Does the size of larval groups influence the effect of metabolic inhibitors on the development of Phormia regina (Diptera: Calliphoridae) larvae?

Abstract

Abstract.A series of experiments were conducted to compare the susceptibility of P. regina larvae reared in isolation or in groups to the effects of diet-borne metabolic inhibitors: chlorogenic acid (CGA) and mimosine. Larvae were presented with diets containing 0.4 mM CGA or 0.4 mM CGA in combination with 22 mM lysine or methionine or with diets containing 1.5, 15 or 30 mM concen trations of mimosine. Methionine and CGA caused significantly reduced pupal weights when compared with larvae presented with lysine and CGA. All concentrations of mimosine resulted in 100% mortality with larvae unable to successfully complete pupation even at the lowest concentration. In general, larvae reared in groups were less susceptible to the toxic effects resulting from dietborne metabolic inhibitors. The results are discussed in relation to the chemical factors that result from the feeding activity of saprophagous dipterans.

Temperature-modified density effects in the black soldier fly: low larval density leads to large size, short development time and high fat content

“…A longer developmental period in suboptimal conditions is a widespread phenomenon in insects (Green et al, 2002;Oonincx et al, 2015;Tammaru et al, 2015;Teder et al, 2014). However, in the case of larval density, the opposite (shorter larval period at high densities) is expected and also shown in several insect species (Bauerfeind et al, 2005;Esperk et al, 2007;Lyimo et al, 1992;Tammaru et al, 2000;Vellau and Tammaru, 2012).…”

“…In this case, larval crowding may be beneficial as it helps to break down their food faster and help in assimilation (Green et al, 2002). However, very high larval densities certainly have disadvantages, such as depletion of a food source (Applebaum and Heifetz, 1999;Tammaru et al, 2000), higher incidence of cannibalism (Pervez and Gupta, 2006;Porretta et al, 2016) and higher concentration of pathogens (Anderson and May, 1981;Wilson et al, 2002).…”

Influence of larval density and dietary nutrient concentration on performance, body protein, and fat contents of black soldier fly larvae (Hermetia illucens)

“…Larval aggregation produces higher temperatures that enhance food assimilation (Rivers & Dahlem, ). For instance, in the blowfly P. regina , larval aggregation has been reported to result in more efficient feeding, because the increased concentration of tryptic and alkaline excretions from groups of P. regina larvae may release more nutrients from the diet and allowed groups of larvae to forestall the toxic effects of some chemicals that interfere with conversion of amino acids and peptides into body mass, such as mimosine (Green et al., ). Probably, the alkaline excretions of groups of larvae neutralises the acidity associated with bacterial growth and pre‐digests the substrate (Green et al., ).…”

“…Insects have a tendency to prolong the larval period (Miller, ), or to increase either the rate of ingestion or the total amount of food ingested during larval development (Green et al., ). Sullivan & Sokal () proposed two basic types of responses to crowding: (1) a reduction in the number of individuals able to complete their life cycles, with the emerging adults maintaining normal body size, and (2) sustaining survival accompanied by reduction in body weight, as has been reported for the dipterans Phormia regina (Meigen) (Calliphoridae) (Green et al., ), Drosophila melanogaster Meigen, Drosophila simulans Sturtevant (Miller, ), and Aedes albopictus Skuse (Yoshioka et al., ). According to Sullivan & Sokal (), for the second type of response substantial losses in numbers will occur only at densities above which adult weight drops below a critical limit.…”

“…Lower larval densities are not always better to maximise growth rate. In some insect species, larval aggregations provide adaptive benefits to individuals due to heat generation, which might enhance food assimilation (Green et al., ) and provide protection from low environmental temperature and possibly predators (Rivers & Dahlem, ). BSF larval weight gain is also affected because of their potential dependence on bacteria as food (Liu et al., ).…”