Pluri-annual study of the reproduction of two Mediterranean Oscarella species (Porifera, Homoscleromorpha): cycle, sex-ratio, reproductive effort and phenology

Abstract

This study presents the phenology of two common Mediterranean sponges belonging to the genus Oscarella (Porifera, Homoscleromorpha). Oscarella tuberculata and Oscarella lobularis are two sibling species, dwellers of shallow benthic communities which tend to have distinct ecological behavior, respectively, euryecious and rather stenoecious. The comparative study of their reproductive cycle showed that both Oscarella species have a seasonal reproductive cycle with a successive phase duration differing from one species to another. In both species, there is a continuous oogenesis, with new oocytes appearing in spring, whereas the spermatogenesis generally starts later with the early warming of the sea. The embryonic development and the larval release are restricted to the warmest months of the year. We also observed a shift in the period of gametogenesis and larval emission depending on species and differences in their sensitivity to changes in thermal regime. It appears that an increase in seawater temperature can affect sex determination, with mainly a shift toward males in both species. Their reproductive efforts are variable in time, and can be in some cases influenced by the temperature regime. This is especially the case of O. lobularis which seems to be the most thermosensitive, its phenology responding significantly to changes in thermal regime, whereas O. tuberculata seems to be less sensitive and/or reactive. By detecting phenological changes among sponges, this study demonstrated the relevance of such monitoring to assess the possible biological response to climate change. Communicated by M. Byrne.

Systematics and Molecular Phylogeny of the Family Oscarellidae (Homoscleromorpha) with Description of Two New Oscarella Species

“…This is also corroborated by the presence of diagnostic positions in both mt DNA markers for each species (Figure S3). Cell composition [12], symbiotic microbe diversity [21], as well as life history traits such as sex ratios and reproductive cycles, also differ between O. lobularis and O. tuberculata, consistent with the presence of two distinct species [14]. Concerning color polymorphism, the type species O. lobularis displays not only the classical purple/ivory color arrangement but can also be blue, pink and purple.…”

“…Recent studies have found soft specimens of Oscarella which do not have the habitual purple/ivory coloring, but which are blue, entirely purple or pink. Similarly, cartilaginous specimens of Oscarella may also be purple or pink in addition to the green, blue and yellow morphotypes [13], [14]. Subsequent, finer histological studies revealed additional differences among various color morphs of Oscarella, and the ‘cosmopolitan’ O. lobularis turns out to be different species (10 new species of Oscarella have been described during the last 20 years) [15], [16], [17], [18].…”

“…The relationships among these 17 Oscarella species and the phylogenetic position of Pseudocorticium jarrei relative to them are also largely unknown [6]. In addition, the relationships between the different color morphs of the two putative sibling species O. lobularis and O. tuberculata [14] have not yet been fully resolved and more loci from more color morphs are needed to elucidate them. This is crucially important, especially because O. lobularis is being developed as a new model species for evo-devo studies [13], [22], [23], [24], [25].…”

Asexual and puzzling sexual reproduction of the Mediterranean sponge Haliclona fulva (Demospongiae): life cycle and cytological structures

“…Despite the large number of specimens of H. fulva investigated, no spermatocysts were observed. A very low ratio of male: Female individuals has been reported for many marine sponges (Hogg 1967;Scalera Liaci et al 1971;Ayling 1980;Corriero et al 1996;Corriero et al 1998;Mercurio et al 2007;Ereskovsky et al 2013). For example, after 2 years of fortnightly monitoring, Ayling (1980) found males of Aaptos aaptos (SCHMIDT 1864) in only 1 year of the study.…”

“…; Ereskovsky et al. ). For example, after 2 years of fortnightly monitoring, Ayling () found males of Aaptos aaptos ( Schmidt 1864) in only 1 year of the study.…”