Reproductive cycles of the oviparous sponges Cinachyrella apion (Spirophorida) and Tethya maza (Tethyida) in a tropical intertidal environment

Abstract

Environmental factors are constantly changing in the intertidal region. Consequently, the various benthic organisms that densely colonize this ocean area had to adapt to these constant changes. Reproductive strategy might be considered one of these adaptations. However, knowledge about this aspect of the biology of marine invertebrates is still contentious for some groups, especially with regard to sponges (Porifera). Here, we investigated the effects of different environmental factors on the timing and effort of sexual and asexual reproduction in Cinachyrella apion and Tethya maza, two oviparous demosponges in Salvador, Bahia, Brazil. We analyzed the influence of humidity, atmospheric temperature, seawater temperature, photoperiod, rainfall, height of low tides, and chlorophyll-a concentration on the density and size of oocytes and buds of these sponges. Both species reproduced aperiodically.Cinachyrella apion had a maximum 2.8 ± 4.04 oocytes/mm 2 and 0.73 ± 0.15 buds/ mm 2 , whereas T. maza had a maximum 6.0 ± 12.21 oocytes/mm 2 and 0.31 ± 0.13 buds/mm 2 . The density of oocytes in C. apion was positively influenced by chlorophyll-a concentration, whereas that of T. maza was negatively modulated by relative humidity. We did not observe any relationship between the environmental factors and bud density in C. apion, but bud density variation in T. maza was positively related to chlorophyll-a concentration and to seawater temperature. It seems that individuals of both species alternated between the production of sexual and asexual propagules, suggesting a trade-off between reproductive modes. Therefore, asexual and sexual reproduction seems to impact population growth and reproduction of both species, likely contributing to the recruitment of new sponges. In tropical intertidal regions, multiple environmental factors seem to contribute more to determining the quantity of sexual and asexual reproductive elements rather than the species' reproductive period.

Ultrastructure of oogenesis in two tropical oviparous Demospongiae (Porifera): Cinachyrella apion and Tethya maza

“…C. apion and T. maza are oviparous and are most likely gonochoric because we could find no spermatic cysts co-occurring with oocytes in active reproductive specimens (Vasconcellos & Lanna, 2022) The gonochorism/oviparity, as well as hermaphroditism/viviparity, were strongly correlated in sponges, similarly, to that observed in cnidarians (Kerr et al, 2011;Riesgo et al, 2014). Hermaphroditism and viviparity seem to be ancestral traits in poriferans, especially within class Demospongiae, with several independent acquisitions of gonochorism and oviparity in different orders, such as Tetractinellida and Tethyida (Riesgo et al, 2014).…”

“…C. apion is an oviparous species with no clear periodic oogenesis (see details in Vasconcellos & Lanna, 2022). We could not find any sign of spermatogenesis in the specimens analyzed during the study, but the presence of buds (asexual reproduction) in some specimens was usually observed (Figure 1a).…”

“…Tethya maza is an oviparous species that also (at this location, at least) lacks a clear reproductive period (see details in Vasconcellos & Lanna, 2022). As for C. apion , we could not detect any spermatic cyst in this species, but it was possible to observe buds (asexual reproduction) around the sponge body (Figure 1b).…”

“…The ecological advantages of viviparity in colonies or animals with high surface areas are related to ventilation of brooded embryos, once oxygen is a limiting factor for egg masses and embryos in marine invertebrates. This could be one of the reasons for the acquisition of oviparity in C. apion and T maza , as both species are spherical and have a maximum of 2.2 cm and 1.6 cm of diameter, respectively (Riesgo et al, 2014; Strathmann, 1986; Vasconcellos & Lanna, 2022).…”

“…In both species, the individuals either reproduced sexually or asexually (by production of buds). These species are abundant in the study region and produce oocytes aperiodically and in high quantities throughout the year (Vasconcellos & Lanna, 2022). To detect the presence of gametes, 10 fragments (ca.…”