The systematics of the poriferan Order Haplosclerida (Class Demospongiae) has been under scrutiny for a number of years without resolution. Molecular data suggests that the order needs revision at all taxonomic levels. Here, we provide a comprehensive view of the phylogenetic relationships of the marine Haplosclerida using many species from across the order, and three gene regions. Gene trees generated using 28S rRNA, nad1 and cox1 gene data, under maximum likelihood and Bayesian approaches, are highly congruent and suggest the presence of four clades. Clade A is comprised primarily of species of Haliclona and Callyspongia, and clade B is comprised of H. simulans and H. vansoesti (Family Chalinidae), Amphimedon queenslandica (Family Niphatidae) and Tabulocalyx (Family Phloeodictyidae), Clade C is comprised primarily of members of the Families Petrosiidae and Niphatidae, while Clade D is comprised of Aka species. The polyphletic nature of the suborders, families and genera described in other studies is also found here.

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Recent molecular studies have shown that the sponge order Haploslcerida is polyphyletic as the freshwater sponges appear to be more closely related to other demosponges than they are to the marine haplosclerids. Within the marine haplosclerid clade relationships viewed via 18S and 28S rRNA gene phylogenies suggest that the suborders and many families and genera are also polyphyletic. However, both of these genes are on the same locus and do not evolve completely independently. We have analysed mitochondrial Cytochrome oxidase 1 gene fragments from 44 species of marine Haplosclerida and show conclusively that the classification of this group needs complete revision. Molecular data show a very complicated phylogeny supporting very few morphological hypotheses and little geographical pattern. However, the molecular data contain a great deal of phylogenetic signal at many taxonomic levels and support phylogenies drawn from the other genes.

The gametogenic cycle of Scrobicularia plana was studied in Mweeloon Bay (Galway, west coast of Ireland) over the periods of February to September 1996 and January to September 1997. Quantitative (reproductive indices and oocytes size) and qualitative (gonad developmental stages) analysis identified a broad annual breeding cycle, with one protracted spawning event occurring from May until September. Early gonad development had begun by January/February. Spawning animals were first recorded at the end of May and continued to mature throughout the summer. The decrease in temperature in September coincided with the end of the spawning season and gonad regression. Although the species is predominantly dioecious, one case of hermaphrodism was recorded. A female to male sex ratio of 1.1:1 was registered. Sexual maturity occurred at a shell length greater than 20 mm; the smallest individual undergoing sexual development had a shell length of 22.4 mm. The timing of the reproductive cycle in S. plana at Mweeloon Bay is in broad agreement with previous findings on the species carried out in northern latitudes.

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