Leiopelma Research Articles

Archaic, terrestrial Hamilton’s frogs (Leiopelma hamiltoni) display arboreal behaviours

New Zealand has three species of endemic amphibians in the genus Leiopelma, all of which are threatened with extinction. The primary threats to their persistence are mammalian predators and habitat loss, and the translocation of these frogs into restored habitat is a common method of conservation. The Maud Island frog (Leiopelma hamiltoni), is considered terrestrial with habitat needs centering on complex boulder-strewn habitat. However, during recent surveys of a translocated population, we found repeated use of arboreal habitat within this species.

Rapid recovery of a population of the cryptic and evolutionarily distinct Hochstetter's Frog, Leiopelma hochstetteri, in a pest‐free environment

SummaryNew Zealand's native frogs (genus Leiopelma) display a very high degree of endemism and belong to a distinctive and ancient evolutionary lineage. All four extant species are considered to be threatened or endangered, but the mechanisms behind their decline are poorly understood. Many of the potential factors causing population declines are confounded for the two species living on the mainland; in particular, habitat degradation and the presence of introduced mammalian pests have been difficult to disentangle in the past. Here we present data on a population of Hochstetter's Frog (Leiopelma hochstetteri) living in a pest‐free mainland sanctuary, the 3363‐ha Maungatautari Ecological Island. Survey data from this population shows a fourfold increase in numbers between 2009 and 2012 from a very low initial density. Our results suggest that for Hochstetter's Frog at least, and possibly the other mainland species of Leiopelma, introduced mammals are a major driving factor in population declines. Given that the frog population at Maungatautari was discovered by serendipity when planning for the pest‐free sanctuary was already well underway, this also highlights the conservation value of large pest‐free areas and ecosystem‐level management.

A Mitogenomic Exploration of the Phylogeny and Evolution of Extant Anurans

Phylogenetic relationships among major clades of anuran amphibians were analyzed using mitogenome sequences of 54 frog species from 41 genera. Anurans are under two major groups Archaeobatrachia and Neobatrachia. Mesobatrachia was introduced later this classification. Our phylogenetic study based on mitogenome authenticated four groups (1. Bombinatoridae + Alytidae; 2. Megophyridae + Pelobatidae + Pelobytidae; 3. Bombinatoridae + Alytidae cluster with Leiopelmatidae; 4. Pipidae + Rhinophrynidae). Our phylogenetic study confirms Neobatrachia is monophyletic and Archaeobatrachia is paraphyletic.

Differential polymorphism in cutaneous glands of archaic Leiopelma species

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 frequency 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 genus 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 ± 0.08 μm in diameter). Type II glands are round and contain larger heterogeneous granules (4.06 ± 0.16 μm) 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 present 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.

Genetic variation in the genus Leiopelma and relationships to other primitive frogs

Allozyme variation was studied the three living species of Leiopelma. L. hamiltoni and L. archeyi are shown to be closely related to each other although L. hamiltoni is slightly more divergent relative to L. hochstetteri. This parallels previous cytoenetic data. The rarity and insularity of L. hamiltoni enables the calculation of a mutation rate based on genetic variance and population size. A mutation rate per generation of 2.7times 10--6 is sufficient to account for the observed levels of variation. Six populations of L. hochstetteri show a pattern of genetic divergence that also closely parallels previously detected cytogenetic variation. L. hochstetteri is genetically distant from its congeneric species while all species of Leiopelma are at an extreme genetic distance from Ascaphus truei, the only other living amphicoelous fro At the limits of resolution of the allozme technique, Ascaphus clusters with the more morphologically advanced frogs, Discogiossus and Bombina, rather than with Leiopelma. Taken with other evidence, this supports recognition of two families, Leiopelmatidae anl Ascaphidae, with Leiopelma the probable sister group of all other frogs.

Chiasma Frequency in Frogs of the Genus Leiopelma (Amphibia; Anura) and a Test of the Hypothesis of Inducible Recombination

The rate of recombination in three species of Leiopelma (Leiopelmatidae, Anura) from New Zealand was estimated by measuring chiasma frequency in spermatocyte bivalents. Both the mean and intra-individual variance of excess chiasmata frequency differed among the three species (L. hochsletteri = 13.17 5 2.96 SD, L. harnilroni = 9.69 + 1.16 SD; L. archeyi = 10.71 1.1 1 SD). L. hochstetteri has one of the highest rates of intra-individual variation in chiasma frequency found in frogs. The presence of supernumerary chromosomes in L. hochsretteri was used to test the theory of inducible recombination. If supernumeraries are parasites, then they will be associated with an increase in either chiasma frequency or an increase in within-individual variance. However, this was not found in L. hochsferteri, Nevertheless, the high variance in chiasma frequency associated with these putative genomic parasites in L. hochstetteri makes it impossible to rule out the Red Queen hypothesis as an explanation.

Chromosome Polymorphism in Archey's Frog (Leiopelma archeyi) from New Zealand

Abstract The most primitive frogs in which a sex chromosome system has been determined are members of the endemic New Zealand genus Leiopelma. Two species, Leiopelma pakeka and Leiopelma hochstetteri, have female heterogamety of the ZW/ZZ and 0W/00 types, respectively. Despite its great karyotypic similarity to L. pakeka, a third species, Leiopelma archeyi, has not been know previously to possess heteromorphic sex chromosomes. Herein a highly differentiated putative W chromosome characterized by the addition of a completely heterochromatic short arm is reported from a female L.archeyi from the Whareorino forest of the North Island of New Zealand.

