Abstract
Neuropeptides are mediators of neuronal signalling, controlling a wide range of physiological processes that cut across many organisms. GFSKLYFamide is a neuropeptide that belongs to the Echinoderm SALMFamide group of peptides. This study was aimed at determining the expression of GFSKLYFamide-like neuropeptide in the female gonad of the sea cucumber Holothuria scabra. Ten female H. scabra weighing between 62 and 175 g were collected at different times between May, 2009 and April, 2010 from the Andaman Sea at Koh Jum Island in Krabi province of Thailand for the study. Using GFSKLYFamide polyclonal antibody and Alexa 488-conjugated goat anti-rabbit IgG as primary and secondary antibodies, respectively, indirect immunofluorescence method and confocal microscope was used to localise GFSKLYFamide-like immunoreactivity in the female gonad of H. scabra. The results show GFSKLYFamide-like immunoreactivity being expressed in the sub-epithelial fibres of the coelomic epithelium. This is the first report providing evidence of GFSKLYFamide neuropeptide existence in the female gonad of H. scabra. It was suggested that further studies be carried out to investigate if there is similar existence of GFSKLYFamide neuropeptide in male gonad of H. scabra and also to know the structure or activity of the peptide(s) producing GFSKLYFamide-like immunoreactivity in H. scabra gonads. Key words: GFSKLYFamide, SALMFamides, immunoreactivity, sea cucumber, echinoderm, gonad.
Highlights
Neuropeptides have been known to play a crucial role in mediating several physiological processes in animals (Ajayi and Withyachumnarnkul, 2015; Semmens and Elphick, 2017)
From the result, it was observed that the lumen (L) of the gonad was almost empty except for few previtellogenic oocytes (PO) lying within the germinal epithelium of the gonad (Figure 3)
This result is similar to an earlier report in H. glaberrima where it was observed that the coelomic epithelium and sub-epithelial fibres of both male and female gonads of H. glaberrima expressed GFSKYLFamide-like immunoreactivity (DiazMiranda et al, 1995)
Summary
Neuropeptides have been known to play a crucial role in mediating several physiological processes in animals (Ajayi and Withyachumnarnkul, 2015; Semmens and Elphick, 2017). Phe-Ser-Lys-Leu-Tyr-Phe-NH2) is a heptapeptide first isolated in the sea cucumber Holothuria glaberrima (DiazMiranda et al, 1992) It belongs to the Echinoderm SALMFamide group of peptides and like many other. Neuropeptides in this family, GFSKYLFamide is believed to play a crucial role in some physiological processes those involving muscular relaxation (Melarange et al, 1999; Elphick and Melarange, 2001). The sea cucumber, Holothuria scabra that is known as sandfish belongs to the Echinoderm phylum in the class of Holothuroidea, of the order Aspidochirotida and in the family of Holothuriidae. It is a tropical sea cucumber species that is overexploited due to its commercial value (Conand 1998; Purcell et al, 2012)
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