Parasabella, AND

Capa, María & Murray, Anna, 2015, Integrative taxonomy of Parasabella and Sabellomma (Sabellidae: Annelida) from Australia: description of new species, indication of cryptic diversity, and translocation of some species out of their natural distribution range, Zoological Journal of the Linnean Society 175 (4), pp. 764-811 : 801-802

MONOPHYLY OF PARASABELLA AND SABELLOMMA AND

RELATIONSHIPS WITH OTHER SABELLIDS

All species in Parasabella share the presence of companion chaetae with bulbous subdistal ends with a dentate appearance and a narrow tapered mucro arising from the centre and compressed laterally, which is unique in Sabellidae ( Knight-Jones, 1983; Perkins, 1984; Fitzhugh, 1989; Capa et al., 2015). Monophyly of the genus was indicated herein (although weakly support- ed) for the first time, after analyses of molecular data. The monophyly of Sabellomma has already been assessed by Nogueira et al. (2010), after analyses of morphological data and considering a comprehensive number of sabellid terminals. It relies on the presence of unpaired eyes distributed along the radioles ( Nogueira et al., 2010; and see explanation as to why some of the phylogenetic hypotheses tested recovered Sabellomma as paraphyletic).

The phylogenetic hypothesis after combining nuclear and mitochondrial sequence data indicated a sistergroup relationship between Parasabella and Sabellomma . This result differs from a previous hypothesis that recovered Parasabella (as Demonax ) as sister-group to Megalomma ( Nogueira et al., 2010) . These three genera, however, share several morphological features, all homoplastic. They bear broadly hooded inferior thoracic notochaetae ( Fitzhugh, 1989; Capa & Murray, 2009; Tovar-Hernández & Carrera-Parra, 2011, and present study; see Nogueira et al., 2010 for a different interpretation in Sabellomma ), also shared by members of Claviramus Fitzhugh, 2002 , Euchoneira Licciano, Giangrande & Gambi, 2009 , Glomerula Nielsen, 1931 Potamilla Malmgren, 1866 , and Terebrasabella Fitzhugh & Rouse, 1999 , amongst others ( Nogueira et al., 2010; Capa et al., 2015). Moreover, Sabellomma and most members of Megalomma and Parasabella bear pinnular appendages associated with the dorsal lips, a feature that has also been reported in other sabellids, for example, Anamobaea Krøyer, 1856 , Bispira Krøyer, 1856 , Branchiomma Kölliker, 1858 , Potamilla Malmgren, 1866 , and Pseudopotamilla Buch, 1905 ( Nogueira et al., 2010; Capa et al., 2015). The presence of a short thorax with fewer than the typical eight chaetigers has been considered as a characteristic of species of Sabellomma and some Parasabella (e.g. Knight-Jones, 1983; Perkins, 1984; Nogueira et al., 2010) but has also been reported in Megalomma ( Knight-Jones, 1983; Tovar-Hernández & Carrera-Parra, 2011) and many other sabellids (e.g. Knight-Jones & Perkins, 1998; Nogueira & Knight-Jones, 2002; Fitzhugh, 2003; Nogueira, López & Rossi, 2004; Capa, Pons & Hutchings, 2013). Members of Parasabella and Megalomma have also been reported with more than eight thoracic chaetigers ( Knight-Jones, 1983; Knight-Jones & Walker, 1985; Tovar-Hernández & Carrera-Parra, 2011). But if an anomalous number of thoracic segments is indeed a consequence of imperfect regeneration after damage or reproduction by scissiparity, ( Knight-Jones & Bowden, 1984; Nogueira & Knight-Jones, 2002; Fitzhugh, 2003; Nogueira et al., 2004; Capa, 2008), then intact specimens with the typical number of thoracic segments may also exist (even if not yet found) and thus this feature would not be diagnostic.

At least some species of each of the three genera bear radiolar eyes, but if considered absent in P. microphthalma (as in Nogueira et al., 2010), their number and arrangement show large differences amongst members of the three genera. Megalomma is characterized by the presence of subdistal, sessile, and compound radiolar eyes, at least on the internal margin of the dorsal-most pair of radioles ( Fitzhugh, 1989; Capa & Murray, 2009; Tovar-Hernández & Carrera-Parra, 2011), a synapomorphy for the genus. Sabellomma bears numerous, unpaired, randomly arranged eyespots along the outer margin of all radioles ( Nogueira et al., 2010), a synapomorphy for the genus. Finally, Parasabella lacks eyes, except for the newly described species P. bioculata , which has paired simple eyespots on both sides of the distal radiolar tips of most radioles.

Morphologically, Sabellomma and Megalomma share the shape of the companion chaetae, with a distal teardrop ‘membrane’, albeit very narrow in the hereindescribed S. cupoculata . By contrast, the mucro is at an angle in Parasabella , appearing as compressed laterally instead of flattened transversely. Some members of Sabellomma and Megalomma also have ventral sacs as a continuation of the ventral lips, whereas they have not been observed in Parasabella . The previously described three species of Sabellomma were characterized by the presence of inter-ramal eyespots, more conspicuous in the abdominal region ( Nogueira et al., 2010), but this is a feature that has also been reported from some Megalomma species ( Capa & Murray, 2009; Tovar-Hernández & Carrera-Parra, 2011) and is lacking (or completely faded) from S. cupoculata sp. nov.

Megalomma and Parasabella resemble each other in the dentition of uncini as they generally have a large number of rows (over eight) with minute teeth all similar in size ( Capa & Murray, 2009; Tovar-Hernández & Carrera-Parra, 2011; Figs 7K, L , 9J , 11H , 13I , 15H , 17E, F ), whereas Sabellomma has both thoracic and abdominal uncini with fewer than eight rows and larger teeth ( Nogueira et al., 2010; Fig. 19H–J ). No distinct morphological features are shared between Parasabella and Sabellomma .

