tetra-, tetr-

A government by four persons jointly; a set of four tetrarchs or rulers; a country divided into four petty governments.

Having four crescentic ridges on molar teeth.

A stanza, epigram, or poem, consisting of four verses or lines.

Duplication of the growth of the eyelashes (in four rows).

Having four loculaments (cell of a pericarp in which the seed is lodged), or thecae: a case, covering, or sheath; such as, the pollen sac of an anther, the spore case of a moss, or the outer covering of the pupa of certain insects.

A religious belief that in the Godhead there are, in addition to the Divine Essence, three other persons; the Father, the Son, and the Holy Spirit; and so making in the Godhead three and one instead of three in one.

1. A highly lethal neurotoxin present in numerous species of puffer fish and in certain newts (in which it is called tarichatoxin).

Ingestion rapidly causes malaise, dizziness, and tingling around the mouth, which may be followed by ataxia, convulsions, respiratory paralysis, and death.

2. A potent neurotoxin found in the liver, skin, and ovaries of the puffer fish, and in the California newt.
3. A powerful nerve poison found in the eggs of the California newt and in certain puffer fish in Japan.

In concentrated form, it is more toxic than cyanide.

You can find more information about tetrodotoxin here.

Poisoning from ingestion of improperly prepared puffer fish.

The clinical signs include tingling of the lips and tongue, motor incoordination, numbness of the skin, salivation, muscle weakness, generalized paralysis, and death.