Biology subjects

Bertram, S. M.

Publications and source records attributed to Bertram, S. M..

8 recordsLinked to original sources

bioRxiv2025

Temperature outweighs diet in shaping developmental performance in two cricket species via growth delays and physiological limits

Understanding how chronic environmental stressors shape animal development is essential for predicting ecological responses and optimizing rearing systems. This perspective complements the use of short-term tolerance assays, which overlook the cumulative effects of sustained stress. Temperature and nutrition affect key life-history traits such as growth, development rate, and survival, which are closely tied to reproductive success and fitness. While both factors have been widely studied, their relative impacts arent clearly defined. We investigated how constant temperature (26- 41{degrees}C) and dietary protein-to-carbohydrate (P:C) ratio (0.15-2.18) influence development in two cricket species, Acheta domesticus and Gryllodes sigillatus. Growth trajectories were modelled using a unified-logistic equation to estimate asymptotic mass and relative growth rate. This approach captures the growth trajectory in a simplified and interpretable way, enabling comparisons across treatments. Asymptotic mass was combined with developmental rate and survival to calculate a composite metric of developmental performance. Developmental performance peaked at 35{degrees}C but fell at thermal extremes due to delayed development (in cold) or reduced mass and survival (in heat). Diet had more modest effects. Performance was stable across most P:C ratios, declining only at extreme imbalances. Notably, the performance cost of the most unbalanced diets was comparable to a 4-5{degrees}C shift from thermal optimum. Our results demonstrate that temperature, more than diet, drives variation in developmental performance during ad libitum feeding. This integrative framework provides a robust approach to quantify environmental sensitivity, define performance limits, and guide us toward the mechanisms underlying those limits and/or performance trade-offs. Summary statementTemperature more strongly influences growth trajectories and developmental performance than diet, due to delayed development and reduced survival at thermal extremes.

physiology↗

bioRxiv2025

Farmed cricket performance remains stable over five generations of rearing on a waste-based diet

Farmed insects like crickets offer a sustainable protein source to feed the growing global population. A benefit of cricket farming is the potential to use waste diets instead of unsustainable, expensive feeds. Brewers spent grain is a nutritionally valuable organic waste product that has been used to rear crickets in single generation studies. However, the long-term effects of spent grain-based feeds are unclear, which makes incorporation into commercial feed risky for producers. We reared a farmed cricket (Gryllodes sigillatus) for five generations on a high inclusion (75%) spent grain diet. Crickets reared on spent grain were 18.5% smaller at adulthood than control crickets reared on farm feed, resulting in decreased yield (mass of crickets harvested), but were able to reproduce and had high survival rates. Cricket performance remained stable over five generations, indicating that spent grain contains adequate nutrition to support long-term cricket production. We also reared crickets on a gradual inclusion spent grain diet that increased from 15-75% spent grain over five generations. While this "weaning" approach did not improve cricket performance on high-inclusion spent grain diets, crickets on low inclusion diets (15-30%) displayed nearly a 30% increase in survival and yield compared to those fed the control. Therefore, inclusion of low amounts of spent grain in cricket feed may not only be beneficial from an environmental and feed cost perspective, but also from a production yield perspective. Our findings are the first to show that spent grain is a suitable feed ingredient for long-term rearing of farmed crickets.

ecology↗

bioRxiv2024

Growth, development, and life history of a mass-reared edible insect, Gryllodes sigillatus (Orthoptera: Gryllidae)

Insects provide a potential source of sustainable, alternative protein that can help meet the protein demands of a growing population. Efficient farming of insects to meet this demand depends on an understanding of insect life history. Yet, detailed information and expertise about a single species are not always available for practitioners to make informed decisions about rearing practices or identify arising issues. The cricket (Gryllodes sigillatus) is commonly farmed for human consumption or animal feed, but few studies have characterized the life history of this species throughout ontogeny. Here, we describe the growth and development of G. sigillatus from hatch to adulthood and quantify reproductive traits relevant to mass-rearing and colony management, including egg development. This information provides foundation to start and manage a cricket colony and to conduct research on growth and performance. We highlight ways that a fundamental understanding of cricket biology can be informative for optimizing cricket growth, reducing variability in yield and informing future precision farming practices.

