Exogone Orsted 1845

Genus Exogone Ørsted, 1845

Type species. Exogone naidina Ørsted, 1845.

Diagnosis. Body short, slender. Palps well developed, completely or almost completely fused. Prostomium with 2 pairs of eyes, sometimes also with 1 pair of anterior eyespots, and 3 antennae. Peristomium with 1 pair of short, papilliform or ovate peristomial cirri. Compound chaetae as falcigers and, frequently, spiniger-like chaetae; falciger blades usually bidentate, subdistal tooth larger, blades partially fused to shafts or absent in some species; shafts of spiniger-like chaetae with triangular processes in some species. Dorsal simple chaetae present from anterior chaetigers, ventral simple chaetae usually only on posterior chaetigers. Aciculae commonly inflated distally, frequently hollow, with slightly curved tip. Pygidium with 1 pair of anal cirri, usually longer than dorsal cirri. Reproduction by epigamy, with ventral incubation of eggs and embryos.

Remarks. The genus Exogone was revised by San Martín (1991) who established 3 sub-genera: Parexogone Mesnil & Caullery, 1918, Exogone Ørsted, 1845 and Sylline Claparède, 1864. Böggemann & Westheide (2004) raised Parexogone to the generic level, and recent studies on the Syllidae have abandoned the subgenera classification, considering Exogone as monophyletic and not recognizing E. (Exogone) and E. (Sylline) as separate subgenera (Aguado & San Martín 2009; Aguado et al. 2012, Paresque et al. 2014). This classification is followed herein.