Amphiglena magna, Capa & Rouse, 2007

Capa, Maria & Rouse, Greg W., 2007, Phylogenetic relationships within Amphiglena Claparède, 1864 (Polychaeta: Sabellidae), description of five new species from Australia, a new species from Japan, and comments on previously described species, Journal of Natural History 41 (5 - 8), pp. 327-356 : 343-345

Amphiglena magna sp. nov.

( Figures 4G, H , 7 )

Material studied

Australia, Victoria. Holotype: MV F109494 , Cheviot Beach, Point Nepean , 38 ° 129 S, 144 ° 409 E, 3.5–5 m, 31 March 1998 . Paratypes: MV F91001 , same locality (46 specimens) , AM W30486, same locality (one specimen, SEM) . Additional material: MV F90998 , Off Eagles Nest, Bunurong , 38 ° 409 S, 145 ° 399 E, 1 April 1997 (13 specimens) .

Description

Holotype 5 mm long (branchial crown 1.5 mm). Eight thoracic and 21 abdominal chaetigers. Seven radioles on each side of the branchial crown. Radioles with numerous pinnules in two rows, alternating along length, similar in size all along; tip of radioles as long as distal pinnules ( Figure 7A ). Palmate membrane inconspicuous and radiolar flanges absent ( Figure 7B, C ). Radiolar skeleton with two rows of cells. Short ventral basal flanges restricted to base of crown, not continuing posteriorly ( Figure 7B ). Dorsal lips with elongate, ciliated, dorsal radiolar appendages of about one-quarter the length of branchial crown. Dorsal pinnular appendages absent. Ventral lips absent. Anterior peristomial ring indistinguishable ( Figure 7A–C ). Posterior peristomial ring with a mid-ventral incision and ventral margins prolonged anteriorly on both sides of incision; collar absent. Peristomial eyes as two brownish spots. Thorax longer than wide with quadrangular ventral shields similar, not in contact with the thoracic tori. Two narrowly hooded superior and three broadly hooded notochaetae on first chaetiger ( Figure 7D ). Other thoracic chaetigers with one or two superior broadly hooded notochaetae and three paleate inferior thoracic notochaetae ( Figure 7F ). Up to 10 thoracic uncini per torus, increasing in size from the ventral side to the lateral margin of torus, with numerous rows of small teeth of similar size above the main fang, arranged in upper half of uncini ( Figure 7E, F ); breast well developed, reaching the level of tip of the main fang, handles medium in length ( Figure 4G ). Companion chaetae geniculated, with straight shaft and elongate mucro with several basal teeth of similar size ( Figure 7E, F ). Abdominal chaetigers with two broadly hooded abdominal neurochaetae per fascicle ( Figure 7G ) and up to eight uncini per torus, with several rows of small teeth of similar size above the main fang ( Figure 7H ), breast well developed, with a convex base, short handle ( Figure 4H ). Pygidial eyes as a brown spot on each side of pygidium. Statocysts not seen. Tube unknown.

Variation

Amphiglena magna sp. nov. is generally larger than other species of Amphiglena , except A. pacifica which can measure up to 20 mm ( Rzhavsky 1995), but small specimens have also been found, measuring 2 mm long and with 15 abdominal chaetigers. Some specimens show slight variation in the number of radioles in that some have six pairs with up to 20 pinnules along radioles. Some specimens have eggs in the anterior abdominal chaetigers.

Remarks

The specimens of A. magna sp. nov. are large compared to other Amphiglena . Additionally, a distinguishing feature is the shape and length of the ventral basal flanges that terminate at the junction of crown and thorax, though this is seen in A. gracilis sp. nov., A. terebro , and A. mediterranea . However, these species are distinguishable from A. magna sp. nov. in having fewer radioles, the pinnules along radioles not being similar in length, and having larger dorsal radiolar appendages.

Etymology

The name of this species refers to its size, one of the largest in the genus.

Figures

Figure 4. Line drawings of uncini. (A, B) A. gracilis sp. nov.: (A) thoracic uncini, seventh chaetiger; (B) midabdominal chaetiger. (C, D) A. bondi sp. nov.: (C) thoracic uncini, seventh chaetiger; (D) mid-abdominal chaetiger. (E, F) A. lenae sp. nov.: (E) thoracic uncini, seventh chaetiger; (F) mid-abdominal chaetiger. (G, H) A. magna sp. nov.: (G) thoracic uncini, seventh chaetiger; (H) mid-abdominal chaetiger. (I, J) A. maiteae sp. nov.: (I) seventh chaetiger; (J) mid-abdominal chaetiger. (K–N) A. nishii sp. nov.: (K, L) seventh chaetiger; (M, N) midabdominal chaetiger. Scale bar: 10 Mm.

Figure 7. Amphiglena magna sp. nov. SEM preparation, paratype, AM W30486. (A) Whole specimens, dorsolateral view; (B) anterior segments and base of crown, ventral view; (C) same, dorsal view; (D) notochaetae, first thoracic chaetiger, ventral view; (E) uncini and companion chaetae second thoracic chaetiger; (F) six and seventh thoracic chaetigers, ventral view; (G) neurochaetae, anterior abdominal segment; (H) uncini, anterior abdominal chaetiger.