Pisione remota Southern 1914

Pisione remota (Southern, 1914)

Material examined. MB29-000245, 1 specimen, site R70; MB29-000246, 1 specimen, site PC91 (Table 1). Additional material: 2 specimens, site R17; 14 specimens, site R28; 2 specimens, site R39; 13 specimens, site R40; 1 specimen, site R46; 4 specimens, site R48; 25 specimens, R51; 2 specimens, site R52; 15 specimens, site R59; 6 specimens, site R68; 13 specimens, site R70; 4 specimens, site PC77; 55 specimens, site PC85; 12 specimens, site PC87; 7 specimens, site PC90; 30 specimens, site PC91; 21 specimens, site PC92; 42 specimens, site PC132; 7 specimens, site PC133; 23 specimens, site PC137; 5 specimens, site PC138; 2 specimens, site PC210; 2 specimens, site PC222; 55 specimens, site G21(1); 2 specimens, site ALG9; 1 specimen, site ALG39; 1 specimen, site ALG48; 1 specimen, site ALG49; 1 specimen, site ALG59; 1 specimen, site ALG60; 3 specimens, site ALG62; 1 specimen, site ALG63; 4 specimens, site ALG68 (Table 1).

Brief description. Width of 10th chaetiger ranged between 0.19 and 0.46 mm, total length up to 25.5 mm and maximum of 97 chaetigers. Buccal aciculae well developed and protruding, with slightly constricted distal ends subdistally and subrounded distal margin. Prechaetal lobe bilobed in anterior parapodia and entire in posterior ones. Dorsal cirri of chaetiger 2 similar to others in size and shape, bulbous with terminal papillae, ranging from 0.022 to 0.060 mm (cf. Table 2). Three types of chaetae: three short-bladed compound chaetae (longest blade up to 21 µm; cf. Table 2), one supra-acicular simple chaeta distally unidentate and one infra-acicular simple chaeta. One stout notoaciculum embedded in all parapodia. Male genitalia with 2 to 8 pairs of consecutive copulatory organs appear between chaetigers 29 and 32 (MB29-000246) or earlier in smaller specimens (16–17; cf. Table 2). Female genital chaetigers with a simple cirriform process developed ventrally at base of parapodium. Female gametes globular, with diameter ranging from 38 µm to 86 µm, 58 µm in average, located in chaetigers 29–74 (MB29- 000245), earlier in smaller specimens (16–36). Pygidium with two long anal cirri.

Distribution and habitat. This species occurred mainly in coarse (42%) and very coarse (36%) sand and fine gravel (18%), with low total organic matter content, usually below 1% of total sediment dry weight and high biogenic content (6.6% in average; cf. Table 3). The species was recorded between 3 and 80 m depth, along the western and southern Portuguese coast (Fig. 1). It is widely distributed along the North Atlantic, Mediterranean and Caribbean, at shelf depths (e.g. Dauvin et al. 2003; Lourido et al. 2010). A detailed revision of specimens from these other areas should be undertaken to confirm its cosmopolitan status (San Martín, 2004).

Remarks. In males, the number of pairs of successive copulatory organs varied between 2 and 8 which differed from the literature (4–18; San Martín, 2004). The distribution of female gametes was clearly related to body size, in agreement with Alikunhi (1951).

The classification and ordination analysis based on selected morphological descriptors of Pisione species showed a clear separation of the four species (Fig. 2). Axis 1 accounted for 46.6% of the total variation. On the positive pole, this axis separated the species with a proportionally longer dorsal cirri of chaetiger 2 and bidentate supra-acicular chaetae. On the negative pole, axis 1 separated the species with single unidentate supra-acicular chaeta, dorsal cirri of proportional similar length and an infra-acicular simple chaeta. This axis separated P. guanche and P. parapari on the positive pole, from P. inkoi and especially P. re m o t a on the negative pole, this latter species being the single one with an infra-acicular simple chaeta. Axis 2 accounted for 31.5% of the total variation and showed the separation of species with higher width of the 10th chaetiger (W10) and with the highest ratio of the protruding length of the notoacicula and W10 on the positive pole (P. in k oi), from species with a lower W10 and aciculae embedded throughout the body (P. parapari and P. re m o ta).

The null hypothesis of no significant differences between the four species, on the basis of the selected morphological descriptors, was rejected with a very large value of the pseudo-F statistic (p <0.0001), shown in Table 4. Such strong rejection of the null hypothesis was due to a much larger sum of squares due to the species than the residual sum of squares, indicating that the intraspecific variability was much lower than the interspecific variability. A similar conclusion can be drawn from the inspection of the mean Euclidean distance within species and between species (cf. Table 4). The highest mean Euclidean distance within species was obtained with P. guanche due to the high variability of the W10 values among the specimens of this species. Pisione parapari presented the lowest mean Euclidean distance within species denoting a reduced intra species variability regarding the analyzed morphological descriptors. All pairwise comparisons between individual species also rejected the null hypothesis at p <0.0001. Overall, the results showed that the interspecific variability was much higher than the intraspecific variability, supporting the validity of the four Iberian species of Pisione. The following key to the Pisione species of European waters is based on the understanding gained from the multivariate analysis: Total 74 370