半月板退变是什么意思

[00:00.00]Seahorse Fathers Take Reins in Childbirth [00:04.96]It’s true that male seahorses never play catch with their children [00:11.31]or help them with their homework. [00:13.28]But they do outdo human dads on one count. [00:16.89]Male seahorses undergo pregnancy and give birth to their sons and daughters. [00:23.00]The trait is unique in these strange and fascinating fish [00:26.07]that inhabit tropical and temperate coastal waters worldwide. [00:30.00]Seahorses, which range from less than an inch to a foot in length, [00:35.04]have evolved a series of unusual adaptations. [00:38.33]They are such an unusual looking fish that [00:41.61]people sometimes don’t realize they’re real fish. [00:44.88]The male seahorse has a pouch on its stomach in which to carry babies— [00:49.80]as many as 2000 at a time. [00:52.77]A pregnancy lasts from 10 to 25 days depending on the species. [00:57.96]The reproductive process begins [01:00.47]when a male and a female seahorse do daily predawn dances [01:05.29]intertwining their tails and swimming together. [01:08.25]Eventually they engage in a true courtship dance, [01:12.29]which can last as long as eight hours. [01:15.02]It ends with the female depositing her eggs in the male’s pouch. [01:19.39]The eggs hatch in the pouch. [01:21.81]The father cares for the young [01:23.57]as they grow regulating the water salinity in the pouch to prepare them for life in the sea. [01:29.78]When the tiny seahorses are ready to be born the male undergoes muscular contractions [01:36.35]to expel the young known as “fry” from the pouch. [01:39.95]While seahorse dads go the extra mile to give birth [01:43.68]the parents do not provide their tiny offspring with any care or protection [01:48.93]after they are born. [01:50.34]Infant seahorses are susceptible to death from predators [01:54.30]and being swept into ocean currents [01:56.69]where they drift away from feeding grounds rich in microscopic organisms. [02:01.39]Fewer than five infant seahorses in every 1000 survive to adulthood [02:06.76]which helps explain why the litters are so large.

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