Heterogeneous activity causes a nonlinear increase in the group energy use of ant workers isolated from queen and brood

Abstract

Increasing evidence has shown that the energy use of ant colonies increases sublinearly with colony size so that large colonies consume less per capita energy than small colonies. It has been postulated that social environment (e.g., in the presence of queen and brood) is critical for the sublinear group energetics, and a few studies of ant workers isolated from queens and brood observed linear relationships between group energetics and size. In this paper, we hypothesize that the sublinear energetics arise from the heterogeneity of activity in ant groups, that is, large groups have relatively more inactive members than small groups. We further hypothesize that the energy use of ant worker groups that are allowed to move freely increases more slowly than the group size even if they are isolated from queen and brood. Previous studies only provided indirect evidence for these hypotheses due to technical difficulties. In this study, we applied the automated behavioral monitoring and respirometry simultaneously on isolated worker groups for long time periods, and analyzed the image with the state-of-the-art algorithms. Our results show that when activity was not confined, large groups had lower per capita energy use, a lower percentage of active members, and lower average walking speed than small groups; while locomotion was confined, however, the per capita energy use was a constant regardless of the group size. The quantitative analysis shows a direct link between variation in group energy use and the activity level of ant workers when isolated from queen and brood.

Propriedades e secreção das enzimas digestivas e caracterização das membranas microvilares intestinais de insetos

“…An aminopeptidase activity was sh by several criteria, to be bound to plasma membrane covering the micr of R. americana midgut caecal cells ( This activity is released into solutio papain treatment as three proteins different electrophoretic migration (F The major aminopeptidase was pu and shown to prefer, in contrast to the cal luminal aminopeptidases from americana (26), tripeptides rather tetrapeptides. This lends support to proposal (1,4,5,26) that interme digestion of protein takes place in th men of the midgut caeca while term digestion occurs at the surface of the lular microvilli, both through the acti aminopeptidases. Carboxypeptidases not very active in R. americana midgu A metal ion is involved in catalysis considering the fol1owing: (a) the action of EDTA upon the enzyme results in a completely inactive enzyme; (b) the order of reaction in relation to EDTA is 0.5, which indicates that the removal of only one metal ion is sufficient to inactivate the enzyme; (c) the presence of a bulky competitive inhibitor in the active site of the enzyme confers total protection against inactivation by EDTA; (d) Zn 2 + not only restores ful1 activity to a phenanthrolineinhibited midgut aminopeptidase, but it also raises the activity of the enzyme to above the control leveI.…”

“…The data support the proposal that the enz a metal ion which is catalytically active and that the enzyme displays two su its active center: a hydrophobic subsite, to which isoamyl alcohol binds expo metal ion, and a polar subsite, to which hydroxylamine binds. <i:l1986 Aeademie Pr... Digestion of proteins in the larvae of the fly Rhynchosciara americana occurs in three spatially organized steps (1)(2)(3). The first takes place inside the peritrophic membrane under the action of a trypsinlike proteinase.…”

“…Midgut membrane-bound aminopeptidases have been found in insects other than 1 To whom ali correspondence should be addressed.…”

“…-Glucosidase activity was measured deterrnining the appearence of p-nitrophenol (Terra et al, 1979) from 10 mM pnitrophenil~-D-glucoside in 50 mM citrate-sodiurn phosphate buffer pH 6.0.…”