Amphiglena Claparède, 1864

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 : 334-335

Amphiglena Claparède, 1864 , emended

Type species. Amphiglena mediterranea Leydig, 1851 designated by Bush (1905).

Diagnosis

Four to eight pairs of radioles. Radiolar skeleton with two rows of cells. Palmate membrane and radiolar flanges absent. Dorsal lips and dorsal radiolar appendages present, without skeleton but with a longitudinal blood vessel and sheath tissue; dorsal pinnular appendages absent. Ventral lips, ventral sacs, or parallel lamellae absent. Anterior margin of anterior peristomial ring narrow, divided ventrally by the midventral incision; posterior peristomial ring of even height all around, collar absent. Peristomial eyes present. Ventral basal flanges from the proximal pinnule of the ventralmost radiole extending posteriorly to peristomium. Chaetae of first chaetiger in two groups, superior chaetae narrowly hooded, inferior broadly hooded; rest of thoracic segments with broadly hooded superior thoracic chaetae, paleate inferior thoracic chaetae arranged in a single row. Avicular uncini with rows of small teeth over the main fang, hood absent; companion chaetae with a long and thin distal mucro, an inflated and subdistally dentate end, and long and straight handle. Abdominal chaetae broadly hooded, arranged in a single row; avicular uncini with a main fang surmounted by several rows of small teeth. Pygidial eyespots present.

Remarks

The value of studying the external and internal structure of the dorsal lips and dorsal radiolar appendages in the taxonomy and the systematics of Sabellidae was highlighted by Fitzhugh (2003). He stated that in A. pacifica dorsal lips have pointed dorsal radiolar appendage with no skeleton cells but only sheath tissue and a longitudinal blood vessel, as well as a dorsal lamella. This observation has been verified in the present study in other species of the genus such as A. magna sp. nov and A. nishii sp. nov., though further study is needed for remaining Amphiglena species. The structure of the peristomium shows clear differences among the Amphiglena species that has not been previously considered. The anterior peristomial ring has been described in the past as low and of even height all around (Rouse 1994; Rouse and Gambi 1997), but it is actually divided ventrally by the midventral incision. The anterior peristomial ring is also not always low and even. It can be distinguished from the posterior ring in being separated from it by a groove ( Figures 2B, C , 5B , 11B, D ) or it can be largely hidden between the posterior ring and the base of the branchial crown ( Figures 7B , 8C , 9B ). The posterior peristomial ring is always broader than the anterior ring. In most Amphiglena species the anterior margin of the posterior peristomial ring is extended on each side of the mid-ventral incision (e.g. Figure 2D ), but these extensions are not the same as the ventral lappets of other sabellids since Amphiglena lacks a posterior peristomial ring collar. All Amphiglena species possess peristomial eyes ( Figure 3B ) as seen in other closely related sabellins (e.g. Kirkia ). The ventral basal flanges, as described by Rouse and Gambi (1997), are not present in all the species of Amphiglena since in some they do not continue beyond the margin of the crown and the peristomium ( A. gracilis sp. nov., A. magna sp. nov., A. mediterranea , and A. terebro ) and so this has been removed from the diagnosis of the genus. Some Amphiglena , such as A. lindae , are described as having the narrowly hooded notochaetae on the first chaetiger ( Rouse and Gambi 1997). Examination of type material shows that the chaetae of the first chaetiger are arranged in two fascicles, with the superior ones as narrowly hooded chaetae but the inferior ones are broadly hooded (following Fitzhugh’s (1989) definition of sabellid chaetal types).

Figures

Figure 2. Amphiglena gracilis sp. nov. SEM preparation, paratypes, AM W30402–AM W30404, AM W30483, AM W30484. (A) Whole specimen, lateral view; (B) anterior end, ventral view; (C) anterior end, dorsal view; (D) detail of base of crown and peristomium, ventral view; (E) base of crown and dorsal radiolar appendages; (F) notochaetae of fourth thoracic chaetiger; (G) mid-abdominal neurochaetae; (H) uncini, second thoracic chaetiger; (I) uncini and companion chaetae seventh thoracic chaetiger; (J) mid-abdominal uncini.

Figure 3. Amphiglena gracilis sp. nov. Micrographs. (A) Whole specimen ventral view; (B) detail of anterior segments, ventral view; (C) pygidium and posterior segment, ventral view; (D) last thoracic and abdominal segments, ventral view.

Figure 5. Amphiglena bondi sp. nov. SEM preparation, paratypes, AM W30480. (A) Whole specimen, ventral view; (B) anterior segments and base of crown, ventral view; (C) anterior segments, dorsal view; (D) first and second thoracic chaetigers, ventral view; (E) uncini and companion chaetae second thoracic chaetiger; (F) parapodia, first abdominal segment; (G) uncini, first abdominal segment.

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.

Figure 8. Amphiglena maiteae sp. nov. SEM preparation, paratypes, AM W30399, AM W30400. (A) Whole specimen, ventral view; (B) anterior segments and base of crown, ventral view; (C) same, dorsal view; (D) second thoracic chaetigers, ventral view; (E) notochaetae, second thoracic chaetiger; (F) uncini and companion chaetae, second thoracic segment; (G) mid-abdominal segment, dorsal view; (H) mid abdominal uncini.

Figure 9. Amphiglena nishii sp. nov. SEM preparation, paratype, AM W30485. (A) Whole specimen, ventral view; (B) anterior segments and base of crown, ventral view; (C) crown and anterior segments, dorsal view; (D) first and second thoracic chaetigers, ventral view; (E) uncini and companion chaetae second thoracic chaetiger; (F) parapodia, mid-abdominal segment; (G) uncini, mid-abdominal segment.

Figure 11. Amphiglena terebro. SEM preparation, AM W30482. (A) Anterior segments and crown, ventral view; (B) detail of anterior segments and base of crown; (C) anterior and posterior peristomial rings; (D) anterior segments and base of crown, dorsal view.