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

Spines of tree- and ground-dwelling chameleons

Spines of tree- and ground-dwelling chameleons

by Alex Laube Tiermedizin Science

Various anatomical adaptations of the spine between ground and tree dwellers are known from mammals, especially primates. In some cases, the different vertebrae are even associated with certain movement patterns and bodily functions. In a comparative study, two scientists from New York (USA) have now investigated how the spine of ground- and tree-dwelling chameleons differs.

They measured the already existing CT scans on Morphosource.org of a total of 28 chameleons of different species. Brookesia perarmata, Brookesia superciliaris, Brookesia thieli, Palleon nasus, Rhampholeon platyceps, Rhampholeon spectrum, Rieppeleon brevicaudatus and Rieppeleon kerstenii were classified as ground dwellers. Archaius tigris, Bradypodion melanocephalum, Bradypodion pumilum, Bradypodion thamnobates, Calumma amber, Calumma brevicorne, Calumma parsonii, Chamaeleo calyptratus, Chamaeleo gracilis, hamaeleo zeylanicus, Furcifer lateralis, Furcifer pardalis, Furcifer verrucosus, Kinyongia carpenteri, Kinyongia tavetana, Kinyongia xenorhina, Nadzikambia mlanjensis, Trioceros feae, Trioceros jacksonii and Trioceros quadricornis were considered arboreal. The vertebrae were counted and the width of the lamina, length, width, height of the vertebral body, and the height of the spinous process and transverse processes on each vertebra were measured. In addition, the so-called prezygapophysial angle was determined. This is the angle of the intervertebral joint, i.e. the contact surfaces between the individual vertebrae. The measurements of ground and tree dwellers were compared and statistically evaluated. Only the vertebral column of the trunk was considered, the caudal vertebral column was left out.

First of all, the results showed that ground-dwelling chameleons generally have fewer trunk vertebrae (15 to 19) than tree-dwelling chameleons (18 to 23). The trunk spine of almost all species could be divided into the already known three areas: Cervical spine and anterior and posterior dorsal spine. A thoracic and lumbar spine as in mammals is generally not distinguished in chameleons because of the continuous ribs. Five chameleon species had four regions instead of three: they had an anterior and a posterior cervical spine, the anterior one consisting of only two vertebrae with rib processes. Six chameleon species had two additional lumbar vertebrae and one species had three transitional vertebrae in the region between the cervical and dorsal spine. In Kinyongia carpenteri, a total of five regions could be distinguished in the trunk spine: The chameleon had anterior and posterior cervical vertebrae as well as anterior and posterior dorsal vertebrae and two additional lumbar vertebrae. Brookesia perarmata was also a special case: the trunk spine of this chameleon consisted of only two regions and at the same time the smallest number of vertebrae of all species studied.

The greatest differences between ground and tree-dwelling chameleons were found in the prezygapophyseal angle (PZA) and the height of the spinous process. The intervertebral joint surfaces in the anterior dorsal vertebrae of tree-dwelling chameleons were clearly more dorsoventrally oriented and smaller than in ground-dwelling species. Several tree-dwellers showed a PZA of less than 90°. In tree-dwelling chameleons, the largest spinous processes were located at the transition from the cervical to the dorsal spine. Among the ground-dwelling species, the spinous processes were similar only in Palleon nasus. In ground-dwelling chameleons, the appearance of the spinous process varied greatly. Rieppeleon, for example, showed narrow, backward-sloping spinous processes, while the spinous processes in Brookesia were more like a kind of bone bridge than a process. Archaius tigris was an exception: The spinous processes in this chameleon hardly differed along the entire spine.

The authors conclude from the results that the anatomy of the different vertebrae is strongly related to the chameleons’ way of life and different locomotion. The intervertebral joint surfaces in tree-dwelling chameleons are probably important for climbing by supporting the function of the shoulder girdle. Reduced mobility in the mediolateral plane provides greater trunk stiffness, which facilitates climbing in arboreal dwellers. Stiffening of the axial skeleton (skull, trunk spine and thorax) is also known from tree-dwelling mammals. The larger spinous processes in larger chameleons could facilitate shoulder girdle rotation and muscle movement, resulting in increased stride length, better head support, and thus possibly easier feeding.

