Tag: reproduction in earthworm

There are two pairs of testes, which are situated in the 10$^{th}$ and 11$^{th}$ segments on each side of the alimentary canal. The germinal epithelium of the testis gives rise to the sperm cells by spermatogenesis. So, the correct answer is option B.

Leech belongs to phylum Annelida. The 'green spoonworm' (Bonellia viridis) lives in a marine habitat. It shows sexual dimorphism. It is also known as the biocidal properties of a pigment in its skin. It is found in the north-eastern Atlantic, Indian and Pacific Oceans and the Mediterranean and Red seas. It is pale- to dark-green in colour, with a 15 cm long, round or sausage-shaped body. Hence, option B is correct.

Earthworms are hermaphrodites; that is, they have both male and female sexual organs.  The two or four pairs of seminal vesicles produce, store and release the sperm via the male pores. Ovaries and oviducts are in segment 13 release eggs. Ovarian funnels are present beneath the ovaries which continue into the oviduct, join together.

The spermathacae are also called as receptaculum seminis. species of earthworms have four pairs of spermathecae one pair each in the 6th, 7th, 8th, and 9th segments. The spermathecae receive and store the spermatozoa of another earthworm during copulation. They are lined with epithelium and are variable in shape: some are thin, heavily coiled tubes.

Two pairs of accessory glands are present in 17th and 19th segments. Four pairs of spermathecae are located in 6th-9th segments. They receive and store spermatozoa during copulation. One pair of ovaries is attached at the inter-segmental septum of the 12th and 13th segments.

Tapeworm and fluke worms belong to class Platyhelminthes. They both are having well developed reproductive systems.

The menstrual cycle refers to the series of events that periodically modifies the female reproductive tract of humans and advanced primates. In other mammals, a cycle of receptivity to sexual activity occurs that is probably less complex than the menstrual cycle and is known as the estrous cycle.

Those structures which are directly concerned with reproduction are considered primary sex characteristics. Secondary sexual characters can be used to differentiate between males and females and usually serve the purpose of attracting potential mates. Testosterone is responsible for male secondary sex characteristics such as a deep voice and facial hair. In the female, the hormones that most nearly parallel testosterone in their actions are the estrogens. Estrogens contribute to the development of the female secondary sex characteristics and stimulate the development of the mammary glands (breast in this question), the onset of menstruation, and the development and functioning of the reproductive organs. The other hormone produced by the female sex glands, called progesterone, assists in the normal development of pregnancy.

The process of formation of mature female gametes is called oogenesis. The reproductive cycle of female primates is called menstrual cycle. Menstrual cycle starts only after attaining sexual maturation (puberty). During ovulation only one ovum is released per menstrual cycle. The cyclical changes in the ovary and the uterus during menstrual cycle are induced by changes in the levels of pituitary and ovarian hormones.