Knysna dwarf chameleons: city vs. forest habitat

Knysna dwarf chameleons: city vs. forest habitat

by Alex Laube Science

How do chameleons change when their natural habitat has to make way for human settlements? International scientists recently got to the bottom of this question. They hypothesised that a chameleon living in a suburban area must differ from its forest-dwelling conspecifics in terms of injury frequency, external characteristics and bite force as an expression of changed living conditions.

Between 2020 and 2022, 276 Knysna dwarf chameleons (Bradypodion damaranum) were studied in South Africa. The locations chosen were George and Knysna, two towns located around 60 kilometres apart on the south coast of South Africa. George was founded in 1811 and now has over 220,000 inhabitants, while Knysna was founded in 1825 and currently has just under 76,000 inhabitants, although they live in much less space and are therefore much more densely populated. In both cities, Bradypodion damaranum were caught in urban environments (private gardens, public parks, roadsides), examined and then released. Chameleons were also studied 10 to 12 kilometres away in their natural habitat (temperate forest). The adult chameleons were measured and photographed. The data was analysed and compared using various methods. Wounds, scars and bone fractures visible to the naked eye were counted as injuries. To measure bite force, the animals were each encouraged to bite five times on a special piezoelectric measuring device.

The analysis showed that the dwarf chameleons in urban environments had significantly lower casques and shorter gulars. The males from the city, however, had larger and wider heads. The female dwarf chameleons from the forest had significantly larger casque spurs. The males in the city had significantly more injuries (88.1%) compared to the males in the forest (72.5%). In the city, the dwarf chameleons also bit harder than in the forest when casque height and parietal crest were included in the calculations. However, when snout-vent length was included instead, there was no difference in bite force.

Differences between urban and natural populations of dwarf chameleons (Bradypodion damaranum): a case of urban warfare?
Melissa A. Petford, Anthony Herrel, Graham J. Alexander, Krystal A. Tolley
Urban Ecosystems 2023
DOI: 0.1007/s11252-023-01474-1

Development of sexual characteristics in African chameleons

Development of sexual characteristics in African chameleons

by Alex Laube Science

Many chameleons show strong sexual dimorphism, meaning that the males look very different from the females of the same species. Bright colours, dorsal sails and bizarre rostral appendages are among the best-known sexual characteristics. However, exactly when the different characteristics developed in chameleons is largely unexplored. A publication by two US scientists now addresses this issue.

The two researchers collected morphological data from two standard works on African and Malagasy chameleons, which they then analysed together with phylogenetic trees. They identified eleven sexual characteristics that could be of interest for intraspecific behaviour: Casque, rostral appendages, supraorbital appendages, occipital lobes, dorsal crest, dorsal spines, gular crest, gular spines, ventral crest, tail crest and tail spines.

Surprisingly, there was no difference between the sexes in terms of the frequency with which traits were acquired or lost throughout evolution. Whether there is a connection to the habitat of the respective species is evaluated contradictorily. The oldest sexual characteristics include the rostral appendages and dorsal crest in males, which were acquired at least 65 million years ago. In contrast, the oldest sexual characteristics in females were the casque and dorsal crest. Six of the eleven features (rostral appendages, supraorbital appendages, dorsal crest/spines, caudal crest/spines) first appeared in males and only 15 million years later on average in females. In males, the number of sexual characteristics correlated significantly with snout-vent-length.

The genera Trioceros (up to 10 features in one species), Chamaeleo and Furcifer (up to seven features each in one species) showed a particularly high number of sexual characteristics at the same time. In contrast, there were particularly few sexual characteristics in the genera Brookesia, Calumma and Rieppeleon. None of the eleven sexual characteristics could be identified in the females of the genera Furcifer, Kinyongia, Nadzikambia and Rhampholeon; presumably they have lost these characteristics in the course of evolution.

Macroevolution of sexually selected weapons: weapon evolution in chameleons
Melissa Van Kleeck-Hann & John J. Wiens

Evolution 70 (10), 2023, pp. 2277-2290
DOI: 10.1093/evolut/qpad138

Histology of the chameleon liver

Histology of the chameleon liver

by Alex Laube Tiermedizin Science

Histological examinations of organ tissue are part of every pathological examination in veterinary medicine. They are also frequently carried out in reptiles, but there are few studies on the histology of healthy organ tissue. An Arabic publication now deals with histological sections of chameleon livers.

Seven adult Yemen chameleons were captured in Abha City in the Aseer region and then killed with ether inhalation. The livers were placed in formalin and then poured into paraffin to make sections.

Morphologically, the liver was found to be a two-lobed, dark brown organ approximately 3.7 x 2 cm in size, which lies in the coelomic cavity in front of the stomach and surrounds the gall bladder. As in other animals, a capsule of connective tissue surrounds the liver.

