Histomorphological development study for tadpoles and different regions of skin to the frogs (Bufotes variabilis) in Babylon city of Iraq

Abstract

Iraq's reproductive and developmental seasons for the frog vary depending on the region and ecological, geographical, and climatic factors, but they always take place from February to April. This study set out to observe the impact factor of water temperature on frog embryo development and tadpoles' development in the frog genus Bufotes variabilis. In central Iraq (semi-arid zones), temperatures are high, and precipitation is low; the temperature plays an important role in the timing of metamorphosis, especially in amphibian populations of Iraq. In the three months of February, March, and April, a hand net was used to gather a total of 100 eggs from the bank of the Babylon River and divided into three groups, tadpole's total snout to vent length (SVL) at stages 25, 35, and 46 were measured during this period. This group experiences varying stages when the water temperature varies from 10°C in February to 25°C in April. Histologically, frog skin is composed of an epidermal and dermal layer. The epidermal layer comprises a mucous-stratified squamous epithelium (keratinized or non-keratinized) with three strata of keratinocytes (basal, intermediate, and apical). The dermis is divided into two strata, a loose connective tissue stratum underneath the epidermis that contains melanin pigment cells, blood vessels, mucous and granular glands, and a dense irregular connective tissue stratum rich in crisscrossed collagen fibers. Histological specimens were taken to study the mucous and granular glands of the frog's skin during the same period using rotund methods; the skin showed changes in mucous and granular gland diameter in April is larger than that in February. We registered in dorsal pectoral skin the mucous gland I, spherical in shape and constituted by a single layer of relatively tall prismatic secretory cells with basal nuclei. While the Mucous gland II is constituted of low cuboidal secretory cells with middle or basal nuclei surrounding a somewhat demanding lumen. In conclusion, the temperature plays a big role in tadpole size and time of metamorphosis as well as skin changes.

Keywords

• amphibians
• desert
• environment
• temperature