RESUMO
The brown rat, Rattus norvegicus, is a model system in ecological and systematic science, but little is known about its skull morphology and developmental patterns. Our objective was to investigate the cranial ontogenetic patterns in the brown rats, from Hai'l, Kingdom of Saudi Arabia. Quantitative analysis of sexual shape dimorphisms (SShD) and age-classes were investigated using 28 landmarks plotted on two-dimensional images for dorsal and ventral views. Our results detected statistically significant sexual dimorphism (P-value <0.0001) in cranial shape and size for R. norvegicus. Nevertheless, males are much larger than females and display variation around the brain-case, while females tend to show greater variation around the occipital bone. In addition, there are subtle age-classes during ontogeny in the skull. However, the older age classes (i.e. age classes 3 and 4) represent well-built crania with an extended case of the brain and shortest nasal, while youngest specimens represent an elongated snout of minimum crania. Future GMM research should therefore examine the pre-defined age-classes and sex-related individuals in brown rat skulls in relation to genotype to characterize trends in skull shape variation that may affect teeth, zygomatic arches, brain case, and compartments of muscle attachments through its ecological patterns.
RESUMO
The House mice (Mus musculus Linnaeus, 1758), play an important role in the transmission of diseases, both in humans and livestock, through ectoparasite carried on their feces, urine and hair remnants. The purpose of this study was to investigate the ectoparasites infestation, as well as their quantitative and qualitative abundance and, prevalence in the house mice captured from Hai'l region, Kingdom of Saudi Arabia (KSA). Parasitological investigations were performed on 70 house mice trapped during 2012-2013 from two localities (Hai'l City residential area and Al-Khitah agricultural farm habitats in Hai'l region). Captured mice were identified as males (34.3% and 48.6%) and females (65.7% and 51.4%) from the residential and agricultural farm habitats, respectively. The findings of the study showed that the sex ratio of the mice found in different habitats did not influence the level of ectoparasite infestation (P > 0.05). Therefore, we combined only sex-wise samples for each habitat and isolated habitats treated separately for our subsequent analyses. A total of 514 ectoparasites individuals belong to four species were recovered from the mice, which included 339 of flea (Xenopsylla cheopis Rothschild, 1903), 39 of sucking lice (Polyplax spinulosa Burmeister, 1835), 37 of sucking lice Polyplax serrata Burmeister, 1839), and 99 of mite species (Laelaps echidninus Berlese, 1887). The presence of zoonotic parasites indicates that Mus musculus as a reservoir, might represent a danger to the public health particularly in the two sampled areas. Results also suggest an increasingly need for further studies to assess the role of the ectoparasites of house mice and their possible involvment in transmission of diseases among these areas.