Behavior and development of larvae in the sponge Haliclona amboinensis

Abstract

Sponges play important roles in marine ecosystems by contributing to habitat complexity and benthopelagic coupling of nutrients. Yet, the reproduction and settlement behaviors of diverse sponge species are not well understood. Here, we examined the brooding demosponge Haliclona amboinensis, which is common on shallow reefs in Bolinao, northwestern Philippines. Gravid sponges were found between the months of May and August, coinciding with warmer sea surface temperature. Sponges released parenchymella larvae from brood chambers in the mid‐morning, suggesting that light and temperature may serve as cues to initiate hatching. Larvae immediately swam toward the surface upon emergence and migrated to the bottom of the tanks 1–2 hr after release. The presence of light and crustose coralline algae induced high larval settlement. Metamorphosis proceeded rapidly in vitro, with larval cells spreading laterally on the substrate. The osculum was first visible at 3 days after settlement. The short pelagic duration of larvae in H. amboinensis promotes local recruitment and may be important for the maintenance of sponge populations in the face of disturbances.

Reproduction and early life stages of the poecilosclerid sponge Crella incrustans

“…The non-tufted parenchymellae of C. incrustans, between 12 and 24 h old, showed no evidence of photosensitivity when exposed to a light source of 2300 lm. In tropical waters light cues are thought to have an important role in release and settlement of larvae (Nada et al, 2020) and also in regulating larval chemoreception (Say & Degnan, 2020). The natural habitat of The posterior pole of the larva of C. incrustans was characterized by an internal aggregation of spicules.…”

The role of photobehaviour in sponge larval dispersal and settlement

“…Other studies document temporal phototactic behavioural responses for sponge larvae [39], interpreted as being a contributor to larval dispersal (40), but these studies focus on experiments using white light. Brooded sponge larvae are commonly released during daylight hours and can be planktonic for hours to days [18,40,52,[56][57][58][59][60]. Sponge larvae are weak swimmers and unlikely to disperse effectively when exposed to hydrodynamics [61] but the use of light to guide navigation may assist dispersal via vertical migration, as is suggested for several invertebrate larvae, including sponges [40,62].…”