1. Marine gastropod mollusks characterized by a reduced or absent shell and gill positioned behind the heart, including sea slugs and sea hares.
Usage: zoology; plural form; singular is opisthobranch; largely obsolete taxonomic classification; modern taxonomy places these organisms in different groups

Examples

• Opisthobranchs are found in oceans worldwide, from shallow coral reefs to the deep sea.
• The colorful opisthobranchs display remarkable adaptations for camouflage and defense.
• Marine biologists study opisthobranchs to understand mollusk evolution and diversity.
• Many opisthobranchs lack a protective shell, relying instead on chemical defenses.
• The term opisthobranchs is less commonly used in modern scientific literature.