Acarine embryology: Inconsistencies, artificial results and misinterpretations

Abstract

In this paper, we discuss how views of early stages in acarine embryology – from the first cleavage to the blastula – have changed over time, starting with historical works of the 19th century and ending with electron microscopic analyses in the 21st century. Our goal is to identify errors and inconsistencies in both observations and the interpretation of information throughout this time span, and to show how they have related to technical improvements. Surprisingly, the questions about cleavage pattern and its implications for acarine classification have not changed, despite the advent of electron microscopy and molecular biology. In the last century authors attempted to develop a general concept of cleavage types and their distribution among the major subgroups of the Acari. Based on available data, all of which was from light microscopy, the type of cleavage for both the Anactinotrichida and Actinotrichida was considered to be interlecithal, with the exception that some actinotrichid mites show mixed/combination cleavage. Newer data obtained by transmission electron microscopy and molecular biology point to a very different generalization: early acarine cleavage seems to be a special type of total cleavage.

Keywords

• total cleavage
• superficial cleavage
• Acari
• macromere
• micromere
• Oribatida