Parasites of Malapterurus Electricus (Gmelin, 1789, Siluriformes, Malapteruridae)

33 Iyaji & Eyo (2014). Parasites of Malapterurus electricus (Gmelin, 1789, Siluriformes, Malapteruridae)

Parasites of Malapterurus electricus (Gmelin, 1789, Siluriformes, Malapteruridae) at Rivers Niger-Benue Confluence, Nigeria Iyaji, F. O 1 and Eyo, J. E 2. 1 Department of Biological Sciences, Kogi State University, Anyigba, Nigeria 2 Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Nigeria

Abstract The electric catfish, Malapterurus electricus , caught with various fishing gears were studied for parasites for a period of 12 months (March 2007 to February 2008) at the confluence area of Rivers Niger and Benue, Lokoja, Nigeria as part of a larger research work on parasites of Siluriformes. A total of 84 fish specimens were examined for parasites and prevalence of infection was 65.47%. The total parasites recovered was 331, comprising one protozoan ciliate (Trichodinids), three Cestodes ( Monobothrioides woodlandi, Electotaenia malapteruri and Proteocephalus largoploglotis ), three Nema- todes ( Procamallanus laevionchus, Rhabdochona congolensis, and Camallanus spp. Electotaenia malapteruri had the highest prevalence (66.67%) among the parasites recovered. All parasites were recovered from the intestines except the Trichodinids which were recovered from the gills and skin of fish hosts. The relationships of host weight/length and parasite infection showed higher infection in fish of larger sizes. There was no significant difference between the infection of male and female fish hosts. Multiple infections of the cestode, Electotaenia malapteruri and the other parasites were observed in some fish hosts. This study provides an overview of parasites of M. electricus in Rivers Niger and Benue at the Confluence area. Keywords : Parasites, Electotaenia malapteruri, Malapterurus electricus , Rivers Niger-Benue confluence, Nigeria.

* Corresponding author: from River Niger and Kainji Lake and M. microstoma from [email protected] (Iyaji, F.O) Published online at http:/www.irjset.com the Zaire River basin. Malapterurus electricus is most com- Copyright © 2014 International Research Journal Group mon in rivers and swamps in Nigeria. 1. Introduction The distribution, morphology and biology, in- cluding the feeding habits have been variously studied (Reed The electric catfish, Malapterurus electricus (Gmelin 1789 1967, Belbenoit et al 1979, Sagua 1979, Olatunde 1984, Malapteruridae, Siluriformes) is endemic to African tropical Gosse 1984, Janet et al 1987, Skelton 1993, Moller 1995 and freshwater systems (Moller 1995). It is the most extraordi- Roberts 2000). At the Confluence area in Lokoja, electric nary of all catfishes due to the possession of the electric or- catfish contribute significantly to the economy of the fishers. gan, evolved from its pectoral muscles and surrounding most They are highly relished as food among consumers, espe- of the length of the fish (Lissmann 1958, Reed 1967, Janet et cially when smoked. Usually, either smoked or fresh, the al 1987) The electric organ is reputed to discharge up to thick unpalatable skin must be removed in order to enjoy the 350v (in 500mm fish) (Kaynes 1957, Skelton 1993). Moller tasty flesh. (1995) identified two more species, Malapterurus minjiriya Few studies exist on the parasites of M. electicus Journal of Science & Multidisciplinary Research (2):33-40 34 Iyaji & Eyo (2014). Parasites of Malapterurus electricus (Gmelin, 1789, Siluriformes, Malapteruridae) (Khalil 1963, 1969, 1971, Khalil and Polling 1997, eletricus , in Rivers Niger and Benue at the Confluence area Onusiruka 2001 and Akinsaya 2007). The present study in Lokoja. deals with the parasites of the electric catfish, Malapterurus

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Iyaji & Eyo (2014). Parasites of Malapterurus electricus (Gmelin, 1789, Siluriformes, Malapteru- ridae)

