Abundance and Annual Distribution of Freshwater Snails and Some Trematode Cercariae at Damietta Governorate, Egypt.

In addition to being a good food source, freshwater snails are considered one of the positively and negatively influencing invertebrates on the environment. Several biotic and abiotic factors are thought to affect the distribution and the dynamics of these snails. Freshwater snails are the most dominant and conspicuous individuals of the freshwater biota in Damietta Governorate. In this study, freshwater snails were collected monthly from 5 geographically and environmentally different sites at Damietta Governorate at the north of Egypt during June 2017-May 2018. Seven snail species; Lanistes carinatus, Lanistes varicus, Pila wernei, Segmentorbis angustus, Melanoides tuberculata, Biomphalaria alexandrina, and Gabbiella senoriansis, were identified. Lanistes carinatus was the most abundant species (56.4%) in the collection sites. Besides, Al-Inaniyyah village had the highest snail species abundance and variety. The abundance of the most recorded species varied seasonally; the highest abundance was recorded during summer while the lowest was during winter. The abundance of some snail species correlated positively or negatively with some physico-chemical parameters; water temperature, dissolved oxygen, conductivity, total dissolved salts, and electrical conductivity. Two types of trematode cercariae; gymnocephalus cercariae and xiphidiocercariae, were harvested from Lanistes carinatus. The highest prevalence of both cercarial types was detected during summer. The correlation between the prevalence of both cercarial types and the physico-chemical parameters were determined. Xiphidiocercariae were the most predominant cercarial type in Damietta Governorate. Our findings suggest that the invasion of some freshwater snails is likely to be the cause of the low prevalence or complete absence of some medically important intermediate snail hosts. We recommend further characterization of the distribution of freshwater snails and the interrelationships among them in Egypt, and suggest a controlled use of selected snail species to combat their medically important analogues.

Correlation between vocal functions and glottal measurements in patients with unilateral vocal fold paralysis.

Observations and analysis of glottal characteristics are critical in choosing the best modality for surgery in patients with unilateral vocal fold paralysis (UVP). This study suggests that multiple glottal characteristics influence the vocal product in patients with UVP. In addition to the horizontal position of the paralyzed vocal fold (deviation from the midline), the glottal area, degree of bowing of the paralyzed and contralateral vocal folds, maximum separation between vocal folds, compensatory glottal maneuvers, and the vertical glottic closure plane significantly influenced the quality of the voice. Clinicians should be aware of these observations to facilitate treatment planning and assessment of the results of surgical procedures used to improve voice quality in cases of UVP.

Ultrastructural observations on the tegument and associated structures of the monogenean Cichlidogyrus halli typicus (Price & Kirk, 1967) Paperna, 1979.

The tegument of the ancyrocephaline monogenean gill parasite Cichlidogyrus halli typicus is basically similar to that of other monogeneans. However, there are some tegumental features shared with relatively few other monogeneans, namely the presence in the surface tegument of extensive regions of homogeneous granular cytoplasm, a close association between myofibres and the basal region of the tegument and the production of two different tegumental secretory bodies by the same cyton. It is suggested that the regions of homogeneous granular cytoplasm found in the troughs between the circular muscle fibres provide some kind of support for the tegument, perhaps related to contraction of the tegumental circular muscle fibres and body shape changes. Three kinds of transtegumental sensory structures are recognized, namely a uniciliated bulb, a bulb bearing a non-ciliary process and a non-ciliated bulb. The latter two kinds are reported for the first time in monogenans. Possible functions of these sensory structures are discussed.

Population dynamics of Enterogyrus cichlidarum (Monogenea: Ancyrocephalinae) from the stomach of Tilapia spp. in Egypt.

In a 1-year seasonal study of the numbers of the stomach-inhabiting monogenean Enterogyrus cichlidarum in Tilapia nilotica in the River Nile, Egypt, prevalence and intensity reached a height in spring and infection levels were surprisingly high in winter. T. zillii harboured fewer parasites but seasonal changes were similar. No parasites were found in T. galilaea. The prevalence and intensity of the infection with E. cichlidarum rose significantly with increasing size of the host. Some of the possible reasons for these fluctuations are discussed. Immature enterogyrids were more abundant in the posterior sector of the stomach and adult enterogyrids showed a preference for the anterior sector. No significant difference was found in the numbers of enterogyrids in male and female hosts.