El-Sokkary SG et al. (2023), Influences of habitat and seasonal changes on g...

ECB-ART-51696

Environ Monit Assess 2023 Aug 24;1959:1088. doi: 10.1007/s10661-023-11713-9.

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Influences of habitat and seasonal changes on gonadal maturation of Echinometra mathaei (Echinodermata: Echinoidea) and Tridacna squamosa (Mollusca: Bivalvia) in the Red Sea, Egypt.

El-Sokkary SG , El-Wakeil KFA , Obuid-Allah AH , Omer MY .

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The present work is aimed at investigating the effects of seasonal changes and habitat conditions on reproductive state and gonadal development of two macrobenthic fauna. Echinometra mathaei and Tridacna squamosa were collected seasonally (summer and winter) in July 2019 and January 2020 from three sites along the Red Sea coast, Egypt: Hamraween, Sedy Malek, and Porto Ghalb. Sexual differences and gonadal maturation in the two species were determined by performing biopsies of their gonads followed by morphologic analyses. Hematoxylin and eosin-stained gonadal sections were examined and analyzed. In E. mathaei, reproductive behavior was more active in the summer than in the winter; in T. squamosa, reproductive behavior was active almost all the year, especially during the winter. The reproductive activity and gonadal maturation of both species were affected by environmental factors. The results indicated that temperature is a vital factor affecting the reproductive activity of both species. This study concluded that temperature fluctuations may pose significant challenges to coastal marine ecosystems.

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References [+] :

Blier, What modulates animal longevity? Fast and slow aging in bivalves as a model for the study of lifespan. 2017, Pubmed

	Fig. 1. Map showing the location of the three investigated sites on the Red Sea coast of Egypt
	Fig. 2. Photographs of reproductive stages of male and female gonads of Echinometra mathaei. a Immature/resting stage in female; b immature/resting stage in male; c premature stage in female; d premature stage in male; e mature stage in female; f mature stage in male; g partially spawned stage in female; h spent stage in male; i spent stage in female. L lumen, MO mature ovum, NP nutritive phagocytes, PO previtellogenic ovum, S sperm, SC spermatocytes, SG spermatogonia
	Fig. 3. Photomicrographs of gonadal tissue of Tridacna squamosa. a Female; b male; c female dominant; d male dominant; e male and female. NP nutritive phagocytes, O ovum, S sperm
	Fig. 4. Photomicrographs of microscopical characteristics of male and female gonads of Echinometra mathaei. a Male; b female; c high level of gametes in male; d high level of gametes and large ovum size in female; e low level of gametes in male; f low level of gametes and small ovum size in female. L lumen, MO mature ovum, NP nutritive phagocytes, PO previtellogenic ovum, S sperm, SC spermatocytes
	Fig. 5. Photomicrographs of microscopical characteristics of Tridacna squamosa. a Male dominant; b female dominant; c high level of gametes in male; d high level of gametes in female; e low level of male gametes; f low level of female gametes; g high level of gametes and large ovum size; h low level of gametes and small ovum size. NP nutritive phagocytes, O ovum, S sperm
	Fig. 6. A Means and standard deviations of gamete ratio of Echinometra mathaei. B Means of gamete ratio for males and females for different sample groups (different characters indicate significant differences among sample groups)
	Fig. 7. Means and standard deviations of ovum area (µm.2) for Echinometra mathaei collected from different sample groups (different characters indicate significant differences among sample groups)
	Fig. 8. A Means and standard deviations of gamete ratio of Tridacna squamosa. B Means of gamete ratio for male and female gonads for different sample groups (different characters indicate significant differences among sample groups)
	Fig. 9. Means and standard deviations of ovum area (µm.2) for Tridacna squamosa collected from different sample groups (different characters indicate significant differences among sample groups)
	Fig. 10. Biplot of principal component analysis (PCA) of environmental variables and reproductive activity of Echinometra mathaei (e) and Tridacna squamosa (t) recorded for different sampling groups. Environmental variables: Airtemp, air temperature; Wtemp, water temperature; WpH, water hydrogen ion concentration; Cond, conductivity; Salinity, water salinity; Carbonate, sediment carbonate content; TOC, sediment total organic matter content; DO, dissolved oxygen; CSG, coarse sediment group; MSG, medium sediment group; FSG, fine sediment group. Reproductive activity: Echin, E. mathaei; Tri, T. squamosa; GSI, gonadosomatic index; G, gamete percentage; OA, ovum area