Reproductive

• Diff. between terrestrial and marine mammals

  Anatomical differences:

  • thermoregulation of testes
  • development of fetus
• Breed in Water

  • Cetaceans, Sirenians, Sea Otters, some Pinnipeds (Walrus)
• Breed on Land

  • Polar Bears, some Pinnipeds (Elephant Seals)
• Breed in both water and on land

  • Some Pinnipeds (Grey Seals)
• Give birth in water

  • Cetaceans, Sirenians, Sea Otters
• Give birth on land or ice

  • polar bears and pinnipeds
• Precocious young (needing little care or protection)

  • Cetaceans and Sirenians
• Young require lots of parental care

  • Pinnipeds, Polar Bears and Sea Otters
• females continually forage for food while feeding young

  • Cetaceans, Sirenians, Sea Otter and some Pinnipeds (Walrus)
• females fast at early stages of feeding young

  • Polar Bears and some Pinnipeds (Elephant Seals)
• ovary, oviduct, uterus, cervix, vagina, clitoris and vaginal vestibule
• Variation in reproductive organs:

  • anatomy, morphology, physiology and cycling or hormones
• Simple uterus = 1 uterine body with no horns or components and 1 cervix -> humans
• Bicornuate = 2 horns forming a single body with no septum and 1 cervix -> Cetaceans, Sirenians, Sea Otters, Polar Bears
• Bipartite = 2 horns separated by a septum with a common area near the cervix and 1 cervix -> Phocids, Otariids have 2 horns and 1 cervix but unsure if they are bicornuate or bipartite
• Duplex = 2 separate horns and 2 cervices -> Walrus
• Uterus

  • supported by broad ligaments
  • wall has 3 layers
  • outside - serous membrane
  • middle - myometrium
  • inner - lining or endometrium
• Ovaries:

  • where eggs mature, released during ovulation
  • always 2 functional ovaries
  • surrounded by ovarian bursa
• Ovaries

  • suspended from abdominal or pelvic cavity by short mesentery (mesovarium)
• Mesovarium- attached to dorsal side of a large ligament → broad ligament
• ovarian bursa- ensures eggs pass into oviduct, ensures implantation in uterus
• Ovaries

  • shape and size varies
  • manatee - flat and broad
  • sea otters - compressed oval
  • odontocetes - spherical or ovoid
  • mysticetes - flat elongated
  • phocids- ovoid, smooth
• Cervix = highly muscular sphincter that separates the uterus from the vagina
• West Indian manatee → rounded cervix
• dugongs → shield that starts in the uterus, surround the cervix and extends into the vagina
• • cetaceans→ thick wall that extends a lumen into the vagina, length of this passage varies depending on the species
  • very short in Narwhals
  • very long in Harbour porpoises
• Maturation Rates of young cetaceans

  • plankton feeders → 4-8yrs
  • fish feeders → 4-10yrs
  • squid feeders → 4-10 yrs
  • manatee → 4-8 yrs
  • dugongs → 6-12 yrs
• Female Reproductive Intervals (time between babies)

  • sea otter; otariids, phocids → 1yrs, Walrus → 2-4yrs
  • Odontocetes → 3-5 yrs, Mysticetes → 1-3 yrs
  • Odontocetes → Sperm and Killer whales > dolphin and porpoises
  • Mysticetes→ Blue and Grey whale > double Minke whales
  • Sirenians; Manatees → 2-4 yrs, Dugong → 3-yrs
  • Polar Bear → 2-4 yrs
• Life Expectancy in Cetaceans

  • smaller species → 14-50yrs
  • Large baleen whales, sperm whales, killer whale → 50-100yrs
  • manatee→ 60yrs
  • dugongs→ 70yrs
• in Cetaceans have long flat mammary glands found in connective tissue under the skin along both sides of ventromedial line and extend from the umbilicus to above anus
• Phocids- mammary glands lying in under their blubber and encased in a connective sheath
• Otariids- form into a thin layer under the blubber covering most of the ventral body surface
• • Cetaceans
  • 2 nipples one on each side
  • during nursing the nipples protrude and the milk is squeezed out under pressure by the contraction of muscles
• • Sirenians
  • 1 nipple located under each of pectoral flippers from which young suckle on
• • Sea Otters
  • 2 nipples on lower abdomen unlike other species of Mustelids which may have 6 or more
• • Polar Bears
  • have 4 nipples, 2 on each side of abs
• • Otariids/Odobenids/ some Phocids
  • have 4 nipples
  • Other phocids
• • Other phocids
  • 2 posterios nipples
• pinniped nipples retract below skin level when not nursing and become erect once nursing occurs
• • lactation period varies between species
  • can range from days to years