Chapter 8 - Phylum Porifera

Abstract

Freshwater sponges, at present considered monophyletic, belong to the suborder Spongillina (Demospongiae, Haplosclerida) and date back to Paleozoic and Mesozoic. Spongillina consists of seven families containing 47 genera, and 238 species with a geographic range from widespread to sensu stricto endemic. Growth form varies from encrusting to massive and branched; color from green to pale or dark brown, and consistency from soft to hard firm or fragile. Skeletal network is pauci- to multi-spicular, alveolate to reticulate with a variable amount of spongin. Skeleton spicules are smooth or variably ornated megascleres ranging from oxeas to styles and strongyles. Microscleres, usually present, are oxeas, strongyles, aster-like, pseudobirotules. Gemmules, when present, are spherical to ovoid with a protective theca. Gemmular theca, typically bi- or tri-layered, usually bears a pneumatic layer and it is armed by gemmuloscleres. Gemmuloscleres are boletiform (tubelliform), parmuliform, pseudobirotules, oxeas, strongyles, birotules, pseudobirotules, club-like, botryoidal. Gemmules functional role is as resistant or dispersal bodies. Larvae are always parenchymella. The present is work is a relatively critical synthesis of the literature, however, a critical phylogenetic revision of established taxa is still in progress.