μm (Tuscany); 37-46 μm long, 3.5-5 μm wide, length of apex 9-14.5 μm (Sardinia); 42-47 μm long, 3.5-5 um wide, length of apex 11-12 μm (Canet).
- Ventral spines differ in morphology among populations. In Tuscan specimens, V spines are 47-65 μm long (holotype: 58-59 µm), 7.5 μm broad at their bases, with straight, very long (18-24 μm) distal tips, and long (11-20 μm) and flat apophyses. Sardinian and French specimens have more recurved and comparatively shorter distal tips, and shorter, ovoid apophyses. Ranges are 47-55 μm long, 7 μm broad, distal tip 11-19 μm long, apophysis 9-12 μm long (Sardinia) and 51-53 μm long, 5-6 μm broad, distal tip 12-17 μm long; apophysis 6-8 μm long (Canet).
With numerous bursal spines, arranged in girdles. Each girdle consists of up to 30 broadly triangular spines, with acute tips, increasing in length from proximal (about 1 μm) to distal (about 5 μm) girdles (Fig. 5A). The arrangement of spines is somewhat variable. In a few specimens they are arranged into a single structure, consisting of about six girdles of spines. In other specimens girdles are less regular, while in others two distinct series of girdles are apparent. However, the level of the variability (either individual or interpopulational) has yet to be ascertained.
Karyotype. Chromosome number: n = 6; FN = 10. The first three pairs of chromosomes are distinctly larger than the three remaining pairs. Karyometrical data were obtained from two populations. Castiglione della Pescaia (Tuscany): Chrom. I = r.l.: 25.46 ± 2.86 ; c.i.: 35.4 ± 1.79 (sm); Chrom. II = r.l.: 24.03 ± 0.84; c.i.: 41.52 ± 3.28 (m); Chrom. III = r.l.: 23.35 ± 0.61; c.i.: 32.39 ± 2.53 (m); Chrom. IV = r.l.: 9.85 ± 1.13; c.i.: 36.95 ± 4.59 (sm); Chrom. V = r.l.: 8.72 ± 0.26; c.i.: 15.93 ± 4.39 (st); Chrom. VI = r.l.: 8.61 ± 1.57; c.i.: 10.12 ± 1.43 (t); haploid genome length: 9.6 ± 0.8 µm (based on measurements of four plates). Le Bombarde (Sardinia): Chrom. I = r.l.: 25.47 ± 2.43 ; c.i.: 44.08 ± 2.09 (m); Chrom. II = r.l.: 25.32 ± 2.63; c.i.: 40.06 ± 0.84 (m); Chrom. III = r.l.: 24.67 ± 0.36; c.i.: 33.15 ± 2.57 (m); Chrom. IV = r.l.: 8.66 ± 0.97; c.i.: 20.8 ± 4.08 (st); Chrom. V = r.l.: 8.43 ± 1.41; c.i.: 39.15 ± 2.73 (m); Chrom. VI = r.l.: 7.45 ± 0.55; c.i.: 8.97 ± 0.95 (t); haploid genome length: 10.1 ± 0.9 µm (based on measurements of five plates).
Remarks.A shallow water species, often common in medium-grained sediments up to the low water mark. In this habitat, it may be the numerically dominating proseriate, as in the Tuscan sites.
P. crassispina is the only species of the group known for a comparatively broad range, extending across the north-western Mediterranean region. Populations in this range appear to differ noticeably, particularly in the morphology of V and G1 spines. The suspicion that different species have been lumped into a single taxon, may thus arise. However, the range of variation of the spines, and thus the reliability as diagnostic markers of the differences observed, should be assessed on more adequate geographical sampling than that presently available. At the moment, given the overall similarity of most spine pairs across the range, and the overlap in measures among populations, differences in morphology are assumed to reflect a degree of interpopulational (clinal?) divergence.