parasites of three economically important fishes

Applied Tropical Agriculture Volume 22, No. 2, 52-62, 2017. © A publication of the School of Agriculture and Agricultural Technology, The Federal University of Technology, Akure, Nigeria.

52

Parasites of Three Economically Important Fishes (Ethmalosa fimbriata,

Chrysichthys nigrodigitatus and Sarotherodon melanotheron) from Lagos

Lagoon, Southwestern Nigeria

Emmanuel, B.E.* and Aromodiu, H.A.W.

Department of Marine Sciences, Faculty of Science, University of Lagos, Akoka Yaba, Lagos, Nigeria

*Corresponding author: [email protected]; [email protected]

ABSTRACT

Parasites in three economically important fishes (Ethmalosa fimbriata, Chrysichthys nigrodigitatus and Sarotherodon

melanotheron) from Lagos Lagoon were studied between March and August, 2015. Out of 90 specimens analyzed, a total of

41 (45.6%) specimens were infected with parasites having a total parasite count of 735. Glochida accounted for the most

abundant parasite in the gills and skin of C. nigrodigitatus having a prevalence of 43.81%, Ergasilus sp. had the least amount

of prevalence with 0.41%, Gyrodactylus had a prevalence of 6.80%, Neobenedenia had a prevalence level of 0.95%. Larvae

forms of Eustrongylides from S. melanotheron had a prevalence level of 4.08% while Piscinodinium which was identified

from the gills of both S. melanotheron and E. fimbriata had a prevalence level of 41.36%, an unidentified worm had a

prevalence of 2.59%. Human beings who consumed raw or under - cooked fish that are infected with larval stages of

Eustrongylides have experienced gastritis or inflammation of the stomach and intestinal perforation requiring surgical

removal of worms.

Key words: Parasite, fish, gill, skin, under - cooked, gastritis intestinal perforation

INTRODUCTION

Fishes are important to man as they serve as a good source

of animal protein for both man and livestock. It also serves

as a source of income in Nigeria and other countries in sub-

Saharan Africa where some 35 million people depend

wholly or partly on the fisheries sector for their livelihood

(FAO, 1996).

Many diseases found in fish are closely linked to

environmental degradation and stress; once the

environment is disturbed the organisms too become

stressed (SEAFDEC, 1999). Parasitism, according to

Marcogliese (2002) reflects a life style whereby one or

more individual organisms (the parasites) live in close

obligate association in or on another (the host) and derives

nutritional benefits at the host’s expense, usually without

killing the host. Parasites are a major concern to freshwater

and marine fishes all over the world, and of particular

importance in the tropics (Iyaji and Eyo, 2008; Bichi and

Dawaki, 2010; Ekanem et al., 2011). They constitute a

major limiting factor to the growth of farmed fish in Nigeria

(Bichi and Yelwa, 2010). The effects of parasites on fish

include nutrient devaluation (Hassan et al., 2010);

alteration of biology and behaviour (Lafferty, 2008);

lowering of immune capability, induction of blindness

(Echi et al., 2009 a, b); morbidity, mortality, growth and

fecundity reduction (Nmor et al.,2004) and mechanical

injuries depending on the parasite species and load (Echi et

al., 2009a, b). Fish is the most parasitized vertebrate and the

presence of parasite is detrimental to fish population which

may cause high mortality, weight loss and reduced

fecundity on both farmed and wild fish species especially

in waters contaminated with industrial and urban pollutants

(Ramollo, 2008). In instances where host are overcrowded

such as in aquaria’s and fish ponds, parasitic disease can

spread very rapidly causing large mortalities (Parpena,

1996) while in natural systems they may threaten the

abundance and diversity of indigenous fish species

(Mashego, 2001).

Parasites can be divided into micro-parasites and

macroparasites on the basis of size, the micro-parasites

include viruses, bacteria, fungi, protozoans, micro-

sporidians and mixozoans. Surveys for microparasites in

fish hosts, most often consider only protozoans

(Marcogliese, 2002). Macro-parasites are multicellular

organisms mainly comprised of the helminthes and

arthropods. Furthermore, parasites can also be divided into

ecto-parasites and endo-parasites on the basis of their

location in the fish’s body. Ecto-parasites are those found

on the external surfaces such as skin or gills while endo-

Parasite in fishes from Lagos lagoon

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parasites are those housed within internal organs or cavities

of a host (Marcogliese, 2002). Klinger and Floyd (2002)

noted common parasites of fishes to include: Protozoans

(Ciliates, Flagellates, Myxozoa, Microsporidia, Coccidia),

monogenean trematodes, digenean trematodes, nematodes

or roundworms (Camallanus, Capileria, Eustrongylides),

Cestodes or tapeworms, acanthocephalans or thorny headed

worms, parasitic crustaceans (Ergasilus, Lernaea, Argulus)

