Morphological and genetic differences in ecologically distinct populations of Petrosia (Porifera, Demospongiae)

High microbiome and metabolome diversification in coexisting sponges with different bio-ecological traits

Marine Porifera host diverse microbial communities, which influence host metabolism and fitness. However, functional relationships between sponge microbiomes and metabolic signatures are poorly understood. We integrate microbiome characterization, metabolomics and microbial predicted functions of four coexisting Mediterranean sponges -Petrosia ficiformis, Chondrosia reniformis, Crambe crambe and Chondrilla nucula. Microscopy observations reveal anatomical differences in microbial densities. Microbiomes exhibit strong species-specific trends. C. crambe shares many rare amplicon sequence variants (ASV) with the surrounding seawater. This suggests important inputs of microbial diversity acquired by selective horizontal acquisition. Phylum Cyanobacteria is mainly represented in C. nucula and C. crambe. According to putative functions, the microbiome of P. ficiformis and C. reniformis are functionally heterotrophic, while C. crambe and C. nucula are autotrophic. The four species display distinct metabolic profiles at single compound level. However, at molecular class level they share a "core metabolome". Concurrently, we find global microbiome-metabolome association when considering all four sponge species. Within each species still, sets of microbe/metabolites are identified driving multi-omics congruence. Our findings suggest that diverse microbial players and metabolic profiles may promote niche diversification, but also, analogous phenotypic patterns of "symbiont evolutionary convergence" in sponge assemblages where holobionts co-exist in the same area.

Comparative structural morphometry and elemental composition of three marine sponges from western coast of India

Three marine sponges Halichondria glabrata, Cliono lobata, and Spirastrella pachyspira from the western coastal region of India were compared for their morphometry, biochemical, and elemental composition. One-way analysis of variance was applied for spicule morphometry results. Length, width, and length:width ratio were calculated independently. The ratio of length:width varied from 35 to 42 among the grown samples, which remained in the range of 10-22 in young sample at the beginning of studies. However, no significant change was observed in spicule width compared to length. Elemental compositions of marine sponges were determined by field emission gun-scanning electron microscope. Scanning electron microscopy data revealed that the spicules of all the three sponges were mostly composed of O (47-56%) and Si (30-40%), whereas Al (14.33%) was only detected in the spicules of C. lobata. Apart from these, K, Ni, Ca, Fe, Mg, Na, and S were additionally detected in all the three samples. Presence of heavy metals in the sponges was analyzed by inductively coupled plasma-atomic emission spectroscopy. Results showed that iron was present in a large amount in samples, followed by zinc, lead, and copper.

Sponge ecology in the molecular era

Knowledge of the functioning, health state, and capacity for recovery of marine benthic organisms and assemblages has become essential to adequately manage and preserve marine biodiversity. Molecular tools have allowed an entirely new way to tackle old and new questions in conservation biology and ecology, and sponge science is following this lead. In this review, we discuss the biological and ecological studies of sponges that have used molecular markers during the past 20 years and present an outlook for expected trends in the molecular ecology of sponges in the near future. We go from (1) the interface between inter- and intraspecies studies, to (2) phylogeography and population level analyses, (3) intra-population features such as clonality and chimerism, and (4) environmentally modulated gene expression. A range of molecular markers has been assayed with contrasting success to reveal cryptic species and to assess the genetic diversity and connectivity of sponge populations, as well as their capacity to respond to environmental changes. We discuss the pros and cons of the molecular gene partitions used to date and the prospects of a plentiful supply of new markers for sponge ecological studies in the near future, in light of recently available molecular technologies. We predict that molecular ecology studies of sponges will move from genetics (the use of one or some genes) to genomics (extensive genome or transcriptome sequencing) in the forthcoming years and that sponge ecologists will take advantage of this research trend to answer ecological and biological questions that would have been impossible to address a few years ago.

'A posteriori' searching for phenotypic characters to describe new cryptic species of sponges revealed by molecular markers (Dictyonellidae : Scopalina)

Cryptic speciation is repeatedly reported in sponge taxonomic studies. Most of the cryptic species, which were revealed by molecular markers, have never been formally described owing to the difficulty in finding diagnostic phenotypic characters. A previous molecular study revealed four genetically distinct species that had been misidentified as Scopalina lophyropoda Schmidt. One species was S. lophyropoda sensu stricto, whereas the other three were new species. Here, the three new species are formally described after careful searching for discriminatory phenotypic characters. The new species are Scopalina blanensis, sp. nov. from the north-western Mediterranean, S. ceutensis, sp. nov. from the Mediterranean coasts of Africa (Atlantic waters) and S. canariensis, sp. nov. from the Canary Islands, Atlantic Ocean. All of them are at first sight morphologically similar and inhabit shallow environments with resuspended sediment. However, a closer examination allowed us to find some differential features: e.g. the amount of spongin embedding the spicules, the degree of complexity of the skeletal tracts, the size and curvature of the styles, the growth habit and the colour tinge. Furthermore, an identification key to the Atlanto-Mediterranean Scopalina species is presented. The differences between the genera Scopalina, Ulosa and Dictyonella are also discussed.