An ozopore is a defensive gland present in harvestmen, which are eight-legged arachnids also known as "daddy long-legs". These glands, also called "scent glands", "repugnatorial glands", "odoriferous glands" or "stink glands" by various authors, are located at the anterior sides of the prosoma.

The name is derived from Ancient Greek

Ancient Greek

Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 ozo "smell" and Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 porus "pore, small opening".

The defensive secretions emitted by them also act as an alarm pheromone

Pheromone

A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...

. The glands are infoldings of the body wall, consisting of three layers. Although the glands themselves have no musculature, there is associated musculature present, which is most elaborate in Cyphophthalmi. Eupnoi

Eupnoi

The Eupnoi are a suborder of harvestmen, with more than 200 genera, and about 1,700 described species.They consist of two superfamilies, the Phalangioidea with many long-legged species common to northern temperate regions, and the small group Caddoidea, which have prominent eyes and spiny...

 and Dyspnoi

Dyspnoi

The Dyspnoi are a suborder of harvestmen, with about 32 genera, and about 320 described species.Several fossil species are known, including two extinct families.The superfamilies Ischyropsalidoidea and Troguloidea are monophyletic...

 have the most reduced muscular system.

This defensive behavior is considered most effective in the suborders Cyphophthalmi

Cyphophthalmi

The Cyphophthalmi are a suborder of harvestmen, with about 36 genera, and more than hundred described species.The six families are currently grouped into two infraorders, the Tropicophthalmi and the Temperophthalmi; however, these are not supported by modern phylogenetic analysis.They are smaller...

 and Laniatores

Laniatores

Laniatores is the largest suborder of the arachnid order Opiliones with over 4,000 described species worldwide. The majority of the species are highly dependent on humid environments and usually correlated with tropical and temperate forest habitats....

.

In the suborder Cyphophthalmi, the ozopores are located on special ozophore

Ozophore

An ozophore is an elevated cone present in the harvestman suborder Cyphophthalmi. It carries the openings of the defensive glands, called ozopores, which are present in many harvestmen....

s, specialized elevated cones.

Many different compounds have been found in various studied harvestman secretions. The chemical composition of the secretions seems to be useful in taxonomic

Taxonomy

Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 recognition. In the Laniatores, Gonyleptoidea

Gonyleptoidea

Gonyleptoidea is the most diverse superfamily of the Grassatores. It includes around 2,500 species distributed in the tropics. They are characterized by the simplified male genitalia, with the glans free subapical in the truncus....

 produce alkylated benzoquinones and phenol

Phenol

Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

s, and Travunioidea produce mainly terpenoid

Terpenoid

The terpenoids , sometimes called isoprenoids, are a large and diverse class of naturally occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures that differ from one another not only in...

s. In the Eupnoi, the Sclerosomatidae

Sclerosomatidae

The Sclerosomatidae are a family of harvestmen with about 1,300 known species.-Name:The name of the type genus is combined from Ancient Greek skleros "hard" and soma "body".-Genera:* Gagrellinae Thorell, 1889* Abaetetuba Tourinho-Davis, 2004...

 secrete short-chain acyclic

Acyclic

Acyclic can refer to:* In chemistry, a compound which is not cyclic, e.g. alkanes and acyclic aliphatic compounds* In mathematics:** A graph without a cycle, especially*** A directed acyclic graph...

 ketone

Ketone

In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...

s and alcohol

Alcohol

In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

s, and the Phalangiidae

Phalangiidae

The Phalangiidae are a family of harvestmen with about 380 known species. The best known is Phalangium opilio. Dicranopalpus ramosus is an invasive species in Europe....

, naphthoquinone

Naphthoquinone

Naphthoquinone is a class of natural phenols based on the C6-C4 skeleton.1,4-Naphthoquinone can be viewed as derivatives of naphthalene through the replacement of two hydrogen atoms by two ketone groups....

s.