Characterization of the Hoyle organ in cephalopods

Hatching of embryos from their eggs begins when unicellular glands release hatching enzymes. The enzymes weaken the chorionic membrane, which is then easily broken by the moving embryo. Although numerous morphological and biochemical studies exist on the hatching glands of invertebrates (such as sea urchins, insects, ascidians) and vertebrates (teleosts, amphibians, and mammals), little is known about the morphology of the hatching glands (Hoyle organ) in cephalopod hatchlings. The glandular system is restricted to the posterior part of the dorsal mantle surface and becomes developed in the late embryonic phase (e.g. in Sepia stage 22-23, Loligo stage 28, Octopus stage 13). The morphology of the Hoyle organ probably differs between the cephalopod species, and little is known about the composition of its secretion. The key objectives of this proposed work are to characterize ultrastructurally the Hoyle organ of Sepia officinalis and Octopus vulgaris from development to degradation and to analyse histochemically the secretory components. The 3D-reconstruction of the glandular structures will help reach a firmer understanding of their overall complexity in both species. The present study will contribute to our knowledge of glandular systems in cephalopods and allow comparison with hatching structures in other invertebrates and vertebrates.

Hatching of embryos from their eggs begins when unicellular glands release hatching enzymes. The enzymes weaken the chorionic membrane, which is then easily broken by the moving embryo. Although numerous morphological and biochemical studies exist on the hatching glands of invertebrates (such as sea urchins, insects, ascidians) and vertebrates (teleosts, amphibians, and mammals), little is known about the morphology of the hatching glands (Hoyle organ) in cephalopod hatchlings. The glandular system is restricted to the posterior part of the dorsal mantle surface and becomes developed in the late embryonic phase (e.g. in Sepia stage 22-23, Loligo stage 28, Octopus stage 13). The morphology of the Hoyle organ probably differs between the cephalopod species, and little is known about the composition of its secretion. The key objectives of this proposed work are to characterize ultrastructurally the Hoyle organ of Sepia officinalis and Octopus vulgaris from development to degradation and to analyse histochemically the secretory components. The 3D-reconstruction of the glandular structures will help reach a firmer understanding of their overall complexity in both species. The present study will contribute to our knowledge of glandular systems in cephalopods and allow comparison with hatching structures in other invertebrates and vertebrates.