Intrauterine Cannibalism in Sharks



Sandtiger Shark (Carcharias taurus)

Two forms of within-the-womb cannibalism are known in sharks. The most extreme form of intrauterine cannibalism  in which the largest and strongest embryo actually consumes its lesser womb-mates  is termed "embryophagy" or, more colorfully, "adelphophagy"  literally "eating one's brother". It was discovered accidentally in 1948, when a researcher probing the uteri of a late-term Sandtiger Shark (Carcharias taurus) was startled by a bite on the hand. To date, adelphophagy is known only in the Sandtiger. The less extreme and by far more common form of intrauterine cannibalism  in which developing embryos feed on a steady supply of tiny, unfertilized eggs  is termed "oophagy" (sometimes called "oviphagy")  meaning "egg-eating". The earliest documented case of oophagy dates back to 1907, in the Porbeagle (Lamna nasus). Both forms of intrauterine cannibalism continue throughout embryonic and fetal development, so that at birth each pups often has aa conspicuously swollen abdomen known as a "yolk stomach".

Until quite recently, intrauterine cannibalism was thought to be restricted to lamnoid sharks. This grisly form of within-the-womb nutrition is now known from two carcharhinoids and even one orectoloboid. Following is a list of all sharks in which intrauterine cannibalism has been documented, or for which exists strong circumstantial evidence:

Order Orectolobiformes

Family Ginglymostomatidae

Tawny Nurse Shark (Nebrius ferrigineus)

Order Lamniformes

Family Carchariidae

Sandtiger Shark (Carcharias taurus)

Family Pseudocarchariidae

Crocodile Shark (Pseudocarcharias kamoharai)

Family Alopiidae

Pelagic Thresher Shark (Alopias pelagicus)

Bigeye Thresher Shark (Alopias superciliosus)

Common Thresher Shark (Alopias vulpinus)

Family Cetorhinidae

Basking Shark (Cetorhinus maximus)

Family Lamnidae

Salmon Shark (Lamna ditropis)

Porbeagle (Lamna nasus)

White Shark (Carcharodon carcharias)

Shortfin Mako (Isurus oxyrinchus)

Longfin Mako (Isurus paucus)

Order Carcharhiniformes

Family Pseudotriakidae

Slender Smoothhound Shark (Gollum attenuatus)

False Catshark (Pseudotriakis microdon)