Determining the species status of one of the world's rarest frogs: a conservation dilemma

AbstractNew Zealand's native frogs (genus Leiopelma) are considered to be archaic amphibians of exceptional scientific interest that appear to have remained virtually unchanged for 160‐200 million years. They are among the rarest extant amphibians and are highly restricted in distribution, confined to isolated, highly disjunct, populations on the North Island and a few small offshore islands in Cook Strait. Previous investigations have suggested, based on patterns of allozyme variation, that the Stephens Island frog (Leiopelma hamiltoni) and Archey's frog (L. archeyi) are sister taxa to the exclusion of the Maud Island frog, a species in close geographical proximity to the Stephens Island frog and previously viewed as a population of this species. As a consequence of these data, a new species, L. pakeka, the Maud Island Frog, has been described. This new species definition has dramatically enhanced the conservation status of L. hamiltoni, of which there are probably fewer than 150 individuals. In this study we re‐examine the systematics of the Leiopelmatidae using mtDNA sequence analyses. Partial 12 S ribosomal RNA and cytochrome b (Cyt b) gene sequences were obtained for 57 frogs from six populations representing all four extant Leiopelma species. Contrary to previous reports we find L. pakeka and L. hamiltoni to be monophyletic. The amount of variation evident between these present species (<1% for Cyt b) is comparable to that seen between populations of L. archeyi. Based on these data, classification of L. pakeka and L. hamiltoni as separate species appears to be unwarranted, but they may be sufficiently distinct to warrant classification as evolutionarily significant units.

Retinal organisation in the native New Zealand frogsLeiopelma archeyi, L. hamiltoni, andL. hochstetteri(Amphibia: Anura; Leiopelmatidae)

This paper presents an account of retinal ultrastructure in three species of the archaic anuran genus Leiopelma. The Leiopelma retina is approximately 150 µm thick from the inner limiting to Bruch'...

Effects of arginine vasotocin on water balance of three leiopelmatid frogs

The effects of arginine vasotocin (AVT) on water movements in three frogs of the anatomically primitive genus Leiopelma were compared in vivo and in vitro. Treatment with AVT in vivo (7 × 10 −13 mol/g body weight) led to significant water retention in the terrestrial species L. archeyi and L. hamiltoni, but not in the semiaquatic species L. hochstetteri. All three species showed increasing water retention over some part of the dose range 7 × 10 −15 −7 × 10 −11 mol/g. Isolated pelvic skin from L. archeyi and L. hamiltoni increased in osmotic water flow (OWF) in response to AVT, whereas that from L. hochstetteri did not. Dorsal skin from all three species, as well as pectoral skin from L. archeyi and L. hochstetteri, showed no hydroosmotic response to AVT. Isolated bladders of all species are small and showed small increases in OWF in response to AVT. Glomerular filtration rate in vivo was reduced significantly by AVT in L. archeyi and L. hamiltoni, but not in L. hochstetteri. These results show that water balance responses to AVT among the three species are correlated with habitat, and indicate that the absence of a cutaneous hydroosmotic response in L. hochstetteri is not a characteristic, primitive feature of the entire genus.

Heteromorphic Sex Chromosomes in the Rare and Primitive Frog Leiopelma hamiltoni from New Zealand

Determination du caryotype et du systeme de chromosomes sexuels chez la grenouille primitive de Nouvelle Zelande Leiopelma hamiltoni

Antipredator behaviour and skin glands in the New Zealand native frogs, genusLeiopelma

Abstract The frogs of the genus Leiopelma exhibit characteristic antipredator behaviours. All three living species utter squeaks or chirps when annoyed. The acoustic structure of the vocalisations varied between individuals within a species. Vocalisations probably serve no function for intraspecific communication. Under duress, the terrestrial species, L. hamiltoni and L. archeyi, both assumed a stifflegged stance while rearing up, extended the legs, raised the body, and butted the head. The more aquatic species, L. hochstetteri, did not assume so rigid a head-butting stance as it rarely raised its body or extended its legs. This species was more apt to try to escape. These behavioural differences correlated with differential distributions of defensive granular glands in the skin. The glands were concentrated into discrete dorsal patches arranged in six longitudinal rows in L. hamiltoni and L. archeyi. The anterior end of the middle row terminates in what has been termed a parotoid gland. In L. hochstette...

The genus Dolichosaccus (Platyhelminthes: Digenea) from amphibians and reptiles in New Zealand, with a description of Dolichosaccus (Lecithopyge) leiolopismae n. sp.

Abstract Two species of Dolichosaccus occur in New Zealand. Dolichosaccus (Lecithopyge) novae-zealandiae Prudhoe, 1970 was described from frogs of the endemic genus Leiopelma. An additional six specimens, one of which is figured, were obtained from preserved frogs. Dolichosaccus (Lecithopyge) leiolopismae n. sp. was described from scincid lizards of the genus Leiolopisma and from the tuatara (Sphenodon punctatus). Information on variability in the new species was presented and discussed. Morphological criteria for distinguishing between species in Dolichosaccus were few and unreliable. The presence of D. leiolopismae in reptiles on Stephens Island, to which no exotic reptiles or amphibians have been introduced, indicated that the species is probably endemic to New Zealand.

Phylogenetic relationships within the New Zealand frog genusLeiopelma —immunological evidence

Abstract Albumin evolution is examined within the anuran genus Leiopelma using the quantitative immunological technique of micro-complement fixation (MC'F). The albumins of L. archeyi and L. hamiltoni are relatively similar to each other, yet both differ greatly from the albumin of L. hochstetteri. Using albumin as a molecular clock, we estimate that L. hochstetteri diverged from the lineage leading to L. archeyi and L. hamiltoni during the Miocene, about 15 million years ago. The divergence of L. archeyi and L. hamiltoni appears to have been a Pliocene event (about 3 million years ago).