Environmental effects on the reproduction and fecundity of the introduced calcareous sponge Paraleucilla magna in Rio de Janeiro, Brazil

Abstract

The calcareous sponge Paraleucilla magna (Porifera, Calcarea) has been the subject of several studies in the last decade. It was first described along the Brazilian coast, where it is considered cryptogenic, and was subsequently found in the Mediterranean, where it is considered invasive. The wide artificial distribution of this species allows us to compare different aspects of the biology of an introduced species in different locations. Here, we analysed the effects of selected environmental parameters on the reproductive dynamics of P. magna in Rio de Janeiro (Brazil) over 18 months and compared our results with those obtained for the same species in the Mediterranean Sea. Specimens were collected monthly and analysed through histological methods. The density of reproductive elements in each month was calculated, and the effects of environmental parameters (photoperiod, precipitation, temperature, phytoplankton and bacterioplankton) were analysed using a regression tree analysis. Paraleucilla magna was reproductive throughout the study period. The densities of the reproductive elements (oocytes, embryos and larvae) showed no seasonality, and this species presented one of the highest reproductive efforts documented to date in the phylum Porifera (99.0 oocytes · mm−3; 89.0 embryos · mm−3; 319.0 larvae · mm−3). The main environmental parameters related to the reproduction of P. magna were temperature, photoperiod and bacterioplankton. Temperature was the main driver associated with the densities of oocytes and embryos, while bacterioplankton was the main driver of larvae (positive relationships). In Rio de Janeiro, larvae were present and continuously released. This strategy is different from that observed in the Mediterranean, where a larger larval output was observed but only during the summer months. Our results show that P. magna is a species with a strong invasive potential, considering its high and continuous reproductive effort. This high fecundity stimulated by high temperatures may be a key factor contributing to the growth of P. magna populations and its invasion of new areas.

V. Gerovasileiou et al.: New Mediterranean Biodiversity Records (July, 2017)

“…magna demonstrates a very high reproductive effort among Porifera and while in Brazil larvae are continuously released year-round, in the Mediterranean they are released mainly in summer but in higher numbers (Lanna et al, 2015). This high fecundity might be related with a strong invasive potential probably stimulated by high temperatures (Lanna et al, 2015), which can explain the spreading success of this species in the Mediterranean Sea. Simple presence records of alien species, although being useful as indicators of species distribution ranges, do not provide quantitative information on the status of their populations.…”

The presence of the diagnostic character of the genus Paraleucilla (Amphoriscidae, Calcarea, Porifera) may depend on the volume and body wall thickness of the sponges

“…We cannot exclude the possibility that other environmental variables not analyzed here may influence the presence or absence of the DZ, as mentioned above, but since the fluctuations of these parameters are usually related to the period of the year in the area where samples were obtained (see Lanna et al. ) and since month was not related to variation in the presence of DZ (see Table ), such relationships are probably not strong.…”

“…,b; Lanna et al. ), most studies dealing with Paraleucilla species are about classical taxonomy, containing descriptions of new species based on the characterization of skeletal organization, and the size and shape of the spicule categories, from a single or a limited set of individuals (Lanna et al. ; Cavalcanti et al.…”

“…There is an increasing effort towards understanding the biology of this species, resulting in P. magna being one of the best studied calcareous sponges (e.g., Lanna et al. , ; Longo et al. , ; Cavalcanti et al.…”

“…Currently, Paraleucilla is composed of 12 accepted species, occurring mainly in circumtropical waters (Cavalcanti et al 2014;Klautau et al 2016). With the exception of Paraleucilla magna KLAUTAU, MON- TEIRO, & BOROJEVIC 2004(e.g., Longo et al 2012Cavalcanti et al 2013a;Padua et al 2013a,b;Lanna et al 2015), most studies dealing with Paraleucilla species are about classical taxonomy, containing descriptions of new species based on the characterization of skeletal organization, and the size and shape of the spicule categories, from a single or a limited set of individuals (Lanna et al 2009;Cavalcanti et al 2014). Therefore, little is known about any aspect of the biology of the representatives of this genus and family as a whole.…”