Investigation of early mussel (Perna canaliculus) development using histology, SEM imaging, immunochemistry and confocal microscopy

ABSTRACT

A comprehensive study, incorporating histology, light microscopy, scanning electron microscopy, immunochemistry and confocal microscopy, was performed to investigate embryogenesis and larval development of the New Zealand Greenshell™ mussel, Perna canaliculus. Detailed observations with this multi-technique approach revealed a gastrula stage at 18 hours post-fertilization, with the appearance of a blastopore, apical sense organ and enclosing vegetal pole. Early D-stage larvae showed limited alimentary organogenesis and clear initiation of a developing nervous system. Shell morphology of D-larvae was characterized by a flat, hinged, pitted–punctate prodissoconch I shell, followed closely by commarginal growth lines within the prodissoconch II shell. Early umbo larvae had a protruding functioning velum, and well-developed posterior adductor and velar retractor muscles. Significant progression in neuronal development occurred just before the umbo stage with noticeable paired cerebral, pedal and visceral ganglia. Shell morphology was characterized by further prodissoconch II secretion with a more rounded umbonate appearance. During the transition through the pediveliger stage, rapid development of the gill rudiment, eye spot and functioning foot was observed with ongoing neuronal development. The first appearance of the dissoconch shell layer took place during this transition, at which point the nervous system was highly distinct with innervations extending throughout muscle regions and between ganglia. This study provides the first comprehensive documentation of the developmental stages of P. canaliculus larvae from fertilization to settlement. The study highlights the advantages of using a combination of techniques to understand larval development and provides crucial information to identify larval performance during larval rearing.

RESPONSIBLE EDITOR:

• Rachel Collin

KEYWORDS:

• Perna canaliculus
• larval development
• embryogenesis
• organogenesis
• neurogenesis
• shell morphology

Acknowledgements

We would like to thank the crew at Cawthron’s Aquaculture Park for their support and guidance: Samantha Gale, Jonathan Morrish and Norman Ragg. We are thankful to the Aquaculture Biotechnology Group (AUT) for their input and support through this research. We are also thankful to Jen Wilkins from Auckland University of Technology and Jacqui Ross from University of Auckland for their technical support with SEM and confocal microscopy, respectively.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the New Zealand Ministry of Business, Innovation and Employment [grant numbers CAWX0802 and CAWX1315] and by Auckland University of Technology. This work forms part of a postgraduate thesis by Adam Rusk under the supervision of A. Alfaro and S. Adams.