zoology↗

bioRxiv2024

Brewery Waste as a Sustainable Protein Source for the Banded Cricket (Gryllodes sigillatus)

Crickets, like other edible insects, can convert organic by-products of the food and agricultural industries into high-value protein. Waste products high in protein like brewers spent grain and brewers spent yeast are particularly attractive replacements for unsustainable protein sources in cricket feed like fishmeal or soy. Such replacement will only be advantageous, however, if feeding on these waste products does not impact, or only minimally impacts, cricket survival, growth, and body composition. In this study, a farmed cricket species, Gryllodes sigillatus, was reared in isolation on experimental diets in which fishmeal was wholly or partially replaced with either brewers spent grain or brewers spent yeast. Cricket survival, development and macromolecular composition were not different across diets. However, wholly replacing fishmeal with brewers spent yeast or brewers spent grain reduced cricket adult body mass by approximately 16%. To extend these findings toward a farm environment, a second cohort of crickets were reared communally on diets in which fishmeal, and fishmeal and soy (a secondary protein source), were replaced by brewers spent grain. We found that in a communal environment, crickets reared on both diets performed equally as well as the control. Therefore, brewing waste products are promising candidates for use as a primary protein source in the feed of G. sigillatus. In addition to contributing towards the goals of a circular bioeconomy through the repurposing of waste, the use of brewing waste in cricket feed may have a positive impact of the cricket farming industry as a cost-effective and sustainable alternative to traditional feed. Conflict of InterestThe authors have an ongoing research agreement with Aspire Food Group and Entomo Farms, who produce crickets as food and feed. Funding StatementThis research was funded by Discovery Grants awarded by the Natural Sciences and Engineering Research Council of Canada (NSERC) to H.A.M. (RGPIN-2018-05322) and S.M.B. (RGPIN-2017-06263). Additional support was provided by an NSERC Alliance Grant (568647-21) and a Deep Space Food Challenge grant (22IUCCAR22) from the Canadian Space Agency awarded to both H.A.M. and S.M.B. Equipment used in this study was purchased with support to H.A.M. from the Canadian Foundation for Innovation (project number 37721).

physiology↗

bioRxiv2024

Larger diet particle sizes cause crickets to grow faster with no effect on final body size

Artificial diets are costly to produce, so diet efficiency is critically important to the success of mass rearing insects. One way to improve feed efficiency is through dietary particle size optimization. We used a commercially reared species, Gryllodes sigillatus, to test whether individual crickets reared from hatch to adulthood on diets of different particle sizes would grow differently. Crickets fed a diet [≥]0.5 mm grew heavier during the first three weeks but weighed the same after six weeks regardless of diet size. We then provided crickets with a choice of particle size throughout development to test for dietary size preference. Given a choice, crickets consumed the most food from the 1.0-1.4 mm diet. Crickets also preferentially select ingredients from mixed diets, so to test whether grinding a conventional diet to a finer particle size could influence performance traits, we ran a large-scale group rearing experiment and found no effect of further grinding on colony mass gain or development time. Pelleting diet is another method for eliminating self-selection of ingredients, and so we tested whether pelleting finely ground conventional cricket feed would result in any substantial changes to the developmental life history of individual crickets. Crickets fed a 2 mm pelleted diet grew larger body size but were not significantly heavier. Overall, our results demonstrate that particle size optimization can be leveraged to enhance cricket life history traits important to mass production, as growth was accelerated on larger particle size diets and crickets preferred to eat larger-sized diets. Researchers focusing on physical properties of insect diets should carefully consider the timing of growth and development through which diet particle size may influence feed efficiency.

