Allen C. Cohen

Organization of digestion and preliminary characterization of salivary trypsin-like enzymes in a predaceous heteropteran, Zelus renardii

Abstract Salivary and intestinal proteolytic enzymes were studied in the predaceous heteropteran, Zelus renardii. Proteinases from Z. renardiis salivary gland complex (SGC), anterior midgut (AMG) and posterior midgut (PMG) were studied with hemoglobin, BApNA, BTNA, HPLA, HA and LPNA used as substrates. The SGC was shown to be an important source of general proteinase and endopeptidase activity, but exopeptidase activity (LPNA, HPLA and HA hydrolysis) was limited to the AMG and PMG. The AMG was also a source of considerable endopeptidase activity. Hemoglobin or BApNA hydrolysis occurred at a broad range of temperatures and pH with most activity observed at 35–45°C and at pH 7.0–8.5. The pH of the prey increased, as it was being pre-orally digested. The salivary trypsin-like enzyme had a molecular weight of approx. 27 kDa and eluted as two major activity peaks from an ion exchange column. BApNA hydrolysis was inhibited by soy proteinase inhibitor. Digestion, with respect to protein hydrolysis, is organized into an orderly and highly efficient process, differing greatly from that of hematophagous reduviids, beginning with pre-oral digestion of the preys internal structures whose liquefaction permits ingestion and further digestive processing of prey within the predators gut.

The potential role of phoresy in the evolution of parasitism: radiolabelling (tritium) evidence from an astigmatid mite

Using tritium as a radiolabel marker of interspecific fluid transfer, we present experimental evidence that the heteromorphic deutonymph of an astigmatid mite (Hemisarcoptes cooremani) acquires materials (at least water) directly from the haemolymph of its beetle host (Chilocorus cacti). This acquisition is above that obtained from atmospheric vapour. The material acquired from the host is necessary for the completion of the ontogeny of H. cooremani and is likely procured through the action of the caudal ventral suckers of the heteromorphic deutonymph (hypopus). On gross morphological criteria, this mite-beetle relationship was previously defined as phoretic (for dispersal). Scanning electron photomicrographs of the physical relationship between the hypopodes and the heetles shed light on the ‘parasitic’ nature of the hypopus of H. cooremani. Our findings are discussed in terms of the evolution of parasitism from a free-living astigmatid form. This transition into parasitism is facilitated by the heteromorphic hypopus and represents a classic ‘wolf-insheeps-clothing’ strategy. The heteromorph retains the characteristic phoretic morphology while exploiting the host in transit.

An egg-specific monoclonal antibody to Lygus hesperus

Abstract A species- and stage-specific monoclonal antibody (MAb) for a Lygus hesperus Knight egg antigen was developed. Positive antigen-antibody reactions were associated only with L. hesperus eggs and adult females. There was no cross-reactivity with any of the other L. hesperus life stages nor with any stage of L. lineolaris (Palisot de Beauvois). Furthermore, this MAb did not cross-react with the eggs of 10 other insect species examined. Electrophoretic and Western blot analyses indicated that the egg antigen had four polypeptides that bound to this MAb with molecular weights estimated at 64,000, 123,250, 140,300, and 150,300 Da. The use of this MAb as a diagnostic probe for gut content analysis of potential natural predators of L. hesperus eggs is discussed.

Nitrogen elimination in Trichoplusia ni parasitized by the insect parasite, Hyposoter exiguae

Abstract 1. 1. The fecal uric acid concentration and total uric acid excreted per mg fresh body weight were sharply increased in Trichoplusia ni larvae parasitized by the insect parasite, Hyposoter exiguae . 2. 2. This result was consistent with previous studies that indicated an elevated rate of gluconeogenesis in parasitized individuals. 3. 3. In contrast, pair-fed larvae had lower levels of excreted uric acid than their unparasitized counterparts.

Metabolic rates of two hemipteran members of a predator-prey complex☆

Abstract 1. 1. Metabolic rates (O 2 consumption) and respiratory quotients (R.Q.) were measured in a predator, Geocoris punctipes Say (Hemiptera: Lygaeidae) and its prey, Lygus hesperus Knight (Hemiptera: Miridae) under different temperature and diet conditions. Effects of sex and age of subjects were also measured. 2. 2. Adult females and all nymphal G. punctipes , regardless of diet, had R.Q. that indicated carbohydrates as a major fuel. Adult male R.Q. indicated fats as a major fuel. 3. 3. Except for third instar nymphs which used fat as fuel, the primary fuel for all ages of L . hesperus was carbohydrate. 4. 4. Q 10 (25–35°C) for G. punctipes had a steeper slope (3.7 max) than did L. hesperus (2.2 max), but G. punctipes had lower rates of O 2 consumption, than did L. hesperus . 5. 5. Diet quality had a strong influence on metabolic rate in G. punctipes , with the rates of individuals fed insect eggs being 2–5 × greater than those fed lepidopteran larvae and green beans. 6. 6. Relative adaptive qualities of the different Q 10 , R.Q. and metabolic rates for both species are discussed.

Temperature tolerance and water balance in feral and domestic honey bees, Apis mellifera L

Abstract Feral and domestic honey bees were compared to determine relative levels of adaptation to the Arizona desert. Feral honey bees were more tolerant to high temperatures than domestic honey bees. Monthly critical thermal maxima (CTMs) of feral bees were significantly different from those of domestic bees (P

Ontogenetic changes in waste purines from eggs of two species of insects

Abstract 1. 1. Waste purines, proteins and carbohydrates were measured in the eggs of Heliothis virescens Fab. (a lepidopteran that lays cleidoic eggs) and Lygus hesperus Knight (a hemipteran that lays non-cleidoic eggs). 2. 2. As development progressed, total purines increased in both species with greater amounts present in the cleidoic eggs. 3. 3. Protein concentrations changed according to a “U” shaped pattern in L. hesperus but showed only a slight, but non-significant decrease in the cleidoic eggs of H. virescens . 4. 4. Glycogen decreased continuously throughout development of both species while free sugars increased in L. hesperus eggs and decreased in H. virescens eggs. 5. 5. A possible pattern of water uptake from surrounding plant tissues is suggested for the non-cleidoic eggs of L. hesperus .