SUMMARY:The morphology and morphometry of the cranial bones of Chaetophractus villosus were studied. The skull components are morphologically similar between adults of both sexes, and follow the generalized pattern for most of described dasypodids. The morphometric analysis, however, demonstrated that the bones lying in the rostrocaudal plane are mostly longest in females, determining higher values of the total, basal and condilobasal lengths of the skull, which are the main variables that contribute to a sexual dimorphism in this species.

Plants and seedlings of Potamogeton pectinatus were obtained from tubers grown under laboratory conditions. Four plants (mean total length: 14.3 m) and two seedlings (mean height: 10.9 cm) were placed in each of twenty 100 1 aquaria illuminated with fluorescent lighting. A 5 cm-thick layer of muddy sediment was then put in each aquarium together with two size-matched fish (mean size classes: 6.8, 14.1 and 23.0 g) of the species Cyprinus carpio. After four weeks, the total length of the plants in the control and small fish aquaria had increased by 71% and 3% respectively, whereas plant total length in the aquaria with medium and large fish had diminished by 33% and 76%, respectively. Few seedlings survived in the presence of the fish. The reduction in plant growth was associated with an increase in water turbidity in all treatments as a result of the benthic feeding habit of C. carpio, and of direct herbivory action in the case of medium-and large-sized fish.

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SQUARCIA, S. M.; SIDORKEWICJ, N. S. & CASANAVE, E. B. The hypertrophy of the tympanic bulla in three species of dasypodids (Mammalia, Xenarthra) from Argentina. Int. J. Morphol., 25(3):597-602, 2007. SUMMARY:The morphology and relative size of the tympanic bulla of three species of dasypodids from Argentina, Chaetophractus villosus, C. vellerosus and Zaedyus pichiy, were studied. The bulla was observed to be morphologically similar and evidently hypertrophied in the three species. The degree of hypertrophy was higher in C. vellerosus and C. villosus than in Z. pichiy. By means of ANCOVA it was clear that, although C. villosus has a bigger skull than C. vellerosus, the relative size of their tympanic cavity was similar in both species. On the other hand, the skull of C. vellerosus and Z. pichiy are of similar size but the bulla was relatively shorter in the later. KEY WORDS: Chaetophractus villosus; Chaetophractus vellerosus; Zaedyus pichiy;Middle ear; Tympanic bulla. SQUARCIA, S. M.; SIDORKEWICJ, N. S. & CASANAVE, E. B. La hipertrofia de la bula timpánica en tres especies de dasipódidos (Mammalia, Xenarthra) de Argentina. Int. J. Morphol., 25(3):597-602, 2007.RESUMEN: Fueron estudiados la morfología y el tamaño relativo de la bula timpánica, en tres especies de dasipódidos de la Argentina, Chaetophractus villosus, C. vellerosus and Zaedyus pichiy. Se observaron una morfología similar y una hipertrofia evidente en la bula en las tres especies. El grado de hipertrofia fue mayor en C. vellerosus y C. villosus que en Z. pichiy. Mediante ANCOVA se demostró que, aunque el cráneo de C. villosus es mayor que el de C. vellerosus, el tamaño relativo de la bula fue similar en ambas especies. Por otra parte, la bula de Z. pichiy es relativamente más pequeña que la de C. vellerosus, a pesar que sus cráneos son de tamaño similar.

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