Histochemical correlations between egg capsule laminae and the female gonoduct reveal the process of capsule formation in the Muricidae (Neogastropoda: Mollusca)

Summary

Limited information is currently available on the process of encapsulation and degree of variation in the micromorphology of egg capsules deposited by muricid gastropods. In this study, a histochemical approach was employed to determine the origin of egg capsule laminae within the female gonoduct of Dicathais orbita. Comparisons of capsule micromorphology from this Australian Rapaninae, with species from the Muricinae and Ocenebrinae, suggest that whole capsule and lamina 1 (L1) thickness, L2 fiber orientation and intracapsular fluid biochemistry display interspecific variability. Furthermore, the method of capsule laminae deposition was found to be substantially different to previous descriptions of muricid capsule formation. Simultaneous examination of capsule and gonoduct biochemistry in D. orbita revealed that the intracapsular fluid nd inner capsule wall (L3) contain secretions from the posterior lobe of the capsule gland; the thick middle lamina (L2) is derived from the lateral capsule gland lobes; and the outer layers (L1 and L0) include dorsal capsule lobe, albumen gland and pedal gland components. The insight gained into the processes involved in capsule formation imply that interspecific differences in capsule micromorphology are dependent on the timing of egg entry during capsule formation, and the protein content of posterior lobe secretory products coupled with the presence or absence of albumen gland secretions. This investigation supplements existing evidence on the origin of capsule components and variability in capsule micromorphology in the Muricidae by providing a simple method for deciphering the complex process of encapsulation in neogastropods.

Key words:

• Laminae
• capsule gland
• pedal gland
• intracapsular fluid
• albumen gland