The genera Spongia and Hippospongia include all of the commercially important bath sponges of the Caribbean fishery. This study examined the uniform presence of immense symbiotic bacterial populations of four of these species: Hippospongia lachne, Spongia barbara, S. cheiris and S. graminea. The nutritional characteristics and antibiotic sensitivities of bacteria isolated from the four species were also examined. A combined light and transmission electron microscopic investigation outlined the reproductive processes and larval development, behaviour, settlement and metamorphosis in these four species. / Symbiotic bacteria in these four sponge species are specific to the sponges and different from ambient seawater bacteria. Populations of intercellular bacteria within the tissues of these sponges are greater than those of ambient seawater. A variety of morphologically different types of sponge specific bacteria were observed. The symbionts are not fastidious organism but utilize a variety of amino acids, carbohydrates and tricarboxylic acid cycle intermediates as sole carbon and energy sources for growth. The bacteria showed sensitivities to a variety of antibiotics but were not susceptible to fluid from the sponges. / These sponges are viviparous and probably dioecious. Egg production and larval development are localized in patches or "nurseries" of endosomal tissue. Statistical analyses of specific morphological characteristics of female reproductive elements have identified four specific stages in the process of oogenesis. Umbilici connect young and maturing embryos to the maternal mesohyl and are the pathway for extracellular transfer of intercellular symbiotic bacteria and other mesohyl substances. These bacteria were observed in the embryos and larvae of all four species. Oocytes and embryos develop asynchronously within a given individual. Spermatogenesis occurs synchronously within cysts by transformation of entire choanocyte chambers. Cysts develop asynchronously within an individual. Male gametes exhibit a bright yellow-white autofluorescence when excited with blue light (460-485 nm). Spermatozoa do not possess intermediate segments or acrosomes. / The incubated parenchymella larvae of these four species are ovoid with dark grey pigmentation and enlarged posterior regions encircled by a black pigmented ring of cells bearing long cilia. Laboratory behavioural studies indicate that free-swimming larvae display directional swimming with constant rotation and negative phototaxis. Larval behaviour probably reflects the ecological situation of adult populations. Larval settlement occurs 26-56 hours after release and involves the rapid formation of a basal lamella between the larvae and substrate. There is no evidence of substrate selection or orientation by larvae. Precocious development of choanocytes does not occur in the larvae or post-larvae of these four species.

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