page_title: Springtail
section_title: Morphology
hierarchical_section_title: Springtail / Morphology
caption_attribution_description: Deutsch: Binokularaufnahme von Isotoma anglicana Lubbock, 1873 (Collembola, Isotomidae). Länge KR 3,5 mmEnglish: Detailed image of Isotoma anglicana Lubbock, 1873 (Collembola, Isotomidae), 3.5mm
context_page_description: Springtails form the largest of the three lineages of modern hexapods that are no longer considered insects. Although the three orders are sometimes grouped together in a class called Entognatha because they have internal mouthparts, they do not appear to be any more closely related to one another than they are to all insects, which have external mouthparts.
  Collembolans are omnivorous, free-living organisms that prefer moist conditions. They do not directly engage in the decomposition of organic matter, but contribute to it indirectly through the fragmentation of organic matter and the control of soil microbial communities. The word Collembola is from the ancient Greek κόλλα kólla "glue" and ἔμβολος émbolos "peg"; this name was given due to the existence of the collophore, which was previously thought to stick to surfaces to stabilize the creature.
  Some DNA sequence studies suggest that Collembola represent a separate evolutionary line from the other Hexapoda, but others disagree; this seems to be caused by widely divergent patterns of molecular evolution among the arthropods.
context_section_description: Members of the Collembola are normally less than 6 mm (0.24 in) long, have six or fewer abdominal segments, and possess a tubular appendage (the collophore or ventral tube) with reversible, sticky vesicles, projecting ventrally from the first abdominal segment. It is believed to be associated with fluid uptake and balance, excretion, and orientation of the organism itself. Most species have an abdominal, tail-like appendage known as a furcula. It is located on the fourth abdominal segment of collembolans and is folded beneath the body, held under tension by a small structure called the retinaculum (or tenaculum). When released, it snaps against the substrate, flinging the springtail into the air and allowing for rapid evasion and migration. All of this takes place in as little as 18 milliseconds.
  Springtails also possess the ability to reduce their body size by as much as 30% through subsequent ecdyses (molting) if temperatures rise high enough. The shrinkage is genetically controlled. Since warmer conditions increase metabolic rates and energy requirements in organisms, the reduction in body size is advantageous to their survival.
  The Poduromorpha and Entomobryomorpha have an elongated body, while the Symphypleona and Neelipleona have a globular body. Collembola lack a tracheal respiration system, which forces them to respire through a porous cuticle, with the notable exception of the Sminthuridae, which exhibit a rudimentary, although fully functional, tracheal system.The anatomical variance present between different species partially depends on soil morphology and composition. Surface-dwellers are generally larger, have darker pigments, have longer antennae and functioning furcula. Sub-surface-dwellers, are usually unpigmented, have elongated bodies, and reduced furcula. They can be categorized into four main forms according to soil composition and depth: atmobiotic, epedaphic, hemiedaphic, and euedaphic. Atmobiotic species inhabit macrophytes and litter surfaces. They are generally 8-10 millimeters in length, pigmented, have long limbs, and a full set of ocelli (photoreceptors). Epedaphic species inhabit upper litter layers and fallen logs. They are slightly smaller and have less pronounced pigments, as well as less developed limbs and ocelli than the atmobiotic species. Hemiedaphic species inhabit the lower litter layers of decomposing organic material. They are 1-2 millimeters in length, have dispersed pigmentation, shortened limbs, and a reduced number of ocelli. Euedaphic species inhabit upper mineral layers known as the humus horizon. They are smaller than hemiedaphic species; have soft, elongated bodies; lack pigmentation and ocelli; and have reduced or absent furca.
  Poduromorphs inhabit the epedaphic, hemiedaphic, and euedaphic layers and are characterized by their elongated bodies and conspicuous segmentation – three thoracic segments, six abdominal segments, and a prothorax.
  The digestive tract of collembolan species consists of three main components: the foregut, midgut, and hindgut. The midgut is surrounded by a network of muscles and lined with a monolayer of columnar or cuboidal cells. Its function is to mix and transport food from the lumen into the hindgut through contraction. Many species of syntrophic bacteria, archaea, and fungi are present in the lumen. These different digestive regions have varying pH to support specific enzymatic activities and microbial populations. The anterior portion of the midgut and hindgut is slightly acidic (with a pH of approximately 6.0) while the posterior midgut portion is slightly alkaline (with a pH of approximately 8.0). Between the midgut and hindgut is an alimentary canal called the pyloric region, which is a muscular sphincter.
caption: Isotoma with visible furcula
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