Histologically, the liver of Yemen chameleons resembles that of other vertebrates in many respects. The liver capsule consists of closely spaced collagenous fibres and smooth muscle fibres. Normally, trabecular connective tissue divides the liver itself into many small lobules, but such a structure does not appear to be present in Yemen chameleons. In contrast to mammals, the liver cells (hepatocytes) are not arranged radially around a vein, but rather irregularly in follicles or alveoli. The hepatocytes are surrounded by capillary blood vessels. So-called melanoma macrophages, which are not found in birds and mammals, can be seen in the blood vessels. The hepatocytes in the Yemen chameleon are polyhedral or pyramid-shaped and usually contain several large, round cell nuclei in the periphery. The nuclei contain conspicuously dark nucleoli. Occasionally nuclei are central. Under haematoxylin-eosin (HE) staining, the hepatocytes appear very eosinophilic. In the connective tissue, branches of the portal vein, hepatic artery, small bile ducts and lymphatic vessels could be visualised. Haematopoietic tissue was found in the area directly under the liver capsule.

In addition to the histological examination, several pieces of liver were also examined using transmission electron microscopy. Images of both examination methods can be found in the publication.

Histomorphological, histochemical and ultrastructural studies on the healthy liver of Yemen Veiled Chameleon (Chamaeleo calyptratus) in Southern Saudi Arabia
Amin A. Al-Doaiss, Mohammed A. Alshehri, Ali A. Shati, Mohammad Y. Alfaifi, Mohammed A. Al-Kahtani, Ahmed Ezzat Ahmed, Refaat A. Eid, Laila A. Al-Shuraym, Fahd A. Al-Mekhlafi, Mohammed Al Zahrani, Mohammed Mubarak
International Journal of Morphology 41(5), 2023: pp. 1513-1526.
DOI: none

Image: Histological section of the liver of a Yemen chameleon from the above-mentioned publication

Genome of South African dwarf chameleons decoded

Genome of South African dwarf chameleons decoded

by Alex Laube Science

After a reference genome for the panther chameleon (Furcifer pardalis) was recently published for the first time in China, scientists from South Africa have now followed with the genome of two dwarf chameleon species.

For the analyses, a male Bradypodion pumilum from Cape Town and a male Bradypodion ventrale from an introduced population in Johannesburg were taken. Muscle and liver tissue was used for long sequencing (HiC). The genome size of Bradypodion pumilum is 2.43 gigabase pairs (Gb), that of Bradypodion ventrale 2.40 Gb. The BUSCO analysis demonstrated a high completeness with about 97% of all existing coding genes in vertebrates. Furthermore, the current publication confirms the six macrochromosomes already found from the karyotype in Bradypodion thamnobates 2017. Various comparisons with Anolis sagrei were made. It remains open which chromosomes in Bradypodion are sex chromosomes.

The genomes can be viewed in the NCBI BioProject under the number PRJNA9861319 and under the BioSample numbers SAMN35825189 and SAMN35825190 respectively.

De novo whole genome assemblies for two Southern African Dwarf Chameleons (Bradypodion, Chamaeleonidae)
Jody M. Taft, Krystal A. Tolley, Graham J. Alexander, Anthony J. Geneva
Genome Biology and Evolution 15 (10), 2023, pp. 1-8
DOI: 10.1093/gbe/evad182

Findings on the synonyms of Trioceros ituriensis

Findings on the synonyms of Trioceros ituriensis

by Alex Laube Verbreitung Science

Synonyms for the Congolese Ituri chameleon (Trioceros ituriensis) have existed for several decades. A recent publication by the herpetologist Wolfgang Böhme questions whether two of them could be separate species.

The US herpetologist Karl Patterson Schmidt described the chameleon as Chamaeleon ituriensis in 1919. At that time, Schmidt gave Medje, Ituri Forest, in the Democratic Republic of Congo as the type locality. He already noticed the external similarity to Chamaeleon johnstoni affinis, which is why he gave exactly that as a synonym of his Chamaeleon ituriensis. At the same time, Chamaeleon johnstoni affinis must not be confused with today’s Trioceros affinis, a separate species from Ethiopia that had already been described in 1845. In the course of the 20th century, Chamaeleo johnstoni affinis was placed in the genus Trioceros, sometimes thought to be a subspecies of its own, sometimes not. Böhme states that Trioceros johnstoni affinis is definitely a synonym of Trioceros ituriensis. Differences between Trioceros johnstoni and Trioceros ituriensis are the body size, the “reversed” sexual dimorphism (in T. ituriensis the females are larger than the males), a white line along the belly, several rows of enlarged scales along the side of the body, conical scales on the sides of the throat and the absence of rostral and preocular horns in male T. ituriensis.

