Chorion surface ultrastructure of loach Misgurnus anguillicaudatus: adaptation to the environment and correlation with the reproductive strategy

Abstract

The ultrastructure of the egg chorion surface in the loach Misgurnus anguillicaudatus was investigated using scanning electron microscopy (SEM). A single micropyle, which belonged to type II, was found at the animal pole of an M. anguillicaudatus egg. Several sinistral grooves which originated at the micropyle probably served for sperm guidance. The egg envelope had numerous pores with bud-like fillings and a regular arrangement like honeycomb. Lots of small knobs were situated on the zona radiata at the vegetal pole. Water contact triggered egg stickiness within about 10 seconds. The egg surface became smooth after treatment with trypsin solution. The features of the micropyle, pores and stickiness were correlated with the reproductive strategy of the loach and are important for egg identification.

Keywords:

• chorion
• micropyle
• adhesiveness
• reproductive strategy
• Misgurnus anguillicaudatus

Acknowledgements

We are much obliged to the anonymous reviewers for their comments and corrections which improved our manuscript. This work was funded by a grant from the Sichuan Key Lab of Meat Processing, the Research Programme for Public Welfare of Science and Technology Department of Sichuan Province and the Sichuan Education Bureau Foundation [no. 072B052].