Effect of geographical location, insect type and cooking method on the nutritional composition of insects consumed in South Africa

Edible insects may be a sustainable source of protein and some other nutrients, especially for low economic status communities. The current study determined the influence of insect type, geographic location and cooking method on the nutritional composition of insects. The investigation would contribute to maximal derivation of the nutritional benefits of insects. Dried samples of four insect types, Gonimbrasia belina (mopani worm), Gynanisa caterpillar, termite soldiers/workers, and termite alates, were procured from different street vendors across Vhembe district in Limpopo Province, South Africa. G. belina samples were cooked by frying, boiling with and without salt addition. Generally, nutrient content varied significantly with insect type and geographic location (P<0.05). Protein content varied from 40 g/100 g in termite alates to 69.75 g/100 g in termite soldiers/workers. Termite soldiers/workers had the highest iron content (range: 545-629.5 mg/kg), whilst Gynanisa caterpillar had the highest zinc content (range: 122.14-150.33 mg/kg). Similarly, Gynanisa caterpillar had the highest levels of lysine (range: 0.80-4.53 g/100 g), threonine (range: 0.79-2.64 g/100 g) and isoleucine (range: 0.63-2.33). On the other hand termite soldiers/workers had the highest levels of valine (range: 2.20-3.47 g/100 g), leucine (range: 2.49-3.87 g/100 g) and phenylalanine (range: 1.38-3.55 g/100 g). Cooking method significantly affected nutrient retention. Boiling with salt added resulted in the highest retention of protein and total mineral content (ash), and, therefore, seems a suitable method for cooking insects. The findings indicate that, if optimally selected and cooked, edible insects can contribute significantly to the alleviation of protein, zinc, and iron deficiencies in target communities.

Age-based soldier polyethism: old termite soldiers take more risks than young soldiers

Who should take on risky tasks in an age-heterogeneous society? Life-history theory predicts that, in social insects, riskier tasks should be undertaken by sterile individuals with a shorter life expectancy. The loss of individuals with shorter life expectancy is less costly for colony reproductive success than the loss of individuals with longer life expectancy. Termite colonies have a sterile soldier caste, specialized defenders engaged in the most risky tasks. Here we show that termite soldiers exhibit age-dependent polyethism, as old soldiers are engaged in front-line defence more than young soldiers. Our nest defence experiment showed that old soldiers went to the front line and blocked the nest opening against approaching predatory ants more often than young soldiers. We also found that young soldiers were more biased toward choosing central nest defence as royal guards than old soldiers. These results demonstrate that termite soldiers have age-based task allocation, by which ageing predisposes soldiers to switch to more dangerous tasks. This age-dependent soldier task allocation increases the life expectancy of soldiers, allowing them to promote their lifetime contribution to colony reproductive success.

Wound treatment and selective help in a termite-hunting ant

Open wounds are a major health risk in animals, with species prone to injuries likely developing means to reduce these risks. We therefore analysed the behavioural response towards open wounds on the social and individual level in the termite group-hunting ant Megaponera analis . During termite raids, some ants get injured by termite soldiers (biting off extremities), after the fight injured ants get carried back to the nest by nest-mates. We observed treatment of the injury by nest-mates inside the nest through intense allogrooming at the wound. Lack of treatment increased mortality from 10% to 80% within 24 h, most likely due to infections. Wound clotting occurred extraordinarily fast in untreated injured individuals, within 10 min. Furthermore, heavily injured ants (loss of five extremities) were not rescued or treated; this was regulated not by the helper but by the unresponsiveness of the injured ant. Interestingly, lightly injured ants behaved ‘more injured’ near nest-mates. We show organized social wound treatment in insects through a multifaceted help system focused on injured individuals. This was not only limited to selective rescuing of lightly injured individuals by carrying them back (thus reducing predation risk), but, moreover, included a differentiated treatment inside the nest.

Purification and Characterization of Cellulase from Termite Ametermes eveuncifer (Silverstri) Soldiers

Cellulase enzyme was purified and characterized from termite soldiers (Ametermes eveuncifer) using 70% ammonium sulphate precipitation, ion exchange chromatography and affinity chromatography. The enzyme isolated had a specific activity of 5.04 U/mg with a percentage yield of 11.7%. The enzyme showed maximum activity at 500C and pH 8. The enzyme was not inhibited by Ba2+ at a concentration of 1mM and Pb2+ at 10 mM concentration but was inhibited by other metal ions at 1 mM and 10 mM concentrations of their salts (NaCl, KCl, MnCl2, and NiCl2),