2. Materials and Methods one protozoan ciliate (Trichodinids), three Cestodes (Monobothrioides woodlandi, Electotaenia malap- The study area is located around the confluence of teruri and Proteocephalus largoploglotis ), three the two major rivers in Nigeria, River Niger and Nematodes ( Procamallanus laevionchus, River Benue between latitude 7º 45N- latitude 8º Rhabdochona congolensis , and Camallanus spp. 12N and longitude 6º 39E- longitude7º 00E (Fig. The proteocephalid cestode, Electotaenia malap- 1). There are extensive flood plains with numerous teruri has the highest prevalence of 66.67%, while perennial ponds and marshes on both banks of the prevalence for Proteocephalus largoploglotis and rivers before and within the confluence. The vege- the caryophyllid cestode Monobothrioides wood- tation along the rivers comprises mainly of wooded landii were 10.71% and 7.14% respectively. Preva- savannah grassland with shrubs and trees. The cli- lence of other parasites ranged between 1.19% mate of the area consists of two seasons, the dry (Camallanus spp.) and 5.95% (Trichodinids). Nem- season and wet season. The wet season begins to- atode parasites had the least infection rate in M. wards the end of March and ends towards the end electricus in this study and were found only in Lo- of October or early November while the dry season cality 3,(Confluence). begins in November and lasts until late March. Table 1: Parasitic infection of Malapterurus elec- Fish were sampled from fishers using a variety of tricus at river Niger-Benue confluence fishing gears (set nets, cast nets, hooks, gill nets, Parasite etc) at the 3 localities for 12 months. Groups Host Examined = 84 Locality 1: Ohono village, along Lokoja - Koton A B C D E Karfe road, (Niger River). Protozoan Trichodinids 5 20 5.95 4±1.58 0.24 Locality 2: Mozum village, located on the eastern Monobothriodes bank, (Benue River). Locality 3: Ganaja village, below the confluence of woodlandii 6 7 7.14 1.17±0.41 0.08 the two rivers, (confluence) Electrotaenia 5 24 Fish were sampled from each locality for a period malapteruri 6 8 66.67 4.43±2.92 2.95 of 12 months, and examined for parasites. Proteocephalus The fish species were indentified according to Reed et al (1967) and Olaosebikan and Raji (1998) Cestodes largoproglotis 9 29 10.71 3.22±1.96 0.35 Examination of fish for parasites followed methods Procamallanus of Arthur and Albert (1994) and Marcogliese laevionchus 3 4 3.57 1.33±0.58 0.05 (2002). Treatment, fixation and preservation of Rhabdochona parasites were adapted from Ash and Orihel (1987). Collected parasites were identified using, Travassos congolensis 2 13 2.38 6.5±2.12 0.15 et al ., (1963); Yamaguti, (1959); Pavanelli and Nematodes Camallanus spp 1 10 1.19 10 0.12 Rego, (1989); FAO, (1996); Moravec, (1998); Key: A = Number fish hosts infected, B= Total number of para- Chambrier and Vaucher, (1999). sites recovered per host, C = Percentage prevalence, D = Mean Infection statistics of Bush et al. , (1997) was intensity of parasite, E= Abundance of parasite used for the determination of prevalence, mean intensity and mean abundance. The correlation be- Locality 2, (R.Benue), though with the least para- tween host factors such as sex, weight and standard site taxa and species, recorded the highest preva- length and parasite infection were done using SPSS lence of 81.82% in Electotaenia malapteruri and version 15. the fish hosts were infected only by cestode parasites. The Confluence (Locality 3) has the highest number of parasite taxa and species but with lower 3. RESULTS AND DISCUSSION infection rates while R. Niger (Locality 1) has the M. electricus Parasitological investigation of 84 highest number of parasites retrieved. (Table 2). revealed that 55(65 47%) fish hosts were infected Electotaenia malapteruri recorded the highest while 29(34.52%) were uninfected. The distribution prevalence in all the localities. of fish hosts in the three localities and the parasitic In the weight categories, the protozoan infections were uneven. In River Niger (Locality 1), parasite, Trichodinids only infected fish in the 34 hosts were examined, 25(73.52%) were infected 100+g category. The cestode parasites were found with a total of 132 parasites recovered. In River with highest prevalence in the 100+g category Benue (Locality 2) 22 hosts were examined, while the nematodes infected fish in the 26- 75g 11(50.00%) were infected with 107 parasites while categories except R. congolensis which infected at the Confluence, (Locality 3) 28 hosts were ex- fish in the 100+g. (Table 3). Higher infection was amined, 19(67.85%) were infected with 92 para- recorded in the 100+g category. sites recovered. Parasite taxa and species encountered were:

