Duplication and parallel evolution of the pancreatic ribonuclease gene (RNASE1) in folivorous non-colobine primates, the howler monkeys (Alouatta spp.)

In foregut-fermenting mammals (e.g., colobine monkeys, artiodactyl ruminants) the enzymes pancreatic ribonuclease (RNASE1) and lysozyme C (LYZ), originally involved in immune defense, have evolved new digestive functions. Howler monkeys are folivorous non-colobine primates that lack the multi-chambered stomachs of colobines and instead digest leaves using fermentation in the caeco-colic region. We present data on the RNASE1 and LYZ genes of four species of howler monkey (Alouatta spp.). We find that howler monkey LYZ is conserved and does not share the substitutions found in colobine and cow sequences, whereas RNASE1 was duplicated in the common ancestor of A. palliata, A. seniculus, A. sara, and A. pigra. While the parent gene (RNASE1) is conserved, the daughter gene (RNASE1B) has multiple amino acid substitutions that are parallel to those found in RNASE1B genes of colobines. The duplicated RNase in Alouatta has biochemical changes similar to those in colobines, suggesting a novel, possibly digestive function. These findings suggest that pancreatic ribonuclease has, in parallel, evolved a new role for digesting the products of microbial fermentation in both foregut- and hindgut-fermenting folivorous primates. This may be a vital digestive enzyme adaptation allowing howler monkeys to survive on leaves during periods of low fruit availability

Dawn chorusing in guereza colobus monkeys

Dawn chorusing by guereza black-and-white colobus monkeys is one of the most impressive spectacles of African rainforests. This vocal behaviour is highly contagious, travelling from one neighbouring group to the next, until a wide forest area is covered by calling monkeys. Chorusing usually occurs up to 2 h before dawn, sometimes more than once, unless the preceding night was cold and wet. We conducted a series of playback experiments, which showed that guerezas' chorusing was difficult to elicit experimentally, suggesting that callers took several variables into account before responding to other monkeys' predawn calls. Acoustic analyses showed that morning calls were individually distinct, but we found no evidence that callers took individual identity into account in their decision to participate in chorusing. The only way to reliably elicit chorusing in our study area was to broadcast recordings of morning choruses for longer than 30 s and at a time when a chorus simultaneously emerged in a distant part of the forest.</p