The Chemistry of Insect Hemolymph

Abstract

A curious feature of insect blood, shown by many analyses, is the apparent absence of all but minute amounts of sugar (for reviews, see Beutler, 1939;Babers, 1941;Buck, 1953). Reducing substances are abundant, but (except in the case of a few species) the greater part of these are not fermentable by yeast and are therefore presumably not sugar. Typical are data on the silkworm, Bombyx mori, in which the reported levels of blood sugar range from zero up to about 30 rag. per 100 ml. (Florkin, 1937;Kuwana, 1937; and others) --remarkably small amounts for a metabolically active animal with a high dietary intake of sugars. Twenty years ago, however, Kuwana (1937) made the significant discovery that acid hydrolysis of Bombyx hemolymph caused release of much reducing sugar from a substance which was not glycogen. Even earlier, Ronzoni and Bishop (1929) had reported an unidentified non-reducing "polysaccharide below glycogen" in the blood of honeybee larvae. These reports received little attention. Recently, unaware of them, we made essentially the same finding. The blood of Bombyx mori and of two other insect species was found to contain large amounts of anthrone-reactive material which was neither a reducing sugar, sucrose, nor glycogen (Wyatt, Loughheed, and Wyatt, 1956).As already reported in preliminary form (Wyatt and Kalf, 1956), we have now identified as a major sugar of insect plasma the non-reducing disaccharide a,a-trehalose. In the present paper, we give details of the isolation and characterization of this sugar together with some quantitative analyses of trehalose and certain other carbohydrates in insect plasma. Their distribution and significance will be considered.

Identification of an animal sucrose transporter

“…However, as depicted in Table 1, the major insect blood sugar trehalose (Wyatt and Kale, 1957) has a certain potential to compete with sucrose for transport, indicating that this disaccharide might also be a substrate for SCRT, yet with a reduced potency. The Drosophila SCRT resembles sucrose transporters in plants, including a crucial region that is considered to be a sucrose transporter signature.…”

Carbohydrate Metabolism in Drosophila: Reliance on the Disaccharide Trehalose

“…Since 1956 it was known that trehalose is a very abundant component of insect hemolymph [39], and also since then, various reports have shown that trehalose levels can vary greatly [36,39]. As stated before, there are several reasons for this: Trehalose levels respond to a variety of environmental conditions including changes in ambient and concomitant bodily temperature, nutritional status, developmental stage, oxidative stress, salinity, etc., such that the term 'enantiostasis' was coined to describe this condition.…”

Parallel ionoregulatory adjustments underlie phenotypic plasticity and evolution ofDrosophilacold tolerance

“…Adult Lepidoptera maintain low haemolymph [Na + ], in some cases low enough to reverse the muscle Na + gradient (Fitzgerald et al, 1996). To maintain haemolymph osmotic balance in the absence of Na + , Lepidoptera maintain high haemolymph concentrations of carbohydrates (Wyatt and Kalf, 1957;Wyatt, 1961), and, as a group, maintain muscle excitability to lower temperatures than members of Diptera and Hymenoptera, which have more 'conventional' (high) extracellular [Na + ] (Natochin and Parnova, 1987;Goller and Esch, 1990). Although we observed low cation concentrations in more cold-tolerant flies, we observed no differences in haemolymph osmolality between warm-and cold-acclimated D. melanogaster, nor among Drosophila species.…”