and leeches. It is usually known that external parasite

constitutes the largest group of pathogenic parasites in

warm water fishes. Parasite infection of the body cavity and

the musculature of fishes have been reported as presenting

marketing problems for commercially exploited species

(Petersen et al., 1993). For instance, heavy infestation of

the Alaska Pollack (Theragra chalcogramme) with

pleroceroid of Nybelinia surmenicola has reduced the

consumable part of the fish to the dorsal musculature

(Grabda, 1970). Similarly, infestation with plerocerocoids

of Gymnorlynchus thyrsitae has seriously affected the

exploitation of the highly valued Thyrsite atun in New

Zealand (Mehl, 1970).

The Piscinodinium pillulare recorded in this study causes a

condition known as velvet disease in which it coats the gills

of the infected fish and heavy infestation is known to cause

mass mortalities as reported by Kunz and Pung (2004).

Other effects of parasite on fish include muscle

degeneration, liver dysfunction, interference with nutrition,

cardiac disruption, nervous system impairment, castration

or mechanical interference with spawning, weight loss and

gross distortion of the body (Kunz and Pung, 2004). Other

severe pathological disorders reported by Bauer (1959);

Sweeting (1977); Mitchell and Hoffman (1980) include

inflammation and atrophy of the viscera, resulting from

compression and displacement of organs by the parasites,

often together with accumulation of blood stained ascetic

fluid.

A review from Nigeria indicated that freshwater fish

parasites belong to protozoans, trematode, nematode,

cestode, acanthocephalan, copepod and hirudinea groups

(Iyaji and Eyo, 2008). Okaeme and Ibiwoye (1988)

revealed that the protozoans constitute an important

economic disease of catfishes in Lake Kainji area in

Nigeria. Ibiwoye et al. (2006) reported the prevalence rate

of 22.5, 76.25 and 1.25% for gastro-intestinal parasites,

Procamallanus laevionchus and Sprironoura petriea

(Nematodes), Polyonchobothrium clariae (Cestode) and

Clinostomum clarias (Trematode) in Clarias anguillaris in

Onitsha area along River Niger. Nyaku et al. (2007) also

reported the occurrence of platyhelminthes parasites as the

most common ectoparasites of three species of fish

(Oreochromis niloticus, Auchenoglanis occidentalis and

Bagrus bayad) in River Benue, Nigeria. Obiekezie et al.

(1988) recorded infections with larval stage of nematode

Hysterothylacium sp of C nigrodigitatus throughout the

year with 64% prevalence. The pericardium inhabiting

nematode, Contracaecum sp, Amplicaecum sp and

Eustrongylides sp were most prevalent in freshwater fish

hosts. Nematode parasite, Procamallanus laevionchus was

found with highest prevalence of 62.2% in S. schall at rivers

Niger and Benue confluence (Iyaji, 2011).

Elsewhere, Raissy et al. (2008) reported the presence of

Dactylogyrus spiralis in the gills of Cyprinus carpio in Iran.

The microsporidean Plistophora sp infections of

Haplochromis angustifrons and H. elegans in Lake George

had very low prevalence of less than 1% out of 302 fish

examined from both sexes (Paperna, 1973). Infections by

Nosemoides tilapia in Tilapia zilli, T. guinensis and

Sarotheradon melanotheron were common in Lake Nakoue

and Porto Novo lagoon with prevalence of 13-30% (Sakiti

and Bouix, 1987). The visceral myxobolus infections of

Oreochromis sp in East African lakes were quite high

(prevalence 89-100%) while in Haplochromis sp they were

only rarely above 25% (FAO, 1996). Prevalence of skin and

gill infections of Myxobolus sp was very low (Paperna,

1973). Prevalence of Henneguya sp infecting Clarias

gariepinus of Okavanga River and the Delta in Botswana

were also generally low, 14.3% in the cartilage of the

accessory breathing organ and primary gill lamallea (Reed

et al., 2003). Kostoingue et al., (2001) reported primary gill

lamellae infections of Henneguya sp and their prevalence

in the following fish genera: Auchinoglanus occidentalis;

Citharinus citherus; Mormyrus cashive; Lates niloticus;

Clarias auguilaris with prevalences of 36.8% (21/57)

25.8% (16/32) 13.3% (12/90) 4.4% (3/63) and 9.1% (4/44)

respectively from freshwater ecosystem of Chad, Central

Africa. Henneguya chrysichthyi gill infection in C.

nigrodigitatus had a prevalence of 37% (Obiekezie et al.,

1988) with the highest intensity of infection in the 21-30

cm class, corresponding to fish in their second year

(Ezenwa and Ikusemiju, 1981).

