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Annotated record of digenean parasites collected from fishes of the River Nile in Qena and Aswan governorates, Egypt

DOI: 10.21608/svu.2021.94053.1148 Received: September 3, 2021 Accepted: November 16, 2021 Published: December 25, 2021 *Corresponding Author: Ali Mansour E-mail: alimansour5661@yahoo.com Citation: Mansour et al., Annotated record of digenean parasites collected from fishes of the River Nile in Qena and Aswan governorates, Egypt. SVU-IJVS 2021, 4 (4): 68-84. Copyright: © Mansour et al. This is an open access article distributed under the terms of the creative common attribution license, which permits unrestricted use, distribution and reproduction in any medium provided the original author and source are created. Competing interest: The authors have declared that no competing interest exists. Abstract


Introduction
Fresh water includes 41.24% of all known fish species. Freshwater fishes are one of the important sources of parasitic infection to human and fish-eating mammals (Mohamed, 1996). Adult trematodes are normally endoparasitic in the gasterointestinal tract, blood vessels or other natural body cavities of vertebrates (Hassan, 2006). Adult trematodes in fishes are usually host specific and rarely cause significant harm to their hosts, although there are some notable exceptions (Paperna and Dzikowski, 2006). The main pathogenic effects from trematode infections in fish hosts occur from larval metacercariae. Metacercariae tend to be less specific host than adult fluke and may affect fish growth and survival, as well as being a source of infection for final hosts and other fish-eating vertebrates, including people (Paperna and Dzikowski, 2006).
This study aimed to conduct a general examination of some larval and adult digeneans infecting four species of important freshwater fishes from Qena and Aswan governorates in Egypt. The present study also aimed to improve the existing data on digeneans of freshwater fishes and to provide a preliminary estimation of digenean biodiversity in different localities along the River Nile, Egypt.

Material and Methods
Fish were caught from commercial fishermen from different localities of the River Nile in Qena and Aswan governorates, Egypt during the period from October 2015 to August 2016. The collected fish were immediately transported to Parasitology Laboratory, Zoology Department, Faculty of Science, South Valley University, Qena, Egypt using special tanks supplied with ice.
Fish samples were dissected and examined for digenean worms. Macroscopic examination of the different organs carried out for the detection of any visible metacercariae. The alimentary canal was opened by a fine pair of scissors and left in an isotonic saline solution (0.9% NaCl) for few minutes in a petri-dish with occasional shaking (for the parasites to set free from the tissue of the alimentary canal). Repeated changes of the saline solution were done to keep it clear, then the alimentary canal was examined using a binocular dissecting microscope.
The recovered parasites were transferred to a clean saline solution using a brush or small pipettes and washed several times by saline solution to remove any mucous or debris which is usually adhere to their body surface. Worms were placed in between two glass slides or between a glass slide and cover slip in 5% formalin, subjected to a pressure until relaxed; some worms were preserved in 5% formalin and others in 70% ethanol. Worms were stained with acetic acid alum carmine for 5-10 minutes (Carleton, 1967), dehydrated in an ascending series of ethyl alcohol, cleared in xylene, mounted in DPX, covered with cover slip and finally they were examined under light microscope.  Fig. 1A):
Uterus was convoluted, descended from zone and pass between the two testes to the posterior end of the parasite, before ascending to open in the genital atrium. Eggs were numerous and elongated. Testes were rounded, tandem with anterior testis situated in mid region of body. Anterior testis measured 0.18-0.27 (0.25±0.02) mm in length and posterior testis was 0.24-0.39 (0.35±0.02) mm in length. Cirrus sac was also variable depending on the state of contraction, it may curve round to right or left of ventral sucker or may be anterior to it. Common genital pore was median, situated between ventral sucker and bifurcation of intestine. Ovary was rounded, its length was 0.17-0.28 (0.23±0.02) mm and it often separated from the ventral sucker by cirrus sac and/or seminal vesicle. Receptaculum seminis was not observed.

