Plastron Respiration in Aquatic Insects

Abstract

SUMMARY The closed tracheal system of the aquatic larvae of insects, together with the typical tracheal gill, can only function if the tracheal tubes themselves have sufficient resistance to compression. The work of Ege showed conclusively that the ‘air stores’ of many aquatic insects can, if they are in communication with the spiracles, function as gills for a limited time. Such bubbles will, however, since they have no resistance to compression, gradually dissolve in the water unless there is opportunity for regular renewal at the surface. The significance of the concept of invasion coefficient is considered in relation to gas‐bubble respiration. The term plastron is restricted to a ‘gas store’ communicating with the tracheal system and usually in the form of a thin film of constant and negligible volume and large surface area, retained in position by a system of hydrofuge hairs or scales in such a manner that it is not subject to the ‘Ege effect’ under the normal conditions of its environment, and is therefore not liable to loss by diffusion. Provided there is adequate oxygen in solution in the medium, such a plastron can enable the insect to remain below indefinitely, obtaining all the oxygen it requires from the surrounding water. The structure and biology of Aphelocheirus as a representative plastron insect is described. The plastron hair‐pile appears to be so perfect that an additional pressure of 4–5 atm. is required before the insect is in danger of losing its plastron and becoming wet. The spiracular adaptations which secure communication between the plastron and the tracheal system are described. The theory of plastron respiration as established by a study of Aphelocheirus is outlined. It is shown that in Aphelocheirus it is fully efficient as a respiratory structure and that this method of respiration has here nearly, if not quite, attained theoretical perfection. The resistance of the plastron hair‐pile to wetting is also discussed, and it is shown that this insect appears to have attained a very nearly perfect compromise between the conflicting requirements of a large area of gas‐water interface for diffusion and a minute scale hair‐pile for efficient resistance to water penetration. The development of the plastron hair‐pile in the individual and the first appearance of gas on its surface are described. A survey of plastron respiration in the Coleoptera is given. There are here three main groups in which the method has been elaborated, and while probably none of them presents as efficient an equipment for the purpose as Aphelocheirus there are several which can be regarded as having reached virtual perfection for the particular environments in which they live. It is shown that the plastron insects can be divided conveniently into three groups on the basis of the scale and arrangement of the hair‐pile and the consequent efficiency of the resistance to wetting. A number of the Coleoptera carry, over and above the plastron, a thicker gas layer, the macro‐plastron, held either by longer hairs or by me...

Aquatic insect diversity in two temple ponds of Silchar, Assam, N.E. India and their conservation values

“…Preponderance of order Hemiptera with very low DO in pond 1 could be explained by the fact that aquatic and semiaquatic Hemipterans do not rely heavily on DO in the water due to their abilities to utilize atmospheric oxygen, by possessing respiratory apparatus (siphon, plastron, presence of hemoglobin etc.) (Fernando and Cheng 1974;Lansbury 1972;Thorpe and Crisp 1947;Thorpe 1950;Wells et al, 1981). In the lakes and rivers of North East India also preponderance of Hemiptera has been noted in several studies (Das and Gupta 2010;Gupta and Narzary 2013;Gupta 2012, 2013;Takhelmayum and Gupta 2011).…”

Change in drag, apparent slip and optimum air layer thickness for laminar flow over an idealised superhydrophobic surface

“…achieving an air layer with a net mass flow rate by constant injection of air upstream of the air layer. However, in the context of superhydrophobic surfaces no air is injected, and the goal is to achieve a trapped air layer covering the surface of an immersed object partially or entirely similar to a plastron encasing some aquatic insects when diving underwater (Thorpe & Crisp 1947;Shirtcliffe et al 2006;Flynn & Bush 2008;Ditsche-Kuru et al 2011). In the case of a sphere covered by a plastron an analytic solution can be found in the Stokes flow limit, and it can be shown that a flow with zero net mass flow rate develops in the gas layer encapsulating the sphere (McHale, Flynn & Newton 2011).…”

Plastron properties of a superhydrophobic surface

“…This ensures the film of air is permanent and of constant volume. 9 It has also been reported that the silk nests of some terrestrial, ground dwelling spiders act as a physical gill extending survival times following flooding by factors of 7 to 16. 12 Plastron structures formed by a hydrophobic open mesh network are also found in the cocoons of some silk-using insects, the egg-shells of terrestrial insects and the silk nests of some terrestrial, ground dwelling spiders.…”

“…Such silvery reflections are also observed from the plastrons on some aquatic insects and spiders. [7][8][9][10] Plastrons are an adaptation to the water environment that allows oxygen to be extracted directly from the surrounding water. We therefore considered whether the submerged surface of a superhydrophobic material could be used to mimic plastron respiration rather than be simply a passive waterrepellent surface.…”