DOI: 10.18195/issn.0312-3162.23(3).2007.259-271 Records of the Western Australian l,1useum 23: 259-271 Direct development in two Myobatrachid Frogs, Arenophryne rotunda Tyler and Myobatrachus gouldii Gray, from Western Australia l 2 Marion Anstis • J. Dale Roberts , and Ronald Altig3 '26 Wideview Rd., Berowra Heights, NSW 2082, Australia. Email: frogpole(litpg.com.au School of Animal Biology (M092), University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009 Australia .1 Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762 USA Abstract The closely related Western Australian myobatrachid frogs Arenophryne rotunda and lv1yobatrachus gouldii deposit eggs in burrows that are dug by the adults in moist sand. Embryonic development requires up to two months and is completed entirely within the jelly capsule. The developmental stages of these two taxa are described and compared with those of the South American direct developing leptodactylid frog Eleutherodactylus coqui. Key words: Australia, direct development, embryo, endotrophic, myobatrachid INTRODUCTION 1950; Wake 1978; Townsend and Stewart 1985), The frogs Arenophryne rotunda and there are no available descriptions of the Australian Myobatrach us gouldii (Myobatrachidae) are widely species which include the myobatrachid genera distributed in semi-arid and arid regions of Arenophryne, A1yobatrachus and Metacrinia and southwestern Australia (Tyler et al. 2(00). Both the microhylid genera Austrochaperina and species are forwards burrowers that oviposit deep Cophixalus. underground in moist sand where embrvos The South American leptodactylid genus undergo direct development, an endotrophic Eleutherodactylus consists of several direct breeding mode in which all embrvonic developing species and the field staging system development through to a froglet takes place \~ithin developed for E. coqui by Townsend and Stewart the jelly layers of the egg (Altig and Johnson ]989). (1985) is the most comprehensive system available Arenophryne rotunda calls from Julv-November for this breeding mode. We describe some (austral winter to spring). Pairs of mal~s and gravid preserved embryonic material in the Western females not in amplexus have been found together Australian Museum of A. rotunda and M. gouldii in November at a mean depth of 45 cm, and in and compare them to E. coqui (see Table 3 and February and April (late summer to autumn) at Discussion). Brief comparisons to Australian direct mean depths of 75-78 cm, but eggs were only found developing microhylids and also to species from in April (Roberts ] 984). Myobatrachus gouldii calls other Australian endotrophic guilds including the from September-February (spring to late summer); nidicolous, paraviviparous and exoviviparous a male and female burrow together, not in species are made where relevant. These are not amplexus, into deep, moist sand where they appear direct developers because they have a hatched to remain together until autumn when they deposit tadpole stage (sensu Altig and Johnston 1989), but eggs at depths of 80-115 cm (Roberts 1981, 1984). have some similar characteristics to A. rotunda and Tyler's (1976a) suggestion of a close relationship M. gouldii in early stages. between these two species and with l\1etacrinia was supported by Maxson and Roberts (] 985), Read et al. (2001) and the recent analysis by Frost et al. MATERIALS AND METHODS (2006). Fifteen embrvos of A. rotunda from four clutches Direct development in amphibians has evolved in collected near Shark Bay, WA and reared in the at least seventeen genera from nine families of laboratory in April 1981 bv J. D. Roberts, were anurans worldwide (Thibaudeau and Altig ]999). preserved at irregular intervals in Tyler's fixative Although the life histories of a number of these (Tyler 1962) and transferred to 70'!<, ethanol when species have been described, especiallv for the accessioned into the West Australian Museum: genus Eleutherodactvlus (e.g. Citlin ]944; Jameson WAM R97047-50, 97053, 97057, R97059-60 (see 260 M. Anstis. LD. Roberts. R. Altig A B F - Figure 1 Stages 3, 4 and 6 (Townsend and Stewart, 1985) of Arenophryne rotunda. A and B = stage 3, anterior and lateral view; C = stage 4, dorsal view; D, E and F = stage 6, anterior, dorsal and posterior views. Scale bar represents 1 mm. Arrows indicate features highlighted in bold in Table 1. Appendix 1). Nine embryos up to stage 13 of Measurements were taken with an ocular Townsend and Stewart (T&S; 1985) from one clutch micrometer attached to a Wild M5 stereoscopic of M. gouldii were collected 15 km north-east of microscope and drawings were prepared with the Perth, WA, then reared and preserved at irregular aid of a camera lucida. The photograph (Figure 4F) intervals: WAM R97036-40. Six individuals just was taken with a Nikon 070 digital SLR camera prior to hatching and recently hatched from four and 60 mm micro lens. Embryos were staged using marked nests in the field were preserved after being the system of Townsend