Stomotheca
Encyclopedia
Stomotheca is the term applied to the feeding apparatus in front of the mouth of harvestmen, and sometimes the related scorpion
s. Usually it consists of the epistome (labrum
), two pairs of coxapophyses (endites, maxilla
ry lobes) and often a labium.
The epistome is a projection that forms the anterior wall of the stomotheca. Its upper side is hardened and divided by a transverse invagination (sulcus
). The part nearer the groove is sometimes called clypeus
, the other one labrum
. The area around the mouth is soft and flexible, often with a distal lobe. On the sides, the walls around the mouth are fused to the medial surfaces of the pedipalpal coxa
e, and a transverse muscle attaches to the inner surfaces of the epistomal walls.
Coxapophyses are extensions from the pedipalps and first pair of legs. While hardened at the base, they end in large soft pads that work as lips. It some species there is a narrow canal (pseudotrachea) on the posterior surface of the pedipalpal coxapophysis, possibly conducting fluids into the digestive tract. Salivary gland
s lead into the preoral chamber from both pairs of coxapophyses. While most harvestmen have coxapophyses on the second pair of legs as well, these do not end in pad-like structures and are reduced in many groups. Where they are fully developed, they probably aid in food intake. Similar lobular structures are sometimes found on the two latter pairs of legs as well, but their function is unknown.
The labium, when present, is a flattened plate derived from the somite
of the first walking leg. While large in many Eupnoi
and Dyspnoi
, it is small in most Laniatores
and absent in Cyphophthalmi
.
The term stomotheca is derived from Ancient Greek
stoma "mouth" and theca "case, box".
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s. Usually it consists of the epistome (labrum
Labrum (arthropod mouthpart)
The labrum is a flap-like structure that lies immediately in front of the mouth in almost all extant euarthropods, the general exception being provided by the probable chelicerate-relatives the pycnogonids. It has proved to be by far the most controversial of all arthropod head structures. It is...
), two pairs of coxapophyses (endites, maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
ry lobes) and often a labium.
The epistome is a projection that forms the anterior wall of the stomotheca. Its upper side is hardened and divided by a transverse invagination (sulcus
Sulcus (anatomy)
A sulcus is a depression or fissure in the surface of an organ, especially the brain.-Elsewhere:* anterior interventricular sulcus* calcaneal sulcus* coronal sulcus* gingival sulcus* gluteal sulcus* interlabial sulci...
). The part nearer the groove is sometimes called clypeus
Clypeus
The clypeus is one of the sclerites that makes up the "face" of an arthropod.In insects, the clypeus delimits the lower margin of the face, with the labrum articulated along the ventral margin of the clypeus. The mandibles bracket the labrum, but do not touch the clypeus. The dorsal margin of the...
, the other one labrum
Labrum (arthropod mouthpart)
The labrum is a flap-like structure that lies immediately in front of the mouth in almost all extant euarthropods, the general exception being provided by the probable chelicerate-relatives the pycnogonids. It has proved to be by far the most controversial of all arthropod head structures. It is...
. The area around the mouth is soft and flexible, often with a distal lobe. On the sides, the walls around the mouth are fused to the medial surfaces of the pedipalpal coxa
Coxa
Coxa may refer to:* Theta Leonis, a star* Nickname of Brazilian soccer team Coritiba Foot Ball Club* Hip, below the lateral side of the abdomen* The short most-proximal base jointed segment of the arthropod leg...
e, and a transverse muscle attaches to the inner surfaces of the epistomal walls.
Coxapophyses are extensions from the pedipalps and first pair of legs. While hardened at the base, they end in large soft pads that work as lips. It some species there is a narrow canal (pseudotrachea) on the posterior surface of the pedipalpal coxapophysis, possibly conducting fluids into the digestive tract. Salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...
s lead into the preoral chamber from both pairs of coxapophyses. While most harvestmen have coxapophyses on the second pair of legs as well, these do not end in pad-like structures and are reduced in many groups. Where they are fully developed, they probably aid in food intake. Similar lobular structures are sometimes found on the two latter pairs of legs as well, but their function is unknown.
The labium, when present, is a flattened plate derived from the somite
Somite
A somite is a division of the body of an animal. In vertebrates this is mainly discernible in the embryo stage; in arthropods it is a characteristic of a hypothetical ancestor.- In vertebrates :...
of the first walking leg. While large in many 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...
, it is small in most 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....
and absent in 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...
.
The term stomotheca 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...
stoma "mouth" and theca "case, box".