Abstract

Successful chondrichthyan reproduction in aquaria is indispensable for ex situ conservation programs.¹ However, conventional sperm analyses do not provide comprehensive insights into functional sperm competence. Employing proteomics analysis on spermatozoa and seminal plasma proteins significantly enhances the current knowledge of sperm composition. This approach not only reveals valuable information about protein biomarkers related to fertility, but also enhances the roles that these proteins play in the male reproductive tract, facilitating the identification of novel biomarkers for sperm quality.^2-3

The objective of the study is to identify and describe the largest number of proteins present in small-spotted catshark (Scyliorhinus canicula) seminal plasma and spermatozoa, with specific focus on their relevance to reproductive processes.^4-5 As the ultimate goal, this study centers on comparing S. canicula groups (aquarium and wild) to gain a deeper understanding of the origin and function of sperm proteins in both environments, and the underlying reproductive adaptations in aquarium sharks.

To do this, pooled samples from 35 male individuals of S. canicula, including seven aquarium sharks from the Oceanogràfic València and 17 from the wild, obtained from bycatch by local fisherman, were analysed. Proteins were studied using mass spectrometry and data was processed with ProteinPilot v 5.0. A list containing gene symbols corresponding to each protein was then submitted to DAVID. Through this methodology, a total of 305 proteins in seminal plasma and 535 proteins in spermatozoa were identified, with 89 proteins found to be common to both spermatozoa and seminal plasma. Additionally, differential proteins were also identified, comprising 107 in spermatozoa and one in seminal plasma (adenosylhomocysteinase), most of which were newly identified in fish. Their functional roles were underscored through Gene Ontology enrichment analysis, highlighting their association with oxidoreductase activity. KEGG analysis revealed their connections with metabolic pathways and carbon metabolism.

This study, for the first time, characterizes the differences in semen (seminal plasma and spermatozoa) protein composition between aquarium and wild in S. canicula. It not only advances our fundamental understanding of their protein composition, but also sheds light on their potential reproductive roles, providing an initial proteome database for seminal plasma and spermatozoa. Identified protein modifications within both populations highlight the need for additional research to explore the relationship between diverse proteins and different environmental cues in aquarium sharks, ultimately influencing their reproductive success.

Acknowledgements

The authors are grateful to the Avanqua-Oceanogràfic and Fundación Oceanogràfic staff, especially to the aquarists and veterinarians for their assistance with animal care in aquarium animals, and the local fishermen for providing wild animals.

Literature Cited

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5.  Jeanne F, Bernay B, Sourdaine P. Comparative proteome analysis of four stages of spermatogenesis in the small-spotted catshark (Scyliorhinus canicula), using high- resolution NanoLC-ESI-MS/MS. J Proteome Res. 2023;22(7):2477–2492.