Fish parasites can be used as bio-indicators to evaluate pollution degree in aquatic ecosystems. Limited research has, however, investigated the potentiality of these parasitic worms to tolerate various environmental factors. This study, therefore, investigated whether the gill, Quadriacanthus monogenean parasites of Bagrus bajad Forska ˚l, 1775 are potential bio-indicators of aquatic ecosystem health. The seasonal differences in prevalence, mean intensity and abundance of Quadriacanthus species of Clarias gariepinus varied between each other and between the three localities. Most Quadriacanthus species exhibited their highest prevalence, mean intensity and abundance in Spring and/or Summer and their lowest values in Autumn and/or Winter. The seasonal differences in prevalence were significant for Q. kearni and Q. clariadis while a significant difference in the mean intensity between different seasons was recorded only for Q. aegypticus. Also, seasonal differences in the abundance were highly significant for Q. aegypticus and significant for Q. kearni. The total dissolved solids, Chlorides, Sulphate, Sodium, Cadmium and Lead were higher at Manzala Lake than standard permissible limits. The pH has significant correlations with the infestation levels of all Quadriacanthus spp. Dissolved oxygen showed a highly significant positive correlation with the mean intensity of Q. clariadis and a significant positive correlation with the abundance of Q. clariadis. Iron was the only heavy metal to record a significant positive relationship with the mean intensity of Q. kearni. It is noteworthy that Quadriacanthus species were found to have a noticeable ability to resist the effect of hazardous concentrations of many physicochemical and heavy metals parameters. Therefore, it is highly recommended that these monogeneans could be regarded as bioindicators for water quality.
Fishes of the River Nile are a promising source of animal protein. The catfishes Bagrus bajad Fabricius 1775 and Bagrus docmak Fabricius 1775 are economically important with well-marketable size and use in fish farming. Digenean parasites cause severe damage to the gut tissue of their fish hosts. There are still some questions regarding the taxonomical features of the genus Acanthostomum Looss 1899. The present study has revealed new morphological features that confirmed the identity of the collected worms as Acanthostomum spiniceps Looss 1896 and aided in elucidating the possible functions of different internal organs and surface features. A long-stemmed excretory bladder was detected but there was no evidence of gonotyl. The circumoral spines (28–30) were detected in the early juvenile stage and adult. The ventral sucker has no tegumental folds in juveniles or crescent-shaped tegumental folds in adults but possesses two overlapping lips. In both juveniles and adults, the oral sucker with the associated circumoral spines assumed retracted, and protracted positions reflecting its highest movement activity. Elongation of the anterior region and partial emergence of the oral cavity in living juveniles and adults were described. The possible functions of the forebody glands and the posterior body openings near the anal pores were discussed. Large, non-ciliated, dome-shaped, and small ciliated, button-like papillae were concentrated on the body surface, particularly the oral and ventral suckers. The tegument possesses densely arranged single-pointed and scale-like spines that gradually decrease in size and number as they proceed posteriorly.
The catfish Bagrus bajad (Forsskål) and B. docmak (Forsskål) (Siluriformes: Bagridae) are well distributed in the River Nile and have an economic value with good marketing and use in aquaculture. Collected specimens of Capillostrongyloides fritschi (Travassos 1914) were redescribed using a phase-contrast microscope and scanning electron microscope. The most remarkable finding was the unique structure of the evaginated cirrus, being composed of a proximal long tube, a middle spherical bulb packed with mature spermatozoa, and a distal funnel-shaped structure. All regions of the cirrus are provided with longitudinal and transverse muscles and covered with transverse cuticular folds. The mechanism of cirrus emergence was discussed based on available musculature data. Other important findings are the short stylet of the mouth, the two lateral oral lobes, 6-10 buried cephalic papillae and the bacillary bands that lack elevations. Stichosome is formed of 35-44 stichocytes that were differentiated into black and white forms, each containing dense granules and translucent vacuoles. The intestine showed a convoluted part at its anterior region. The vulvar lips are slightly elevated, many mature eggs are cleaved, and their shells are 3-layered. The anus was found in a groove bounded by two unequal lobes.
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