Sex chromosomes in chameleons

Sex chromosomes in chameleons

by Alex Laube Science

Which sex chromosomes are present in chameleons has so far been studied rather sparsely. The Madagascan chameleon genus Furcifer is known to have Z and W chromosomes, although sometimes several Z chromosomes occur, so-called neo-sex chromosomes. Recently in the Czech Republic, scientists examined this deeper.

Blood and tissue samples were taken from 13 chameleons to isolate DNA. The animals sampled included one male and one female each of the species Brookesia therezieni, Calumma glawi, Calumma parsonii, Chamaeleo calyptratus, Furcifer campani, Furcifer labordi, Furcifer lateralis, Furcifer oustaleti, Furcifer pardalis, Furcifer rhinoceratus, Furcifer viridis, Kinyongia boehmei and Trioceros johnstoni. Only in Furcifer oustaleti were two females sampled. Subsequently, the Z1 chromosomes of the panther chameleons and the Z and W chromosomes were analysed by microdissection. Gene coverage analyses were performed for carpet and panther chameleons. In addition, qPCRs were performed to compare the homology of the Z chromosomes.

The results show that the morphology of the Z1 chromosomes of panther chameleons corresponds to the Z chromosome of the entire genus Furcifer. The Z1 chromosome of panther chameleons thus corresponds to the Z chromosome of Furcifer oustaleti. The Z2 chromosome of panther chameleons, on the other hand, is a neo-sex chromosome. Both the Z and W chromosomes in Furcifer oustaleti are probably pseudautosomal. 42 genes have been described as specific for the W chromosome.

A total of 16,947 genes were identified in Furcifer lateralis and 16,909 genes in Furcifer pardalis. The ratio of the number of genes between females and males is 0.35 and 0.65 for the two species. In panther and carpet chameleons, most of the genes on the W and Z chromosomes were found to be the same, with relatively few genes found only on the W chromosome. This finding is surprising, as the researchers had actually expected that the heterochromatic W in Furcifer species would have lost most of its genes compared to the Z chromosome.

The sex chromosomes of the genus Furcifer probably evolved at least 20 million years ago, which roughly corresponds to the time when the species Furcifer campani split off from the other Furcifer species.

Heteromorphic ZZ/ZW sex chromosomes sharing gene content with mammalian XX/XY are conserved in Madagascan chameleons of the genus Furcifer
Michail Rovatsos, Sofia Mazzoleni, Barbora Augstenová, Marie Altmanová, Petr Velenský, Frank Glaw, Antonio Sanchez, Lukáš Kratochvíl
Scientific Reports 14, 2024: 4898.
DOI: 10.1038/s41598-024-55431-9

New case reports on hemipenes amputation

New case reports on hemipenes amputation

by Alex Laube Tiermedizin

The University of Sofia (Bulgaria) has published a new paper with several case reports involving chameleons. The authors describe 16 cases of different lizards that suffered a hemipenis prolapse and their treatment.

The lizards included a panther chameleon (Furcifer pardalis) and two Veiled Chameleons (Chamaeleo calyptratus). All three patients were presented to the veterinarians with bilateral hemipenes prolapse. Initially, the prolapses were bathed in 20% dextrose solution, after which the hemipenes were manually repositioned. However, the prolapses then recurred, so surgery was the final solution. Under general and local anaesthesia administered intramuscularly, the hemipenes were removed, the wound sutured and the remaining small stump repositioned in the respective hemipenes pocket. Meloxicam was administered as an analgesic once a day for 5 days after the operation. Only lizards in which the surgical field appeared to be dying off during the follow-up examinations were given antibiotics for 10 days.

Hemipenectomy in leopard geckos, chameleons and bearded dragons
Seven Mustafa & Iliana Ruzhanova-Gospodinova
Tradition and Modernity in Veterinary Medicine, 2024
DOI: nicht vorhanden

Photo: Panther chameleon, photographed by Alex Laube in Madagascar

Mosquito bites may induce skin colour change

Mosquito bites may induce skin colour change

by Alex Laube Tiermedizin Science

Sometimes science starts small: last year, someone posted a photo of a Calumma globifer with a mosquito sitting on it on the online platform iNaturalist. Right there you could see a black discoloration of the scales. I wonder if there was a connection?

A handful of curious people searched for more photos of mosquitoes on chameleons and found what they were looking for: On Facebook there were some of Veiled chameleons, on iNaturalist more of Furcifer minor and Furcifer nicosiai. However, there were also six observations of mosquitoes on chameleons that did not appear to have black spots.

