Prey capture and digestion in the carnivorous sponge Asbestopluma hypogea (Porifera: Demospongiae)

Abstract

Asbestopluma hypogea (Porifera) is a carnivorous species that belongs to the deep-sea taxon Cladorhizidae but lives in littoral caves and can be raised easily in an aquarium. It passively captures its prey by means of filaments covered with hook-like spicules. Various invertebrate species provided with setae or thin appendages are able to be captured, although minute crustaceans up to 8 mm long are the most suitable prey. Transmission electron microscopy observations have been made during the digestion process. The prey is engulfed in a few hours by the sponge cells, which migrate from the whole body towards the prey and concentrate around it. A primary extracellular digestion possibly involving the activity of sponge cells, autolysis of the prey and bacterial action results in the breaking down of the prey body. Fragments of the prey, including connective cells and muscles, are then phagocytosed and digested by archaeocytes and bacteriocytes. The whole process takes 8-10 days for a large prey. This unique feeding habit implies the capture and digestion of a macro-prey without any digestive cavity. It would appear to be an adaptation to life in deep-sea oligotrophic environments. Carnivorous sponges provide actual evidence, through a functional example, that a transition is possible from the filter-feeder poriferan body plan towards a different organizational plan through loss of the aquiferous system, a transition that has been hypothesized for the early evolution of Metazoa.

Cell death and renewal during prey capture and digestion in the carnivorous spongeAsbestopluma hypogea(Porifera: Poecilosclerida)

“…As described by Vacelet and Duport (Vacelet and Duport, 2004), the capture of prey induces a drastic shortening and regression of the filaments (Fig.2A, Fig.3A, Fig.4B). The digestion lasts a variable number of days according to the size and number of prey, after which the filaments regenerate and extend again (Fig.4A).…”

“…During regression, some cells die, especially spiculocytes and spongocytes, due to the elimination of megasclere spicules and anisochele microscleres of the filament skeleton. Other cells migrate towards the prey and differentiate as digestive cells (Vacelet and Duport, 2004).…”

“…Carnivorous sponges are a unique example of metazoans digesting macroprey without any digestive cavity. This implies that cells, likely responding to a presently unknown signal, migrate toward the prey in order to degrade and digest it (Vacelet and Duport, 2004). These sponges represent a fascinating evolution of the body plan among poriferans.…”

Screening of Bioactive Compounds From Unknown Marine Sponges Collected From Kovalam, Chennai

“…Very less proportion of marine species has been studied [2]. Sponges (phylum porifera) are marine invertebrates, known to be multicellular and immobile but sessile [3]. These are a vital source for the researchers to look for novel bioactive compounds [4].…”

Isolation and cultivation of fungal strains from in vitro cell cultures of two marine sponges (Porifera: Halichondrida and Haplosclerida)

“…Of the different organisms, bacteria are the most thoroughly investigated and usually reported as participating in the chemical defenses or physiological processes of their hosts (32,35,37).…”