Journal of Science & Multidisciplinary Research (2):33-40 36

Iyaji & Eyo (2014). Parasites of Malapterurus electricus (Gmelin, 1789, Siluriformes, Malapteruridae)

Table 2. Parasitic infestation of M. electricus at the three localities (R.Niger, R.Benue and Confluence).

Locality 1: River Niger Locality 2: River Benue Locality 3: Confluence Hosts Examined =28 Hosts Examined =34 Hosts Examined =22

Parasites A B C D E A B C D E A B C D E 4.33±1. 14.2 Trichodinids 3 13 17.7 5 0.76 2 7 9 3.5±2.12 0.5 21.4 Monobothriodes woodlandii 1 1 5.9 1 0.06 2 2 18.18 1 0.18 3 4 3 1.33±0.6 0.29 4.67±2. 57.1 Electrotaenia malapteruri 22 110 64.7 5±3.10 3.24 18 84 81.82 5 3.82 16 54 4 3.38±3.2 1.93 2.67±2. 3.5±2.0 Proteocephalus largoproglotis 3 8 17.7 1 0.47 6 21 54.55 7 1.91 21.4 Procamallanus laevionchus 3 4 3 1.33±0.1 0.29 14.2 Rhabdochona congolensis 2 13 9 6.5±2.12 0.93

Camallanus spp 1 10 7.14 10 0.71

Key: A = Number of fish hosts infected, B= Total number of parasites recovered per host, C = Percentage prevalence, D = Mean intensity of parasite, E= Abundance of parasite

Table 3. Parasitic infestation of M. electricus by body weight at the River-Niger Benue Confluence.

0-25 N=0 26-50 N=12 51-75 N=2 76-100 N=6 100+ N=64 A B C D E A B C D E A B C D E A B C D E A B C D E Trichodinids 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 20 15.6 0.6 0.6 M. woodland 0 0 0 0 0 2 3 33 1 1 0 0 0 0 0 0 0 0 0 0 4 4 12.5 0.1 0.1 E. malapteruri 0 0 0 0 0 6 12 50 1 1 0 0 0 0 0 2 14 33 2.3 2.3 48 222 75 3.5 3.5 P.largoproglotis 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 33 0.3 0.3 8 28 25 0.9 0.9 P. laevionchus 0 0 0 0 0 2 3 33 1 1 0 0 0 0 0 0 0 0 0 0 1 1 3.1 0 0 R congolensis 0 0 0 0 0 1 8 17 1 1 1 5 100 5 5 0 0 0 0 0 0 0 0 0 0 Camallanus spp 0 0 0 0 0 0 0 0 0 0 1 10 100 10 10 0 0 0 0 0 0 0 0 0 0 Key: A = Number fish hosts infected, B= Total number of parasites recovered per host, C = Percentage prevalence, D = Mean intensity of parasite, E= Abundance of parasite

Journal of Science & Multidisciplinary Research (2):33-40 37 Iyaji & Eyo (2014). Parasites of Malapterurus electricus (Gmelin, 1789, Siluriformes, Malapteruridae) category (prevalence 84.62% and 23.08% respectively) In the length categories, Trichodinids infected fish in the while P. largoproglotis infected fish in the 11-30+cm with 11-30+cm category with the highest prevalence of 50% in highest prevalence of 100% in 30+cm. Low infections of the 30+g category. The cestodes, Electotaenia malapteruri nematode parasites were found in fish of 0-20cm categories, and Monobothrioides woodlandii infected fish in the 0-30cm (Table 4). Table 4. Parasitic infestation of M. electricus by standard length at the River-Niger Benue confluence.

