Perkinsiana brigittae Tovar-Hernández, Yáñez-Rivera, Giangrande & Gambi, 2012, sp. nov.

Perkinsiana brigittae sp. nov.

Figures 1 D–R, 2A–L, 3A–J, 4C

Type material: Holotype (USNM 1180547) and four paratypes (USNM 1180548): Antarctica, Wilkes Land, Budd Coast, Wilkes Station, Station DX, 66° 21’ 14’’ S, 110° 28’ 09’’ E, U. S. Antarctic Research Program (USARP), Antarctica, December 0 3, 1961, 237 m.

Additional materials: Smithsonian Oceanographic Sorting Center, U.S. Antarctic Research Program (USARP), Antarctica, Wilkes Station, Sta. DX, 66° 21’ S, 110° 28’ E, December 0 3, 1961, 238 m (38 spec.); 66° 22’ S, 110° 29’ E, December 13, 1961, 237– 256 m (2 spec.); 66° 17’ S, 110° 13’ E, January 0 5, 1962, 155– 326 m (12 spec.). ENSR, Marine and Coastal Center: Cruise ELTANIN 22, Sta. 1581, 56 ° 19’ S, 27° 29’ W, March 0 6, 1966, 148– 210 m (>100 spec). Cruise ELTANIN 27, Sta. 1885, 74 ° 30’ S, 170° 10’ E, January 16, 1967, 311– 328 m (95 spec). Islas Orcada, Sta. 575, 50 ° 11’ S, 37° 41’ W, May 0 9, 1975, 68–80 m (45 spec).

Description (measurements based on holotype, data in brackets correspond to paratypes)

Holotype and paratypes entire. Branchial crown longer than thorax, 18 mm length (23.5 mm, 17–27, n=4) with 16 pairs of radioles (19 pairs, 14–21, n=4). Radioles with 3–5 brown bands, each color band occupying five pinnules and color extending onto pinnules. Radioles united at the base by short web palmate membrane (Fig. 2 L). Flanges present (Figs 2 K, 4C). Tfwo or three ventralmost radiolar pairs poorly developed. Longest pinnules at midradioles. Radioles with filiform tips, as long as equivalent space of 10–12 pinnules (Fig. 2 K, 4C). Dorsal lips triangular erect with distinct longitudinal mid-rib forming two wide lateral lamellae (Figs 1 H–I, 2D) and dorsal pinnular appendages. Ventral lips broadly rounded (Figs 1 H–I, 2D). Lamellae parallel present. Triangular dorsal keel situated dorsal to mouth. A pair of ventral sacs located below mouth. Dorsal collar margins diagonal, not fused to faecal groove (Figs 1 D, 2A, E). Anterior peristomial ring level dorsally, exposed (Figs 1 D, F, 2A, E). Ventral lappets of collar rounded, not overlapped (Fig. 1 E, 2B, F). Lateral collar margins oblique, higher ventrally, not covering the basal union of radioles (Figs 1 F, 2C, G). Ventral shield of collar divided transversally in two parts, the anterior one rectangular and the posterior one trapezoidal (Figs 1 E, 2B, F). Collar with narrowly-hooded chaetae. Thin body, 101 mm length (88.25 mm, 65–102, n=4). Thorax with 10 segments (10, 8–13, n=4). Thorax width 3 mm (2.7 mm, 2.5–3, n=4). Thoracic ventral shields rectangular (Figs 1 E, 2B). Thoracic torus of equal length in all segments, contacting ventral shields (Figs 1 E, 2B–C). Superior thoracic chaetae narrowly-hooded (Figs 1 P, 3A). Inferior thoracic chaetae paleate (Figs 1 Q, 3A–B). Thoracic uncini with several rows of teeth of equal size above main fang (Fig. 3 D), occupying a half of main fang length, hood absent, breast well developed, handles as long as three times the length of crest (Fig. 1 J). Companion chaetae with tear-drop shaped membranes (Figs 1 M– O, 3C, E). Abdomen with 151 segments (139, 100–158, n=4). Anterior abdominal segments with bundles of short, narrowlyhooded chaetae (type C) (Fig. 3 G–I). Posterior abdominal segments with very long, narrowly-hooded chaetae (Fig. 3 I–J). Abdominal uncini with dentition similar to those from thorax (Fig. 3 F) but with handles short, a half of handles in thoracic uncini (Fig. 1 K–L). Pygidium lobed (Fig. 1 G) or bilobed. Two groups of small pygidial eyes located dorsally in one paratype (Fig. 2 I). Anus ventral (Figs 1 G, 2J). Tubes chitinized, translucent, vertical distally, irregularly spiralled posteriorly, with incrusting ascidians at mid-length.

Gametes: Holotype and paratypes mature, simultaneous hermaphrodites with male and female gametes distributed in abdomen. Spermatozoa with a spherical nucleus and rounded cap-like acrosome, four mitochondria and a long flagellum. Oocytes diameter 0.1041 mm ±0.042 (min 0.025, max 0.175, n=30). Brooding unknown.

Symbiosis: Paratype with a female gastrodelphyid copepod attached to the fifth ventralmost radiole (Sabellacheres antarcticus Suárez-Morales and Boxshall, 2012) (Fig. 2 H).

Remarks: Perkinsiana brigittae sp. nov., is characterized by a long and thin body, distinguished from other species in the genus by a unique combination of features: the presence of a low palmate membrane, an anterior peristomial ring level dorsally and exposed beyond margins of collar (dorsal and laterally), abdominal chaetae narrowly-hooded (type C) and handles of thoracic uncini as long as three times the length of crest.

