Dispersal strategies in sponge larvae: integrating the life history of larvae and the hydrologic component

Abstract

While known to be uniformly non-feeding, short-lived, and potentially short dispersing, sponge larvae display different behaviours (swimming ability and taxis). Our aim was to show whether sponge larvae with different behaviours exhibit different dispersal strategies under variable intensity of water movements. We first assessed the distribution of larvae of six taxa: Dictyoceratida spp., Dysidea avara, Crambe crambe, Phorbas tenacior, Scopalina lophyropoda, and Cliona viridis, collected through plankton sampling, and the abundance of the corresponding adult sponges across three hard bottom communities and a sandy bottom from a north-west Mediterranean rocky shore. We then tested adult-larvae couplings (abundance of larvae vs abundance of adults) under increasing levels of water movements (surge) to assess the importance of this environmental factor in driving differences in dispersal strategies. Adults of Dictyoceratida spp., D. avara, and P. tenacior were most abundant in semi-dark caves (SDC), C. crambe and C. viridis in communities of sciaphilic algae (SA), whereas the distribution of S. lophyropoda was extremely patchy, being present almost only in the SA community of one of the five stations studied. Larvae of Dictyoceratida spp. and P. tenacior were more abundant in the SDC, whereas D. avara and C. crambe were homogeneously distributed across the communities. The larvae of C. viridis were more abundant in the SA communities and the S. lophyropoda larvae were mostly present in one station and one community (SA). Increased water movement did not modify the adult-larvae coupling for Dictyoceratida spp., D. avara, and C. crambe, whereas it broke up the positive association for P. tenacior and to some extent S. lophyropoda. For C. viridis, possible variability in adult-larvae coupling was not tested because the larvae were collected on only one day under calm sea conditions. We confirm that efficient-swimming larvae with some cue response can actively counteract hydrodynamic forces and highlight the importance of both larval behaviour and environmental conditions in determining small-scale patterns of dispersal.

Small-scale spatial genetic structure in Scopalina lophyropoda, an encrusting sponge with philopatric larval dispersal and frequent fission and fusion events

“…A significant absence of inbreeding also occurs in other geographically distant populations of this species (Blanquer 2007), and consequently, outcrossing seems to be a general trait for S. lophyropoda at the several spatial scales analysed (ranging from cm to 100s of km). However, the absence of inbreeding in this species with aggregated populations and short larval dispersal , Mariani et al 2006, although difficult to interpret, is in agreement with the conclusions of the several studies on other modular invertebrates, which report that restricted (both sexual and asexual) dispersal, strong population structure, and even consanguinity do not necessarily imply inbreeding depression (e.g. Grosberg 1987, Cohen 1990, Bishop & Ryland 1993, Jones et al 1994, McFadden 1997, Ayre & Miller 2006.…”

“…Our predictions on restricted dispersal in the species, based on its presumed philopatric larval behaviour , Mariani et al 2006, have been confirmed by autocorrelation statistics (Fig. 2), which detected the formation of pedigree structures.…”

“…Uriz et al 1998, Mariani et al 2006) but the extent of sponge sperm dispersal is unknown. Graft acceptance and rejection experiments indicate that clonality may be important in shaping the genetic structure of a sponge population (see Boury-Esnault & Solé-Cava 2003 for review).…”

“…The present study focuses on another encrusting sponge: Scopalina lophyropoda (Schmidt), which has an aggregated distribution (Blanquer 2007) and philopatric larval behaviour , Mariani et al 2006). …”

Diversity patterns and zoogeography of the Northeast Atlantic and Mediterranean shallow-water sponge fauna

“…Sponges are sessile in their adult stage and exhibit low dispersal capabilities during their larval stage, due to the production of lecithotrophic larvae with a short life span and philopatric behaviour (Mariani et al, 2005(Mariani et al, , 2006Maldonado, 2006;Uriz et al, 2008). As in many other marine organisms, the reproductive timing in sponges is highly correlated with water temperature (see Riesgo & Maldonado, 2008 and references therein).…”