Morphological and functional regionalization of trunk vertebrae as an adaption for arboreal locomotion in chameleons
Julia Molnar, Akinobu Watanabe
Royal Society Open Science 10, 2023: 221509
DOI: 10.1098/rsos.221509

Illustration: Spines of different chameleon species

Keeping and breeding Calumma linotum

Keeping and breeding Calumma linotum

by Alex Laube Haltungsberichte

The keeping and breeding of small chameleons of the genus Calumma has so far, apparently, only found enthusiasts on a rather small scale. So it is all the nicer that a new report on the keeping and especially the successful breeding of Calumma linotum has just been published. Michael Nash from the USA has been keeping the species for over three years and gives a detailed account of his experiences.

He keeps his animals in the terrariums commonly used over here with a completely ventilated lid and either vents in the front bottom or the entire front as ventilation, living plants, and living substrate. T5 tubes with and without UV-B are used for lighting. For food he uses fruit flies (Drosophila spp.) to a good 50%, and otherwise among other things small crickets, house crickets, blowflies, and mantid nymphs.

The best breeding successes are achieved by keeping them individually and putting them together for a few days to mate during the imitation rainy season. To induce mating behaviour, dry and rainy seasons are imitated. The dry season is mainly characterised by a massive night-time drop in temperature to 10°C and less irrigation. During the imitated rainy season, temperatures rise to around 26°C during the day and 18-21°C at night, and there is also increased irrigation during the day.

The females lay 2-3 eggs after an average of 22 to 40 days of gestation. So far, it has been noticed that mated females of the species are capable of fertilisation for an unusually long time, namely up to five clutches. The eggs are first incubated at 16 to 21°C for two to four weeks. This is followed by a diapause of 30 to 45 days at 10 to 15°C. The eggs then lie in daytime conditions. Afterwards, the eggs lie at 22°C during the day and between 16.7 and 19.5°C at night. If the eggs do not show any embryonic and vascular development during shearing after the diapause, it is possible to imitate a second diapause – at the latest, after this, the first egg development should be visible. After 5 to 7 months, active young hatched under these incubation conditions. The author has successfully hatched eleven clutches so far.

All in all, a very readable husbandry report, which hopefully supports other keepers in breeding and long-term conservation of this interesting, small species in the terrarium.

Keeping and breeding Calumma linotum
Michael Nash
Responsible Herpetoculture Journal 7, 2023
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Species diversification in chameleons

Species diversification in chameleons

by Alex Laube Science

From earlier studies, we know that the first chameleons evolved in the late Cretaceous, about 90 million years ago, on mainland of Africa. Around the border between the Cretaceous and Tertiary periods, about 65 million years ago, different species began to evolve. It is still unclear today which factors contributed to the diversity of species. Two researchers from Swansea University in Wales have now used various computational models of phylogenetics to investigate what might have influenced diversification (the splitting of chameleons into many different species).

First, they studied the diversification of chameleon species in Madagascar. In terms of evolutionary history, there are two points in time when chameleons apparently spread across the sea from mainland Africa to Madagascar. One is about 65 million years in the past, the other 45 million years. You could now think that the climatically extremely different habitats in Madagascar could have driven the evolution of the species very quickly after the spread across the sea. To the surprise of the researchers, however, no evidence of this was found. The species richness of chameleons on Madagascar must therefore come from the fact that chameleons spread there very early and thus simply had much more time to develop into different species than elsewhere.

Furthermore, the researchers investigated whether switching between two ecomorphs – from ground-dwelling stub-tailed chameleons to tree-dwelling chameleons with longer tails – had an impact on species diversity. Rather surprisingly, this did not seem to be the case. The evolution to tree-dwellers with longer tails occurred relatively early on one or two occasions. No evidence could be found that different ecomorphs accelerated diversification. Instead, speciation rates were found to slow down progressively over the last 60 million years. Only a very early dispersal event of the genus Bradypodion in South Africa around 10 million years ago was accompanied by a two- to fourfold diversification rate.

As a third focus of the study, the researchers examined the genus Bradypodion. During the climate change in the Miocene around 10 million years ago, South Africa changed a lot. Forests disappeared, leaving behind isolated forest habitats and, in between, savannahs, some of which are now so-called hot spots of biodiversity. Two of them, the Cape Floristic Region at the southwestern tip of South Africa and Maputuland-Pondoland-Albany on the east coast of South Africa, are home to a particularly large number of Bradypodion species. Each species is limited to a geographically very clearly defined area. The researchers, therefore, suspect that Bradypodion species have actually evolved faster under the influence of habitat change. It should be noted that the diversification rate of the genus Bradypodion is probably rather underestimated, as there are still many hidden species to be assumed.

Diversification dynamics of chameleons (Chamaeleonidae)
Stephen Giles, Kevin Arbuckle
Journal of Zoology, 2022
DOI: 10.1111/jzo.13019