Differential Polymorphism in Cutaneous Glands of Archaic Leiopelma Species Sabine Melzer, 1 * Stefan Clerens, 2 and Phillip J. Bishop 1 1 Department of Zoology, University of Otago, Dunedin 9054, New Zealand 2 Protein Quality & Function Team, AgResearch Ltd, Christchurch, New Zealand ABSTRACT Endemic New Zealand frogs of the genus Leiopelma are from a basal lineage of extant anurans that release defensive secretions onto their skin when disturbed. Here, we characterize the gross anatomy and microscopic structure of the skin of L. archeyi, L. hochstetteri, and L. pakeka using stereoscopic, light and transmission electron microscopy. The terrestrial L. archeyi and L. pakeka possess dimorphic granular glands, categorized as type I and II, based on their fre- quency and morphological traits, whereas the semi- aquatic L. hochstetteri lacks type I glands. This is the first report of differential dimorphism in anurans of the same genus. This dimorphism could be interpreted as an adaptation to different physiological or ecological needs of these species. However, species within this ancient ge- nus share similar general gland morphology with other anurans, namely, a secretory unit containing storage granules ensheathed by myoepithelial cells. Type I glands are ellipsoid, large and contain a homogeneous mass of electron-dense granules (1.8 6 0.08 lm in diam- eter). Type II glands are round and contain larger heter- ogeneous granules (4.06 6 0.16 lm) of varying densities. Exposure to noradrenaline causes the contraction of myoepithelial cells, resulting in bulk discharge of type I glands through the epidermal duct onto the skin surface. Differential release of secretions from dimorphic glands may be indicative of their functional specialisation in antipredatory or regulative roles. Mass spectrometric techniques were used to de novo sequence peptides pres- ent in the skin secretions of Leiopelma species. A total of 30 previously undescribed peptides from Leiopelma species were fully or partially sequenced. These peptides exhibited no similarity to any known compounds. J. Morphol. 000:000–000, 2011. Ó 2011 Wiley-Liss, Inc. KEY WORDS: amphibia; parotoid; venom release; antipredator mechanism; peptide INTRODUCTION Amphibian skin plays a fundamental role in gas exchange, temperature regulation and water exchange, and acts as a physical barrier to desicca- tion and pathogens (Duellman and Trueb, 1986). The basic gland types in anuran skin are granular (also known as serous or poison), mucous, (Engel- mann, 1872) and lipid glands (Noble and Noble, 1944). Granular glands secrete a wide variety of chemical compounds used in predator defence (Daly and Myers, 1967; Brodie and Tumbarello, 1978; Daly et al., 1994; Williams et al., 2000), dis- ease defence (Bachmeyer et al., 1967; Preusser et al., 1975; Davidson et al., 2007; Mangoni et al., 2008; Rollins-Smith et al., 2009) and possibly in communication (Wabnitz et al., 1999; Waldman and Bishop, 2004; Mitchell, 2005; Belanger and Corkum, 2009). This has been a key selection pres- sure in the evolution of the rich arsenal of chemi- cal compounds which are found in amphibian skin secretions (Daly and Myers, 1967; Williams et al., 2000; Rollins-Smith, 2009). Peptides constitute a major component of the granular gland content and their biological activity has been subject of intense investigation since the isolation of Bombi- nin in the 1960s (Kiss and Michl, 1962; Erspamer et al., 1986; Zasloff, 1987). The presence of more than one type of granular gland with distinctive secretory products is gener- ally considered rare and is currently only recog- nized in a few anuran species in the families Bomb- inidae (Delfino, 1976), Bufonidae (Delfino et al., 1990; Delfino et al., 1998b) and Hylidae (Delfino et al., 1998a; Nosi et al., 2002). Three bombinid and two bufonid species showed the presence of two gland types, whereas two Phyllomedusa species possess three gland types. True morphological dif- ferences in granular glands arise as a result of the divergent evolution of secretory units as opposed to gland variation due to maturational processes during the gland cycle (Delfino et al., 1999). There- fore, glands that are truly morphologically distinct are characterized by the absence of intermediate forms, the origin of biosynthetic products from dif- ferent organelles, distinctive ultrastructure of se- rous products and difference in the maturation paths of serous products (Delfino et al., 1998b). Contract grant sponsor: University of Otago. *Correspondence to: Sabine Melzer, Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand. E-mail: sabine.melzer@gmail.com Received 7 November 2010; Revised 24 January 2011; Accepted 20 February 2011 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/jmor.10960 JOURNAL OF MORPHOLOGY 000:000–000 (2011) Ó 2011 WILEY-LISS, INC.