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The skin secretions of female and male Litoria splendida have been monitored monthly over a three-year period using HPLC and electrospray mass spectrometry. Two minor peptides are present only in the skin secretion of the male. The first of these is the female-attracting aquatic male sex pheromone that we have named splendipherin, a 25 amino acid peptide (GLVSSIGKALGGLLADVVKSKGQPA-OH). This pheromone constitutes about 1% of the total skin peptides during the breeding season (January to March), dropping to about 0.1% during the period June to November. Splendipherin attracts the female in water at a concentration of 10-11-10-9 M, and is species specific. The second peptide is a wide-spectrum antibiotic of the caerin 1 group, a 25 residue peptide (GLLSVLGSVAKHVLPHVVPVIAEKL-NH2) named caerin 1.10. The neuropeptides of L. splendida are also seasonally variable, the change identical for both the female and male. During the period October to March, the sole neuropeptide present in skin secretions is caerulein [pEQDY(SO3)TGWMDF-NH2]; this is active on smooth muscle and is also an analgaesic. During the southern winter (June to September), more than half of the caerulein is hydrolysed to [pEQDYTGWMDF-NH2], a peptide that shows no smooth muscle activity. In place of caerulein, a new peptide, Phe8 caerulein [pEQDY(SO3)TGWFDF-NH2], becomes a major component of the skin secretion. Perhaps this seasonal change is involved in thermoregulation, that is, with the initiation and maintenance of the inactive (hibernation) phase of the animal.

A combination of electrospray mass spectrometry, Lys-C digest/mass spectrometry and automated Edman sequencing provides the amino acid sequences of nineteen citropin peptides isolated from the granular dorsal and submental glands of the Blue Mountains tree frog Litoria citropa. Citropin 1.1 [Gly Leu Phe Asp Val Ile Lys Lys Val Ala Ser Val Ile Gly Gly Leu (NH(2))] and citropin 1.2 [Gly Leu Phe Asp Ile Ile Lys Lys Val Ala Ser Val Val Gly Gly Leu (NH(2))] are the two major skin peptides: both show significant wide-spectrum antibacterial activity., (Copyright 1999 John Wiley & Sons, Ltd.)

The glandular secretions of the skin of Litoria rubella specimens collected from five locations on the eastern seaboard of Queensland (Australia) contain the three tryptophyllin peptides Phe Pro Trp Leu (NH2), Phe Pro Trp Pro (NH2) and Phe Pro Phe Pro Trp Leu (NH2). The relative proportions of these peptides in the glandular secretion are associated with geographic location, i.e. Phe Pro Trp Pro (NH2) is a minor component of the peptide mixture in frogs from southern Queensland, but becomes significantly more abundant as the location becomes more northerly. This trend indicates an evolutionary change in the animal, but for what reason, and over what timescale is not known at this time.