To test the connection, scientists in Madagascar placed two Furcifer oustaleti and four carpet chameleons alone in an enclosure with 25 female Asian tiger mosquitoes (Aedes albopictus), which had not been fed for 24 hours beforehand. At the same time, all six chameleons were pricked in the skin with a needle to test whether this “trauma” would also trigger a color change in the skin. The results were surprising: in the four Furcifer lateralis, numerous black skin discolorations developed after mosquito bites, in the two Furcifer outaleti not a single one. The punctures with the needle remained without consequences in all six.

The authors of the recently published article propose three possible theories as to how the color change in the chameleon’s skin could come about: The mosquito saliva could contain a type of local anesthetic, nitric oxide or other proteins that cause the skin’s melanophores to become exclusively visible. Further research in this field would certainly be exciting!

Mosqito bite-induced color change in chameleon skin
Pablo Garcia, Raul E. Diaz Junior, Christopher V. Anderson, Tovo M. Andrianjafy, Len de Beer, Devin A. Edmonds, Ryan M. Carney
Herpetological Review 54(3), 2023, pp.353-358

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

Zoonotic potential of Yemen chameleons in Gran Canaria (Spain)

Zoonotic potential of Yemen chameleons in Gran Canaria (Spain)

by Alex Laube Science

The Canary Islands are located northwest of Africa near the coast of Morocco. On Gran Canaria, the second largest island, around 290 of over 1000 plant and animal species have been introduced, i.e. species that do not originally occur there. Since at least 2017, there have been free-living Veiled chameleons (Chamaeleo calyptratus) on Gran Canaria. Spanish scientists have now investigated whether this introduced chameleon population could have zoonotic potential.

They examined 40 Veiled chameleons that had previously been caught and killed by Red de Alerta Temprana de Canarias para la Detección e Intervención de Especies Exóticas Invasoras in Arucas. 36 of the chameleons were adults, four were juveniles. Intestinal contents were taken from each chameleon and analysed for the presence of different bacteria using various methods.

At least one of the bacteria sought was found in 28 of the Veiled chameleons. About half of the chameleons had Yersinia enterocolitica, which is the highest prevalence ever recorded for this bacterium in reptiles. The bacterium can cause diarrhoea in humans, among other things. It is unclear how the Veiled chameleons became infected with it – possibly via insects. 16 of the Veiled chameleons had salmonella in their intestines. Salmonella is very common in reptiles and has even been found in endemic species on Gran Canaria. Pseudomonas is also frequently found in reptiles and was detected in the intestines of 13 animals. Two Veiled chameleons were infected with Campylobacter, in one of them Campylobacter lari could be identified. This bacterium can rarely cause illness in humans, but no pathogenic potential for humans is known for the species otherwise common in reptiles. Campylobacter lari has so far been detected mainly in seafood and birds – it is possible that the Veiled Chameleons picked up the bacterium on the coast and did not bring it with them. Three Veiled chameleons had Escherichia coli, which in rare cases can lead to haemolytic uraemic syndrome (HUS) in humans. Another two chameleons had Listeria monocytogenes in their intestines, which can be dangerous for pregnant women if ingested with food. Five Veiled Chameleons had mycobacteria, several of which were found to be non-tuberculous infections. Staphylococci were detected in seven chameleons, but they are part of the normal skin flora. However, five isolates were positive for resistance to certain antibiotics, which is becoming an increasing problem with Staphylococcus aureus in humans. Most recently, Vibrio was detected in a single Yemen chameleon, some species of which can cause diarrhoea in humans. The bacterium has previously been detected in introduced anoles on Tenerife.

The authors state that there is a zoonotic potential for humans due to the handling of introduced Veiled Chameleons on Gran Canaria. However, the extent to which there is a real risk for humans as well as endemic species needs to be further investigated.

Study of zoonotic pathogens in alien population of Veiled Chameleons (Chamaeleo calyptratus) in the Canary Islands (Spain)
Román Pino-Vera, Néstor Abreu-Acosta, Pilar Foronda
Animals 13 (14), 2023
DOI:  10.3390/ani13142288

Twins in Veiled Chameleons in Latvia

Twins in Veiled Chameleons in Latvia

by Alex Laube Short messages Nachzuchten

The hatching of two pairs of twins of Veiled Chameleons (Chamaeleo calyptratus) in Latvia has been reported from Riga. The parents live at Riga Zoo and the young hatched in March 2022. The twins were two male and two female Veiled Chameleons, each pair in one egg. They came from a clutch of 85 eggs, of which 48 eventually hatched. All four young animals were active at first and accepted food. At the age of two months, one of the juveniles died, the remaining three were still alive in February 2023.

