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SYSTEMATIC BIOLOGY					KINGDOM ANIMALIA
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SUBPHYLUM MYRIAPODA

INTRODUCTION TO THE MYRIAPODA

Myriapoda (mir-i-O-po-da) is formed from two Greek roots that mean "many feet" [myriad -myriada (μυριάδα); and feet -podi (πόδι)]. The reference is to many walking legs, one or two pairs of walking legs for most body segments.

The myriapods (millipedes, pauropods, centipedes, and symphylans) are similar in that they have a head and a long, multisegmented body, each with a pair of walking legs (the "segments" of the millipedes are fused pairs; Figures A-D). Thus, their body is not separated into thorax and abdomen. The legs articulate with the sternum by a single joint. They have Malpigian tubules that likely are convergent, not homologous with those of the Hexapods. Almost all are terrestrial. The myriapods and hexapods have been grouped together in a group called the Uniramida (Barnes 1984; Willmer 1990) or Mandibulata (Margulis and Schwartz 1998), but the two groups do not seem to be part of a natural assemblage except within the phylum Arthropoda.

A. A millipede with the presence of two pair of legs per diplosegment.

B. A diagram of a pauropod.

C. A photograph of a centipede.

D. A photograph of a symphylan.

Images taken from:
A&C: http://www.ucmp.berkeley.edu/arthropoda/uniramia/myriapoda.html
B: http://www.qvmag.tas.gov.au/zoology/multipedes/taspauro/pauintro.html
D: http://www.qvmag.tas.gov.au/zoology/multipedes/tassymph/symintro.html

SYNOPTIC DESCRIPTION OF THE SUBPHYLUM MYRIOPODA

The following information came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), and Tudge (2000).

I. SYNONYMS: myriapods, millipedes, centipedes, arthropods.

II. NUMBER: >11,500 species known.

III. PHYLUM CHARACTERISTICS:

A. Structure

Symmetry: Bilateral; presegmental acron and postsegmental telson with 19 to >200 intervening segments, each with a pair of limbs (although the limbs may be highly modified or lost).

Body Cavity: True coelom reduced and absent in adults. Haemocoel the only body cavity.

Body Covering: Covered by chitinous exoskeleton.

Support: Hardened exoskeleton.

Digestive System: Food tube simple. Mouth anterioventraly with mandibles, maxillae (second maxillae sometimes fused into labium) and often bears palps. Food tube of three regions: fore-, mid-, and hindgut. No caecae. Anus terminal.

Circulatory System: Open. Haemocoel of blood sinuses with a dorsal heart. No respiratory pigments in the plasma .

Locomotion: Each segment bears one pair of unbranched, jointed legs. Millipedes have fused paired segments (diplosegments) with two pairs of walking legs attached to each diplosegment.

Excretory System: Malpighian tubules discharge into gut at junction of mid- and hindgut.

Nervous System: Circumesophagial brain and a double, ventral nerve cord with segmental ganglia. The head capsule (fused segments at the anterior end) has simple and compound eyes as well as antennae, sensory hairs.

Endocrine System:

Respiratory System: Tracheal system, usually paired spiracles at each segment. Likely, this is convergent with the tracheal system of the hexapods.

B. Reproduction:

Reproductive System: Dioecious. Gonads one to many. Fertilization internal (by spermatophores). Oviparous.

Development: Direct development.

C. Ecology: Mainly terrestrial.

HIERARCHICAL CLASSIFICATION OF THE SUBPHYLUM MYRIAPODA

This fairly standard taxonomic system is from Brusca and Brusca (2003). Although the taxonomy at this level has been quite stable, the taxonomy of the the classes, especially the Diplopoda, has been and still is in flux.

CLASS DIPLOPODA (10 ORDERS IN 2 SUBCLASSES)

All but first 4 trunk segments fused into pairs, each diplosegment with 2 pairs of legs, ganglia and heart ostia; simple, 7-jointed antennae; maxillae fused into gnathochilarium; integument normally reinforced with calcium carbonate; gonopores opening on or near coxae of 2^nd pair of legs; 1^st trunk segment legless; without compound eyes; each with diplosegment covered by dorsal tergum, 2 lateral pleura, and 2-3 sterna, with various degrees of fusion; young usually hatch with 3 pairs of legs.

Polyxenus, Glomeridesmus, Glomeris, Platydesmus, Striaria, Polydesmus, Julus, Spirobolus.

CLASS PAUROPODA (1 ORDER)

Small; eyeless; poorly developed mouthparts including 1 pair of maxillae; branched antennae; without heart or limbs on 1^st postcephalic segment, mostly without tracheae; gonopores on 3^rd trunk segment; trunk usually with 11 segments, the central 9 each with 1 pair of legs; some tergal plates large, extending over 2 segments and bearing long tactile setae; integument soft, uncalcified.

Pauropus.

CLASS CHILOPODA (5 ORDERS IN 2 SUBCLASSES)

Elongate; dorsoventrally flattened; numerous segments, each with 1 pair of legs except 1^st trunk segment, which bears one pair of large poison fangs, and last 2 segments; simple antennae, two pairs of maxillae; integument without calcium carbonate, eyes ocelli, compound or absent; poison fangs occupy undersurface of head; last 2 segments small, forming pregenital and genital segments; female with 1 ovary and 1 gonopore on genital segment, male with 1-24 testes and 2 gonopores on genital segment.

Scutigera, Lithobius, Geophilus, Scolopendra.

CLASS SYMPHYLA (1 ORDER)

Small; eyeless; trunk with 14 segments, the last fused to the telson; first 12 trunk segments each with 1 pair of legs, penultimate segment with cerci and 1 pair of long sensory hairs; dorsal surface with 15-22 tergal plates; antennae long, simple, thread-like; 2^nd maxillae fused together; 1 pair of spiracles on head, tracheae supplying first 3 segments; 1^st pair of legs short; young hatch with 6 or 7 pairs of legs; gonopores on 3^rd trunk segment; soft uncalcified integument.

Scutigerella.

This page is maintained by Jack R. Holt. Last modified: 03/10/08