THE STRUCTURES OF NEW PEPTIDES FROM THE AUSTRALIAN RED TREE FROG LITORIA-RUBELLA - THE SKIN PEPTIDE PROFILE AS A PROBE FOR THE STUDY OF EVOLUTIONARY TRENDS OF AMPHIBIANS

Seventeen peptides have been isolated and characterized from specimens of the red tree frog 'Litoria rubella', collected from 15 locations t hroughout Australia. These can be classified into two families of pept ides, viz. (i) the tryptophyllins L, of which PheProTrpLeu(NH2), PhePr oTrpPro(NH2) and pGluPheProTrpPro(NH2) are the major constituents, (ii ) two types of rubellidins, the first of which is unique to 'Litoria r ubella' [e.g. ValAspPhePheAla(OH)], and the second [e.g. GlyLeuGlyAspI leLeuGlyLeuLeuGlyLeu(NH2)], containing peptides of the caeridin type ( like those isolated from Litoria caerulea and Litoria splendida). Thes e peptides show no significant antimicrobial activity. The tryptophyll ins are thought to be neuromodulators or neurotransmitters, but the ro les of the anionic rubellidin peptides in the amphibian integument are not understood. A comparison of the skin peptide profiles of live spe cimens of 'Litoria rubella' collected from different locations suggest s that there are a number of discrete populations (perhaps different s pecies or subspecies) in (i) an area from Kakadu National Park to the Adelaide River in the Northern Territory, (ii) in and around Alice Spr ings, (iii) in the north of South Australia, and (iv) in several areas of the Kimberley region of Western Australia. In addition, there appe ar to be evolving populations along the eastern seaboard of Queensland .