The article also gives a brief overview of cases of twins in reptiles from the existing literature.

A review of twinning in lizards and a report of Veiled Chameleon (Chamaeleo calyptratus) twin births
Alessandro di Marzio, Elza Birbele, Lucia Puchades, Andris Lazdiņš
Herpetology Notes 16: 471-476, 2023
DOI:

Photo: One of the twin pairs at hatching

How and when Veiled Chameleons show biotremors

How and when Veiled Chameleons show biotremors

by Alex Laube Science

Some chameleon species can vibrate like smartphones – most chameleon keepers know this. The best-known example of this ability is the Veiled Chameleon (Chamaeleo calyptratus). Two new articles by scientists from the USA now deal with what these vibrations are good for, how they occur, and how the Veiled Chameleon uses them in the first place.

Nine adult Veiled Chameleons (three females, six males) and six juvenile Veiled Chameleon (three females, three males) took part in the first experiments. Eleven of them were placed individually one after the other on a 77 cm long and 5 mm thick wooden stick. As soon as the chameleon sat in the middle, the wooden stick was subjected to vibrations of 25, 50, 150, 300, and 600 Hz. After each stimulus, a comparison was made to see whether the chameleon moved faster, slower, or the same as before. In order to motivate the young animals to move, a plant was placed near the end of the wooden stick. In addition, a small fan was used to imitate a light wind. For the second experiment, all 15 Veiled Chameleons were placed one after the other in a wooden box open at the top on a 122 cm long wooden stick. The animals were poked in the upper arm with a 27 G cannula. An acceleration sensor stuck to the helmet, or to the branch in the case of young animals, measured the reactions (vibrations) of the chameleons.

The results are exciting: Adult Veiled Chameleons reacted reliably to 50 and 150 Hz with “freezing”, i.e. complete immobility. Juveniles, on the other hand, reacted with this behaviour to other frequencies, namely 50 and 300 Hz. All adult Veiled Chameleons showed biotremors (vibrations). In the juveniles, the scientists could feel vibrations in all of them, but not all could be detected with the sensor. The vibrations were divided into two classes: “hoots” with an average of 7.5 dB and “mini-hoots” with -32.5 dB. The longer the larger vibrations lasted, the lower the frequency.

A second series of experiments used six adult Veiled Chameleons (four males, two females), four juvenile Veiled Chameleons, and one adult Chamaeleo gracilis. Two chameleons each were placed in a wooden box separated into two compartments by a plexiglass pane. Video recordings and accelerometers were used to measure their reactions to each other. Same-sex Veiled Chameleons, pairs of Veiled Chameleons, a Veiled Chameleon with a Chamaeleo gracilis and adult versus juvenile Veiled Chameleons were tested. The adult Veiled Chameleons showed vibrations in association with other adults in about 85% of the trials. The strength of the vibrations varied greatly from individual to individual. The clear trigger of the biotremors seemed to be visual contact with another chameleon. Threatening gestures and aggressive behaviour were more likely to cause vibrations. In the second series of experiments, a third variant of biotremors was discovered in addition to honking, rumbles.

Communication via biotremors in the Veiled Chameleon (Chamaeleo calyptratus): Part I – Biotremor production and response to substrate-borne vibrations
Kathryn L. Denny, Steve Huskey, Christopher V. Anderson, Michael E. Smith
Integrative and Comparative Biology, 2023
DOI: 10.1093/icb/icad085

Communication via biotremors in the Veiled Chameleon (Chamaeleo calyptratus): Part II – Social contexts
Kathryn L. Denny, Steve Huskey, Christopher V. Anderson, Michael E. Smith
Integrative and Comparative Biology, 2023
DOI: 10.1093/icb/icad084

Long-term study on sperm collection in chameleons

Long-term study on sperm collection in chameleons

by Alex Laube Tiermedizin Science

Assisted reproduction has become increasingly common in the conservation of extremely rare animals such as the Spix’s macaw or northern white rhinoceros in recent years. In reptiles, on the other hand, there have only been a few studies on assisted reproduction, and only a few on chameleons in particular. Scientists from the USA have now conducted a study on male Veiled and Panther Chameleons (Chamaeleo calyptratus and Furcifer pardalis).

At Louisiana State University, 16 males of each species were kept under standardised conditions for over a year. The panther chameleons were purchased from a US breeder, the Yemen chameleons from a dealer who had taken them from the introduced wild chameleon population in Florida. All males were kept individually in ZooMed screen cages, 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. They were fed with crickets and zophobas.

