Thomas M. Doherty-Bone

Batrachochytrium dendrobatidis infection and lethal chytridiomycosis in caecilian amphibians (Gymnophiona)

Batrachochytrium dendrobatidis (Bd) is commonly termed the ‘amphibian chytrid fungus’ but thus far has been documented to be a pathogen of only batrachian amphibians (anurans and caudatans). It is not proven to infect the limbless, generally poorly known, and mostly soil-dwelling caecilians (Gymnophiona). We conducted the largest qPCR survey of Bd in caecilians to date, for more than 200 field-swabbed specimens from five countries in Africa and South America, representing nearly 20 species, 12 genera, and 8 families. Positive results were recovered for 58 specimens from Tanzania and Cameroon (4 families, 6 genera, 6+ species). Quantities of Bd were not exceptionally high, with genomic equivalent (GE) values of 0.052–17.339. In addition, we report the first evidence of lethal chytridiomycosis in caecilians. Mortality in captive (wild-caught, commercial pet trade) Geotrypetes seraphini was associated with GE scores similar to those we detected for field-swabbed, wild animals.

Cryptic infection of a broad taxonomic and geographic diversity of tadpoles by Perkinsea protists

Significance Amphibians are among the most threatened animal groups. Population declines and extinctions have been linked, in part, to emerging infectious diseases. One such emerging disease has been attributed to Perkinsea-like protists causing mass mortality events in the United States. Using molecular methods, we evaluated the diversity of Perkinsea parasites in livers sampled from a wide taxonomic collection of tadpoles from six countries across three continents. We discovered a previously unidentified phylogenetically distinct infectious agent of tadpole livers present in a broad range of frogs from both tropical and temperate sites and across all sampled continents. These data demonstrate the high prevalence and global distribution of this infectious protist. The decline of amphibian populations, particularly frogs, is often cited as an example in support of the claim that Earth is undergoing its sixth mass extinction event. Amphibians seem to be particularly sensitive to emerging diseases (e.g., fungal and viral pathogens), yet the diversity and geographic distribution of infectious agents are only starting to be investigated. Recent work has linked a previously undescribed protist with mass-mortality events in the United States, in which infected frog tadpoles have an abnormally enlarged yellowish liver filled with protist cells of a presumed parasite. Phylogenetic analyses revealed that this infectious agent was affiliated with the Perkinsea: a parasitic group within the alveolates exemplified by Perkinsus sp., a “marine” protist responsible for mass-mortality events in commercial shellfish populations. Using small subunit (SSU) ribosomal DNA (rDNA) sequencing, we developed a targeted PCR protocol for preferentially sampling a clade of the Perkinsea. We tested this protocol on freshwater environmental DNA, revealing a wide diversity of Perkinsea lineages in these environments. Then, we used the same protocol to test for Perkinsea-like lineages in livers of 182 tadpoles from multiple families of frogs. We identified a distinct Perkinsea clade, encompassing a low level of SSU rDNA variation different from the lineage previously associated with tadpole mass-mortality events. Members of this clade were present in 38 tadpoles sampled from 14 distinct genera/phylogroups, from five countries across three continents. These data provide, to our knowledge, the first evidence that Perkinsea-like protists infect tadpoles across a wide taxonomic range of frogs in tropical and temperate environments, including oceanic islands.

Batrachochytrium dendrobatidis in amphibians of Cameroon, including first records for caecilians

Amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has been hypothesised to be an indigenous parasite of African amphibians. In Cameroon, however, previous surveys in one region (in the northwest) failed to detect this pathogen, despite the earliest African Bd having been recorded from a frog in eastern Cameroon, plus one recent record in the far southeast. To reconcile these contrasting results, we present survey data from 12 localities across 6 regions of Cameroon from anurans (n = 1052) and caecilians (n = 85) of ca. 108 species. Bd was detected in 124 amphibian hosts at 7 localities, including Mt. Oku, Mt. Cameroon, Mt. Manengouba and lowland localities in the centre and west of the country. None of the hosts were observed dead or dying. Infected amphibian hosts were not detected in other localities in the south and eastern rainforest belt. Infection occurred in both anurans and caecilians, making this the first reported case of infection in the latter order (Gymnophiona) of amphibians. There was no significant difference between prevalence and infection intensity in frogs and caecilians. We highlight the importance of taking into account the inhibition of diagnostic qPCR in studies on Bd, based on all Bd-positive hosts being undetected when screened without bovine serum albumin in the qPCR mix. The status of Bd as an indigenous, cosmopolitan amphibian parasite in Africa, including Cameroon, is supported by this work. Isolating and sequencing strains of Bd from Cameroon should now be a priority. Longitudinal host population monitoring will be required to determine the effects, if any, of the infection on amphibians in Cameroon.

