Biological Journal of the Linnean Society, 2004, 83, 207–217. With 4 figures © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83, 207–217 207 Blackwell Science, LtdOxford, UKBIJBiological Journal of the Linnean Society0024-4066The Linnean Society of London, 2004? 2004 832 207217 Original Article REPRODUCTION IN CAECILIANS A. KUPFER ET AL. *Corresponding author. Current address. Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. E-mail: alexk@nhm.ac.uk Reproductive ecology of female caecilian amphibians (genus Ichthyophis): a baseline study ALEXANDER KUPFER 1, *, JARUJIN NABHITABHATA 2 and WERNER HIMSTEDT 1 1 Institute of Zoology, Darmstadt University of Technology, Schnittspahnstrasse 3, D-64287 Darmstadt, Germany 2 National Science Museum, Technopolis, Klong 5, Klong Luang, Pathumthani 12120, Thailand Received 10 July 2003; accepted for publication 23 January 2004 The remarkable diversity of reproductive modes, including levels of parental care that are extensive relative to those of the other major amphibian groups, makes the limbless tropical caecilians ideally suited for evolutionary repro- ductive studies. Here we present key life history data for the oviparous caecilian Ichthyophis cf. kohtaoensis. We used non-invasive methods to analyse reproductive traits, seasonality of breeding and characteristics of oviposition sites in the field (Mekong valley, north-eastern Thailand). A correlation was established between reproductive activity and season, indicated by the age of egg clutches found in the field. Eggs at early developmental stages were found at the beginning of the rainy season, those with well-developed embryos at the peak of the monsoon. The body condition of females guarding younger clutches was superior to that of females with older clutches, indicative of a loss of energy reserves during the period of parental care. Maternal total length correlated positively with the number of eggs as well as with the total length of newly hatched larvae. The terrestrial oviposition sites of females were located close to temporary and permanent ponds, small brooks and rivers. It is hoped that the study will, in addition to contrib- uting to our understanding of the evolution of caecilian reproduction, provide a basis for further comparisons of reproductive strategies among amphibians and other terrestrial tetrapods. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83, 207–217. ADDITIONAL KEYWORDS: evolution of terrestriality - Gymnophiona - oviposition - parental care - seasonality. INTRODUCTION Amphibians pioneered the vertebrate colonization of the terrestrial environment. Since most amphibians have an aquatic larval stage, the amniotes are gener- ally considered to have completed the transition to land, through the invention of the terrestrial amniotic egg (see Skulan, 2000 for a recent discussion). How- ever, compared to reptiles, birds and mammals, amphibians have a much greater diversity of repro- ductive modes. This includes direct development and viviparity, both of which remove the ancestral require- ment of aquatic reproduction (Duellman & Trueb, 1994). All three groups of modern amphibians - frogs (Salthe & Duellman, 1973; Duellman & Trueb, 1994), salamanders (Salthe, 1969) and caecilians (Wake, 1977; Wilkinson & Nussbaum, 1998) - show trends toward the terrestrialization of reproduction. The deposition of eggs out of water is a major evo- lutionary step towards a colonization of the terrestrial habitat. Phylogenetically, the amphibians with terres- trial eggs and aquatic larvae are the first lineages that started the transition to land. This reproductive mode is found in frogs (Modes 12–14, after Duellman & Trueb, 1994), in salamanders (Mode IIB, after Salthe, 1969) and in caecilians (Wake, 1977; Wilkinson & Nussbaum, 1998). Terrestrial egg clutches are exposed to desiccation, predators and fungal infections. Their survival is highly increased with parental care (Salthe & Macham, 1974), although this investment may reduce the parent’s ability to produce more offspring.