Before the start of the study, all 32 chameleons were clinically examined and parasites were treated. Only after a month of acclimatisation did the actual study begin. During the study year, all chameleons were put under anaesthesia twice a month. Each time, blood was taken from the ventral tail vein or the jugular vein to determine the testosterone concentration. Ultrasound was used to measure the size of the testicles. In addition, each time an attempt was made to obtain sperm by electroejaculation. Electroejaculation involved inserting a small metal probe into the cleaned cloaca. Each chameleon was then treated up to three times in succession with up to 15 electric shocks of 0.1/0.2/0.3 mAs. The semen collection experiments were stopped as soon as the animal ejaculated. The sperm collected was preserved and examined for ejaculate volume, presence of sperm, sperm motility, concentration, and morphology.

The results suggest that Veiled Chameleons follow a so-called prenuptial reproductive strategy under constant husbandry conditions. The testosterone concentration in the blood already increased before the sperm volume of the males had reached its maximum. The months of May, April, and June brought the best sperm volumes, the most sperm was produced by electroejaculations in the third attempt. Testicle sizes also varied throughout the year, with the largest measurements from August to December.

Panther chameleons, on the other hand, seem to follow a postnuptial reproductive strategy. In them, most sperm could only be obtained well after the highest point of testosterone concentration. The electroejaculations worked best in March, April, May and June. Much more often than in Yemen chameleons, electroejaculation in panther chameleons worked already in the first attempt. The size of the testicles also varied throughout the year, but most were largest in the months mentioned above. Together with the factors mentioned above, the volume of ejaculate, sperm concentration, sperm motility and sperm morphology also changed during the year.

The authors recommend that electroejaculation in chameleons should generally only be performed under anaesthesia. The success rate for spermatozoa in the two highest cases was 82 and 88%, which is similar to the success in other reptiles during their reproductive season. The mortality rate among the 32 animals was only 0.12% over the whole year. One panther chameleon died after 10 months during the 20th anaesthesia, after death kidney damage was detected. From the low mortality rate, the authors conclude that electroejaculation rather does not play a role in the development of kidney disease, as was suspected in other studies. However, an examination of the blood for kidney values was not carried out on any of the surviving chameleons after the study. It also remains unclear what role the lack of imitation of rainy and dry seasons during the year plays for both species and their reproductive cycle.

Characterizing the annual reproductive cycles of captive male veiled chameleons (Chamaeleo calyptratus) and panther chameleons (Furcifer pardalis)
Sean M. Perry, Sarah R. Camlic, Ian Konsker, Michael Lierz, Mark A. Mitchell
Journal of Herpetological Medicine and Surgery 33 (1), 2023, pp. 45-60
DOI: 10.5818/JHMS-D-22-00037

Comparisons on limbs of Hadramaut agama and Veiled Chameleon

Comparisons on limbs of Hadramaut agama and Veiled Chameleon

by Alex Laube Science

A Yemeni biologist at Al Saeed University recently took measurements on two different reptile species to compare their forelimbs and hindlimbs structurally and functionally. Both the Hadramaut Agama (Acantocercus adramitanus) and the Veiled Chameleon (Chamaeleo calyptratus) occur in the same habitats in Yemen, but they inhabit different microhabitats and move differently. While the agama lives mainly on the ground and in low bushes, the Veiled Chameleon is a pure tree dweller.

For the study, 10 specimens of each species were taken from the wild in Taiz. The head-torso length of the agamas ranged from 52 to 125 mm, and that of the chameleons from 90 to 200 mm. The animals were killed and the limbs were removed, stained, and then measured.

The structure of the limbs was basically the same in both species, but the hands and feet were clearly different. The Hadramaut Agama has five carpal bones, whereas, in the Veiled Chameleon, the distal carpal bones 2,3, and 4 are fused. Both species lack distal tarsal bones 2 and 5. The Veiled Chameleon lacks the sesamoid ossicles, which are variable in the agama. As expected, the long bones of the Veiled Chameleons were almost equally long on the forelimbs and hindlimbs, while in the agamas the forelimbs were significantly shorter than the hindlimbs. Overall, all long tubular bones were longer in the chameleon than in the Hadramaut Agama.

The skeletal characteristics of limb of two endemic lizard species (Acantocercus adramitanus and Chamaeleo calyptratus) in Yemen
Yaser H.A. Obady
Al-Saeed University Journal of Humanities and Applied Sciences 06 (1) 2023: pp. 188-210
DOI: 10.17161/randa.v30i1.18614