Superfamily
Testes were longitudinally elongated, smooth, diagonal or sometimes nearly tandem; anterior testis was dextral, measured 0.13-0.35 (0.25±0.02) mm long by 0.14-0.26 (0.46±0.02) mm wide, posterior testis was sinistral, measured 0.11-0.3 (0.15±0.02) mm long by 0.13-0.26 (0.19±0.02) mm wide. Cirrus sac was thickwalled and muscular. Ovary was sinistral, smooth, longitudinally elongated but sometimes nearly rounded, measured 0.11-0.18 (0.16±0.02) mm long by 0.12-0.25 (0.23±0.02) mm wide. Vitelline follicles were overlapping ceca in lateral fields; uterus in mature adults was filling most of hindbody and posttesticular space, lying ventral to gonads and proximal part of cirrus sac, occasionally overlapping ceca and vitellaria laterally. Eggs were yellow to yellow-brown and operculated. 2) mm in length and 0.3-0.52 (0.41±0.02) mm in width. Body surface was covered with fine spines, which were most numerous on the anterior portion of body and became more scarce toward the posterior end. Oral sucker was funnel-shaped, measured 0.15-0.4 (0.35±0.02) mm in length and 0.23-0.47 (0.30±0.02) mm in width. Outer surface of this sucker was armed with a row of large simple spines. Ventral sucker was almost rounded, measured 0.12-0.28 (0.25±0.02) mm x 0.1-0.29 (0.24±0.02) mm. Pharynx was strongly muscular and oval, measured 0.04-0.15 (0.07±0.02) mm x 0.05-0.11 (0.08±0.02) mm. Esophagus was relatively short. Intestinal caeca were relatively narrow and run along the body approximately up to the level of the posterior margin of the second testis, where they open to the body surface by distinct anal openings.
This species is distinguished from the rest members of Astiotrema by the following characters; the oral sucker is large and twice that of the ventral, the caeca is short in which it terminates at the posterior border of the second testis or the junction of the third-and fourth-quarters of the body and vitellaria are restricted to anterior half of the worm. The eggs in our specimens were elongated, thin shell operculated whereas no mention was made of this by Looss (1899), Odhner (1911 and Yeh and Fotedar (1958).
Odhner (1911) noted that the testes occasionally were slightly lobed and almost symmetrical; whereas, all the previous authors and the present study noted smooth testes at all times and a more diagonal position. Testes in the present study were separated by a distinct intertesticular space while Odhner (1911) and Fischthal & Kuntz (1963a) noted that the testes were in contact or closer together. El-Naffar (1984) stated that vitellaria in his specimens extending from the level of intestinal bifurcation to the end of the intestinal caeca but his illustration shows that the distribution of vitellaria reaches only to the beginning of posterior testis. Morphometry of A. impletum specimens collected by the previous authors were comparatively similar to our specimens as shown in Table  1.
The presence of unipartite external seminal vesicles and vitelline follicles that start at the level of the ovary until they meet at the posterior end of the body distinguishes the species. The vitelline follicles are grouped in two lateral fields limited in the middle of the body, according to Bhure and Nanware (2011) and Abdel-Gaber et al. (2015). In our specimens, external seminal vesicle was not observed. Measurements of the present specimens were very compatible with those previously described, as indicated in Table 2.
Further records of Glossidium pedatum from Egypt included those from Clarias gariepinus (Abdel-Gaber et al., 2016) or Clarias gariepinus (as C. lazera) (El-Shahawi andAl-Bassel 1992, Imam et al., 1991) or from bagrid fishes (Ibraheem, 2007). This is characterized by a short prepharynx and a four lobed pharynx. The ovary and testes are both in the same position. Caeca wide ends close to the posterior testis and does not extend to the posterior extremity. Vitellaria extend from the postacetabular to the posterior testis level. As shown in Table 3, the measurements of the current specimens were comparatively consistent with those given by the previous authors.

1814) Braum, 1899:
Ukoli (1966a) classified C. complantum metacercariae based on the following characteristics: cirrus pouch on the right margin of the anterior testis in front of the ovary; genital pore on the right margin of the anterior testis near its middle, or occasionally displaced to its anterior margin. He also noted that the position of the genital pore is a useful character for distinguishing Clinostomum species, despite the fact that other authors have argued that this character can change with different fixation or flattening techniques (Baer, 1933), or during development (Vianna et al., 2003). Li et al. (2018) identified Clinostomum complantum metacercariae in Myxocyprinus asiaticus from China. Maleki et al. (2018) found C. complantum metacercariae from some freshwater fishes in western Iran. Menconi et al. (2020) examined metacercariae of C. complantum in an Italian Subalpine Lake. Additional research was conducted on the metacercariae of C. complantum (Caffara et al, 2011;Simsek et al., 2018;Wang et al., 2017).
El-Shahawy et al. (2017) recorded metacercariae from some freshwater fishes in Qena Governorate, Egypt. They only studied the prevalence of infection and they didn't provide any morphological or morphometric description for their examined metacercaria. Measurements of the present specimens were remarkably similar with that given by Shini (2015) as shown in Table 5.

1809) Travassos, 1928:
Euclinostomum heterostomum was reported among Tilapia spp. and Clarias sp in Egypt by Fischthal and Kuntz (1963c in the kidneys of Oreochromis niloticus and Tilapia zillii in Lake Nasser, Aswan, Egypt. He did not provide morphological or morphometric descriptions for his specimens. More research was done on E. heterostomum metacercariae (Donges, 1974;Jhansilakshmibai and Madhavi, 1997;Caffara et al., 2016). As shown in Table 6, the measurements of the current specimens were remarkably similar to those provided by the previous authors.

Conclusion
In this study, six species of digenean trematodes were examined from four freshwater fish species from different regions along the River Nile in Qena and Aswan governorates, Egypt. Worms were described morphologically and morphometrically using light microscopy. More scanning, transmission electron microscopy and molecular studies are recommended to justify the exact taxonomic position of these species.  (Looss, 1896) and A. absconditum (Looss, 1901), from African bragrid fishes. Folia Parasitology, 23 (3)