Among the 18 nominal species of Perkinsiana, P. brigittae sp. nov., P. acuminata and P. m i n u t a are unique in having the abdominal chaetae narrowly-hooded in all chaetigers (type C). Perkinsiana brigittae sp. nov., and P. minuta have the ventral lappets of collar that do not overlap (overlapping in P. acuminata). Perkinsiana brigittae sp. nov., differs from P. minuta in having the anterior peristomial ring exposed dorsally and laterally (exposed only dorsally in P. m i n u t a) and handles of thoracic uncini as long as three times the length of crest (two times in P. minuta).

Perkinsiana brigittae sp. nov., P. fonticula, P. ceylonica, P. linguicollaris and P. anodina have thoracic uncini with handles as long as three times the length of crest, but in P. brigittae sp. nov., the thoracic tori are contacting the ventral shields (not contacting the ventral shields in P. fonticula, P. ceylonica, P. linguicollaris and P. anodina) and abdominal chaetae are type C (type B in P. fonticula, P. ceylonica, P. linguicollaris and P. anodina).

Perkinsiana brigittae sp. nov., P. m i l a e, P. borsibrunoi, P. s o c i a l i s, P. fonticula, P. linguicollaris, P. anodina and P. longa have the anterior peristomial ring exposed dorsally and laterally; however, among these species only Perkinsiana brigittae sp. nov., P. m i l a e and P. borsibrunoi have thoracic tori contacting the ventral shields (not contacting shields in the remainder five species). Perkinsiana borsibrunoi has long radiolar tips compared to medium-sized tips in P. m i l a e (Fig. 4 B) and P. brigittae sp. nov. (Figs 2 K, 4C). Perkinsiana brigittae sp. nov., and P. milae have similar lateral collar margins, but in the first species the anterior peristomial ring is level dorsally (triangular in P. milae); it has abdominal chaetae type C (type A in P. m i l a e); the length of handle of thoracic uncini is three times the length of crest (2–2.5 times in P. m i l a e) and large body size about 65–102 mm excluding the branchial crown (small size about 24 mm excluding branchial crown in P. m i l a e).

Among the currently valid species distributed in Antarctica, P. antarctica (Kinberg) (Fig. 4 A), P. decorata, P. magalhaensis (Kinberg 1910, Pl. 27, Fig. 7V) and P. milae (Fig. 4 B) have radioles without flanges while radiolar flanges are present in P. borsibrunoi and P. brigittae sp. nov. (Fig. 4 C). Radiolar flanges in P. littoralis sensu Giangrande and Gambi (1997) or Knight-Jones (1983) are unknown. The presence or absence of radiolar flanges is unknown in P. pusilla, but this species has triangular lappets as long as the height of three thoracic segments and abdominal chaetae type A (ventral lappets as long as two thoracic segments and abdominal chaetae type C in P. brigittae sp. nov.). Perkinsiana brigittae sp. nov., P. littoralis sensu Giangrande & Gambi (1997) and P. magalhaensis have abdominal chaetae type C, but in the first species the ventral lappets of collar are not overlapped (overlapped in P. magalhaensis and P. littoralis sensu Giangrande & Gambi (1997)) and the anterior peristomial ring is exposed dorsal and laterally (exposed only dorsally in P. magalhaensis and P. littoralis sensu Giangrande & Gambi (1997)).

As pointed out in the introduction, Perkinsiana is not only a genus with a high morphological variability, but it exhibits variability of reproductive features, sperm morphology and oocyte sizes. Among sub-antarctic and Antarctic species, P. a n t a rc t i c a (Kinberg) is a brooder simultaneous hermaphrodite (Gambi & Patti 1999), P. littoralis (sensu Gambi et al. 2000) and P. borsibrunoi are gonochoric and free spawners, whilst P. milae showed asexual reproduction via scissiparity (Gambi et al. 2000), although a few large specimens were found mature and gonochoric (Cigliano et al. 2007). Perkinsiana brigittae sp. nov., is a simultaneous hermaphrodite as seen in P. antarctica, but probably is a free spawner, in having spermatozoa with spherical nucleus and rounded cap-like acrosome or ect-aquasperm type (barrel shaped nucleus and pointed acrosome or ent-aquasperm type in P. antarctica), oocytes diameter ranging from 25 to 175 µ (30–250 µ in P. antarctica) and gametes female and male distributed together in abdomen (oocytes in anterior abdomen and sperm in posterior abdomen in P. antarctica). A similar ect-aquasperm spermatozoa type to P. brigittae sp. nov., is present in both P. littoralis (sensu Gambi et al. 2000) and P. borsibrunoi, but these latter species are gonochoric with oocytes diameter ranging from 30 to 225 µ (Gambi et al. 2000). Among the remaining species of Perkinsiana, information on spermatozoa morphology are available only for the type species P. r u b r a, which shows spermatozoa with a barrel-shaped nucleus and pointed acrosome (Chughtai 1986), similar to P. a n t a rc t i c a.

The knowledge of reproductive features plus consideration of types abdominal chaetae, could be of valuable help in clarifying the taxonomy of species currently assigned to Perkinsiana. Perkinsiana littoralis (sensu Gambi et al. 2000), P. borsibrunoi and P. brigittae sp. nov., have abdominal chaetae type C and spermatozoa with rounded cap-like acrosome while P. rubra and P. a n t a rc t i c a have pointed acrosomes and types A and B abdominal chaetae, respectively.

Etymology: This species is named in honor of Brigitte Ebbe (Senckenberg Institut) in recognition of her expertise and enthusiastic interest to promote the taxonomy of polychaetes from the Southern Ocean.