Can Diopatra neapolitana (Annelida: Onuphidae) regenerate body damage caused by bait digging or predation? A. Pires, R. Freitas, V. Quintino, A.M. Rodrigues * Department of Biology and CESAM, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal article info Article history: Received 19 September 2011 Accepted 21 December 2011 Available online 31 January 2012 Keywords: segment regeneration sub lethal predation polychaete abstract The regenerative ability of Diopatra neapolitana was evaluated under laboratory conditions following nine experimental amputation levels: before the beginning of the branchiae (chaetiger 3 or 4), in the branchial region, at chaetigers 10, 15, 20, 25, 30, 35 and 40 and after the branchiae, at chaetigers 45e55. Specimens amputated at the 20th chaetiger were not able to regenerate and did not survive. The posterior portion of the specimens amputated up to chaetiger 15, regenerated the anterior part but the anterior ends were unable to survive. The anterior end of the specimens amputated at and beyond the 25th chaetiger regenerated the posterior part but the posterior ends were not able to regenerate an anterior part. Percent survival was directly related to the number of branchial segments left in the regenerating specimen and reached 100% only when the specimens were amputated beyond the branchial region. These results indicate that the species has regenerative ability and should survive the loss of a few anterior chaetigers, namely caused by predation. However, the results also indicate that bait digging could impair the survival of the posterior part remaining in the tube, as usually more than 20 chaetigers are harvested by bait collectors. Regarding field-collected specimens, D. neapolitana was found regenerating a mean of 9.0  2.51 chaetigers, and Diopatra marocensis 7.5  1.93 chaetigers, at the anterior end. The higher percentage of field-collected specimens showing regeneration of the anterior end belonged to D. marocensis. Only very few specimens, for both species, were found regenerating the posterior part of the body. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Annelids have the reputation to be able to regenerate. This ability however varies widely within the phylum, and while some species do not have this capacity, others are able to regenerate an entire individual from a single mid-body segment (Bely, 2006). Among polychaetes, the regeneration ability also differs from species to species. Almost all polychaetes can regenerate append- ages, such as palps, tentacles, cirri and parapodia, and most are capable to regenerate the posterior end of the body. Many poly- chaetes, such as nereids, capitellids and some eunicids, cannot regenerate the anterior part of the body while others have this ability, namely sabellids, syllids, onuphids, maldanids, serpulids, cirratulids and spionids (Brusca and Brusca, 1990; Bely, 2006). Some Diopatra species are capable to regenerate anterior segments and prostomial structures: Diopatra sugokai (Pflugfelder, 1929, as Diopatra amboinensis), Diopatra dexiognatha (Bailey-Brock, 1984, as Diopatra leuckarti; Paxton and Bailey-Brock, 1986), Diop- atra neapolitana (Bely, 2006; Pires et al., 2012), Diopatra tuber- culantennata (Budaeva and Fauchald, 2008), Diopatra cuprea (Berke et al., 2009), Diopatra micrura (Pires et al., 2010) and Diopatra marocensis (present study). Paxton and Bailey-Brock (1986) stated that D. dexiognatha can readily regenerate anterior and posterior damaged or autotomized regions. Safarik et al. (2006) observed Diopatra aciculata individuals regenerating posterior ends. The same authors observed an increase of the regenerating frequency of posterior chaetigers at higher worm densities, pointing out that aggressive encounters among individuals could be density-related. Field-collected specimens of Diopatra neapolitana and Diopatra marocensis in Ria de Aveiro (North-western coast of Portugal) were found regenerating, the anterior and posterior ends, (Pires et al., 2012 and present study). Diopatra neapolitana is a tubicolous Onuphid polychaete common in Ria de Aveiro, where it inhabits intertidal sand-flats and shallow sub tidal areas. The species grows up to 70 cm long and is harvested as fresh bait, but often only the anterior part (10e15 cm) is collected by bait diggers. In this study we evaluate the regenerative ability of D. neapolitana under laboratory conditions following nine experimental amputation levels, in order * Corresponding author. E-mail address: anarod@ua.pt (A.M. Rodrigues). Contents lists available at SciVerse ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss 0272-7714/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecss.2011.12.039 Estuarine, Coastal and Shelf Science 110 (2012) 36e42