Biology subjects

PARES-CASANOVA, P. M.

Publications and source records attributed to PARES-CASANOVA, P. M..

2 recordsLinked to original sources

bioRxiv2022

Correlated variation between the splanchnocranium and basicranium in the Toy rabbit

The aim of this study was to explore and compare patterns of morphological covariation, including symmetrical deviations, between splanchnocranium and the basicranium in Toy rabbit, a type of paedomorphic rabbit. A sample of 32 skulls of adult Toy rabbits was studied on digital pictures on ventral aspects by means of geometric morphometric methods. A set of 7 landmarks were located on the horizontal plane of the splanchnocranial ventral bones (palatine process of the maxillary bone [processus palatinus maxillae] + palatine bone [lamina horizontalis ossis palatini]), and a set of 8 landmarks were on the basicranium (sphenoid [os sphenoidale] + basilar part of the occipital bone [pars basilaris] + bulla tympanica). Both fluctuating and directional asymmetries were detected on both blocks, being the asymmetry more important among splanchnocranial bones. It appeared also a significant relationship (allometry) between size and shape, especially in the basicranium, as well a significant relationship between the two blocks. From results we deduce that, although normally cranial base usually reaches adult size before the face, in paedomorphic animals the face stops its growth earlier than basicranium, resulting in their proportionally reduced splanchnocranium, the typical brachyfacial morphology for paedomorphy. In other words, our results support the hypothesis of an early stop of facial pattern development in neoteny -the retention of juvenile characteristics into adulthood-, which can affect vital structures. So, further research should expand on clinical data of paedomorphic animals in order to advance in the understanding of pathological results of this growth anomaly.

zoology↗

bioRxiv2022

No modular shape changes in the mandible of Andean white-eared opossum (Didelphis pernigra, Linnaeus, 1758)

Morphological integration and modularity are concepts that refer to the covariation level between the components of a structure. Species of the opossums, genus Didelphis, have been the object of several taxonomic and morphometric analyses but no study has so far analysed mandibular morphological integration and modularity at a species-level. The aim of this work was to check whether the body (corpus mandibulae, mandibular corpus) and the ramus (ramus mandibulae, ascending mandibular ramus) are separate modules in Didelphis pernigra using a two-dimensional geometric morphometric approach. For this purpose, a sample of hemimandibles from 36 D. pernigra (13 males and 23 females) was analysed using 17 landmarks in lateral view. The modularity hypothesis based on different developmental origins was tested, by using the RV coefficient. Later, the integration level was assessed applying a partial least-squares analysis (PLS). The underlying aim was to know whether the traditional division between mandibular body and ramus has a modular basis, as well as the morphological integration level between these two structures. Results reflected that landmarks integration was not uniform throughout the mandible but structured into two distinct modules: ramus and body. Results allow to conclude that allometry plays an important role in shape variation in this species, and that the hypotheses of two-module organization in males cannot be confirmed. Models that accurately represent the biting mechanics will strengthen our understanding of which variables are functionally relevant and how they are relevant to performances, not only masticatories.

zoology↗