Amphiglena messapica, 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 : 217-218

Amphiglena messapica sp. nov.

( Figs 12 , 13 )

Material examined. Holotype ( MNCN 16.01/18907): Italy: Santa Caterina-Torre Inserraglio (Apulian Coast, Ionian Sea), 40° 8’22.13”N 17°58’47.31”E, collected in 2002 from hard bottom at 1 m depth, covered by Halopteris sp. and Dictyota sp.

Paratypes: MNCN 16.01 /18908: 7 specimens from the same locality and date as the holotype; 118 specimens all collected in the same locality and date as the holotype PCZL S.A. 6.1. 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 3 mm, branchial crown 1 mm; maximum body width 0.35 mm ( Fig. 12A ). Crown with five pairs of radioles with 11 pairs of pinnules arranged in two longitudinal rows not alternating along the radiolar length. Gap between pinnule pairs constant along the radiole. Pinnules quite short and with a similar length (1/4 of the total radiolar length), being shorter only in the first two basal pairs and in the last two distal pairs. Radiolar tip reaching between 1/3 and 1/4 of the total radiolar length and with a blunt tip ( Fig. 12C ). Radiolar skeleton with two rows of cells. Dorsal radiolar appendages long 1/3 of total radiolar length. Anterior peristomial ring not visible. Posterior peristomial ring short but oblique, appearing as having pointed margin ( Fig. 12D, E ). Ventral basal flanges high extending as prominent ridge from base of the ventralmost radioles across the anterior peristomial ring and highly connected with the peristomial ring ( Fig. 12D, E ). Peristomial eyes not visible. Pygidial eyes brown spots on lateral margins of pygidium. Thorax longer than wide. The first thoracic chaetiger bearing only 3 chaetae similar in shape to the superior thoracic chaetae. From the second to the eighth thoracic chaetiger, 6 uncini on each torus, with well-developed breast, large distance to main fang, and approximately four rows of long teeth above main fang, and medium handles, measuring more than 1/3 of the total uncinus length (0.43) so that the uncinus appears longer than higher ( Fig. 13A ). Companion chaetae present, with straight shaft and long mucro ( Fig. 13B ). From the second to the eighth thoracic chaetiger, 2 superior broadly hooded chaetae ( Fig. 13D ) and 4 paleate chaetae in inferior group with mucro long as the hood ( Fig. 13E ). Four abdominal uncini with similar-sized small teeth above main fang, longer than thoracic ones and with short handle ( Fig. 13C ). Spermathechae not visible. Up to 3 abdominal hooded neurochaetae with hood similar to the inferior chaetae in the first abdominal segments ( Fig. 13F ) becoming longer and more geniculate in the median abdominal segments ( Fig. 13G ).

Staining pattern. In both thorax and abdomen stain only ventral shields with a large rectangular pattern in the thorax, and a double clear squared pattern on each abdominal segment ( Fig. 12B ).

Variation. Individuals always with eight thoracic chaetigers and up to 28 abdominal chaetigers. Mean body length of 2.3 mm and mean crown length of 0.9 mm ( Table 1).

Remarks. Although being a compact form like the previous described species, this taxon is larger and with a longer appearance, especially in the abdominal chaetigers. The handles of the thoracic uncini, although having a similar length as A. cf. mediterranea , appear more pointed. Amphiglena messapica sp. nov. differs from this taxon especially in the shape of the peristomial ring which is ventrally higher and with more developed basal flanges, connected to the peristomial ring, so that it appears as pointed. The staining pattern is similar to A. aenariensis sp. nov., and to all the related taxa of the group from the Gulf of Naples. This species is distinguished from this group of taxa for the length of the handles of the thoracic uncini, and for the body/crown ratio, this last feature being similar to A. cf. mediterranea ( Table 1). Among the non Mediterranean taxa, A. gracilis Capa & Rouse (2007) has the most similar ventral peristomial appearance, however, this species does not have the peristomial edge so connected to the ventral basal flanges, moreover, A. gracilis is a very thin species with only four pair of radioles, has a shorter handle of thoracic uncini, and a longer dorsal radiolar appendages. Lastly A. messapica sp. nov. is among the few Mediterranean species not showing an alternate arrangement of the pinnnule rows along the radiole.

Etymology. The species was named from the “Messapi”, an ancient tribe inhabiting in pre-Roman time the Southern Apulia (Salento), where the species was collected.

Distribution and ecology. The species is distributed on shallow and sheltered hard shallow substrates.

Figures

FIGURE 12. Amphiglena messapica 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 13. Amphiglena messapica 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.