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)

 
 

ReefQuest Centre for Shark Research
Text and illustrations R. Aidan Martin
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