Siphonophorida

Snout Millipedes

Siphonophorida is an of in the subclass Colobognatha containing two : Siphonophoridae and Siphonorhinidae. These millipedes are characterized by super-elongated, -like bodies with up to 190 and extreme numbers of legs—up to 750 in Illacme plenipes, the leggiest animal known. They lack and exhibit euanamorphosis, adding segments throughout life even after sexual maturity. The order shows a scattered, disjunct distribution across multiple continents including North America, South America, Africa, Madagascar, India, Southeast Asia, and Australia.

Siphonophoridae by (c) Paul Marek, some rights reserved (CC BY). Used under a CC-BY license.

Siphonophoridae by (c) Helen J. Read & Henrik Enghoff, some rights reserved (CC BY). Used under a CC-BY license.

Siphonorhinidae by (c) Marek, P.; Shear, W.; Bond, J. (2012), some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Siphonophorida: /sɪfəˌnɒfɔrɪdə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other by the combination of: extremely elongated body with many (often 100+); absence of ; simple, leg-like lacking complex specialization; presence of a -like snout in Siphonophoridae (absent in Siphonorhinidae); and euanamorphic development with continued segment addition after maturity. Siphonophoridae differs from Siphonorhinidae by having straight with sensory pits on 5–6 and beak-like mouthparts, versus antennae lacking sensory pits and no beak in Siphonorhinidae.

Images

Appearance

Elongated, thread-like, -shaped bodies reaching up to 36 mm in length with up to 190 body . are absent. Many in Siphonophoridae have the elongated into a long -like snout with highly reduced ; the beak may function in suctorial feeding. Body covered with dense fine . Each body segment consists of unfused tergite, two , and . Male (reproductive appendages) are simple and leg-like, composed of the ninth and tenth leg pairs with seven podomeres. straight with sensory pits on fifth and sixth segments in Siphonophoridae, or (elbowed) lacking such pits in Siphonorhinidae. Coloration typically pale or unpigmented.

Habitat

Deep soil microhabitats, endogean (underground) environments, and spaces. Found under decaying wood, stones, and within soil layers near leaf litter. North Siphonorhinidae inhabit subterranean micro-; Chilean occur under decaying wood in fragmented forest; Malagasy species occur in degraded central highland rainforests. Requires moist conditions with access to decaying matter.

Distribution

Scattered, disjunct distribution: southwestern USA to Brazil and Peru in the Western Hemisphere; South Africa; Madagascar; India; Southeast Asia; Indonesia (Java, Flores); and Australia. In the Americas, exhibits antitropical distribution at approximately 37° North (California) and 38° South (Chile). Siphonorhinidae: California (USA), southern Africa, Madagascar, India, Southeast Asia, Malay Archipelago, Indo-Burma, and Chile. Family Siphonophoridae: more widespread in Neotropics and other regions. Fossil record includes Late (Cenomanian) Burmese amber assignable to extant Siphonophora.

Life Cycle

Euanamorphosis: individuals emerge from with at least four leg pairs and incrementally add legged during development, continuing even after sexual maturity. Gradual development of with continuously changing shape between leading to adulthood. This developmental mode is a of the .

Behavior

Very slow . Burrows through narrow underground crevices using concertina-like movement enabled by compressible due to primitively unfused , extensible flexible body, continuous metachronal wave gait, and action of concentric tubular rings sliding within one another. Longitudinal and oblique muscles pull rings together to facilitate forward locomotion. Burrowing resembles that of and geophilomorph .

Similar Taxa

PolyzoniidaAlso exhibits super-elongation with many and euanamorphosis; of elongated body form in Colobognatha. Distinguished by different structure and .
PlatydesmidaAnother colobognathan with simple ; differs in having fewer and different body proportions.
PolydesmidaLarge common with many but with highly specialized, complex and different body shape; not euanamorphic.

More Details

Taxonomic difficulty

The simple, leg-like lacking complex specialization have led to Siphonophorida being called a 'taxonomist's nightmare'. Jeekel reportedly gave the the 'taxonomists' award for least popular group among diplopods' due to the difficulty in distinguishing based on male .

Phylogenetic relationships

Siphonorhinidae is with respect to Siphonophoridae. The Illacme in California is the only representative of Siphonorhinidae in the Western Hemisphere; its closest known relative is Nematozonium filum in southern Africa, with divergence estimated at over 200 million years when continents were united in Pangaea.

Extreme leg counts

The contains the leggiest animals on Earth: Illacme plenipes with up to 750 legs (females) and 562 (males); Eumillipes persephone with up to 1306 legs; and Illacme tobini with 414 legs. Leg proliferation may be an for burrowing or clinging to substrates.