Amphiglena phlegreensis, 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 : 214-217

Amphiglena phlegreensis sp. nov.

( Figs 10 , 11 )

Material examined. Holotype ( MNCN 16.01 /18905): Italy 30 November 2015, 14 m depth, Secca delle Fumose (Gulf of Pozzuoli), 40◦ 490 23 00 N 14◦ 050 500 E, among algae, mainly Dictyota sp.

Paratypes: MNCN 16.01 /18906: 8 specimens from the same locality and date as the holotype; 21 specimens collected in the same locality and date as the holotype. PCZL S.A. 5.1. Most material fixed in ethanol 70%; some specimens in ethanol 95 %.

Description. Holotype complete, with eight thoracic and about 32 abdominal chaetigers. Body length 3 mm, branchial crown 2 mm; maximum body width 0.4 mm ( Fig. 10A ). Brown colouration present especially in the thorax. Crown with five pairs of radioles each with 17 pairs of long pinnules arranged in two alternating rows along the radiole, especially in the distal half of radiole. Pinnule show a similar length (around 1/6 of the total radiolar length) and are slightly shorter in the last two distal pairs and in the first two basal pairs which appear more separated from the other pairs. Tip of radioles extremely elongated reaching 1/3 of the total radiolar length, slender but with a blunt end ( Fig. 10C ). Radiolar skeleton with two rows of cells. Anterior peristomial ring not visible. Posterior peristomial ring low and higher ventrally with a well separated ventral incision connected to well-developed ventral basal flanges, extending as a prominent ridge from the base of ventral-most radioles ( Fig. 10D, E ). Peristomial eyes brown red. Dorsal lips with a rounded dorsal radiolar appendages measuring 1/4 of radiolar length. Pygidial eyes as brown clusters on lateral margins of pygidium. Thorax longer than wide. The first thoracic chaetiger bearing only two chaetae similar to the superior chaetae of the following chaetigers. From the second to the eighth thoracic chaetiger, 5 uncini in each torus. Thoracic uncini with well-developed breast, large as the distance to main fang, with approximately four rows of similar teeth above main fang, and a handle measuring approximately 1/3 of the total uncinus length, and considered as medium-short handle (0.35) ( Fig. 11A ). Companion chaetae present, with straight shaft and long mucro ( Fig. 11B ). Second to eighth thoracic chaetigers with 5 thoracic chaetae of which two superior broadly hooded chaetae ( Fig. 10D ) and three inferior paleate chaetae with a mucro as long as the hood ( Fig. 10E ). Abdominal uncini, in number of 4 on each torus, with 3-4 similar-sized small teeth above main fang and short handle, appearing higher than longer ( Fig. 11C ). Three broadly-hooded abdominal neurochaetae, very similar to the thoracic paleate chaetae in the first abdominal segments ( Fig. 11G ) and becoming narrower and more geniculate in the median abdominal segments ( Fig. 11F ). Spermathechae whitish.

Staining pattern. In both thorax and abdomen stain only ventral shields. Peristomium, thorax and abdomen intensely coloured, with larger rectangular pattern in the abdominal segments ( Fig. 10B ).

Variation. Individuals with 8 thoracic chaetigers and up to 32 abdominal chaetigers. Mean body length of 2.2 mm and mean crown length of 1.4 mm ( Table 1).

Remarks. Excluding A. cf. mediterranea , this taxon is very similar to the group of species here described from the Gulf of Naples, however it has a greater number of pinnules on the radioles. The peristomial ring is more similar to A. pithecusensis sp. nov., but thoracic uncini are more similar to A. nisidensis sp. nov., from which it differs in having longer handles. Additionally, it has very long abdominal chaetae, similarly to A. aenariensis sp. nov.

Etymology. Named from type locality, since the Secca delle Fumose is within the Gulf of Pozzuoli, part of the Phlegrean Fields, a large and still active volcanic area in the Gulf of Pozzuoli (Naples). The name derives from the ancient Greek word phlego =to burn.

Distribution and Ecology. The species is known only from this location (Secca delle Fumose). This site is a rocky area which is formed by rocky columnar structures (named pilae) representing the columns of the ancient Roma harbour of Baia, submerged due to the tectonic subsidence of the area (bradeysism). This site is a hydrothermal vent system, where CO 2,sulphur (H 2 S) emissions, and also hot water fluids, emerge from the bottom.A description of the area and its benthic community was provided by Donnarumma et al. (2019).

Figures

FIGURE 10. Amphiglena phlegreensis 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 11. Amphiglena phlegreensis 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 anterior abdominal segment.