Nervous system - Bio eNotes

Shark: Excretory System, Reproductive System, Nervous System, and, Sense Organs

The excretory system is closely related to the reproductive system. Males and females differ significantly in several key ways. A pair of opisthonephric kidneys, which are long, thin, highly vascularized strips of tissue that filter nitrogenous wastes from the blood, chiefly urea, make up the excretory system. The archinephric ducts are responsible for kidney drainage. The more caudal section of the archinephric duct also carries urea produced by the kidneys in males, whereas the cranial portion of the duct serves primarily a reproductive purpose. The female has smaller and shorter archinephric ducts. The two tiny auxiliary urinary ducts in males that drain into the urogenital sinus receive urine from the archinephric ducts. The male auxiliary urinary ducts and the archinephric ducts discharge into the urinary papilla, a little projection into the cloaca. In males, the urogenital papilla is another name for the urinary papilla. Materials from the digestive, reproductive, and excretory systems are delivered to the cloaca. Excretory waste leaves the cloaca and travels outside. A duct connects the rectal or digitiform gland to the big intestine. This tubular organ helps the dogfish maintain a healthy osmotic equilibrium in its bodily fluids by excreting extra sodium chloride.

Starfish: Characteristic Features, Body wall, Water Vascular System, Digestive System, Excretion System, Nervous System, Circulatory System

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Asterias forbesi can be found from low tide to a depth of about 50 meters along the majority of the eastern seaboard, from Maine to the Gulf of Mexico. This species integrates with closely related species, as is typical of the more specialized groupings of Asteroidea. On rocky or shelly bottoms, specimens are found alone or in sizable groups. Because it is a predaceous oyster-eating creature, this starfish is economically significant and has been the subject of in-depth research. This animal causes the oyster business to lose a lot of money every year. Along with oysters, the starfish also consumes clams, mussels, sea snails, dead fish, worms, and in some rare instances, other starfish.
It is known that starfish migrate at certain seasons, however, it is unclear what this migration looks like or how far it goes. This organism moves quite slowly, on average 6 inches per minute, according to observations of its locomotion. The isolated geographic distribution of this species, however, seems to suggest that the range of these creatures’ wanderings is quite small.
Like all other living things, starfish have natural adversaries. Cold and fresh water, different fish, gulls and crows, and parasites are a few of these harmful agents and natural enemies. The menhaden is undoubtedly the foe that causes the most damage to starfish. This fish only consumes the tiny aquatic organisms that float or swim in the water. Only once the sun has set are the starfish larvae safe from this fish. The scene involves a transformation procedure and attachment to a bottom-level object. The tiny algae and other small types of plankton make up the nutrition of the free-swimming larvae.
The starfish is vulnerable to parasite attack. The parasite organisms assault the starfish’s gonads, damaging the tissue and partially or completely rendering it sterile.

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