Toxicity of marine pollutants on the ascidian oocyte physiology: an electrophysiological approach

Abstract

In marine animals with external fertilization, gametes are released into seawater where fertilization and embryo development occur. Consequently, pollutants introduced into the marine environment by human activities may affect gametes and embryos. These xenobiotics can alter cell physiology with consequent reduction of fertilization success. Here the adverse effects on the reproductive processes of the marine invertebrate Ciona intestinalis (ascidian) of different xenobiotics: lead, zinc, an organic tin compound and a phenylurea herbicide were evaluated. By using the electrophysiological technique of whole-cell voltage clamping, the effects of these compounds on the mature oocyte plasma membrane electrical properties and the electrical events of fertilization were tested by calculating the concentration that induced 50% normal larval formation (EC50). The results demonstrated that sodium currents in mature oocytes were reduced in a concentration-dependent manner by all tested xenobiotics, with the lowest EC50 value for lead. In contrast, fertilization current frequencies were differently affected by zinc and organic tin compound. Toxicity tests on gametes demonstrated that sperm fertilizing capability and fertilization oocyte competence were not altered by xenobiotics, whereas fertilization was inhibited in zinc solution and underwent a reduction in organic tin compound solution (EC50 value of 1.7 µM). Furthermore, fertilized oocytes resulted in a low percentage of normal larvae with an EC50 value of 0.90 µM. This study shows that reproductive processes of ascidians are highly sensitive to xenobiotics suggesting that they may be considered a reliable biomarker and that ascidians are suitable model organisms to assess marine environmental quality.

Reprotoxic Impact of Environment, Diet, and Behavior

“…Cadmium in a dose-dependent manner induces oxidative damages and heat shock protein expression, even in toxi-tolerant liverwort species [29]. In the ascidian Ciona robusta, cadmium exposure affects the electrical proprieties of oocyte plasma membrane and embryo development [30][31][32][33]. Chronic exposure to cadmium has been demonstrated to affect sperm quality, oocyte size and to impair fertilization and embryo morphology in sea urchin [34,35].…”

Analysis of the transmembrane potential of embryos exposed to action of nickel, cobalt, tin and zinc

“…У водних тварин гамети виділяються у воду, де відбувається запліднення. З літературних даних відомо, що, залежно від концентрації, іони важких металів акумулюються у клітинах (Boiko & Sanagursky, 2000) і впливають на гамети та ембріони, змінюючи фізіологічні властивості клітин і генерацію потенціалу дії (Boiko & Sanagursky, 2000;Gallo, 2018).…”

“…Численні літературні дані вказують, що іони важких металів здатні викликати порушення ембріонального розвитку у різних видах організмів, наприклад, безхребетних (Sisman, 2011;Gallo et al, 2016;Gallo, 2018), риб (Blewett et al, 2016;Blewett & Leonard, 2017), чи молюсків (Ringwood et al, 2010). Наслідками негативного впливу на метаболічні процеси в ембріогенезі, зумовлені іонами нікелю, кобальту, олова та цинку, стали сповільнення розвитку (Behra, 1993;Blewett & Leonard, 2017), виникнення морфологічних та функціональних аномалій (Dineley et al, 2003;Hwang et al, 2012;Tualla & Bitacura, 2016), або смерті зародка (Cavas, 2008;Cai et al, 2012;Kucukoglu et al, 2013).…”

Sperm Motility Impairment in Free Spawning Invertebrates Under Near-Future Level of Ocean Acidification: Uncovering the Mechanism

“…Exposure to acidified seawater (AcSW) has been demonstrated to negatively affect fertilization and embryo and/or larval development in different species of sea urchin (Kurihara and Shirayama, 2004;Carr et al, 2006;Havenhand et al, 2008;Byrne et al, 2009;Brennand et al, 2010;Lenz et al, 2019) bivalve molluscs (Kurihara et al, 2007;Parker et al, 2009;Guo et al, 2015;Kong et al, 2019) and polychaetes (Díaz-Castañeda et al, 2019). On the contrary, the effects of OA on gamete quality is poorly investigated despite several evidence for the impairment of reproductive success by chemo-physical stressors through altering the gamete quality (Gallo et al, 2011(Gallo et al, , 2018aGallo andTosti, 2013, 2015;Boni et al, 2016;Gallo, 2018;Rotini et al, 2018).…”