Amage giacomobovei Schiaparelli & Jirkov 2021, sp. nov.

Amage giacomobovei sp. nov.

urn:lsid:zoobank.org:act: DFCD9E3C-9F02-49EF-8FA0-410B23D37A57

Figs 1A, C–I, 2–3

Amage sculpta – Benham 1927: 121–123, pl. III, figs 94–99 (non Ehlers, 1908).

Amage benhami – Reuscher, Fiege & Wehe 2009: 21–22, fig. 1a–g (partim).

Diagnosis

The new species is characterized by having 16 AU and four pairs of branchiae.

Etymology

This species is dedicated to the Italian piemontese explorer Giacomo Bove (1852–1877, https://en.wikipedia.org/wiki/Giacomo_Bove), lieutenant of the Italian Royal Navy, who joined the Vega expedition of Adolf Erik Nordenskîld (1878–1879) in search of the North–East Passage. He was the first Italian to attempt to organize an expedition to Antarctica, however, it was not funded due to its prohibitive costs following the union of Italy.

Material examined

Holotype

ANTARCTICA • 1 spec. (BL = 21 mm); Terra Nova Bay; 74.69478º S, 164.18458º E; depth 454 m; 24 Jan. 2013; Vacchi leg.; station: Vacchi 4; XXVIII PNRA Expedition (2012-2013); MNA-06373.

Paratypes

ANTARCTICA • 1 spec. (BL = 22 mm); same collection data as for holotype; MNA-06354 • 1 spec. (incomplete, BL = 15 mm); same collection data as for holotype; MNA-06374 • 1 spec. (BL = 20 mm); same collection data as for holotype; MNA-06377 • 1 spec. (BL = 22 mm); same collection data as for holotype; MNA-07930 • 1 spec. (BL = 18 mm); same collection data as for holotype; MNA-07931 • 1 spec. (BL = 14 mm); MNA-07932.

Other material

ANTARCTICA • 2 specs; McMurdo Sound; opposite Granite Harbour; - 75.933º S, 164.200º E; depth 293 m; station: 340; Terra Nova Expedition (1910); BMNH 1928.2.29.2/3, previously identified by Benham (1927) as A. sculpta.

Description

Holotype

MEASUREMENTS. BL = 21 mm.

PROSTOMIUM. Prostomium with T-shaped middle lobe encircled by inflated lobe (trilobed); middle lobe with eyespots at the posterior corners; couple of NO present along the posterior margin, separated by a narrow gap; without glandular ridges (Fig. 1A).

BUCCAL TENTACLES. Buccal tentacles few, smooth; tentacle upper surface with rows of warts stained with methylene blue much more intensively than other tentacles’ surfaces (Fig. 1C).

BRANCHIAE. Four pairs of branchiae, places of attachment of two branchostyles in transversal row, large median gap (equal to several diameters of branchostyles) between groups of branchiae; branchiae gap with longitudinal folds; other two branchostyles form longitudinal line behind the first two; branchostyles cirriform, smooth, without additional structures visible even after staining; anterior outermost branchiae originating from C1, next from C2 and posterior branchiae from C3; anterior innermost branchiae originating from S2.

NEPHRIDIAL PAPILLAE. Nephridial papillae behind notopodia of TU1–TU3; hardly visible even after staining, usually invisible at all.

PALEAE. Paleae absent.

NOTOPODIA AND NEUROPODIA. 15 TC; notopodia well developed, slightly flattened throughout body, all with globular lateral cirrus (Fig. 1 D–H); elevated or modified notopodia absent; notochaetae organized in two slightly irregular transversal rows, anterior ones shorter (nearly half) than posterior ones; neuropodial tori with uncini from C4 (= TC4) (Fig. 1D), present in 12 thoracic uncinigers; first pair of tori very long, extending far onto ventral side; size of neuropodia gradually decreasing caudally, tori without cirri; all thoracic neuropodia tori, all abdominal pinnuli (Fig. 2G); there are 16 AU with rudimentary notopodia (Fig. 1G, I); thoracic and abdominal uncini similar (Fig. 3).

PYGIDIUM. Pygidium with lateral cirri long and slender (MNA-06377, MNA-07930, MNA-07931, MNA-07932) (Fig. 2I), short and stout (MNA-06354) or rudimental (MNA-06373).

TUBE. The tubes of A. giacomobovei sp. nov. are characterized by a large amount of sponge spiculae (Fig. 2 D–G) and other (less abundant) foreign materials.

LIVING COLOR (Fig. 2 A–C). Body whitish on the ventral side and pale brown on the dorsal one; nuchal organs orange; branchostyles with pair of blood vessels each; there are white strips connecting neuropodia.

Methylene blue staining

Anterior halves of the lower lip and ventrum of the next S2 or S2 only stained differently from their posterior halves: immediately after staining with dense small dark blue patches, later when the stain moves inside the body, patches are still dark, while the stain from the posterior halves dissolves. There is a dark violet or blue band between notopodia ventrally (except for one–two last thoracic segments) (Fig. 1E). Parapodia and ridges connecting notopodia and neuropodia (both thoracic and abdominal) (Fig. 1G) and branchiae (Fig. 1E) stained more or less intensively than the rest of the body. A scattered distribution of small intensively stained spots, denser in neuropodia. Spots form narrow strips behind bands connecting neuropodia (Fig. 1H).

Differential diagnosis

Only four species of Amage have 15 TC and 12 TU, but they differ by smooth buccal tentacles (not known for A. tasmanensis) and the number of AU. Amage imajimai described off Japan from a depth of 990–1060 m and A. tasmanensis described from Tasman Sea (3830 m deep) have 11 AU. Amage imajimai has thoracic uncini with two rows of teeth and abdominal uncini with several rows of teeth. Amage tasmanensis has both thoracic and abdominal uncini with a single row of teeth. Amage longitorus described off Japan from a depth of 1060–3016 m has 12 AU, and three pairs of branchiae instead 16 AU and four pairs of branchiae. Amage benhami known from a bioherm off Oregon coasts (North East Pacific, 44.669100º, -125.111417º, depth 625 m), has 15 AU instead of 16 AU. Amage benhami also differs in the shape of thoracic (each uncinus has a single row of teeth) and abdominal uncini (each uncinus has numerous teeth arranged in three non-parallel vertical rows), while in A. giacomobovei sp. nov. both thoracic and abdominal uncini are similar.

Specimens of Amage (BMNH 1928.2.29.2/3) found in McMurdo Sound at - 75.9333 S, 164.2000 E, 293 m, identified by Benham (1927) as A. sculpta and by Reuscher et al. (2009) as A. benhami, have 16 AU as it was correctly reported by Reuscher et al. (2009) and thus belong to A. giacomobovei sp. nov., not to A. benhami.

Distribution

Only known from the Ross Sea (Antarctica) in 290– 500 m.

Remarks

Benham (1927) described the tubes of A. giacomobovei sp. nov., which he considered to be A. sculpta, as filled with sponge spicules: “ The tube if of grey mud with abundant sponge spicules embedded and foreign bodies adherent. The tube measures 35 mm. by 4 mm. at its upper end. The contained worm is 15 mm. in length ”. Although no data are available about the bottom type where our specimens and those examined by Bentham were collected, it seems probable, given the high amount of sponge spicules embedded in the tube walls, that this species might be typically occur only associated to “ spicule mats ” fields (Gutt et al. 2013). Amage giacomobovei sp. nov. tubes are also quite similar to those of A. auricula, type species of the genus, which occurs in the North Polar Basin and North Sea. The high level of variation in pygidium later cirri shape is probably the result of different levels of contraction of cirri due to fixation.