Among the heminths, Obiekezie et al. (1988) found the

monogenean Protancylodiscoides chysichthes occurred

throughout the year on the gills of the fish with monthly

prevalence of infection consistently above 70% (Except in

August) and low mean intensity during heavy rain months

(July - Oct). Data on cestode infestations of fish are mostly

from wild fish species (FAO, 1996).

Despite all these reports, very little is known about the

parasitic infestation and prevalence in Ethmalosa fimbriata,

Chrysicththys nigrodigitaus and Sarotherodon

melanothron in Lagos lagoon. The aim of this study is

provide information on the types and relative abundance of

several parasitic species found in three brackish water fish

families of economic importance (E. fimbriata, C.

nigrodigitatus, S. melanotheron) in Lagos lagoon and the

effects of these parasites on the survival of these species in

the lagoon.

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Emmanuel and Aromodiu / Applied Tropical Agriculture 22 (2), 52-62, 2017

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MATERIALS AND METHODS

Description of study site The Lagos lagoon shares its name with the city of Lagos,

Nigeria. The Lagoon (Fig 1) lies between longitudes 30 20’

and 30 40’E and latitudes 60 15’ and 60 40’ the estimated

area of the main body is 150.56km2 and has an area of 208

km2 (FAO, 1969 cited by Nwankwo, 2004) and an average

depth of less than two meter. The lagoon is the largest of

the of the four lagoon systems of the gulf of guinea (Webb,

1958 cited by Nwankwo, 2004 ) and is one of the nine

coastal lagoons of South-western Nigeria (Webb, 1958;

Nwankwo, 2004; Onyema, 2008a). It provides the only

opening to the sea for the nine lagoons of South Western

Nigeria. Owing to the dynamics of river inflow and

seawater incursion, the Lagos lagoon experiences brackish

condition that is more discernable in the dry season

(Nwankwo, 2004). In the wet season, the increased river

inflow creates freshwater and low brackish conditions in

various parts of the lagoon. The harmattan, a short season

of dry, dusty North-East Trade winds are experienced

sometimes between November and January in the region

reducing visibility and lowering temperatures (Onyema et

al., 2003). Characteristically, Lagos Lagoon has a seasonal

fluctuation in salinity and high brackish water during the

dry season (From December to May), while freshwater

condition exists in the rainy season (June – November)

(Kusemiju, 1975; Ugwumba and Kusemiju, 1992; Solarin,

1998; Lawal-Are, 2006). The lagoon is fairly shallow and

is not plied by ocean going ships but by smaller barges and

boats. Lagos Lagoon receives freshwater from Lekki

Lagoon via Epe Lagoon in the North-east, and dis-charges

from Majidun, Agboyi and Ogudu creeks as well as Ogun

River in the North-west (Soyinka, 2008; Lawal-Are et al.,

2010).

In the dry season, freshwater inflow is greatly reduced and

seawater enters the lagoon through the harbour giving rise

to marine conditions near the harbour and brackish water

extending far inland (Hill and Webb, 1958; Nwankwo,

1996; Onyema et al., 2003). Hence, areas located in close

proximity to the harbour experience greater marine

influence than places further inland.

Collection of fish specimens Fish species were landed at the market by artisanal

fishermen using casts nets, drag nets and set gill nets.

Samples of Ethmalosa fimbriata (30), Sarotherodon

melanotheron (30) and Chrysichthys nigrodigitatus (30)

were collected from the Better-life fish market in Makoko

area of Lagos state between March-August 2015 (6

months). Five 5 specimens of each species was collected

each month for analysis of parasitic prevalence throughout

the six months of the project.

Laboratory analysis of fish samples

Determination of Morphometric Characteristics

In the laboratory, the total length (TL) and standard length

(SL) of each individual fish was measured in centimeters

(cm) using a fish measuring board. The weight of each

individual fish was also taken in grams (g) using a weighing

balance (Camry EK 5055).

Gill Examination for Parasites

The gill of the individual fish specimen was extracted by

dissecting the fishes using a dissecting scissors. The

extracted gill sample was placed on a microscopic glass

slide, a drop of water was added and the sample is covered

using a cover slip then view under microscope for parasitic

prevalence using a magnification of 60X as described by

omeji et al. (2010); Bichi and Ibrahim (2009) and Emere

and Egbe (2006). This procedure was repeated for all fish

samples for consistency.

