So just HOW do marine CARNIVORES manage

INTERNAL FERTILIZATIONwith NO HANDS???

Recommended Reproduction Notes & Videos

• http://www.elasmo-research.org/education/ecology/intertidal-nurse.htm

So what’s the big deal with Twilight?Male sharks have been biting females for millions of years!

NOT your average

hickey!

So Now What?

Egg - Laying…

1. Extended Oviparity –paired eggs are laid, one from each oviduct; embryos derive nourishment solely from yolk in external yolk sac and undergo most of their development outside the mother’s body; the egg membrane is sclerotinized to form a collagenous, sulphur-rich case that often has antifouling properties. Found in skates (Rajiformes).

Egg – Developing … 2. Ovoviviparity - eggs are packaged in thin cases

and retained until development is complete, whereupon parturition occurs; embryos derive nourishment solely from yolk supply in external yolk sac. Found in cow sharks (Hexanchiformes), dogfishes (Squaliformes), angel sharks (Squatiniformes), some catsharks (Galeus spp.), shovelnosed guitarfish (Rhynchobatiformes), Bowmouth Guitarfish (Rhiniformes), sawfishes (Pristidae), electric rays (Torpediniformes), and stingrays and eagle rays (Myliobatiformes).

Live Birth 1…(Eat your eggs, now!)

3a. Matritrophic Viviparity with Oophagy – embryos feed initially on yolk in external yolk sac; after yolk sac is absorbed, embryos feed on unfertilized ova produced and shed by their mother. Found in all mackerel sharks (Lamniformes) except the Sandtiger (Carcharias taurus).

Great White Embryo – 4.9 ft long!

Live Birth 2…(Eat your little brother, now!)

3b. Matritrophic Viviparity with Adelphophagy - embryos feed initially on yolk in external yolk sac, then unfertilized ova produced and shed by their mother, then cannibalize siblings, Found in the Sandtiger (Carcharias taurus).

Live Birth 3 & 4 (Got Milk? – or a belly button?)

3c. Viviparity with Oophagy and Histotroph – embryos feed initially on yolk in external yolksac, then unfertilised ova produced and shed by their mother, these ova are consumed by embryos to replenish the external yolk sac; vilified embryonic surfaces indicate absorption of histotroph (“uterine milk”). Found in false catsharks (Pseudotriakidae).

3d. Matritrophic Viviparity with Placenta – also termed “viviparity” or “placental viviparity”; embryos feed initially on yolk in external yolk sac, then depleted yolk sac interdigitates with endometrial tissues (lining of mother’s uterus) to form a direct placental blood vessel link to mother; some species may also supplement placental nutrition with histotroph; vilified surfaces on the embryo or placental stalk (“appendiculae”) allow absorption of histotroph in addition to nutrients transferred via the placental link. Found, with some exceptions, in smoothhounds (Triakidae), weasel sharks (Hemigaleidae), whaler sharks (Carcharhinidae), and hammerhead sharks (Sphyrnidae)

How Long does it Take?

Grey Bambooshark(Chiloscyllium griseum)

70 days (2.3 months)

1278 days (3.5 years)

Frilled Shark(Chlamydoselache anguineus)

When do sharks mature?

Mosquitofish – 1month/1.5 years

Largemouth Bass – 16months/5 years

Great Hammerhead – 10-15yrs/25-30yrs

Spiny Dogfish – 20 yrs/70 yrs

Great White - ??/??