However, the author is not sure about the species status of Chamaeleo laevigularis. The species was originally described from South Africa in 1926, then considered a synonym of Trioceros johnstoni and last identified as T. ituriensis by Tilbury in 2010. Böhme considers, because of different scaling of the throat, whether either a wrong locality was noted in the first description or it is a separate species, but could be extinct or lost.

Böhme also comes to the conclusion that Trioceros tremperi, which was described by Neĉas in 1994, could possibly also represent an already extinct species or a lost species and that the locality simply corresponded to incorrect information. Trioceros tremperi was last given as a synonym of Trioceros ituriensis by Tilbury 2010 and Spawls 2018. The chameleons had not been found in the type locality in Kenya before.

Documenting synonymies in Trioceros ituriensis (Schmidt, 1929) with remarks on sexual dimorphism in chameleons (Squamata: Chamaeleonidae)
Wolfgang Böhme
Revue Suisse de Zoologie 130(2), 2023: pp. 521-264
DOI: 10.35929/RSZ.0099

Photo: Trioceros ituriensis in the Budongo forest, Uganda, photographed by Katja Rembold

Effect of human chorionic gonadotropin in chameleons

Effect of human chorionic gonadotropin in chameleons

by Alex Laube Tiermedizin Science

After a study on sperm collection in chameleons was already published this year, further results from the largely same team of authors now follow. The aim is to further research the basics of assisted reproduction, i.e. medical assistance in reproduction, in chameleons.

At Louisiana State University, 24 Veiled Chameleons were kept under standardised conditions for over a year. All animals came from a dealer who had taken them from the population of wild Veiled Chameleons in Florida. All were kept individually in ReptiBreeze, equipped with automatic sprinklers and artificial plants. Temperatures were around 28-29°C during the day with spots to seek higher values. 12 h UV-B irradiation per day was offered. Crickets and zophobas were fed. Before the start of the study, all 24 chameleons were clinically examined and several parasite treatments were carried out. Only after a month of acclimatisation did the actual study begin.

The first experiment tested what dose of human choriogonadotropin (hCG) is needed to increase the hormone levels of testosterone in the blood by 50%. Eleven Veiled Chameleons were randomly assigned to one of three groups. The three groups received injections of 100, 200 or 300 IU hCG under the skin at two-week intervals. Blood samples were taken before the first hormone injection and at 30 minutes, one hour, two hours, four hours, eight hours, 12 hours and 24 hours afterwards.

The second experiment tested the effect of hCG treatment on sperm production. 13 Veiled Chameleons were randomly assigned to a treatment or a control group. Once a week for one month, the animals in the first group were treated with 100 IU of hCG, while the second group was only injected with the same volume of isotonic saline. After a four-week break, the groups were switched and the experiment repeated. Blood samples to measure testosterone levels were taken before treatment and on day 15 and 30 afterwards. Semen was collected by electroejaculation under anaesthesia on the day before treatment and 30 days after.

The results showed that the testosterone level in male Veiled Chameleons increased significantly directly after the administration of hCG and remained elevated for about 24 hours. However, it did not matter which dose of hCG had been given beforehand. It could also be shown that the testosterone level increased significantly after the administration of hCG compared to the control group, which only received saline solution. The number of successful electroejaculations could be increased under hCG.

Effects of exogenous human chorionic gonadotropin administration on plasma testosterone and semen production in the Veiled Chameleon (Chamaeleo calyptratus)
Sean M. Perry, Sarah R. Camlic, Michael Lierz, Mark A. Mitchell
Journal of Herpetological Medicine and Surgery 33 (3), 2023, pp. 180-191
DOI: 10.5818/JHMS-D-22-00038

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

Concerning Florida’s introduced panther chameleons

Concerning Florida’s introduced panther chameleons

by Alex Laube Verbreitung Science

The “Sunshine State” Florida in the USA has the largest number of non-native species of reptiles in the world because of its warm climate. The panther chameleon (Furcifer pardalis) is one of the invasive species, i.e. those that do not actually belong in Florida but are now reproducing there. A study has now investigated the question of what the human inhabitants of Florida actually think of the chameleons.

It has been discussed for a long time whether panther chameleons belong to the species that were deliberately released for the purpose of “ranching”, i.e. to collect the offspring of the released chameleons for sale. That private individuals collect panther chameleons is not in dispute. According to the authors, ranching populations in Florida are mostly kept secret. They became aware of a small population in Orange County via social media in 2019. They then searched for the animals at night with torches and actually found 26 panther chameleons during several walks. They encountered private individuals on several occasions who were also looking for chameleons.

In 2020, questionnaires were distributed in person and via flyers with QR codes to 248 households located within the presumed 0.9 km² distribution area of the panther chameleon population. They were asked about concerns regarding the occurrence of panther chameleons, but also about existing knowledge about invasive species in general. The residents were also divided into three areas: A core region where chameleons had been observed several times, a peripheral region with few findings, and an outer region where no chameleons had been sighted at all.

