Ontogenetic integration between force production and force reception: a case study in Ctenomys (Rodentia: Caviomorpha)

Vassallo, A.I., Becerra, F., Echeverr�ia, A.I., Casinos, A. 2015. Ontogenetic integra- tion between force production and force reception: a case study in Ctenomys (Roden- tia: Caviomorpha) —Acta Zoologica (Stockholm) 00: 000-000. During ontogeny, complex adaptations undergo changes that sometimes entail different functional capabilities. This fact constrains the behaviour of organisms at each developmental stage. Rodents have ever-growing incisors for gnawing, and a powerful jaw musculature. The incisors are long enough, relative to their diameter, to be affected by bending stresses. This is particularly true in the sub- terranean Ctenomys that uses its incisors for digging. We measured bite force (BF) in individuals of different ages using a force transducer. We estimated inci- sor section modulus Z, a geometrical parameter proportional to bending strength. A relative strength indicator was calculated as S = Z/BF incisor length. We found that ontogenetic BF scales to body mass with positive allometry. How- ever, an ANOVA showed non-significant differences in S, neither between sexes nor among age classes. This result implies that during growth, incisors might have a rather similar ability to withstand bending stresses from increasing masti- catory forces, what may be considered evidence of ontogenetic integration of force production (by muscles) and force reception (by the incisors). This fact well correlates with the observation that pups and juveniles of C. talarum incor- porate solid foods shortly after birth, and they are able to dig burrows early in life.