ecology↗

bioRxiv2024

Farmed crickets raised with dermestids suffer from reduced and delayed growth, but not enough to explain reports of dramatic yield loss

The mass production of crickets for food and feed is an expanding North American industry. Facilities that mass rear insects are at risk of pest infestations because the optimal environmental conditions for rearing beneficial species may also support the development of pest species. Here, we present the first recorded results detailing the interactions between dermestids and farmed crickets. Cricket farms have reported extremely low harvest yield during heavy dermestid infestations, but the exact reasons for this low yield are unknown. Many dermestid larvae are covered in dense, detachable, barbed setae called hastisetae, which are used by the larvae as an active trapping system against arthropod predators. We designed a series of experiments to test the hypotheses that dermestids (Dermestes ater DeGeer) may be directly impacting cricket (Gryllodes sigillatus Walker) yield through the physical effects of hastisetae ingestion and/or indirectly impacting cricket yield through competition for fishmeal, a primary source of protein in conventional cricket feed. Our predictions that cricket life history and survival would be negatively affected by dermestids were largely refuted. Females fed infested diets grew less mass, but not smaller body size, compared to females fed uninfested diets. We also found that while crickets experienced delayed growth early in life after living with dermestids, they were able to tolerate living with, and consuming, dermestid larvae. We discuss how these findings have led to new hypotheses concerning how dermestid infestations drive reductions in cricket farm yield.

ecology↗

bioRxiv2024

Applying nutritional ecology to optimize diets of crickets raised for food and feed

Increasing yield is a primary goal of mass insect rearing for food and feed, and diet shapes insect life history traits important to yield, such as survival, development time, and body size at adulthood. Little is known about how developmental macronutrient intake impacts survival, growth, and adult body size of mass reared insects. Here, we applied the nutritional geometry framework and reared individual tropical house crickets (Gryllodes sigillatus) from hatch to adulthood on a wide range of protein:carbohydrate diets. We measured weekly food consumption, survival, development time to adulthood, and adult body size and mass, and calculated a yield metric to extrapolate our individual-level results and predict how diet influences yield at the mass rearing level. Yield was maximized on a 3P:1C diet, as crickets fed this diet were most likely to develop into adults and grew maximum mass and body size. When provided with a choice between diets, crickets selected a relatively balanced 1.05P:1C diet throughout development, but males consumed 17% more protein than females. Our results represent a crucial first step towards determining the optimal standard feed formulation required to maximize cricket farming yield.

ecology↗

bioRxiv2022

Fruitful female fecundity after feeding Gryllodes sigillatus royal jelly

Dietary honey bee royal jelly increases insect growth rates and adult body size. Royal jelly could enhance mass insect production as a dietary supplement, but it is costly to produce. The mechanisms underlying the effects of royal jelly on growth remain unclear, and so it is valuable to understand the effects of royal jelly on a mass reared model species to try and augment body size in a more cost-effective manner. To determine the effect of royal jelly on a cricket species (Gryllodes sigillatus) farmed on mass for human consumption, we ran two experiments. In one experiment we tested the dose-dependent response of Gryllodes sigillatus to royal jelly using a range of diets across 0-30% w/w royal jelly. In another experiment we measured the individual-level life history responses of Gryllodes sigillatus to royal jelly over time by individually rearing freshly-hatched Gryllodes sigillatus on two separate diets: half were fed a commercially available cricket diet, while the other half were fed the same diet mixed with 15% w/w fresh royal jelly. Body size and mass measurements were recorded weekly for five weeks. We found the effects of royal jelly to be sex-dependent within crickets: females fed the royal jelly diet grew to be 30% heavier, and this effect was driven by significantly longer abdomens containing 67% more eggs compared to those fed the basal diet. There was a higher probability of crickets reaching adulthood after 35 days when fed royal jelly, and female mass was optimised at approximately 17% w/w royal jelly. Our results reveal that while a royal jelly dietary supplement can increase the yield of mass-reared insects, the life-history responses are species- and sex-specific.

ecology↗