May’s issue of Cold Spring Harbor Protocols marks the end of Volume I of our collection of material on Emerging Model Organisms. The final two featured organisms are the bichirs and the African butterfly.

The lineage leading to the teleost fishes, like the zebrafish, has undergone a whole-genome duplication, and there are many differences in the molecular and cellular mechanisms of embryogenesis between teleosts and other actinopterygians (ray-finned fishes) and sarcopterygians (fleshy, or lobe-finned fishes). Polypterus (bichir) is a taxonomic order of fish that diverged from all other actinopterygians ~400 million years ago during the Devonian period, soon after the divarication of an ancestral bony fish into Actinopterygii and Sarcopterygii. Polypterus share several characteristics of cartilaginous fishes and basal bony fishes. Bichirs exhibit holoblastic cleavage, like that seen in amphibians, and different from the meroblastic cleavage of teleosts. As such, it makes for an excellent system to study ancestral states and the divergence of embryonic processes in teleosts and amphibians. The Genus Polypterus (Bichirs): A Fish Group Diverged at the Stem of Ray-Finned Fishes (Actinopterygii) presents an overview of bichirs, and protocols for microinjection and whole-mount in situ hybridization are also available.

The African Butterfly Bicyclus anynana is a valuable model organism for a variety of reasons. A range of phenotypes are readily examined, such as wing color patterns (including eyespots), seasonal forms, male androconia (secondary sexual traits), and a range of life-history traits (relevant to aging research). Many of the phenotypes are directly related to the drastically different environments found during the dry and wet seasons in East Africa, offering an opportunity to study adaptation to environmental conditions. The genus Bicyclus and closely related genera are highly speciose, giving a great variety of closely related species for diversity studies. B. anynana is small and can be reared in large numbers. The African Butterfly Bicyclus anynana: A Model for Evolutionary Genetics and Evolutionary Developmental Biology provides an overview of the species as a model system. Protocols are available for culture and propagation, surgical manipulations, grafts, fixation and dissection, wing dissection, in situ hybridization, immunohistochemistry (embryos), immunohistochemistry (wings), analysis of pheromones, fat content and weight, respirometry, hemolymph extraction, and injection of chemicals.

As noted, this completes the first set of Emerging Model Organisms, and the collected articles are available in a laboratory manual. The second volume begins next month, and the list of species is available here.