and Stewart (1985) which excavated in April 1982: WAM R97041-42, 97044-45 was devised for the direct developing leptodactylid (see Appendix 2). All embryos were reared in total E. coqui, with additional references to toe darkness at ambient room temperatures in the development based on the staging table for aquatic laboratory which were lowered slightly larvae of Gosner (1960). For the sake of (approximately 17-20°C) to better simulate cooling completeness, descriptive observations on egg conditions at the nest sites in the field. clutches provided for A. rotunda and M. gOll/dii by Development in Arenophryne and lHyobatrachus 261 Figure 2 Stages 6, 7, 9, and 15 (Townsend and Ste\var\, 1985) of Arenophryne rotunda. A stage 6, dorsolateral view; Band C stage 7, lateral and anterior vIews; D and E stage 9, lateral and ventral views; and F; stage 15, just prior to hatching, ventral view. Scale bar represents 1 mm. Arrows indicate features highlighted in bold in Table 1. Roberts (1984 and 1981, respectively) are characteristics in common. Both have a generally summarised prior to the descriptions for each similar parallel progression through the species, with additional notes on development developmental stages described in Tables 1 and 2. (Roberts, unpubl. data). Embryos in stages 1,2, 3-7, Measurements of embryos for each species are 9-11, 13 and 15 are described and most stages are given in the Appendices and Table 3 summarises illustrated (Figures 1 Brief observations were key differences between the Australian species and made on live embryos during early cell division. E. coqui. The partial deterioration of the youngest preserved embrvos of A. rotunda (stages 1 and 2), and Development of Arenophryne rotunda specimens of ;\1. gou/dii at stages 11 and 13, limited Clutch sizes of fertilised eggs ranged from 4-11 their descriptions. (mean 7, n = 5). Ovarian development commences in spring (late August), but ovum maturation is not Results completed until late summer. Three females The two have various morphological collected in February 1981 contained 8, 8 and 4 pale N C7\ N Table 1 Development of Arenophryne rotunda. T&S = Townsend and Stewart (1985) stages. Figure numbers in parenthesis. Features indicated by arrows in Figures 1 and 2 are highlighted in bold. T&S Head and Body Tail Limbs Eyes Mouth Pigmentation 3 - head region small and narrow - tail bud short, - none - optic bulges small, - stomodaeum a small - unpigmented (Fig. - narrow neural tube raised and narrow, indistinct, central pit in narrow lA,B) groove closed, myotomes adpressed unpigmented crevice beneath top of indistinct around base of snout, broad anterior - yolk sac large and round yolk, tip bulge on either side - slight gill arch bulges pointed - small indent in yolk in region - dorsal fin a of vent shallow ridge 4 - head region slightly broader, - tail bud narrow, - small round - upper crescent of - mouth slit open, - unpigmented (Fig. adpressed against yolk longer, wraps external hind limb optic bulges slightly about one-third lC) - narrow cleft separates indistinct over limb buds buds pigmented head width narial regions and vent to one - small round - no external gills or adhesive side around forelimb buds organs yolk beneath fold of - small vent opening - fin ridges just operculum that - some blood vessels present visible extends from side of head across to yolk s: ;r.. ::s 6 - head broader, slightly raised - fins low, - forelimb buds - mostly pigmented, - mouth opening about - some fine Cl! :::to (Fig. above yolk; snout short, broad, slightly longer, alongside slight choroid fissure one-third head width melanophores ,Cl! lD-F, blunt vascular near head beneath in lower half of iris - upper and lower jaws stippled over ~ 2A) - vertebral region broader and tip operculum - eye diameter 0.7 mm further developed brain, vertebral - ::::l thicker - muscle narrow - hind limb buds region and o er - no spiracle develops - tip rounded to longer, as in Gosner onto yolk III ::I- - nares perforated acuminate stages 30-31, slight - tail !!' - blood vessels anteriorly over yolk knee constrictions unpigmented ? - early gut development begins and foot paddle ~ faint arc in yolk anteriorly OQ. Cl (1) 7 - body broadens , - tail longer, - limbs lengthen, - diameter notIceably mouth WIdens further <: (1) - vertebral region flatter and tightly indent on increased to denser over 0' 2B-D) recessed within yolk (Fig. 2C) adpressed each side of foot I.J4mm -0 head, vertebral :3 - no extl'rnal d around yolk paddle as for - fully pigml'ntl'd, (1) " and ::l IIlternal flap IIlsIde nans extends to Gosner stage 33 choroid fissure down sides first gut wall in each side of about midwav left forelimb partly closed ::l- of ;.. yolk; vItl'lIine blood vessels around yolk protrudes through .... It Increased - fins low operculum (Fig. 2C) ::: groove down eItlwr side of ~ vertebral :::- '3~ 9 head well ddllled and prominent, - tail remains forelimbs - eyes lateral, - mouth about half - entIre dorsum ::l '"c.