A Comparison of the Nitrogen Requirements of the Eastern Pygmy Possum,Cercartetus nanus, on a Pollen and on a Mealworm Diet

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Abstract
The eastern pygmy possum, Cercartetus nanus, is known to feed both on flower products and on invertebrates. This study compares its ability to meet its nitrogen requirements on pollen and on insect larvae. Captive C. nanus were fed diets in which nitrogen was provided either by Eucalyptus pollen or by the mealworm Tenebrio molitor. The apparent digestibility of the nitrogen from both sources was high, with a mean value of 76% for the pollen and 73% for the mealworms. This was much higher than would have been inferred from the common practice of measuring the percentage of empty pollen grains in fecal samples. The truly digestible maintenance nitrogen requirements of C. nanus on pollen were exceptionally low: 2.6 mg N d-1 compared with 9.5 mg N d-1 on mealworms. The value for pollen is the lowest yet recorded for any mammal. The difference between the requirements of C. nanus on the two diets appeared to be related to the composition of the mealworm and pollen protein. The biological value of the pollen nitrogen was exceptionally high for a plant protein, at 72%, whereas the biological value of the mealworm nitrogen was only 42%. This suggests that the amino acid composition of the pollen corresponded more closely to the requirements of C. nanus than the composition of the mealworm protein did. Pollen is an excellent source of nitrogen for C. nanus, and it should be considered as a potential nitrogen source for other flower-feeding animals.