Main anatomical and histological features of the tonsils in the camel (Camelus dromedarius).

The tonsils, located around the pharyngeal cavity, constitute the first defence barrier against intruding microorganisms and antigens. The present work aimed to study the anatomical and histological aspects of camel tonsils in order to elucidate their role. The study was carried out on 12 camel heads fixed by infusion with 10 % neutral buffered formalin. A careful dissection of the oral cavity, the soft palate and the pharynx was conducted to explore the morphological aspect of different tonsils. Sagittal sections of some camel heads were also performed to explore their internal conformation, whereas the histological study was carried out on five specimens. All the six types of tonsils exist in the camel. Compared to other domestic species, they are well developed and all visible particularly the palatine one. The lingual, palatine, velar and paraepiglottic tonsils are arranged into closely assembled lymphoid follicles and show multitude crypt opennings into the oropharyngeal tube. The crypts epithelium is infiltrated with lymphoid cells allowing close contact with antigens. While the nasopharynx tonsils (pharyngeal and tubal) include loosely connected follicles which extend into the overlaying epithelium. The relatively great development and particular arrangement of the tonsils in the camel as well as the abundance of cryptic formations in all these tonsils constitute another aspect of adaptation and resistance of this species to its environment.

Frequency of the severe combined immunodeficiency disease gene among horses in Morocco.

Severe combined immunodeficiency disease (SCID) of horses is an autosomal, recessive hereditary disease occurring among Arabian or crossbred Arabian horses. The genetic defect responsible was previously identified as a 5-base pair deletion in the gene encoding the catalytic subunit of the DNA dependant protein kinase (DNA-PKcs). This study was carried out to determine the frequency of SCID and identify horses carrying the gene for SCID among Arabian and Arabian crossbred stallions and mares in Morocco using a DNA-based test. Twenty-one horses were SCID carriers: 14 (7%) Arabians, 6 (4%) Arab-Barbs and one (33%) Anglo-Arab. After analysing their genealogy, 3 imported stallions were identified that disseminated the mutant gene of DNA-PKcs in Morocco.

Seasonal variations in the nycthemeral rhythm of plasma melatonin in the camel (Camelus dromedarius).

Seasonal changes in the pattern of plasma melatonin were investigated in two groups of camels (Camelus dromedarius): 11 adult and six young camels. Animals were subjected to the outdoor conditions of a desert environment. Blood samples were taken at regular intervals of about 3 hr (added to particular samples at 1 hr before then 30 min and 1 hr after sunset, and 1 hr before and 1 hr after sunrise) for 24 hr at both solstices and equinoxes of the year. The plasma melatonin levels steeply increased soon after sunset and remained elevated throughout all the night. Then, melatonin concentrations progressively declined shortly before sunrise and returned to daytime basal levels 1 hr later. There was no seasonal variation in the amplitude or in the offset of the melatonin peak or in the daytime basal levels. The onset of the nocturnal peak was delayed by 2 hr in June at the summer solstice (P < 0.05), which can be related to the changes in night length between the two solstices. A significant effect of age was observed in all seasons. Melatonin levels were higher in the young camel group (fall equinox: P < 0.001; spring equinox: P < 0.01; winter solstice: P < 0.01; summer solstice: P < 0.05). The pattern of melatonin secretion in the camel showed a significant seasonal variation parallel to the photoperiodic changes of the year. The observed decline of melatonin levels during an extra-light pulse in the middle of the night indicates the light control of melatonin synthesis. It is not yet known if, in this low latitude desert region, the seasonal breeding period of the camel is cued by the photoperiod. The data obtained, however, clearly demonstrate that the camel has the capacity to follow and to integrate photoperiodic changes through melatonin changes.