Morphology of anterior regeneration in two spionid polychaete species: implications for feeding efficiency

Abstract

Abstract. In marine soft‐sediment habitats, tissue loss by infuanal invertebrates can provide significant energetic input to higher trophic levels, have substantial impacts on individual behavior, growth, and fecundity, and resulting changes in bioturbation rates can secondarily affect community dynamics. The degree to which a community is affected by such sublethal predation depends in part on whether injured individuals can regenerate and on the speed at which they do so. Previously, we demonstrated differences in the rate of anterior segment and palp regeneration by the spionid polychaetes Pygospio elegans and Dipolydora quadrilobata. The current study examined the morphology of the anterior segment and palp regeneration in these species using scanning electron microscopy (SEM) and indirect immunohistochemistry with confocal laser scanning microscopy at 3, 6, 9, and 12 d post‐ablation. Antibodies for acetylated α‐tubulin and the neural tetrapeptide FMRFamide were used to label the regenerating nervous system. SEM revealed that the morphology of anterior tissue regeneration was similar for both species, but the ciliated food groove tended to form sooner on palps in P. elegans than on those of D. quadrilobata. In both species, palp regeneration and ciliated food groove formation were faster when only palps were removed. A shortened ciliated food groove is likely to reduce particle contact and transport efficiency in suspension and deposit feeding. Regenerating palp nerves were initially visible at 3 d following ablation of palps only, but at 6 d following ablation of five anterior segments. Following ablation of anterior segments, the regenerating nervous system was largely complete by 9 d, nuchal organs were innervated by 6 d, and processes of palp sensory cells were visible at 12 d. Contact chemoreception by sensory cells on the palps may be diminished during the early stages of regeneration, but chemoreception of waterborne cues via the nuchal organ should not.

Systematics, evolution and phylogeny of Annelida – a morphological perspective

“…In developing and regenerating spionids the palps buds appear at the posterior edge of the prostomium and their peristomial position is achieved later on (e.g. Blake and Arnofsky, 1999;Lindsay et al, 2008). This feature may suggest a prostomial origin in general.…”

Structure and anterior regeneration of musculature and nervous system inCirratuluscf.cirratus(Cirratulidae, Annelida)

“…In contrast, we do not have data illustrating the transition from the lateral loops to the dorsal root of the circumesophageal connective, but they are obviously linked. Although distinct roots of the circumesophageal connective appear during anterior regeneration in other annelids (M€ uller et al, 2003;M€ uller, 2004a, 2004bM€ uller and Henning, 2004;Lindsay et al, 2008), the tripartite loop-like structure observed in C. cf. cirratus has not been described in these other species.…”

Regeneration in spiralians: evolutionary patterns and developmental processes

“…A. C. Nicol, unpublished data in Wells 1952). Regeneration of feeding palps (following removal of only these structures) has been well documented in several genera of spionids (Hentschel and Harper, 2006;Lindsay et al, 2007;Lindsay et al, 2008), as has the regeneration of the operculum in serpulids (Okada, 1933;Szabó and Ferrier, 2014). Amputation and regeneration of parapodia has also been described in one species of nereid (Boilly and Boilly-Marer, 1995).…”