Heterogeneidade morfológica escapular e umeral em micromamíferos terrestres (Rodentia: Sigmodontinae): relações com as estratégias de uso dos habitats

Abstract

The skeleton plays a fundamental functional role in the survival of the species and presents plasticity to solve different demands of the habitat availability. Analyses were developed to evaluate the possible relationships among the scapular morphology and of the humerus in 7 genus of Sigmodontinae (Bolomys, Calomys, Nectomys, Oecomys, Oligoryzomys, Oryzomys and Rhipidomys), family Muridae, and the strategies of use of the habitats. Each genus were allocated in modal categories of habitat use form. Twenty-eight scapular dimensions and seven humeral dimensions were taken. The analysis of the correct allocation of the habitat use categories were evaluated by Discriminant Function analysis. The design of the same structures is involved in the mechanics of the locomotion and use of the habitats. The disposition of groups in the morphologic space evidenced three main class of variation: arboreal, scansorial and semiaquatic. The arboreal shows wide scapulas and articulation area with a robust humerus. The scapular spine is relatively high and the acromion is wide. A narrow scapula as well as a robust coracoid process and a relatively low scapular spine characterize the scansorial forms. The contrast between arboreal and scansorial forms suggests plasticity in the use of the structural resources of the environment, especially for the scansorial forms. The semi-aquatic forms are characterized by large scapulas that are related to body size that reflects its importance for aquatic small mammals when compared to terrestrial forms. The morphologic space evidenced two main variation for the humerus regarding scansorial and arboreal forms. The arboreal forms are characterized by long humerus, robust articulation areas, prominent head of the humerus and epicondylus, and large deltoid tuberosity. The scansorial forms present delicate humerus which reflects their small dimensions. This may facilitates the use of vegetation strata in a similar way as shown by terrestrial forms.