The endemic Australian red algal families Mychodeaceae Kylin and Mychodeophyllaceae fam. nov.
are described and characterized in vegetative and reproductive detail. The Mychodeaceae is composed
of the single genus Mychodea and 11 species which are distinguished on habit features and vegetative
differences. Plants are uniaxial with a distinctive pattern of axial development, monoecious, zonately
tetrasporangiate, procarpic and polycarpogonial. Supporting cells of carpogonial branches function as
auxiliary cells which remain unfused to adjacent cells after diploidization and emit numerous
gonimoblast filaments towards the centre of the thallus. The gonimoblasts become secondarily pitconnected
to gametophytic cells which they lie next to and eventually appear to break up into isolated
groups of cells which both initiate additional carposporangial precursors and enlarge directly into carposporangia
themselves. Carposporangial initials can form secondary pit-connections to any type of
adjacent cell, which results in irregularly branched carposporangial clusters whose cells are frequently
attached to sterile gametophytic cells within and around the periphery of the cystocarp. Mature cystocarps
consist of a non-ostiolate pericarp and pockets of carposporangia isolated between persistent
sterile cells throughout the fertile region. The genera Neurophyllis Zanardini and Ectoclinium J. Agardh
are placed in synonymy with Mychodea, and all extra-Australian records of the group are discounted
or questioned.
A new family, the Mychodeophyllaceae, is created for Mychodeophyllum papillitectum gen. et sp.
nov. from Western Australia. Mychodeophyllum shares spermatangial and tetrasporangial features with
Mychodea, as well as sexual elements such as polycarpogonial procarps, lack of a fusion cell, and multiple,
inwardly growing gonimoblast initials. Gonimoblast filaments develop quite differently from
Mychodea, however, and carposporangia form radiating chains around the periphery of a central placenta
composed of mixed and secondarily connected gonimoblast and gametophytic filaments. Plants
of the genus are also apparently rnultiaxial.
The Mychodeaceae and Mychodeophyllaceae appear to be highly specialized in vegetative and carposporophyte
structure, and have given rise to no known higher lines of development. It is speculated
that both families may represent offshoots from ancestors at a level of carposporophyte complexit)
represented by present-day Rhabdoniaceae, Solieriaceae and Rhodophyllidaceae.
Telocytes: Supporting cells participating in ventricular arrhythmogenesis?