Figures

Figure 7. Parasabella aberrans spp. complex, scanning electron microscope photographs. A, anterior thoracic chaetigers and base of radiolar crown, ventral view. B, same, showing collar, lateral view. C, collar dorsal margins, lateral view. D, collar dorsal margins and fleshy swelling divided in two by faecal groove, dorsal view. E, fleshy swelling continuous across dorsum. F, elongate, narrowly hooded collar chaetae. G, inferior thoracic notochaetae (broadly hooded, type B). H, thoracic uncini and companion chaetae. I, J, thoracic uncini from specimens with continuous and divided dorsal swellings, respectively. K, L, companion chaetae from specimens with continuous and divided dorsal swelling, respectively. M, midabdominal, narrowly hooded neurochaetae. N, abdominal uncini. O, posterior abdominal chaetigers and pygidium, ventral view. A, B, D, F, G, H, M, N, AM W.36935; C, E, J, L, O, AM W.32018; I, K, AM W.36430.

Figure 9. Parasabella sp. cf. Parasabella aulaconota scanning electron microscope photographs. A, anterior thoracic chaetigers and base of radiolar crown, ventral view, with ventral shields in contact with neuropodial tori. B, same, showing the collar, lateral view. C, collar dorsal margins, lateral view. D, anterior thoracic chaetigers and base of radiolar crown, showing collar dorsal margins, dorsal view. E, collar chaetae, elongate, narrowly hooded. F, thoracic elongate, narrowly hooded superior notochaetae and inferior, broadly hooded (type B) chaetae. G, detail of inferior thoracic chaetae. H, I, thoracic uncini from specimens collected in temperate and tropical sites, respectively. J, companion chaetae. K, complete row of uncini in abdominal notopodia, showing the range in size from dorsal- to ventral-most uncini. L, midabdominal narrowly hooded neurochaetae. M, abdominal uncini. B, C, F, H, K–M, AM W.22017; A, D, E, G, I, J, AM W.22480.

Figure 11. Parasabella bioculata sp. nov. scanning electron microscope photographs. A, anterior thoracic chaetigers and base of radiolar crown, ventral view, showing ventral shields separated from neuropodial tori. B, same, lateral view. C, same, dorsal view. D, inside of radiolar crown, frontal view, showing dorsal lips and long radiolar appendages. E, elongate, narrowly hooded collar chaetae. F, midthoracic chaetiger, elongate, narrowly hooded superior thoracic chaetae, and inferior, broadly hooded type B chaetae. G, thoracic uncini. H, companion chaetae. I, midabdominal, narrowly hooded neurochaetae. J, abdominal uncini. A–J, AM W.36449.

Figure 13. Parasabella crassichaetae sp. nov. complex, scanning electron microscope photographs. A, anterior thoracic chaetigers and base of radiolar crown, ventral view, showing ventral shields in contact with neuropodial tori, and ventral lappets. B, anterior chaetigers, ventral view, of specimens with crown removed. C, anterior body, lateral view. D, same, dorsal view. E, elongate narrowly hooded collar chaetae. F, midthoracic parapodium, elongate, narrowly hooded superior chaetae (arrow) and broadly hooded type A chaetae in inferior group. G, detail of inferior, broadly hooded type A chaetae. H, thoracic uncini. I, companion chaetae. J, midabdominal, narrowly hooded neurochaetae. K, abdominal uncini. L, posterior abdominal chaetigers and rim-like pygidium. A, C, D, E, L, AM W.36298; B, F–K, AM W.31103.

Figure 15. Parasabella sp. cf. Parasabella japonica, scanning electron microscope photographs. A, anterior thoracic chaetigers and base of radiolar crown, ventral view, showing ventral shields separated from neuropodial tori, and ventral lappets. B, anterior chaetigers, lateral view. C, same, dorsal view. D, midthoracic parapodium, elongate, narrowly hooded superi- or chaetae and broadly hooded type B chaetae in inferior group. E, detail of inferior, broadly hooded type B chaeta. F, thoracic uncini and companion chaetae. G, thoracic uncini, detail. H, companion chaetae showing the laterally compressed hood. I, midabdominal narrowly hooded neurochaetae. J, abdominal uncini. A–J, AM W.36450.

Figure 17. Parasabella sp. cf. Parasabella rugosa, scanning electron microscope photographs. A, anterior thoracic chaetigers and base of radiolar crown, dorsal view, showing large collar dorsal margins. B, midthoracic parapodium with elongate, narrowly hooded (arrow) superior chaetae and broadly hooded (type B) in inferior group. C, detail of inferior thoracic broadly hooded chaetae of type B. D, thoracic uncini. E, companion chaetae, lateral view. F, companion chaetae, frontal view. G, midabdominal neurochaetae narrowly hooded. H, abdominal uncini. I, posterior abdominal chaetigers and (damaged) pygidium. A–I, AM W.36431.

Figure 19. Sabellomma cupoculata sp. nov., scanning electron microscope photographs. A, whole specimen, ventral view. B, anterior thoracic chaetigers and base of radiolar crown, ventral view, showing collar with low ventral lappets. C, same, lateral view. D, same, dorsal view. E, midthoracic parapodium with elongate, narrowly hooded superior chaetae (arrow) and broadly hooded type A chaetae in inferior group. F, detail of inferior, broadly hooded chaetae of type B. G, thoracic uncini. H, I, companion chaetae, frontal view. J, companion chaetae, lateral view. K, midabdominal narrowly hooded neurochaetae. L, M, midabdominal uncini. N, posterior abdominal chaetigers and pygidium. A–N, AM W.39545.