Amphiglena nisidensis, 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 : 212-214

Amphiglena nisidensis sp. nov.

( Figs 8 , 9 )

Material examined. Holotype ( MNCN 16.01 /18903): Italy: Nisida Island (Naples), 40°47’31.52”N 14° 9’47.29”E, 14 November 2011; 2 m depth. Collected on hard bottom with algal cover, mainly Halopteris scoparia .

Paratypes: MNCN 16.01 /18904: 6 specimens from the same locality and date as the holotype; 22 specimens from the same locality and date as the holotype PCZL S.A. 4.1. Most material fixed in formalin 4% (including holotype and paratypes) and preserved in ethanol 70%; some material fixed in ethanol 95 %.

Description. Holotype complete with eight thoracic and 28 abdominal chaetigers. Body length 2.5 mm, with crown 1.8 mm long, and 0.4 mm wide. Body light brown coloured on ventral side and with flattened abdomen ( Fig. 8A ). Crown with five pairs of radioles with 12 pairs of pinnules of medium length each, arranged in two longitudinal rows with a small space gap between the pinnules of the same pair, and with space increasing at the base of the radiole. The pinnules appear longer in median position where they measure 1/4 of the total radiolar length, and becoming considerably shorter towards the end of the radiole. Tip of radiole long, slender and pointed ( Fig. 8C ). Dorsal lips measuring 1/5 of the total radiolar length.Anterior peristomial ring not visible. Posterior peristomial ring higher ventrally with a mid-ventral incision where low ventral basal flanges attach, extending as prominent ridges from base of ventral-most radioles ( Fig. 8D, E ).

Small brown peristomial eyes present. Pygidial eyes present as clusters of red spots on lateral margins of pygidium. Thorax longer than wide. First thoracic chaetiger with only 3 chaetae similar in shape to the superior chaetae of the following chaetigers. From the second to the eighth thoracic chaetiger, 5 uncini on each torus. Thoracic uncini with rounded and flattened breast, with four rows of teeth above main fang, and with handles long approximately 1/3 of the total uncinus length (0.35) so considered between medium and short length ( Fig. 9A ). Companion chaetae present, with straight shaft and long mucro ( Fig. 9B ). Thoracic chaetae from second to eighth chaetigers, number 4, of which one superior broadly-hooded chaeta ( Fig. 9D ) and three paleate chaetae in inferior row with mucro long as the hood ( Fig. 9E ). Abdominal uncini in number of 3, with similar-sized small teeth above the main fang, higher than the thoracic one and with short handle ( Fig. 9C ). Three abdominal neurochaetae thin and broadly hooded, similar to paleate of the thorax but longer in the first abdominal segments ( Fig. 9G ) and becoming longer and more geniculate starting from mid abdomen ( Fig. 9H ). Spermathechae present brown/red coloured.

Staining pattern. In both thorax and abdomen stain only ventral shields. Peristomium, thorax and abdomen showing an intense colouration in the central part, but with a pattern covering most of the segment width ( Fig. 8B ).

Variation. Individuals have eight thoracic chaetigers and up to 31 abdominal chaetigers. Mean body length of 1.65 mm and mean crown length of 1.5 mm. ( Table 1).

Remarks. The material from Nisida is very similar morphologically to A. pithecusensis sp. nov. previously described. The specimens from Nisida, however, appeared highly flattened in the abdomen and with wider bands of stained tissue as wide as the thoracic segment. Moreover, specimens have a larger ratio between body and crown ( Table 1), with a longer and slender tip of radioles and pinnules arranged in pairs, not alternating along the radiolar length. Thoracic uncini are also similar in the length of the handles but with a slender main fang. The main difference is, however in the shape of the ventral margin of the peristomial ring showing an incision without separated margins, and with a lower basal flange. Ventral peristomial ring appears similar to A. bondi Capa & Rouse, 2007 , from which it is distinguished by the short handle of thoracic uncini, and by the number of radioles.

Etymology. Named from type locality, the Island of Nisida, located between the Gulf of Naples and the Gulf of Pozzuoli.

Distribution and Ecology. Distributed on hard bottoms with algal cover. This species belongs to the same group of similar taxa that includes specimens from Ischia vent and non-vent’s areas, except the San Pietro site.

Figures

FIGURE 8. Amphiglena nisidensis sp. nov. A. entire worm, photo from the holotype; B. staining pattern; C. tip of the radiole; D. photo from anterior end, ventral view, material coloured with Shirlastain A; E. scheme of the anterior end ventral view.

FIGURE 9. Amphiglena nisidensis sp. nov. A. thoracic uncinus; B. companion chaeta; C. abdominal uncinus; D. superior thoracic chaeta; E. inferior thoracic chaeta; F. abdominal chaeta from anterior abdominal segment; G. abdominal chaeta from a middle abdominal segment.