Reptiles show remarkable diversity in modes of reproduction and sex determination, including high variation in the morphology of sex chromosomes, ranging from homomorphic to highly heteromorphic. Additionally, the co-existence of genotypic sex determination (GSD) and temperature-dependent sex determination (TSD) within and among sister clades makes this group an attractive model to study and understand the evolution of sex chromosomes. This is particularly so with Lizards (Order Squamata) which, among reptiles, show extraordinary morphological diversity. They also show no particular pattern of sex chromosome degeneration of the kind observed in mammals, birds and or even in snakes. We therefore speculate that sex determination sensu sex chromosome evolution is labile and rapid and largely follows independent trajectories within lizards. Here, we review the current knowledge on the evolution of sex chromosomes in lizards and discuss how sex chromosome evolution within that group differs from other amniote taxa, facilitating unique evolutionary pathways.

Dragon lizards (Squamata: Agamidae) comprise about 520 species in six subfamilies distributed across Asia, Australasia and Africa. Only five species are known to have sex chromosomes. All of them possess ZZ/ZW sex chromosomes, which are microchromosomes in four species from the subfamily Amphibolurinae, but much larger in Phrynocephalus vlangalii from the subfamily Agaminae. In most previous studies of these sex chromosomes, the focus has been on Australian species from the subfamily Amphibolurinae, but only the sex chromosomes of the Australian central bearded dragon (Pogona vitticeps) are well-characterized cytogenetically. To determine the level of synteny of the sex chromosomes of P. vitticeps across agamid subfamilies, we performed cross-species two-colour FISH using two bacterial artificial chromosome (BAC) clones from the pseudo-autosomal regions of P. vitticeps. We mapped these two BACs across representative species from all six subfamilies as well as two species of chameleons, the sister group to agamids. We found that one of these BAC sequences is conserved in macrochromosomes and the other in microchromosomes across the agamid lineages. However, within the Amphibolurinae, there is evidence of multiple chromosomal rearrangements with one of the BACs mapping to the second-largest chromosome pair and to the microchromosomes in multiple species including the sex chromosomes of P. vitticeps. Intriguingly, no hybridization signal was observed in chameleons for either of these BACs, suggesting a likely agamid origin of these sequences. Our study shows lineage-specific evolution of sequences/syntenic blocks and successive rearrangements and reveals a complex history of sequences leading to their association with important biological processes such as the evolution of sex chromosomes and sex determination.

Studies on the population status, distribution and conservation issues of the Gangetic dolphin Platanista gangetica gangetica were undertaken in the river Buriganga from November 2003 to November 2004. A total of 29 sightings with the highest of five sightings and a best-high-low estimate of 9-11-7 individuals were recorded in November 2004, while in the months of August and October no dolphin was observed. The mean density was 0.25 dolphin/km and the highest encounter rate was 0.29 sightings/km. Of the total sightings, 41.38% were in the groups of more than one individuals. Of the observed dolphins, 71.43% were adults,16.66% maturing and 11.9% young. The dolphins were found in 15 locations with both single as well as multiple sightings. Main threat to the dolphins was found to be pollution followed by traffic load and dredging activities. DOI: http://dx.doi.org/10.3329/bjz.v40i1.12890 Bangladesh J. Zool. 40(1): 21-31, 2012

Freshwater ecosystem degradation in the Turag River basin is increasing due to rising human settlement, reduced water flow during the dry season, new large land development projects, and toxic emissions caused by brick kilns. The population of river dolphins was estimated through surveys carried out from December 2012 to November 2013. Surveys were conducted on a fortnightly basis. The dolphins were counted within an 18.4 km stretch (known to be the most polluted stretch) of the 75 km long river. A total of 62 dolphin sightings were recorded, both as individual sightings and as groups. The highest monthly count was in August. The besthigh-low estimates of 9-11-7 individuals were recorded in August 2013 in river ecology. Seasonal changes in spatial distribution were observed. The survey revealed that rising floodwater stimulated an increase in the dolphin population in the study area from July to October. The maximum encounter rate was also 0.49 sightings km −1 for the month of August. The sightings and encounter rates of dolphins were lower from December to July (dry and premonsoon period) likely due to reduced water flow and adverse water quality of this river.

Social interactions of Hanuman langurs (Semnopithecus entellus)were studied from August, 2013 to July, 2014 at Keshabpur and Manirampur Upazila, Jessore, Bangladesh. The study was mainly based on direct field observations from dawn to dusk and data was collected through focal animal sampling in 10-minutes duration. During the study period seven groups of Hanuman langurs were found in urban and rural habitats. Eight behavioral activities like resting, feeding, grooming, moving, parental care, playing, submission and aggression were recorded. They interacted with each other through grooming, parental care, playing, submission and aggression. Social interactions varied in urban and rural habitats. Aggression was mostly observed in rural habitat and generally showed by the males. Adults were engaged in playing to encourage infants, juveniles and sub-adults. Significant seasonal variation of grooming was observed between age classes. Females were engaged more in grooming and parental care than males. Allomothering was also observed within a group. More submission was received by dominant males within a group. Langurs of focal groups spent 41.04% of their total activity budget in resting which was the highest activity followed by 33.75% in feeding, 11.73% in grooming, 4.87% in moving and 8.61% time for other activities.