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

Comparative anatomy of the forearms of different chameleons

Comparative anatomy of the forearms of different chameleons

by Alex Negro Tiermedizin Science

The anatomy of chameleons seems to be strongly adapted to their way of life. Tree-dwellers differ in many aspects from ground-dwellers. Several studies at the University of South Dakota this year have already looked at various anatomical aspects of chameleons. A new study is dedicated to the hands and arms.

For the investigation, the arms and hands of a total of 12 chameleons were isolated from existing microcomputer tomography scans and displayed in 3D. These were measured to about 30 different lengths and widths using software. Scans of the species Bradypodion damaranum, Bradypodion occidentale, Calumma hilleniusi, Calumma crypticum, Chamaeleo namaquensis, Chamaeleo zeylanicus, Furcifer balteatus, Furcifer campani, Rhampholeon spinosus, Rhampholeon temporalis, Trioceros goetzei goetzei and Trioceros werneri were evaluated. When selecting the species, care was taken to select one strictly tree-inhabiting chameleon and one more ground-inhabiting chameleon per genus.

The evaluation revealed that tree-dwelling chameleons show few differences in forelimb anatomy compared to ground-dwelling chameleons. Tree-dwelling species showed a majority of separated metacarpal bones 1-3, while ground-dwelling species showed fused metacarpal bones. Interestingly, this study differs from earlier studies by other authors, which yielded different results. The relatively small number of animals studied may be related to this. Larger studies could be helpful here.

Ecological and evolutionary drivers of chameleon forelimb variation
Ellie M. Schley
Honors Thesis 302 der Universität von South Dakota, 2023
DOI: gibt es nicht

Comparison of pelvic girdles in chameleons

Comparison of pelvic girdles in chameleons

by Alex Negro Science

The anatomy of chameleons is strongly adapted to their way of life. Tree-dwellers differ in many aspects from ground-dwellers. The pelvic girdle has been little studied anatomically in chameleons so far – a publication from the USA now deals with it in more detail.

For the study, the pelvic girdles of 22 chameleons were isolated from existing microcomputer tomography scans and displayed in 3D. These were measured to 16 different lengths and angles using software. Archaius tigris, Bradypodion damaranum, Calumma gallus, Calumma parsonii parsonii, Chamaeleo zeylanicus, Furcifer balteatus, Kinyongia matschiei, Kinyongia tavetana, Nadzikambia mlanjense and Trioceros quadricornis gracilior were assigned to tree dwellers. Brookesia brygooi, Chamaeleo namaquensis, Palleon nasus nasus, Rhampholeon temporalis and Rieppeleon brachyurus were attributed to ground-dwelling species. The species Bradypodion occidentale, Brookesia ebenaui, Chamaeleo anchietae, Furcifer campani, Rhampholeon spinosus, Rieppeleon kerstenii kerstenii and Trioceros goetzei goetzei were classified as semiarboreal. Mainly males were examined.

As expected, the evaluation showed that tree-dwelling chameleons had narrower, shorter girdles than ground-dwelling ones. The narrower pelvic girdle makes it easier to hide behind branches and flatten the body to the maximum. It also ensures that the body’s centre of gravity is closer to the branch and thus increases stability when climbing. Ground-dwelling chameleons, on the other hand, had larger and wider pelvic girdles. These allow them to step more quickly and provide greater stability when walking on ground surfaces.

How phylogeny and arboreality affect pelvic girdle anatomy of chameleons
Dakota J. John
Honors Thesis 299, University of South Dakota, 2023
DOI: none