Hello, I am looking for someone to write an essay on The Effects of Androgen on te Mate-Finding Behavior of Stingray. It needs to be at least 2250 words.Download file to see previous pages… The mati

Hello, I am looking for someone to write an essay on The Effects of Androgen on te Mate-Finding Behavior of Stingray. It needs to be at least 2250 words.

Download file to see previous pages…

The mating season begins in August and continues until April of the following year. Female stingrays begin to mature upon reaching approximately 22-23cm. Development of secondary female characteristics and other morphological changes such as development of large disc width occurs because males would grasp on the females’ discs for copulation (Chapman et al. 241). Males, on the other hand, mature at approximately 21cm. Their claspers calcify and production of sperm begins (Johnson and Snelson Jr. 74). During breeding seasons, reproductively active female stingrays proceed to the shore lines or in the shallow freshwater grounds in the case of the fresh water stingrays (Potamotrygonidae) and burry themselves to the sandy bottom. Females would usually burry themselves next to the other female stingrays. Solitary males then search the area for the females hidden under the sand (Tricas et al. 129). Upon location of a potential mate, the male stingray excavates the female in the sand and pursues the female closely. An aggressive courtship behavior follows. The courtship behavior in the wild species of southern stingrays, Dasyatis americana (Dasyatidae) was described in detail by Chapman. The male orally grasp the female’s pectoral disc leaving the female with mating scars and wounds. If the male is successful, copulation and internal fertilization will occur. The male will keep copulating with other females until the end of the breeding period. The female keeps the embryos inside her body, in the womb without a placenta. The embryos absorb nutrients from the yolk sac, and later directly from the mother. The pregnancy period lasts from three to nine months depending on the species (Charvet-Almeida et al. 165). The mating and reproductive behaviors of stingrays can be affected by several factors. For example, certain changes to the gonadal steroid hormones in male stingrays have been shown to coincide with the reproductive behavior, aggression and morphological changes in them (Wilkens and Hofman). One of the many hormones shown to affect mating behavior of male stingrays is androgens. Androgens are naturally occurring hormones that stimulates the development of masculine characteristics. This hormone is common to males of all species, including humans. In stingrays, one of the most important roles of these hormones in stingrays is the development of gonads. Androgens also signal and control the production of sperm (Oliveira et al. 985). Androgen levels of stingrays have been shown to naturally fluctuate throughout the year. Tricas (2000) has reported four phases of annual fluctuation in the levels of androgens. The first phase occurs in April to July in between the reproductive seasons. In this phase, called the androgen suppression (AS) phase, the testis is inactive and the androgen levels are very low to nearly undetectable. In August, androgen levels increase constantly until November (primary androgen increase, PIA). This is the longest time when androgen levels in male stingrays are at the highest, spermatocytes begin to develop and gonad sizes are at the maximum (Tricas et al.). The surge of androgen levels is followed by a period of androgen decrease (AD) in the months of December to January.

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