George Keeney

High temperature effects on water loss and survival examining the hardiness of female adults of the spider beetles, Mezium affine and Gibbium aequinoctiale

Abstract A remarkable ability to tolerate temperatures as high as 52°C for Mezium affine Boieldieu and 56°C for Gibbium aequinoctiale Boieldieu (Coleoptera: Anobiidae) was discovered as part of a water balance study that was conducted to determine whether desiccation-resistance (xerophilic water balance classification) is linked to survival at high temperature. Characteristics of the heat shock response were an intermediate, reversible level of injury, appearing as though dead; greater recovery from heat shock by G. aequinoctiale (57%) than M. affine (30%) that supplemented higher temperature survival by G. aequinoctiale; and lack of protection generated by conditioning at sublethal temperature. Heatinduced mortality is attributed to an abrupt, accelerated water loss at 50°C for M. affine and 54°C for G. aequinoctiale, not to the species (M. affine) that loses water the slowest and has the lower activation energy, Ea as a measure of cuticular boundary effectiveness. These temperatures where water loss increases sharply are not critical transition temperatures because Arrhenius analysis causes them to be erased (uninterrupted Boltzmann function) and Ea fails to change when cuticular lipid from these beetles is removed. Our conclusion is that the temperature thresholds for survival and accelerated water loss closely match, and the key survival element in hot and dry environments contributing to wide distribution of G. aequinoctiale and M. affine derives from rising temperature prompting entry into quiescence and a resistance in cuticular lipid fluidity.

Role of permanent host association with the Madagascar hissing-cockroach, Gromphadorhina portentosa, on the developmental water requirements of the mite, Gromphadorholaelaps schaeferi.

We provide the first complete description of the water requirements for the hissing-cockroach mite, Gromphadorholaelapsschaeferi, focusing on characteristics that result from the restriction of all stages to the Madagascar hissing-cockroach (Gromphadorhinaportentosa). Particularly, we determine how G. schaeferi spends its entire life on the same individual cockroach. This mite is not parasitic, rather they feed on cockroach saliva and other moist organic debris that accumulates between the cockroach’s legs. Water balance characteristics of this mite show that it is extremely hydrophilic and that it must maintain a high percentage body water content to function properly despite being very porous (high net transpiration rate) and sensitive to water loss, tolerating only 20% loss of their water content before death. This hydrophilic trend starts with the larva and is retained into adulthood. Developmentally, a shift occurs during postlarval development from an emphasis on water gain (low critical equilibrium activity for water vapor absorption from drier air) in the protonymph to an emphasis on water retention (reduced net transpiration rate for water conservation) in the adult. The minute-sized larva is prevented from replenishing water stores by water vapor absorption or feeding because it lacks functional mouthparts, thus dries up rapidly. To avoid dehydration and survive, the larval stage utilizes a quick shoot-through molt to the protonymph that can feed and grow. Our conclusion is that the hissing-cockroach creates an ideal, stable moisture-rich microhabitat that satisfies the high water demand for G. schaeferi during all stages, fixing this mite to a single cockroach as an ecological niche.

The role of gut microbiota in the regulation of standard metabolic rate in female Periplaneta americana

Insect gut microbiota contribute significantly to host nutritional ecology. Disrupting insect gut microbial assemblages impacts nutrient provisioning functions, and can potentially affect host standard metabolic rate (SMR), a measure of host energy balance. In this study, we evaluated the effect of disrupting gut microbial assemblages on the SMR of female Periplaneta americana cockroaches fed dog food (DF, high protein/carbohydrate (p/c) ratio), and cellulose-amended dog food (CADF, 30% dog food, 70% cellulose, low p/c ratio) diets, supplemented with none, low, or high antibiotic doses. Bacterial loads decreased significantly between diet types (P = 0.04) and across antibiotic doses (P = 0.04). There was a significant diet type x antibiotic dose interaction on SMR of females on both diets (P = 0.05) by the end of the seven-day experimental period. In CADF-fed females, SMR decreased linearly with decreasing bacterial load. However, SMR of DF-fed females on the low dose was significantly higher than those in the control and high dose groups. This is interpreted as a diet-dependent response by low dose DF-fed females to the loss of nutritional services provided by gut bacteria. Severe reductions in bacterial load at high doses reduced SMR of females on both diet types. This study provides insights into the potential role of gut bacteria as modulators of host energy expenditure under varying dietary conditions.

Compositional differences among female-associated and embryo-associated microbiota of the viviparous Pacific Beetle cockroach, Diploptera punctata

ABSTRACT All cockroach species, except one, harbor the endosymbiont Blattabacterium, transmitted from females to embryos. Adult cockroaches acquire non‐Blattabacterium bacteria as part of their gut microbiota over time, but our knowledge of the possible transmission of these non‐Blattabacterium bacteria from females to embryos is rudimentary. We characterized the gut microbiota of gravid viviparous Diploptera punctata females and the non‐Blattabacterium microbiota of associated developing embryos, as well as the gut microbiota of non‐gravid females, and the microbiota of orphan embryos (females not included), following high‐throughput sequencing of the 16S rRNA gene to assess bacterial transference. We determined significant differences in community composition between gravid females and associated embryos and overall greater similarity in community composition among embryos than adult females. Results suggest various routes of transference of bacteria from females or the environment to embryos. The bacterial families Halomonadaceae and Shewanellaceae were more abundant in embryos than in gravid females. The functional relevance of these families remains to be elucidated, but provisioning of amino acids deficient in the brood sac secretion is a possibility. Overall, our results highlight the need for further studies investigating the uptake and selective screening of microbes by D. punctata embryos, as well as their functions. &NA; Graphical Abstract Figure. Diploptera punctata females and their corresponding developing embryos differ in microbiota composition.

Rearing and storage in mung beans reduce medically significant molds by the seed beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae), utilized in science classrooms

To examine whether colonies of seed beetles, Callosobruchus maculatus, may be a health concern as a source of mold allergens to students and teachers, we compared the amount and type of molds present on adult beetles reared with mung beans and cowpeas, Vigna radiata and Vigna unguiculata, respectively (Family Fabaceae). Specimens were analyzed from two elementary schools, a commercial supplier and a university insectary. A total of nine fungal genera were isolated from live and dead adult beetles, consisting primarily of Aspergillus (a large proportion of which was Aspergillus niger) and Penicillium, with lower, variable numbers of Alternaria, Cladosporium, Fusarium, Mucor, Rhizopus, Scopulariopsis, and Trichoderma. Absidia, Geotrichum, and Paecilomyces were additional genera isolated from dead beetles. These molds are medically significant as potential allergens, and others (Aspergillus, Rhizopus, Mucor) can cause secondary infections in people. The mold profile of different beetle colonies are similar in quality and quantity, thus suggesting that beetles are acquiring molds that are commonly found or can develop on seeds in their rearing/storage containers. Rearing on mung beans suppresses total mold growth by nearly 63% compared to the amount observed when raised on cowpeas. In fact, most cultures of beetles reared in mung beans were entirely fungus-free. Our conclusion is that the amount and diversity of allergenic molds from seed beetles for use in classrooms can be minimized considerably by using mung beans for beetle rearing, along with routine colony maintenance and proper hygiene.