44 households answered the questionnaire.  In fact, all 11 interviewed residents in the outer region had not sighted any chameleons. Of the 33 residents interviewed in the core and peripheral region, about a third said they had already observed panther chameleons. The same number had seen the light of torches at night. 86% of the residents surveyed knew that panther chameleons are not actually native to Florida. Only a few residents said they were concerned about the occurrence. Seven residents had approached collectors with torches and said the collectors had all said they were looking for chameleons for research purposes. Only one of the collectors had said he/she was looking for animals to sell, according to the residents. One resident reported an altercation after strangers entered his property several times looking for chameleons. Another resident called the police because of a whole group of collectors on the neighbouring property.

Unfortunately, the questionnaire was given out after the search efforts of the authors themselves, so it is not apparent from the responses how many of the encounters were indeed with people looking for chameleons for sale purposes. The publication is also a preprint, so no review process has taken place yet.

Colorful lizards and the conflict of collection
Colin M. Goodman, Natalie M. Claunch, Zachary T. Steele, Diane J. Episcopio-Sturgeon, Christina M. Romagosa
Preprint, 2023
DOI: 10.1101/2023.08.10.552819

Picture: Alex Laube

Unknown chameleon discovered in Ivohiboro forest (Madagascar)

Unknown chameleon discovered in Ivohiboro forest (Madagascar)

by Alex Laube Verbreitung Science

There are still almost unexplored areas on Madagascar today. The Ivohiboro rainforest is located in the southeast of the island in the protected area of the same name, southwest of the southernmost foothills of the Andringitra Mountains. The forest itself is about 8.58 km² in size and thus only occupies a small part of the protected area. It is surrounded by savannahs and spans altitudes from 650 to 1460 m above sea level. The protected area is currently managed by local organisations and Madagascar’s Ministry of Environment. The last expedition to explore the Ivohiboro forest took place in 1924. Since 2016, researchers from the USA and Great Britain have now undertaken six expeditions to the small forest to study the biodiversity of plants, birds, mammals, reptiles, and amphibians there in more detail.

To detect reptiles and amphibians, the forest was divided into nine transects of about 200 x 20 m, each more than 200 m apart. The transects were searched for several days and nights. All animals found were documented and, if possible, identified down to genus or species level.

As a result, the scientists were able to identify 107 species of vertebrates and 219 plants. This enormous diversity of species underlines the importance of preserving the forest in terms of species conservation and indicates a well-functioning ecosystem. Among the species found were two chameleons: a Palleon species and a small Calumma. Unfortunately, the publication does not provide any further information on the former. The small Calumma had a conspicuous blue coloured rostral appendage, as it is found in Calumma linotum or Calumma boettgeri in the far north of Madagascar. As genetic studies are still lacking, it is unclear whether these chameleons are an extremely wide range extension – Ivohiboro lies about 1000 km south of the ranges of Calumma boettgeri and Calumma linotum – or whether it is perhaps even a new, as yet undescribed species.

A surprising haven: The biodiversity of an old-growth forest amidst a scorched landscape in Madagascar
Beatriz Otero Jimenez, Ren Montaño, Ryan S. Rothman, Rachel C. Williams, Patricia C. Wright
Conservation Science and Practice, 2023
DOI: 10.1111/csp2.12993

Genome of the panther chameleon decoded

Genome of the panther chameleon decoded

by Alex Laube Science

In recent decades, genetic research has developed rapidly. Since 2009, the so-called high fidelity (HiFi) Pacbio sequencing method has been available for sequencing genomes. Nevertheless, relatively little is being done in the reptile field. There are only about a hundred so-called reference genomes for reptiles, and none at all for chameleons. Scientists from China have now published a reference genome for the panther chameleon (Furcifer pardalis).

For the analysis, a 5-year-old male captive panther chameleon was killed using isoflurane and then dissected. Different tissues were frozen in liquid nitrogen. Skeletal muscle was used for short genome DNA sequencing and HI-C sequencing. Liver was used for HiFi sequencing. RNA from heart, liver, spleen, testis, lung, kidney, and skin were used for transcriptome sequencing.

The genome size of the panther chameleon from the K-mer analysis is 1.61 gigabase pairs (Gbp), containing only 22 so-called contigs, sets of overlapping DNA. The karyotype contains 11 chromosomes, each consisting of one to four contigs. Ten out of eleven chromosomes have repeat sequences (TAACCC). BUSCO analysis demonstrated a high completeness of the genome. The genome can be viewed in the NCBI BioProject under the number PRJNA974816 and in ScienceDataBank.

Efficient and highly continuous chromosome-level genome assembly of the first chameleon genome
Hongxin Xie, Zixuan Chen, Shuai Pang, Weiguo Du
Genome Biology and Evolution 131, 2023
DOI: 10.1093/gbe/evad131

 

Picture: Alex Laube