Amphiglena gravinae, Giangrande & Putignano & Licciano & Gambi, 2021

Giangrande, Adriana, Putignano, Matteo, Licciano, Margherita & Gambi, Maria Cristina, 2021, The Pandora’s box: Morphological diversity within the genus Amphiglena Claparède, 1864 (Sabellidae, Annelida) in the Mediterranean Sea, with description of nine new species, Zootaxa 4949 (2), pp. 201-239 : 219-222

Amphiglena gravinae sp. nov.

( Figs 14 , 15 )

Material examined. Holotype: ( MNCN 16.01 /18909): Italy: Adriatic Sea , Brindisi, 40°38’53.39”N 18° 0’42.01”E, in 1985, 5 m depth, on corallinae algae.

Paratypes: MNCN 16.01 /18910: 5 specimens from the same locality and date as the holotype ; 296 specimens, all collected in the same locality and date as the holotype. PCZL S.A. 7.1. Material fixed in formalin 4% and preserved in ethanol 70 %.

Description. Holotype complete with 8 thoracic and 22 abdominal chaetigers. Total body length 4 mm, crown 0.6 mm; maximum body width 0.3 mm ( Fig. 14A ). Crown holding five pairs of radioles with 11 pairs of short pinnules arranged in two alternating rows of similar length (between 1/5 and 1/4 of the total radiolar length. The gap between pairs remains quite constant along the radiole. First basal pair and last distal pair with pinnules shorter than that in the medial radioles. Elongated radiolar tip, reaching more than 1/3 of the total radiolar length and of uniform width, and with a blunt tip ( Fig. 14C ). Radiolar skeleton with two rows of cells. Dorsal lips with long and pointed dorsal radiolar appendages (1/3 of crown length). Anterior peristomial ring with similar height all around, visible also on ventral side. Posterior peristomial ring elongate and connected to high ventral basal flanges, which extends as prominent ridge from base of ventralmost radioles ( Fig. 15D, E ). Peristomial eyes not visible, pygidial eyes present, as very small spots on lateral margins of pygidium. Thorax longer than wide. The first thoracic chaetiger bearing only 3 chaetae similar in shape to the thoracic superior chaetae. From the second to the eighth thoracic chaetiger, 6 uncini on each torus with well-developed breast, and approximately four rows of similar teeth above main fang, large space to main fang, handle elongated, substantially longer than 1/3 of the total uncinus length and considered long handles (0.52) ( Fig. 15A ). Companion chaetae present, with straight shaft and long mucro ( Fig. 15B ). Second to eighth thoracic chaetigers with 4 chaetae, one superior broadly hooded chaeta ( Fig. 15D ), and three inferior paleate chaetae with a short mucro, long slightly less than the hood ( Fig. 15E ). Four abdominal uncini on each torus with similar-sized small teeth above the main fang and medium handle ( Fig. 15C ). Four abdominal broadly hooded neurochaetae, but with a very large hood similar to the thoracic paleate chaetae, even if longer. The shape of the chaetae is similar along the abdominal segments even if in the last segments they become longer and with a more geniculate appearance ( Fig. 15G, F ). Pair of light spermathechae present at the base of dorsal lips.

Staining pattern. In both thorax and abdomen stain only the ventral shields, with a pale colouration, abdomen with a double rectangle in each segment ( Fig. 14B ).

Variation. Individuals always with 8 thoracic chaetigers and up to 30 abdominal chaetigers. Up to 7 thoracic uncini. Mean body length of 2.6 mm and mean crown length of 0.9 mm ( Table 1).

Remarks. This new taxon has a more elongate appearance than other species in the genus, including the peristomial rings, and the base of the crown appearing sometimes bearing a high basal web, and making difficult to see the separation between the peristomial ring and the base of the crown. In this feature it is very similar to A. panareensis sp. nov., which is the other elongate Mediterranean species, described in the present paper. The two species, however show a different development of both first and second peristomial rings. Among the non Mediterranean species, high developed ventral flanges are present also in A. lenae Capa & Rouse, 2007 , but this is a thin and more compact species, with smaller radiolar appendages.

The staining patter is similar to A. messapica sp. nov., even if it appears narrower and more elongated following the elongated shape of the segments. It is distinguished from this species by the shape of the peristomial rings and for the abdominal chaetae, maintaining a paleate appearance long all the abdomen. This feature is present also in A. nisidensis sp. nov., and in A. vulcanoensis sp. nov. where, however, chaetae are less broadly-hooded.

Lastly, A. gravinae has the thoracic uncini with the longest handle compared to all the Mediterranean species here described, although very similar in shape to A. messapica sp. nov.

Etymology. The species is named after the Dr. Maria Flavia Gravina who collected the material, in honor of her valuable contribution to the knowledge of the taxonomy and ecology of polychaetes, as well as for our estimation, long-lasting friendship and collaboration.

Distribution and Ecology. The species was collected in a polluted and stressed area, characterized by the presence of high sedimentation rate, and in the vicinity of a power plant.

Figures

FIGURE 14. Amphiglena gravinae sp. nov. A. entire worm, photo from the holotype; B. staining pattern; C. tip of the radiole; photo from anterior end, ventral view, material coloured with Shirlastain A; E. scheme of the anterior end ventral view.

FIGURE 15. Amphiglena gravinae sp. nov. A. thoracic uncinus; B. companion chaeta; C. abdominal uncinus; D. superior thoracic chaeta; E. inferior thoracic chaeta; F. abdominal chaeta from a middle abdominal segment; G. abdominal chaeta from anterior abdominal segment.