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Contribution to the ecology of the sponge Suberites domuncula (Olivi, 1792): Cox1 gene population and colour analyses

Focusing on the Adriatic Sea, past research of sponge diversity provided illustrative descriptions decisive for a systematic compilation. Suberites domuncula (Olivi, 1792) (Porifera, Demospongiae, Tetractinomorpha, Hadromerida, Suberitidae) was originally described from the Adriatic Sea, but subsequently was widely recorded from all over the world. Due to a small amount of discriminatory morphological characteristics it was suggested that this widespread occurrence is an artefact. Consequently, worldwide known S. domuncula should be a complex of similar but different sponge species. Suberites domuncula is generally found on muddy sand bottoms between 5-40 m in the northern Adriatic Sea, but can occur down to 200 m of depth in the Mediterranean Sea. As S. domuncula is in an almost obligatory symbiosis with a hermit crab, the sponge obtains certain mobility and unknown seasonal migration which can affect gene population analyses. During collection of biological material by means of bottom trawls and SCUBA diving, we observed S. domuncula specimens of different colour patterns living at the same time and site together. The red- orange coloured specimens were dominant (cca 85% abundance), with unpredictable appearance of differently colored specimens (blue, yellow, brown, white, as well as combinations of them). Therefore, the present research was directed towards the study of sponge colour source and pigment origin, followed by specimen identification and barcoding population analysis using mitochondrial cox gene. Specimens of S. domuncula were collected at two distinct areas: 2 km off Rovinj westwards and at site in front of Umag (7 km, open sea), northern Adriatic, Croatia. By solvent extraction (water/chloroform) we separate blue and red colour. The red chloroform fraction was identified as β-carotene by spectrometry analyses comparing spectra (300-700 nm), and blue colour was separated by acetone precipitation, and SDS PAGE. The protein analyses and sequencing (MALDI) are underway. Beside sponge reversible contraction, different colours probably also have an adaptive, stress- protective function with far-reaching consequences on the life of S. domuncula specimens in situ. Ex situ, in aquaria with artificial seawater, after certain time (several months) sponges lose their colour and body mass, (food restriction, absence of phytoplankton and carotene, adequate lightening). The population analysis of cox1 gene was applied as tool for sponge specimens’ identification (barcoding) and determination of possible haplotypes abundance. The red and blue S. domuncula morphs were proved as single species by sequencing and DNA analyses (blastn, NCBI), with few haplotypes at both sampling sites.

Suberites domuncula, Cox1 gene population

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