Perkinsiana magalhaensis Kinberg 1867

Perkinsiana magalhaensis (Kinberg, 1867), redescription

(Figs 22–24)

Sabella magalhaensis Kinberg, 1867: 353.— Ehlers 1901: 215.— Kinberg 1910: 72, pl. 27, fig. 7.— Johansson 1925: 22, fig. 7.

Not Bispira magalhaensis.— Fauvel 1916: 471, pl. 9, figs. 34–43.— Monro 1930: 201.— Hartman 1966: 123, pl. 39, figs 2–6 = Parasabella sensu Knight-Jones & Perkins (1998: 430).

Perkinsiana magalhaensis.— Tovar-Hernández et al. 2012: 61.

Potamethus littoralis Hartman, 1967: 174 –176, pl. 51.

Perkinsiana littoralis.— Knight-Jones 1983: 288 –289, fig. 20.— Giangrande & Gambi 1997: 268 –270, figs 3–4.

Material examined. CHILE, Beagle Channel, HF 9, Costa Holgar, UANL 8087, dive 17, sample C 440, 15 m depth, 23 December 2010, coll. D. Bybee, 1 specimen; HF9, Islas Gemelos, UANL 8088–8091: 10–15 m depth, 14–15 December 2010, coll. D. Bybee, 4 specimens. Seno Ibáñez, UANL 8092–8093: 3–20 m depth, 19 December 2010, coll. G. Forsterra, 2 specimens. Isla Martínez, UANL 8094–8095: 10–16 m depth, 21 December 2010, coll. D. Bybee, 2 specimens. Isla Dumas, UANL 8096–8097: 10 m depth, 22 December 2010, coll. D. Bybee, 2 specimens. Islas Holger, UANL 8098–8103: 10–14 m depth, 23 December 2010, coll. D. Bybee, 6 specimens.

Redescription. Trunk length 19–35 mm, width 3–5 mm. Branchial crown length 7–10 mm, with 11–26 pairs of radioles, 4–5 radioles involute mid-ventrally. Six–8 thoracic and 70–94 abdominal segments. Body plump, dorso-ventrally flattened (Fig. 23 G). Radioles with irregular brown bands in pinnules along radiole length, radioles lacking pigmentation. Palmate membrane very low. Radioles with narrow flanges along entire length (Fig. 23 A, F). Longest pinnules at mid-radioles (Fig. 23 B). Radioles with long tips, as long as equivalent space of 8–10 pinnules (Fig. 23 A, B). Dorsal lips 1/4 branchial crown length, with a rigid radiolar appendage and two broad lateral lamellae (Fig. 23 C, D), 2–4 dorsal pinnular appendages. Ventral lips broadly rounded, ear-shaped (Fig. 23 E), two ventral pinnular appendages. Parallel lamellae present (Fig. 22 B, E). Dorsal collar margins not fused to faecal groove (Fig. 22 A, C). Faecal groove wide and depth in thorax (Fig. 22 A, C). Anterior peristomial ring margin exposed dorsally (Fig. 22 A, C). Ventral lappets of collar distally rounded, overlapping (Fig. 22 B, D). Lateral collar margins oblique, higher ventrally, covering junction of anterior peristomial ring and radioles (Fig. 22 F). Ventral shield of chaetiger 1 divided transversely, anterior part slightly narrower and shorter than posterior (Fig. 22 B, D). Sometimes shield is also divided mid-ventrally, forming four square areas (Fig. 22 B). Chaetiger 1 with elongate narrowly hooded notochaetae. Thoracic ventral shields rectangular (Fig. 22 B, C). Thoracic neuropodial tori of equal length, contacting ventral shields (Fig. 22 B, C, F). Superior thoracic notochaetae narrowly hooded, hood one-quarter width of shaft (Fig. 24 B). Inferior thoracic notochaetae paleate with hoods same width as shafts (Fig. 24 A). Thoracic uncini with 9–10 rows of teeth of equal size above main fang, occupying one half main fang length, hood absent, breast well developed, handles as long as three times the length of main fang. Companion chaetae with symmetrical, teardrop-shaped membranes (Fig. 24 C). Abdominal neurochaetae Type C (elongate with narrow hoods, hood one-quarter width of shaft, slightly curved at base of hooded area) (Fig. 24 F). Abdominal uncini with dentition similar to those in thorax, 8–10 rows of teeth and handles short, as long as main fang (Fig. 24 D). Pygidium bilobed, with two groups of small dorsolateral pygidial eyes located dorsally, unequal in size only in larger specimens (Fig. 24 E). Anus ventral. Tubes amber.

Type locality. Bucket Island (Isla Sánchez), Bahía San Nicolás, Strait of Magellan (Chile).

Remarks. Kinberg (1867: 353) described this species as Sabella magalhaensis. Ehlers (1901: 215) only listed S. magalhaensis, indicating its type locality, without any new records or remarks accompanying the species name. Illustrations of chaetae, radioles, ventrum and chaetigers were provided by Kinberg (1910: 72, pl. 27, fig. 7). Fauvel (1916: 471, pl. 9, figs 34–43) transferred S. magalhaensis to Bispira Krøyer, 1856 and recorded it from Roy Cove (Falkland Islands). Johansson (1925: 22, fig. 7), in his revision of sabellariid and sabellid species described by Kinberg, mentioned that the type of S. magalhaensis was broken into four pieces (branchial crown, two pieces of thorax, and two pieces of the abdomen, nearly to 100 segments) and provided a new illustration for a thoracic paleate chaeta (not broadly-hooded as Kinberg illustrated). Monro (1930: 201) recorded Bispira magalhaensis from East Falkland Island and Hartman (1966: 123, pl. 39, figs 2–6) recorded it from Antarctica but provided an illustration re-drawn from Fauvel (1916). Knight-Jones & Perkins (1998) examined the type (Naturiska Rikmusset Stockholm, 1086) of S. magalhaensis and transferred it to Perkinsiana but they did not provide a description or illustrations to accompany this new combination, perhaps due to the bad condition of the type. They also examined Fauvel’s material of “ Bispira ” magalhaensis (MNHN A412) and found it to be Parasabella leucaspis (Kinberg, 1867) (as Demonax Kinberg, 1867). But as indicated in remarks for the genus Parasabella, all records of D. leucaspis require exhaustive revision and must be used with caution because more than one species are involved.

Hartman (1967) described Potamethus littoralis from the South Shetlands Island at a depth of 79 m and provided illustrations for chaetae. Later, Knight-Jones (1983) re-examined the holotype of P. littoralis, transferred it to Perkinsiana and provided illustrations of the branchial crown, thorax and chaetae. Giangrande & Gambi (1997) also examined the holotype, providing a description that agreed to that of Knight-Jones (1983). Tovar- Hernández et al. (2012) suggested that P. magalhaensis and P. littoralis should be considered as synonyms.

Perkinsiana magalhaensis and P. littoralis share the presence of overlapping ventral lappets, anterior peristomial ring exposed only dorsally, abdominal chaetae narrowly-hooded (type C), radiolar tips long, narrow flanges, dorsal lips with a rigid, radiolar appendage, with two broad lateral lamellae, and both species were described from the Antarctic region, Magellan Strait and South Shetland Islands, respectively. The name P. magalhaensis has priority over P. littoralis. For comparisons of P. magalhaensis with other Magellanic Perkinsiana species, see remarks on P. antarctica and P. assimilis.