Intersexuality in aquatic invertebrates: Prevalence and causes

Area of Science:

• Marine Biology
• Ecotoxicology
• Invertebrate Zoology

Background:

• Intersexuality is defined as the presence of oocytes or spermatogonia within the gonad of the opposite gender in gonochorist species.
• This phenomenon has been documented in aquatic invertebrates, primarily within the Phyla Mollusca and Arthropoda, with gastropod mollusks and crustaceans showing the highest prevalence.
• While natural baseline levels may exist, intersexuality is often associated with environmental contamination by endocrine-disrupting chemicals (EDCs), parasitism, and abnormalities in sex determination.

Purpose of the Study:

• To compile and review existing information on intersexuality in aquatic invertebrates across various environments.
• To discuss the causes, prevalence, and knowledge gaps concerning intersexuality in these organisms.
• To highlight future research directions, particularly leveraging omics technologies.

Main Methods:

• Literature review and data compilation up to 2016.
• Analysis of documented cases of intersexuality and imposex in aquatic invertebrates.
• Discussion of contributing factors including environmental pollutants, parasitism, and genetic/environmental sex determination.

Main Results:

• Approximately 340 records of intersexuality were identified in aquatic invertebrates by the end of 2016.
• Gastropod mollusks (256 species) and crustaceans (decapods, copepods, amphipods) exhibited the most documented cases.
• Causes are multifaceted, involving estrogenic and organotin EDCs, parasitism, and sex determination anomalies.

Conclusions:

• Intersexuality is a significant issue in aquatic invertebrates, particularly mollusks and arthropods, driven by anthropogenic and natural factors.
• A comprehensive understanding of the molecular mechanisms underlying intersexuality in response to multiple stressors remains a critical knowledge gap.
• Future research should integrate omics approaches to investigate the molecular underpinnings of intersexuality and its ecological implications.