Systematics and ecology of the caecilian Crotaphatrema lamottei (Nussbaum) (Amphibia: Gymnophiona: Scolecomorphidae)

New observations on Crotaphatrema lamottei are reported based on fieldwork on Mount Oku between 2006 and 2008. This species was encountered by pitfall trapping and digging, but encounter rates were low. Six new specimens of C. lamottei add substantially to the previous hypodigm for the species and genus, and new morphometric and meristic data are presented. Analysis of mitochondrial DNA sequence data supports strongly the monophyly of Crotaphatrema. The genetic and morphological distance between C. lamottei and Crotaphatrema tchabalmbaboensis is small, although there is a clear difference in colour pattern. The Data Deficient IUCN conservation status of all three species of Crotaphatrema is likely to change most readily as a result of better data on distribution.

A New Small Phrynobatrachus (Amphibia: Anura: Phrynobatrachidae) From Southern Cameroon

We describe a new small Phrynobatrachus species from southern Cameroon. The new species exhibits a combination of unique morphological characters and a distinctive colour pattern consisting of a black lateral face mask, a black throat in males, a white throat with uniform black lower mandibles in females and a white belly in both sexes. Morphologically it is characterized by small size, absence of an eyelid cornicle, presence of black spines on anterior part of vocal sac in males, spines on flanks, presence of discs on toe and finger tips, distinct webbing, absence of nuptial pads on male thumbs and scapular ridges converging in a straight line. Analysis of mitochondrial 16S rRNA revealed that the new species differs from 34 other West and Central African species of the genus by a minimum distance of 4.5% and is most similar to several Phrynobatrachus species which are almost all endemic to the Cameroon volcanic line or parts of it, i.e. P. chukuchuku (4.9%), P. werneri (5.1%), P. steindachneri (5.2%), P. schioetzi (5.6%), P. batesii (5.9%), P. cricogaster (5.5%), P. danko (6.1%), and P. manengoubensis (6.1%), respectively. The new species is most similar to P. batesii, which was described from forests close to the type locality of the new species. Morphologically the new species differs from P. batesii by much smaller size (< 20 mm vs. 25-31 mm), shape of scapular ridges, belly colour, shorter shanks, absence of nuptial pads and presence of gular spines in breeding males.

Rediscovery, natural history, and conservation status of Idiocranium russeli Parker, 1936 (Amphibia: Gymnophiona: Indotyphlidae)

The indotyphlid caecilian amphibian Idiocranium russeli Parker, 1936 is the only nominal species in its genus. Apart from two additional, largely overlooked locality records that we consider to be of an undescribed species, I. russeli is known with certainty from only a single collection of c.50 specimens from a single locality in 1933. We report new material from fieldwork in 2012 carried out in the vicinity of the type locality. Digging surveys at 34 sites for a total of >2000 person minutes found 50 I. russeli at 15 of these sites, extending the known range of the species by more than 40 km south and from an elevation of c.670 m to 104–820 m. The species probably occurs in nearby Nigeria and in some protected areas, is tolerant of some human disturbance, and is likely to move from Data Deficient to Least Concern on the IUCN Red List. Males have relatively longer and wider heads than females. Total length measured for preserved specimens is less than for freshly anaesthetized specimens, by up to 14.1%. Previously, preserved I. russeli were reported as having a maximum length of 114 mm, but the new sample includes specimens with total lengths of 145 mm in preservation and 167 mm when fresh. The sex of the smallest independent specimens (total length 62 mm in preservation) could be determined from examination of the gonads, hatchlings are c.30 mm, and I. russeli is confirmed as one of the smallest known caecilian species.

The tadpoles of nine Cameroonian Leptodactylodon species (Amphibia, Anura, Arthroleptidae)

We describe and compare the tadpoles of nine Leptodactylodon species from Cameroon. The tadpoles of Leptodactylodon bicolor, L. mertensi, L. ovatus, L. perreti and L. ventrimarmoratus are herein reinvestigated, partly based on larger series than previously available. In addition we present first descriptions for the tadpoles of L. boulengeri, L. erythrogaster, L. ornatus, and L. cf. polyacanthus. The morphology of these exotrophic, lotic and neustonic tadpoles is discussed in comparison with other stream-dwelling tadpoles. Based on the assumed biology of these tadpoles, living in interstices of gravel or debris, the functioning of several special morphological features, in particular the funnel-mouth of Leptodactylodon tadpoles, are interpreted.