Temperature cues gametogenesis and larval release in a tropical sponge

Determining the reproductive processes of benthic invertebrates is central to our understanding of their recruitment and population dynamics. Sexual reproduction of the gonochoric and viviparous Great Barrier Reef sponge, Luffariella variabilis (Poléjaeff 1884) was quantified from histological samples collected over two reproductive seasons (2004 and 2005). Gametogenesis commenced for females at a water temperature of 21°C, the lowest water temperature of the year. Spermatogenesis occurred above 22.5°C with sperm asynchronously developed and released from August or September to October. Oocytes developed asynchronously from July to September, embryos from September to December, and larvae from November to December. Female reproduction terminated in December (after larval release) prior to the highest mean annual water temperature of 30°C in January. There was a significant (35%) decrease in female reproductive output in 2005 compared to 2004, as measured by the reproductive index (0.68 ± 0.12 female reproductive propagules mm−2 of mesohyl in 2005 compared with 1.05 ± 0.10 mm−2 in 2004). This corresponded with delayed oogenesis and spermatogenesis, and a shortened larval development cycle corresponding with a delayed minimum temperature (21°C) in August of 2005 compared with July 2004. Accordingly, the maximum percentage of the mesohyl occupied by female reproductive propagules (eggs, embryos and larvae) was also reduced by 60% in 2005 (overall mean of 13.04% in October 2004 compared with 5.35% in October 2005). However, the mean sizes of individual female propagules remained the same from year to year. Males in contrast, showed no overall difference in either reproductive index or percentage occupation of the mesohyl between 2004 and 2005. The lowered reproductive output (∼35%) of females of L. variabilis associated with delayed minimum water temperatures may have important implications for population reproductive success where oogenesis and spermatogenesis and larval release are cued by minimum and maximum water temperatures, respectively

Sexual reproduction of the brooding sponge, Rhopaloeides odorabile

Sexual reproduction of Rhopaloeides odorabile, a common Great Barrier Reef sponge, was quantified using histological sections from samples collected over two reproductive seasons. Rhopaloeides odorabile is viviparous and gonochoristic with a male biased sex ratio (2.5:1). Commencement and cessation of gametogenesis coincides with rising and falling sea surface temperatures (≈24–29°C). Spermatogenesis occurs from October until January. Females initiate oogenesis in September with the asynchronous development of oocytes, embryos and larvae occurring within the brood chambers. A larval release period of 5–6 weeks occurs during January and February. The minimum size of reproductive individuals was 176 cm3 for females and 192 cm3 for males. The total reproductive output for both sexes shows a positive correlation with size. A relative reproductive output index quantified the maximum reproductive investment at approximately 1 and 3% of the total choanoderm for females and males, respectively, which represents a lower range of reproduction in comparison to other viviparous sponges. Low reproductive output in R. odorabile may be offset by an extended spawning period, alleviating the risk of releasing larvae in potentially adverse conditions via one synchronised spawning event and increasing overall larval survival

Environmental Impacts of an Alien Kelp Species (Undaria pinnatifida, Laminariales) along the Patagonian Coasts

Undariapinnatifida(Harvey) Suringar was recorded in Argentina for the first time in December 1992. Since then, it shows an invasive and competitive behavior, spreading quickly from the initial focus and increasing its population density. The first individuals were found attached to the port of Puerto Madryn, suggesting that the vector of introduction was the ballast water of cargo ships arriving to Golfo Nuevo from overseas. Since U. pinnatifidawas recorded, it has been spreading along the Argentina coasts, extending its range within and outside Golfo Nuevo, along the coasts of Argentina from Puerto Deseado (Santa Cruz province) to Mar del Plata (Buenos Aires province) far as 1850 kilometers from each other. The invasive condition of this species creates an awareness of the effects inflicted upon the indigenous biodiversity of this region, as well as, on the commercially-important benthic community structure. Moreover, the detachment of subtidal algae, especially during the summer, and its deposition upon the beach, have altered the sedimentary balance along the overall transverse beach profile. This effect, in addition with algal extraction by trucks mainly during tourist seasons, may increase beach erosion processes along Patagonian coasts.Fil: Bunicontro, Maria Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Marcomini, Silvia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Casas, Graciela Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin