Oophagy literally "egg eating", is the practice of embryos feeding on eggs produced by the ovary

Ovary

The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...

 while still inside the mother's uterus

Uterus

The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

. The word oophagy is formed from the classical Greek ᾠόν (ōion, egg) and classical Greek φᾱγεῖν (phāgein, to eat).

Oophagy is thought to occur in all shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s in the order Lamniformes

Lamniformes

Lamniformes is an order of sharks commonly known as mackerel sharks . It includes some of the most familiar species of sharks, such as the great white shark, as well as more unusual representatives, such as the goblin shark and the megamouth shark.Members of the order are distinguished by...

 and has been recorded in the bigeye thresher

Bigeye thresher

The bigeye thresher is a species of thresher shark, family Alopiidae, found in temperate and tropical oceans worldwide. Like other thresher sharks, nearly half its total length consists of the elongated upper lobe of the tail fin. Its common name comes from its enormous eyes, which are placed in...

 (Alopias superciliosus), the pelagic thresher

Pelagic thresher

The pelagic thresher is a species of thresher shark, family Alopiidae; this group of sharks are characterized by the greatly elongated upper lobes of their caudal fins. The pelagic thresher occurs in the tropical and subtropical waters of the Indian and Pacific Oceans, usually far from shore but...

 (A. pelagicus), the shortfin mako (Isurus oxyrinchus) and the porbeagle (Lamna nasus) among others. It also occurs in the tawny nurse shark

Tawny nurse shark

The tawny nurse shark is a species of carpet shark in the family Ginglymostomatidae, and the only extant member of the genus Nebrius. It is found widely along coastlines in the Indian and Pacific Oceans, preferring reefs, sandy flats, and seagrass beds from very shallow water to a depth of 70 m...

 (Nebrius ferrugineus), and in the family Pseudotriakidae

Pseudotriakidae

Pseudotriakidae is a small family of ground sharks, order Carcharhiniformes, containing the false catsharks and gollumsharks. It contains the only ground shark species that exhibit intrauterine oophagy, in which developing fetuses are nourished by eggs produced by their mother.-Genera and...

.

This practice may lead to larger embryos or prepare it for a predatory lifestyle.

There are variations in the extent of oophagy among the different shark species. The grey nurse shark

Grey nurse shark

The sand tiger shark or grey nurse shark is a species of shark that inhabits coastal waters worldwide. It lives very close to the shorelines and beaches of North America, hence the name, sand tiger shark. Despite a fearsome appearance and strong swimming abilities, it is a relatively placid and...

 (Carcharias taurus) practices intrauterine cannibalism, the first developed embryo consuming both additional eggs and any other developing embryos. Slender smooth-hound

Slender smooth-hound

The slender smooth-hound or gollumshark is a species of ground shark in the family Pseudotriakidae. It is endemic to the waters around New Zealand, where it is usually found close to the bottom over the continental slope at depths of...

s
(Gollum attenuatus), form egg capsules which contain 30-80 ova within which only one ovum develops while all other ova are ingested and packed to an external yolk sac. The embryo then develops normally without ingesting further eggs.

Oophagy is also used to refer to more general egg-eating behaviours such as those practised by some snakes or the differential oophagy practiced by the Polistes biglumis

Polistes

Wasps of the cosmopolitan genus Polistes are the most familiar of the polistine wasps, and are the most common type of paper wasp. It is also the single largest genus within the family Vespidae, with over 300 recognized species and subspecies...

species of wasp.

Ovophagy

Ovophagy is a rare though widely observed condition in the reproduction of certain animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, whereby fetus

Fetus

A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

es will devour each other prior to birth

Birth

Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...

. Subsequent research has shown ovophagy to be sporadic and highly uncommon among the vast majority of animal species.