Oral Presentation ESA-SRB Conference 2015
Phthalate ester-induced cytoskeletal disruption in early embryogenesis of an Australian native marine invertebrate Galeolaria gemineoa (Polychaeta: Serpulidae) (#16)
Galeolaria gemineoa is a marine invertebrate inhabits along the mid-littoral zone of Australia’s east coast. As a broadcast-spawning species, G. gemineoa releases its gametes to the water column before fertilization, which provides more opportunity for the gametes being exposed to marine pollutants. In this study, the toxic effect of six phthalate esters (PAEs, common environmental pollutants) on the early embryogenesis was investigated by conducting sperm- and oocyte-exposure tests.
Sperm exposure to PAEs resulted in decreases of embryogenesis success in a dose-dependent manner and embryonic abnormalities with a distinctive pattern, while oocyte exposure mostly had no effect. Exceptionally, oocyte exposure to a relatively high concentration of dibutyl phthalate (20 mg/L) induced a dramatic decline in the success of embryogenesis. Based on these tests, we concluded that impaired embryonic development originates largely from PAE-induced damage to the male germ line.
Instead of undergoing a symmetrical and synchronous embryonic cleavage, the PAE-exposed spermatozoa resulted in abnormal embryos with disrupted karyokinesis and cytokinesis. From 2-cell stage, only one blastomere could divide further while the other one was arrested. Double staining for microtubules and chromosomes revealed that the mitotic spindles in the abnormal embryos were disorganised, shortened and unanchored to the cytoplasmic membrane, which resulted in unequal segregation of chromosomes. Within the non-dividing blastomeres of such embryos, nuclear divisions were found to continue as indicated by the presence of multiple spindle poles. However, cytokinesis had been disrupted due to a failure to form contractile actin rings. This abnormality indicated that in addition to any sperm DNA damage, PAEs induced changes in the sperm centriole, leading to a disruption of cytoskeletal proteins during cleavage. Such sperm damage could originate from oxidative stress caused by PAE-induced intracellular suppression of superoxide dismutase.
This study highlights the potential of this species for monitoring developmental toxicants in the marine environment.
