Fertilization and development of Arbacia lixula eggs are affected by osmolality conditions. (August 2021)

• Record Type: Journal Article
• Authors: Limatola, Nunzia; Chun, Jong Tai; Santella, Luigia
• Is Part Of: Bio systems. Volume 206(2021)
• Publication Date: 2021-08
• Subjects: Salinity -- Actin -- Calcium -- sea urchin -- Cortical reaction -- Morphogenesis; NSW natural filtered seawater -- CCD charge-coupled device -- JC jelly coat -- CF cortical flash -- CW Ca2+ wave -- CG cortical granule -- FE fertilization envelope -- VL vitelline layer; Biological systems -- Periodicals; Biology -- Periodicals; Biology -- Periodicals; Evolution -- Periodicals; Biologie -- Périodiques; Évolution -- Périodiques; 570
• DOI: 10.1016/j.biosystems.2021.104448
• Languages: English
• ISSNs: 0303-2647

Abstract

Abstract: The sea urchin Arbacia lixula coexist with Paracentrotus lividus in the Mediterranean, but the two sea urchin species are quite different from each other. Concerning the female gamete, A. lixula eggs are much darker than those of P. lividus due to the characteristic pigmentation. Upon insemination, the fertilization envelope formed by A. lixula eggs is remarkably thinner than that of P. livius eggs, which implies that the cortical organization of the eggs in the two species may be quite different. In this communication, we examined the phenotypic plasticity of A. lixula eggs in the changing osmolality. The plasma membrane, cortical actin cytoskeleton and vesicles are extensively altered in the eggs exposed to 40% seawater for 15 min. When fertilized, the Ca 2+ response in these eggs was significantly compromised and the sperm often failed to enter the eggs. Remarkably, the pattern of the Ca 2+ response was restored when these eggs were transferring back to the natural seawater before fertilization, while the actin cytoskeleton partially reverted to the original state. Nonetheless, these eggs restored in seawater failed to regain the innate sperm receptivity that allows only one sperm to enter in natural seawater. Thus, the ability to guide monospermic fertilization is lost by water entry into the eggs, and the eggs incorporated either multiple or no sperm. On the other hand, eggs briefly exposed to hypertonic seawater exhibited no evident morphological anomaly. Nonetheless, the monospermic eggs that experienced a brief exposure (15 min) to hypertonic seawater prior to fertilization in natural seawater displayed a subtly altered sperm-induced Ca 2+ response and morpho-functional anomaly around the pluteus stage. Our results suggest that A. lixula eggs attain only a limited extent of cytological plasticity, and that the osmolality shock affects the physical nature of the egg surface which in turn affects the developmental programming. Highlights: Osmotic changes alter egg surface topography. Water entry into unfertilized sea urchin eggs affects the egg cortex structure. Hypotonic and hypertonic treatment cause alteration of the sperm-induced Ca 2+ response. Salinity changes affect embryogenesis.