Lenght categories 0-10N=4 11-20 N=50 21-30 N=26 30+ N=4 A B C D E A B C D E A B C D E A B C D E Trichodinids 0 0 0 0 0 1 3 4 0.1 0.1 3 11 23 0.9 0.9 1 6 50 3 3

M. woodlandii 1 1 50 0.5 1 4 5 16 0.2 0.2 1 1 7.7 0.1 0.1 0 0 0 0 0

E. malapteruri 2 6 50 1.5 2 32 118 64 2.4 2.4 22 124 85 4.8 4.8 0 0 0 0 0

P.largoproglotis 0 0 0 0 0 4 16 16 0.6 0.6 3 6 23 0.5 0.5 2 7 100 3.5 4

P. laevionchus 1 2 50 1 1 1 1 4 0 0 0 0 0 0 0 0 0 0 0 0

R congolensis 1 8 50 4 4 1 5 4 0.2 0.2 0 0 0 0 0 0 0 0 0 0

Camallanus spp. 0 0 0 0 0 1 10 4 0.4 0.4 0 0 0 0 0 0 0 0 0 0 Key: A = Number fish hosts infected, B= Total number of parasites recovered per host, C = Percentage prevalence, D = Mean intensity of parasite, E= Abundance of parasite Infections of M. electricus by sex showed that males were more infected by Trichodinids and P.largoproglotis while females were more infected by E. malapteruri . Infections by nematode parasites were negligible in both sexes. E.malapteruri was documented as parasite of M. electricus. 4. DISCUSSION Alain de Chambrier et al (2004) also reported E.malapteruri Parsitological examination of M. electricus in Rivers Niger as being specific to M. electricus. In the research work on and Benue at the Confluence area in Lokoja, showed that parasites of siluriformes in Rivers Niger and Benue (Iyaji 65.47% of the fish hosts were infected. Of the 7 species of 2011) E.malapteruri was not found in other siluriid fish hosts, parasites recorded, the cestodes, ( E. malapteruri, confirming the earlier reports of Khalil (1963,1969) in P.largoproglotis and M. woodlandii ) were most prevalent in Sudan. Proteocephalus largoproglotis which ranked second in the 3 localties, with the proteocephalid cestode, E. prevalence in this study has similar life cycle but has not malapteruri having the highest prevalence of 66.67%. been found to be strickly host specific (Iyaji, 2011). All Cestode (tapeworms) parasites have been reported to be cestode parasites were retrieved from the intestines of fish widespread in all major freshwater systems of Africa, hosts. Minimal inflammation of the intestinal walls due to infecting several species of fish and demonstrating high bothridal attachments was observed. degree of host specificity (FAO 1996, Iyaji et al 2009). The low prevalence of nematode parasites in this study According to Cheng (1999), infection of fish hosts by could be explained by the fact that M. electricus is an proteocephalid cestodes involves a complex life cycle of eggs opportunistic feeder (Sagua 1979, Akinsaya 2007) and would with fully developed unciliated oncospheres, ingested by the feed on any available prey in the habitat with nematode eggs first intermediate hosts which could be copepods. or larval forms which may eventually develop into adult (crustacians) where they develop into procercoid larvae with forms. Species of nematode parasites found have been three pairs of hooks. When the intermediate hosts are eaten reported in several other fish families (FAO 1996, Iyaji and by the right definitive hosts, they develop further in tissues Eyo 2008 and Iyaji 2011), indicating they are not host into plerocercoid larvae with inverginated scolices and specific. migrate to the lumen of the gut where they metamorphose The gill/skin attaching cilliate parasites, Trichodinids, into strobilate adults. This complex life cycle could explain have been reported to parasitize a variety of aquatic why E.malapteruri has been described as being host specific. invertebrates, fish and amphibians (Cheng 1999) and could In the host parasite checklist of Khalil and Polling (1997), cause damage to the gills of fish with heavy infestation. In Journal of Science & Multidisciplinary Research (2):33-40 38 Iyaji & Eyo (2014). 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