Karyograms of five Malagasy chameleons described

Karyograms of five Malagasy chameleons described

by Alex Negro Science

It has been known for many years that the sex of chameleons is genetically determined. However, the karyograms of many species, i.e. the chromosome characteristics, are not yet known for all species. Italian scientists have now analysed the karyograms of five Madagascan chameleon species.

Existing, preserved chameleons were used for the study. One female each of the species Furcifer balteatus, Furcifer petteri, Furcifer major and Furcifer minor were sampled. One male and one female Brookesia superciliaris were also used for the study. All samples were subjected to DNA barcoding analysis using the mitochondrial gene fragment COI as a marker. The extracted DNA was amplified by PCR and then sequenced to create a karyogram for each animal.

The karyogram of Brookesia superciliaris is 2 n = 34 for both sexes. Of the 34 chromosomes, six are macrochromosome pairs and eleven are microchromosome pairs. All macrochromosomes are metacentric. Morphologically, the chromosomes do not differ from each other, so that it remains unclear which could be the sex chromosomes.

Furcifer balteatus has a very special karyogram, which actually fits better with those of the genera Brookesia and Palleon than with the genus Furcifer. The karyogram is 2n = 34, which is the highest number of chromosomes among the chameleons. Of the 34 chromosomes, six are macrochromosome pairs and eleven are microchromosome pairs. The former are all metacentric. There are no morphological differences between the chromosome pairs, so that the sex chromosome has not yet been determined.

The karyogram of Furcifer major is 2n = 24. Nine of the chromosome pairs are macrochromosome pairs and three are microchromosome pairs. Seven of the macrochromosome pairs are metacentric, only pairs two and three are submetacentric. The eleventh chromosome pair, a microchromosome pair, codes for the sex chromosome W.

Furcifer minor has a karyogram of 2n = 22 chromosomes. Of these, eight pairs are macrochromosome pairs and three are microchromosome pairs. Among the macrochromosomes, the first five pairs are metacentric, while the remaining three pairs are acrocentric. A portion of the sixth pair of chromosomes was almost completely heterochromatic and probably represents the sex chromosome W.

The karyogram of Furcifer petteri is also 2n = 22, of which eight pairs of chromosomes are macrochromosomes and three microchromosomes. Seven pairs of macrochromosomes are metacentric, only the fifth pair is submetacentric. The sex chromosome W is part of the seventh pair of macrochromosomes.

All newly described karyograms are deposited in GenBank under the number PQ272538-4. In this study, the genus Furcifer was also found to have the highest diversity in the karyograms. It also appears to be the only genus among all vertebrates that shows all variants of sex chromosome diversification.

New insights on Chromosome Diversification in Malagasy Chameleons
Marcello Mezzasalma, Gaetano Odierna, Rachele Macirella, Elvira Brunelli
Animals 2024, 14: 2818
DOI: 10.3390/ani14192818

Graphic: Karyograms of Brookesia superciliaris and Furcifer balteatus from the above-mentioned study

Chameleons in Bobaomby (Madagascar)

Chameleons in Bobaomby (Madagascar)

by Alex Negro Verbreitung Science

The Bobaomby complex is located at the northernmost tip of Madagascar, north and west of the largest coastal town in the north, Antsiranana (Diego Suarez in French). It consists of dry forest at sea level up to a maximum of 200 metres above sea level as well as extensive savannahs on karst rock and various rock formations. The area has not been protected to date.

Scientists from Madagascar conducted reptile counts in the Bobaomby complex in 2018. The counts were carried out in February and March, i.e. during the rainy season. Five different locations were analysed: Beantely, Antsisikala and Ambanililabe as examples of varying degrees of degraded dry forest, Anjiabe for its intact dry forest and Ampombofofo with relatively intact forest. To find animals, the visual survey was used on 25 days during the day and at night in selected transects, sometimes specifically in suitable habitats such as leaf axils or under dead tree trunks, and pitfall traps along erected fences were also used.

A total of 42 reptile species have been recorded. All of them, except one gecko species, originally only occur on Madagascar, while two other gecko species are now also found on neighbouring islands. There is a small novelty among the chameleons: the leaf chameleon Brookesia ebenaui was recorded for the first time in Bobaomby, more precisely in Beantely. Brookesia stumpffi and Furcifer petteri were found in Beantely, Anjiabe and Ampombofofo. Furcifer pardalis and Furcifer oustaleti occurred as expected throughout the whole Bobaomby complex.

The authors suggest that the Bobaomby complex – especially the three forests where most of the reptiles were found – should be protected to preserve the local herpetofauna.

Overview of reptile diversity from Bobaomby complex, northern tip of Madagascar
Randriamialisoa, Raphali R. Andriantsimanarilafy, Alain J. Rakotondrina, Josué A. Rakotoarisoa, Nasaina T. Ranaivoson, Jeanneney Rabearivony, Achille P. Raselimanana
Animals 13: 3396, 2023
DOI:  10.3390/ani13213396

Photo: Furcifer petteri, male, in the north of Madagascar, photographed by Alex Laube

Chameleons in the Montagne des Français (Madagascar)

Chameleons in the Montagne des Français (Madagascar)

by Alex Negro Verbreitung Science

The Montagne des Français is a limestone massif with dry forest in northern Madagascar. It reaches up to 425 m above sea level and is within sight of the largest coastal town in the north, Antsiranana (French Diego Suarez). It has been a protected area since 2007. Scientists from Madagascar and the USA conducted counts of reptiles and amphibians in the Montagne des Français in 2014 and 2020.

Counts were made in January and May, i.e. during and at the end of the rainy season. In 2014, the focus was on the region around Andavakoera, while in 2020 it was on Sahabedara, Ampitiliantsambo, and Andavakoera. In order to find animals, the search was conducted during the day and at night along predefined paths, partly in suitable habitats, and partly in pitfall pits.

A total of 20 amphibian and 50 reptile species were recorded. Four new amphibians and one reptile were found for the first time in the Montagne des Français. The snake Langaha pseudoalluaudi was discovered again for the first time since 2007. Among the chameleons, there were minor new discoveries. Brookesia stumpffi could only be found in 2014, but no longer in 2020 – however, due to the relatively wide distribution of the species, this should not be a problem for the entire population. Brookesia tristis, one of the smallest chameleons in the world, was also only seen in 2014. Here, the body size, which makes it very difficult to find, and the time of year (May is relatively late for this species) could play a role. Brookesia ebenaui was detected in Andavakoera in 2014 and in Sahabedara in 2020. The two tree dwellers Furcifer oustaleti and Furcifer pardalis were found in both years in Andavakoera and Ampitiliantsambo. Furcifer petteri, on the other hand, was present at all the sites surveyed in both years.

Amphibians and reptiles of the “Montagne des Français”: Update of the distribution and regional endemicity
Herizo Oninjatovo Radonirina, Bernard Randriamahatantsoa, Rabibisoa Harinelina Christian Nirhy, Christopher J. Raxworthy
Preprint
DOI: 10.20944/preprints202306.1499.v1

Photo: Furcifer petteri on Madagascar, photographed by A. Laube