The microbiome of dwarf chameleons

The microbiome of dwarf chameleons

by Alex Laube Tiermedizin Science

The term microbiome has been very popular for some years now. In humans and animals, it refers to the totality of all microorganisms that colonise a living being. Most of them colonise the gastrointestinal tract. In the case of chameleons, there is only very limited literature on this topic. A master’s thesis from South Africa now deals with the bacterial composition of the microbiome in South African dwarf chameleons of the genus Bradypodion.

60 cheek swabs were collected from wild chameleons in KwaZulu-Natal. Of these, 20 were cheek swabs from Bradypodion melanocephalum, 20 from Bradypodion thamnobates and 20 from Bradypodion setaroi. After sampling, the same 60 animals were transported in cloth bags to the research base, where the animals were kept in 3.3 l boxes for 24 hours to obtain faecal samples. Since not all of the original 60 chameleons defecated, faeces were collected from additional chameleons.

The samples were all genetically tested. 40.43% of the samples contained Firmicutes, a similarly large proportion of the samples contained Proteobacteria with 36.86%. Bacteroidota followed with some distance, which could be detected in just under 16% of the samples. Verrucomicrobiota, Fusobacteriota, Actinobateriota, Spirochetes, Desulfobacteroa, Cyanobacteria, Thermoplamatota, Deferribacterota, Synergistota, Campylobacterota, Deinococcota, Halobacterota, Euryarchaeota, Elusimicrobiota and Myxococcota were found in significantly smaller numbers (up to 2%).

The microbiome of dwarf chameleons of the species Bradypodion melanocephalum, Bradypodion thamnobates and Bradypodion setaroi is similar to that of other reptiles. It consists mainly of proteobacteria and firmicutes, which may contribute to digestion. One particular bacterial species also suggests that the diet of the studied dwarf chameleons may include beetles of the genus Dendrophagus. The microbiome of all three dwarf chameleon species was very similar in the cheek swabs – this is called phylosymbiosis – while there were differences in composition between the species in the faeces. In all three dwarf chameleon species, significantly more different bacteria were found in the faeces than in the cheek swabs. A comparison between males and females did not reveal any significant differences in the microbiome of all three chameleon species. The author assumes that the bacterial species depend on the different habitats of the respective species. It is still unclear to what extent the microbiome is related to bacteria that a chameleon may ingest with feeding insects or from the soil of its environment. A detailed list of the bacterial species found can be found in the appendix of the publication.

The Hitchhiker’s Guide to dwarf chameleons (Bradypodion): The composition and function of the microbiome
Matthew G. Adair
Master of Science dissertation at the university of Johannesburg, 2023
DOI: not available

Minimally invasive methods for obtaining DNA samples from chameleons

Minimally invasive methods for obtaining DNA samples from chameleons

by Alex Laube Tiermedizin Science

To reliably identify or compare chameleon species, genetic samples of the animals concerned are necessary. Traditionally, scientists have used organ or muscle samples from euthanized chameleons in museum collections or – less commonly – cut tail tips or blood samples from living chameleons. Researchers at the American College in Athens, Greece, have studied whether more minimally invasive methods would also be a good alternative.

They sampled 23 Chamaeleo africanus in the area of the lagoon of Pylos (Divari wetland between Gialova and the bay of Voidokilia) in the Peloponnese in Greece using buccal swabs. This involves running a sterile swab on the inside of the cheek through the chameleon’s mouth for six seconds. Blood was taken from the ventral tail vein of eight other Chamaeleo africanus for comparison. Sampling took less than a minute. Afterward, the chameleons were returned to where they were found. The swabs were transported refrigerated in a special buffer solution in Eppendorf cups and then frozen.

In the laboratory, the researchers were able to extract both nuclear and mitochondrial DNA from all the swabs. However, the quantity and quality of the DNA extracted were lower than in the blood samples. For most applications such as PCR amplification and gene sequencing, however, the scientists said the quantity was sufficient. In terms of invasiveness and destructiveness, buccal swabbing is certainly preferable to killing or injuring individual chameleons. Studies on other reptiles suggest that rapid freezing is not mandatory either – in the field, a functioning cool chain could become a problem in many chameleons’ countries of origin. The current study advises against ethanol as a fixing solution; the buffer solutions used lead to better results.

Buccal swabbing appears to be less applicable for cases where additional material for future studies might be preserved, for example when describing new species, or when sequencing the entire genome. However, the method is certainly a good alternative, especially for particularly small chameleon populations where lethal sampling could already significantly limit the breeding pool.

Buccal swabs as an effective alternative to traditional tissue sampling methods for DNA analyses in Chamaeleonidae
Maria Koutsokali, Christina Dianni and Michael Valahas
Wildlife Biology
DOI: 10.1002/wlb3.01052