Non-systemic metamorphosis in male millipede appendages: long delayed, reversible effect of an early localized positional marker?

Leandro Drago , Giuseppe Fusco and Alessandro Minelli

Department of Biology, University of Padova, Via Ugo Bassi 58/B, I-35131 Padova, Italy

author email corresponding author email

Frontiers in Zoology 2008, 5:5doi:10.1186/1742-9994-5-5


Published:	8 April 2008

Abstract

Background

The development of specialized appendages involved in sperm transfer in the males of julid millipedes is an extreme case of specialized, complex structures differentiating in a very advanced phase of post-embryonic development. Here, a non-systemic metamorphosis affects the external morphology and the internal anatomy of a trunk double segment only.

Presentation of the hypothesis

We hypothesize that during early (possibly embryonic) development a segmental marker is produced that remains unexploited throughout late embryonic and early post-embryonic development, until, activated by a systemic signal, it finally determines the release of a segmentally localized but anatomically major change.

Testing the hypothesis

Key to testing the hypothesis are (1) the identification of both the putative segmental marker involved in the localization of the legs to be eventually metamorphosed into gonopods and the systemic signal activating it, (2) the identification of the cell population from which the gonopods are built, and (3) a longitudinal study of the marker's expression throughout late embryonic and, possibly, post-embryonic development.

Implications of the hypothesis

Proving the validity of this hypothesis would demonstrate the existence of a cryptic developmental module that will be activated only months, or years, after it has been first laid down during early development. This study also opens a window onto the very poorly explored domain of late expression of developmental genes and molecular control of late developmental events.