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How can male and female flatfishes differ in appearance?
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pleuronectiform
Body plan and sexual dimorphism in the common sole (Solea solea) and dusky flounder (Syacium papillosum).
Many species of flatfish (order Pleuronectiformes) exhibit sexual dimorphism, meaning males and females differ in physical appearance. Males often possess distinct characteristics that females lack, including:
- Elongated pectoral fin rays1
- Wider interorbital bones1
- Spines on the head1
- Tentacles on the eyes1
- More elaborate pigmentation1
While these external features can help distinguish the sexes, internal differences also exist. In females, the ovaries extend posteriorly from the body cavity beneath the skin and a thin layer of muscle located just above the anal fin ray muscles, making them visible externally in some cases. In contrast, the testes of male flatfishes are not visible without dissection.1