Abstract Ultrastructure of cutaneous glands is de- scribed in the Australian hylid Litoria caerulea. Three main types of glands could be distinguished in both ven- tral and dorsal skin: mucous, serous or granular, and lip- id glands. Both mucous, and to some extent, serous glands show a PAS-positive reaction. Some of the granu- lar-serous glands react to lipid staining. In addition, a very large gland confined to the dorsal skin of the head reacts to lipid staining. Apparently more than one type of dermal gland is involved in lipid secretion. The subject of skin lipid secretion is discussed in relation to the eco- physiological adaptations of this xeric-inhabiting frog. Key words Amphibian skin · Dermal glands · Lipids · Water balance · Xeric adaptations Introduction Amphibians from xeric habitats have solved their water shortage problems mainly by behavioural and physiolog- ical ways (Warburg 1972, 1989, 1997). The fossorial mi- crohylid, leptodactylid, pelobatid and bufonid anurans burrow into the ground, some species form coccoons made of several layers of stratum corneum, and retreat into microclimatically favourable sites. These anurans are capable of storing dilute urine in their distended uri- nary bladder that lasts them through the dry season. Some hylids or rhacophorid anurans enter into deep cre- vices in rocks. Others, arboreal phyllomedusine anurans from South America, African hyperoliids and the rhacophorid Chiromantis, remain exposed to harsh ambi- ent conditions. In some of these arboreal frogs, lipid- containing glands have been demonstrated in their skin (Blaylock et al. 1976; McClanahan and Shoemaker 1987; Lillywhite et al. 1997; Delfino et al. 1998). About 30% of the cutaneous glands in four Phyllomedusa spe- cies are alveolar and secrete lipids (Blaylock et al. 1976). These lipids, mostly esters with small quantities of tri- glycerols, hydrocarbons, cholesterol and free fatty acids (McClanahan et al. 1978), do not appear to correlate with a waterproof lipid barrier (Withers et al. 1984). The large hylid Litoria caerulea, is capable of with- standing dry conditions in exposed places in arid Austra- lia, losing very little water through evaporation (Warburg 1967, 1972; Christian and Green 1988; Amey and Grigg 1995; Christian and Parry 1997). This capability has been partly attributed to a skin secretion containing 30% lipids (Christian and Green 1988), but also to other chemical components present in the amphibian skin (Christian and Parry 1997). Following dehydration, this species is capable of rapid water uptake (Warburg 1967, 1972). Evidence of a continuous layer of lipids in the dorsal skin of L. peroni and L. fallax was demonstrated by Amey and Grigg (1995). Since the arboreal hylid L. cae- rulea is not unlike Phyllomedusa in its behavioural ecol- ogy (Christian and Green 1988), it was of interest to ex- amine its dermal glands in order to see if cutaneous lipid glands were present. Materials and methods Pieces of ventral, dorsal and head skin of adult Litoria caerulea (White 1790) frogs, weighing 17–27 g, were fixed in Bouin’s so- lution, embedded in paraffin and stained in haematoxylin and eo- sin for histological examination. For transmission electron micros- copy (TEM), tissue was fixed in 3% glutaraldehyde in 0.05 M ca- codylate buffer (pH 7.4) for 2 h at room temperature, rinsed in 8% sucrose in 0.05 M cacodylate buffer, and post-fixed in 1% OsO 4 for 1 h at 4 °C containing 1.5% ferrocyanide (FRO). The tissues were dehydrated in graded ethanols and embedded in Epon 812. Semi-thin sections 2-μm-thick were cut with the aid of an LKB M.R. Warburg ( ✉ ) · M. Rosenberg Department of Biology, Technion, Haifa 32000, Israel e-mail: warburg@tx.technion.ac.il; Fax 972–4-8225153 J.R. Roberts Department of Physiology, University of New England, Armidale, NSW, 2351 Australia H. Heatwole Department of Zoology, University of North Carolina, Raleigh, NC 27695–7616, USA Anat Embryol (2000) 201:341–348 © Springer-Verlag 2000 ORIGINAL ARTICLE M.R. Warburg · M. Rosenberg · J.R. Roberts H. Heatwole Cutaneous glands in the Australian hylid Litoria caerulea (Amphibia, Hylidae) Accepted: 12 November 1999