Behaviour of the nuclei in pre- and postfertilization stages in Kallymenia (Kallymeniaceae, Rhodophyta)

Abstract

Listen

Translate article

C. Rodríguez-Prieto and M.H. Hommersand. 2009. Behaviour of the nuclei in pre- and postfertilization stages in Kallymenia (Kallymeniaceae, Rhodophyta). Phycologia 48: 138–155. DOI: 10.2216/08-75.1.The female reproductive complex in Kallymenia is composed of separate (nonprocarpic) carpogonial branch and auxiliary cell branch systems that link by means of connecting filaments. We describe the development of these systems and their functioning up to the time of carpospore formation in relation to the behaviour of the nuclei, using hematoxylin stain, in the Mediterranean species of Kallymenia – K. feldmannii, K. lacerata, K. patens and K. requienii – compared to those of the type species, K. reniformis, from Atlantic Europe. Derivatives of the putative fertilization nucleus (diploid) were generally twice the diameter (2.0–3.0 µm) of the vegetative gametophytic (haploid) nuclei (1.0–1.5 µm). Nuclei in the supporting cell and subsidiary cells of the carpogonial branch system are large, with amplified levels of DNA, and increase in size and fuse as the subsidiary cells fuse with the supporting cell and the fusion cell enlarges after presumed fertilization. Putative diploid nuclei inside the fusion cell remain the same size. The fusion cell cuts off numerous uninucleate connecting filament initials some of which elongate into connecting filaments of uniform diameter, each of which is provided with a single terminal diploid nucleus. Connecting filaments seek out and fuse with auxiliary cells, whereupon the diploid nucleus divides repeatedly, producing many derivative nuclei that line the connecting filament and give rise to gonimoblast filaments laterally. Gonimoblast filaments may link up with gametophytic cortical and medullary cells and produce secondary gonimoblast filaments. Branches of the gonimoblast filaments bear carposporangia in chains that mature basipetally and separate forming clusters of carpospores. The carpospores are either released or commonly germinate in situ and connect secondarily with gametophytic cells and with each other to produce a pseudoparenchymatous mat that may function as a propagule.