Brief note on the Male and female urinogenital systems in scoliodon

In scoliodon:

The organs of reproduction and those of excretion are clearly related to each other. Therefore, they are considered together.

Male Urino-genital System:

The kidneys in the male are a pair of long-strap-shaped glandular structures situated dorsal to the parietal peritoneum, and extend from the roof of the liver in front and right up to the cloacae behind.

Thus, the kidneys extend almost to the entire length of the body-activity. Kidney is mesonephric in origin. Each consists of an anterior slender part, called the genital kidney or cranial mesonephros and a posterior thicker part, called renal mesonephros or caudal nephrons. This type of kidney found in scoliodon is called opisthonephros kidney.

The anterior part is called the epididymis and is without excretory tubules and extends forward to the body cavity beneath the peritoneum. The posterior part is the functional excretory organ of the adult scoliodon. The mesonephros kidney is made up of coiled glandular uriniferous tubules, each consisting of a peritoneal funnel, a Bowman’s capsule enclosing the glomerulus and a coiled renal tubule, many of which open into a common collecting tubule or ureter, which opens posterior into the cloaca through a small urogenital papilla.

The ureter of the scoliodon is not regarded to be strictly homologous with the ureter of higher vertebrates, viz., reptiles, birds and mammals in which the kidneys is metanephric. Therefore, sme zoologists consider the posterior thickened part of the kidney in selachians as metanephros.

Testes are a pair of elongated structures sitated outside the parietal peritoneum of the abdominal cavity. They are attached to the dorsal body wall by double folds of peritoneum called mesorchia and to the caecal gland behind.

Each testis is joined at its anterior end with the kidney of its own side by a few minute ducts, called vasa efferent, which opens into the greatly coiled Wolffian duct or vas deferens. Behind the thicker part of the kidney, the Wolffian duct or vas deferens enlarges so as to form vesicular seminal is which serves to store ripe spermatozoa in the breeding season.

The two vesicular seminalis open posteriorly into a large triangular chamber called urinogenital sinus, which opens into the cloaca on an elevated out growth called the urinogenital papilla. On either side of the urinogenital sinus is situated a club shaped sperm sac. Siphons are a pair of long, glandular sacs found in the male only, situated beneath the skin of the ventral surface of the body. These sacs run anteriorly, up to the level of pectoral fins, where they terminate blindly. Posteriorly, these sacs are continued as siphon tubes which open into the groove of the claspers. Leigh sharp (1920) proved that these sacs serve to force the sperms into the groove of the claspers.

During copulation, the male scoliodon transfers its spermatozoa to the female by inserting its claspers into cloaca of the female.

Female Urinogenital Organs: in the female, there is no direct connection between the kidneys and the genital organs. The anterior part of each kidney extremely reduced to a long, narrow strand extending forward, while the posterior regioin of the kidney is thick and massive as in male and extends posteriorly up to the cloaca.

In the female, the wolffian duct is completely absent. Ureters are long, thin walled tubes, which are formed by the union of the collecting ducts of the mesonephric tubules. They unite posteriorly to open in to single median urinary aperture into the cloaca through a pore, situated at the top of the urinary papilla.

Ovaries are paired and situated on either side of the vertebral column behind the base of the liver. Each ovary is suspended by a double fold of peritoneum, called mesovarium. The form and the size of ovaries vary according to the Shark. During the breeding season, the mature ova, enclosed in the follicle cells, project out of ovary.

Between the ovary in front and the caecal gland behind extends a long tubular strand of tissue, called the epigonal organ. The oviduct or mullein ducts are independent ducts having no connection with the kidneys. Both these independent ducts having no connection with the kidneys. Both these ducts originate from the pericardia peritoneal septum or septum transversum in the mid dorsal line near the base of the liver in front of the ovaries. Both the anterior ends of the oviduct meet to form a longitudinal slit, called oviductal funnel.

The mature ova, from the ovaries are at first shed into the abdominal cavity. From where they are forced into the oviducal funnel by the action of the body muscles. Just behind funnel, oviducts curve around towards the mid dorsal line till each enlarges of form a shell-gland, which is simply a dilated part of each oviduct. The fertilization of the mature eggs takes place in the part of the oviduct between the oviducal funnel and the shell gland.

In scoliodon, shell gland also dwindles down an it is a viviparous form which gives birth to livings young ones. In the posterior region, each oviduct expands into a uterus in which embryo develops. The two uteri unite to form a vagina, which opens into the cloaca by a large medium aperture.