Environmental factors related to the production of a complex set of spicules in a tropical freshwater sponge

Abstract

Adverse natural conditions will, generally, induce gemmulation in freshwater sponges. Because of this environmental dependence, gemmoscleres are given exceptional value in taxonomic, ecological and paleoenvironmental studies. Other spicules categories such as microscleres and beta megascleres have received little attention with regard to their occurrence and function during the sponge biological cycle. Metania spinata, a South American species common to bog waters in the Cerrado biome, produces alpha and beta megascleres, microscleres and gemmoscleres. To detect the environmental factors triggering the production of all these kinds of spicules, the species annual seasonal cycle was studied. Artificial substrates were devised, supplied with gemmules and placed in Lagoa Verde pond which contained a natural population of M. spinata. Field monitoring was conducted for eight months in order to observe the growth of sponges and spicules formation. Samples of water were taken monthly for physical and chemical parameters determination. The appearance of the alpha megascleres was sequentially followed by that of microscleres, gemmoscleres and beta megascleres. The first ones built the new sponge skeleton, the last three were involved in keeping inner moisture in the sponge body or its gemmules. The water level, temperature and the silicon (Si) concentration in the pond were the most important factors related to this sequential production of spicules, confirming environmental reconstructions based on the presence or absence of alpha megascleres and gemmoscleres in past sediments.

Volcanic, tectonic and climate controls on lacustrine sedimentary supplies over the last millenia in NE Chilean Patagonia (Lake Esponja, Aysen, 45°S)

“…The Si/Al values decrease after 75 cm would be related to less winter precipitation and therefore a reduced water input from the river and/or the watershed. Calm water conditions were favourable expansion of benthic diatoms, mainly Surirella, a genus that lives in shallow environments with high silica requirement (Matteuzzo et al, 2015). The predominance of benthic diatoms in the assemblage for the upper part of the core (Figure 6), added to sedimentological changes (Figure 2), could corroborate a main tectonic control, with lesser climatic control reflected in discrete variations in the relative abundance of benthic diatoms and the sudden occurrence of Aulacoseira spp.…”

“…DZ2a corresponds to an oligosaprophic, oligotrophic, very low alkalinity and calm conditions. The presence of gemmosclere and microsclere sponge spicules (<20%) observed between 70 and 80 cm is associated to seasonal fluctuations in lake level and high concentration of dissolved Si (Matteuzzo et al, 2015). The presence in sample DZ2b 55–65 cm of Aulacoseira records more turbid conditions due to sudden detrital inputs and nutrient availability in the lake.…”

Trends and Gaps in Scientific Production on Freshwater Sponges

“…In a generic context, there was a survey of the sponges assembly in the Central Amazon, where they were characterized by habitats (Batista et al 2003). Also noteworthy are studies on sponges as bioindicators of some coastal environments in South America (Volkmer-Ribeiro & Machado 2007), and with environmental factors related to the production of a complex set of spicules (Matteuzzo et al 2015).…”

Figure 3: Morphological diversity of selected marine sponge spicules.

“…Both, surface sediment spicules (Łukowiak, Pisera & O'Dea, 2013) and spicules from assemblages of coralligenous conglomerates (Bertolino et al, 2014(Bertolino et al, , 2017a(Bertolino et al, , 2017b(Bertolino et al, , 2019 were shown to reflect the living sponge communities to a good degree of accuracy and can be used, with some cautions, for reconstructing former sponge communities. In turn, Matteuzzo et al (2015) investigated the factors that influence the formation of spicules in freshwater sponges. They showed that the sequential production of a complex set of spicules (alpha megascleres followed by microscleres, gemmuloscleres and beta megascleres) in the neotropical freshwater sponge Metania spinata depends on the water level, temperature, and silicon concentration.…”