Tetramerocerata is an
order
Order, ORDER or Orders may refer to:
* A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
...
of
pauropods containing 11 families and more than 900 species.
This order was created in 1950 to distinguish these pauropods from those in the newly discovered genus ''
Millotauropus'', which was found to have such distinctive features as to warrant placement in a separate order (
Hexamerocerata) created to contain that genus.
The order Tetramerocerata includes the vast majority of pauropod species, as there are only eight species in the order Hexamerocerata, which remains the only other order in the class
Pauropoda
Pauropoda is a class of small, pale, millipede-like arthropods in the subphylum Myriapoda. More than 900 species in twelve families are found worldwide, living in soil and leaf mold. Pauropods look like centipedes or millipedes and may be a sist ...
.
Description
Adult pauropods in the order Tetramerocerata feature
antennae that have four stalk segments and are not telescopic, whereas species in the order Hexamerocerata have strongly telescopic antennae with six stalk segments.
Two antennal branches emerge from the distal end of the fourth segment in Tetramerocerata, one dorsal and one ventral; in Hexamerocerata, however, the dorsal branch emerges from the distal end of the fifth segment, and the ventral branch emerges from the distal end of the sixth segment.
In Tetramerocerata, the ventral branch features two long flagella, one anterior and one posterior, but the dorsal branch features only one; in Hexamerocerata, each branch features only one flagellum. In Tetramerocerata, the distal part of the ventral antennal branch also features a spheroid sense organ, the globulus. The lateral sides of the head feature two large eye-like organs, and in Tetramerocerata, these temporal organs are flat or somewhat convex; in Hexamerocerata, these organs are shaped like cups or umbrellas attached to a shallow depression in the head.
Adults in the order Tetramerocerata have trunks with six
tergites that may be entire or divided, whereas those in the order Hexamerocerata have twelve entire tergites.
Although there are twelve trunk segments, in Tetramerocerata, the first, fourth, sixth, eighth, tenth, and twelfth segments are so short that the entire dorsal surface is covered by the tergites of the second, third, fifth, seventh, ninth, and eleventh segments. In Tetramerocerata, the ventral surface of the first trunk segment, the collum, features two appendages with a plate in between protruding in the anterior direction; in Hexamerocerata, this ventral surface is smooth. In Tetramerocerata, the
tergum
A ''tergum'' (Latin for "the back"; : ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton wi ...
of the last trunk segment, the
pygidium
The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...
, features four pairs of
setae
In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms.
Animal setae
Protostomes
Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae ...
; this tergum in Hexamerocerata features five to eight pairs of setae.
Most adults in the order Tetramerocerata have nine leg pairs.
Adults in four genera (''
Cauvetauropus'', ''
Aletopauropus'', ''
Zygopauropus'', and ''
Amphipauropus'') have only eight pairs, however, and adult females in the genus ''
Decapauropus'' (in the
Pauropodidae family) have either nine or ten pairs of legs.
Adults in the order Hexamerocerata have eleven leg pairs.
Feeding
The mouthparts in the order Tetramerocerata are weaker than those found in the order Hexamerocerata. The
mandibles in Tetramerocerata are adapted for sucking fluids and are used to puncture cell walls. No solid food has been found in the midgut of pauropods in the order Tetramerocerata. The mandibles in the order Hexamerocerata, however, are strong enough to allow the consumption of solid food, and the midgut of pauropods in Hexamerocerata can contain fungus, spores, and plant tissue.
Development
Most species in the order Tetramerocerata develop through a series of five post-embryonic stages, from the first
instar
An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...
to the adult. Juveniles in this order begin with three pairs of legs and three tergites, then in most species in this order, they become adults with nine leg pairs and six tergites. Pauropods in this order have three leg pairs in the first stage, then five pairs in the second, six pairs in the third, eight pairs in the fourth, and for most species in this order, nine pairs in the fifth (adult) stage. Juveniles in the order Hexamerocerata, however, begin with six leg pairs and eight tergites, then become adults with eleven leg pairs and twelve tergites, going through stages with six, eight, nine, ten, and eleven leg pairs.
Distribution
Tetramerocerata has a
subcosmopolitan distribution, with species found nearly worldwide.
Families
This order includes the following families:
*
Amphipauropodidae Scheller, 2008
*
Antichtopauropodidae Scheller, 2010
*
Brachypauropodidae Silvestri, 1902
*
Colinauropodidae Scheller, 1985
*
Diplopauropodidae Scheller, 1988
*
Eirmopauropodidae Scheller, 2010
*
Eurypauropodidae Ryder, 1879
*
Hansenauropodidae Remy, 1954
*
Pauropodidae Lubbock, 1867
*
Polypauropodidae Remy, 1932
*
Sphaeropauropodidae Verhoeff, 1934
References
External links
*
{{Authority control
Myriapod orders
Pauropoda