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Batoids reproduce in a number of ways. As is characteristic of elasmobranchs, batoids undergo internal fertilization . Internal fertilization is advantageous to batoids as it conserves sperm, does not expose eggs to consumption by predators, and ensures that all the energy involved in reproduction is retained and not lost to the environment. [ 6 ]
There are also aquatic spiders, although they tend to prefer other modes of locomotion under water than swimming proper. Examples are: Some breeds of dog swim recreationally. Umbra, a world record-holding dog, can swim 4 miles (6.4 km) in 73 minutes, placing her in the top 25% in human long-distance swimming competitions. [35]
Sharks are denser than water and must swim continually to maintain depth, using dynamic lift from their pectoral fins. Bone and muscle tissues of fish are denser than water. To maintain depth, bony fish increase buoyancy by means of a gas bladder. Alternatively, some fish store oils or lipids for this same purpose.
Females are larger than males, and Pacific swordfish reach a greater size than northwest Atlantic and Mediterranean swordfish. [6] They reach maturity at 4–5 years of age and the maximum age is believed to be at least 9 years. [6] The oldest swordfish found in a recent study were a 16-year-old female and 12-year-old male.
Most fish species spawn eggs that are fertilized externally, typically with the male inseminating the eggs after the female lays them. These eggs do not have a shell and would dry out in the air. Even air-breathing amphibians lay their eggs in water, or in protective foam as with the Coast foam-nest treefrog, Chiromantis xerampelina.
Spiders are often confused with insects, but they are not insects; instead, they are arachnids. [5] [6] Spiders have separate male and female sexes.Before mating and copulation, the male spider spins a small web and ejaculates on to it.
Say you have a 4-year-old Labrador named Comet — with the new equation, Comet's real "dog age" would be slightly older than 53. The reason for the difference is actually pretty simple.
Some particular types of migration are anadromous, in which adult fish live in the sea and migrate into fresh water to spawn; and catadromous, in which adult fish live in fresh water and migrate into salt water to spawn. [2] Marine forage fish often make large migrations between their spawning, feeding and nursery grounds. Their movements are ...