Skin Mucus Examination for Parasites The body mucus from the caudal part of fish was scrapped

using a scrapper. Scraping was done carefully so as to avoid

scales in the mucus which may impair the visibility of small

protozoan. Mucus was then placed on glass slide and a drop

of water was added and then covered with a cover slip

before being viewed under microscope for ecto-parasites as

described by omeji et al. (2010); Bichi and Ibrahim (2009)

and Emere and Egbe (2006). The procedure was repeated

for all samples.

Ecto-parasites found were identified and their number

counted. Examination of fish gill and mucus from skin were

done on the same day the fish were caught (live or fresh) as

some ecto-parasites die after the host is dead.

Analysis of Parasitic Infestation

The analysis for parasitic infestation for finding the

incidence and prevalence were carried out by following

equations (Poulin and Rhode, 1997)

Prevalence of infection = ��

�� x 100

Incidence of infection = �.� � � ��

�.� ��

Prevalence of individual parasites = �� !!� ��" �# � ��$�!�

�� #�� " %�� & '((

Analysis of Data All data were analyzed using descriptive statistics.

Prevalence (P) was represented in bar graphs and pie chart

using Microsoft excels.

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RESULTS

Length - weight relationship of the fishes used for

the study The 90 specimens used consisted of different size groups,

the length of S. melanotheron mean ranged from

17.42±0.77cm - 20.38±2.41cm with average range weight

from 103.4±12.26 g - 138.4±16.37g (Table 1), C.

nigrodigitatus mean ranged from 26.92±1.20`cm -

35.76±2.61cm with average range weight from

165.2±28.07 - 412.4±114.14g (Table 2) and E. fimbriata

mean length ranged from 13.12±1.42cm- 17.76±1.88cm

with average range weight from 20.4±6.68 - 53.6±19.47g

(Table 3).

Table 1: Mean monthly variation of length and weight for S.

melanotheron

Month Total length

(cm)

Standard

length (cm) Weight (g)

March 20.38±2.41 15.16±1.78 135.6±50.07

April 18.31±1.31 13.96±1.02 125.6±24.14

May 19.62±1.39 15.18±1.03 138.4±16.37

June 17.42±0.77 13.20±0.57 107.0±10.26

July 19.42±1.20 14.64±1.34 132.4±12.26

August 18.06±0.95 13.68±0.59 103.4±12.26

Table 2: Mean monthly variation of length and weight for C.

nigrodigitatus

Month Total length

(cm)

Standard


March 33.36±2.29 24.60±1.46 285.6±53.20

April 35.76±2.61 26.88±2.71 412.4±114.14

May 30.72±4.54 22.84±3.74 236.8±119.72

June 33.38±2.46 24.68±2.13 311.4±98.88

July 31.54±3.87 22.72±1.77 240.8±45.41

August 26.92±1.20 20.28±0.76 165.2±28.07

Table 3: Mean monthly variation of length and weight for E.

fimbriata

Month Total length

(cm)

Standard


March 14.68±1.62 12.10±1.36 28.2±8.97

April 17.76±1.88 14.14±1.65 53.6±19.47

May 15.36±1.98 13.78±3.42 32.0±13.52

June 15.46±0.66 12.62±0.49 33.4±5.08

July 13.12±1.42 10.44±1.36 20.4±6.68

August 14.28±1.02 11.34±0.96 25.4±6.15

Parasites of fishes in Lagos Lagoon Parasite species recorded in 90 specimens analyzed are

Glochida (parasitic larvae of mussels), Gyrodactylus,

Neobenedenia, Ergasilus (parasitic copepod),

Piscinodinium (protozoa) and Eustrongylides (nematode)

as shown in Table 4.

Out of the 90 specimen analyzed, a total of 41 (45.6%)

specimens were infected with parasites having a total

parasite count of 735 from infected specimens. Glochida

accounted for the most abundant parasite in the gills and

skin of C. nigrodigitatus having a prevalence of 43.81%,

Ergasilus sp. had the least prevalence value with 0.41%,

Gyrodactylus had a prevalence of 6.80%, Neobenedenia

had a prevalence level of 0.95, larvae forms of

Eustrongylides from S. melanotheron had a prevalence

level of 4.08% while Piscinodinium which was identified

from the gills of both S. melanotheron and E. fimbriata had

a prevalence level of 41.36%, an unidentified specimen had

a prevalence of 2.59%. This is shown in Fig. 2.

Prevalence with respect to species Chrysichthys nigrodigitatus had a total prevalence 50.16%

of parasite consisting of Gyrodactylus (6.8%) and Glochida

(43.36%) making it the species of fish having the highest

amount of parasitic infestation. S. melanotheron had a total

prevalence of 28.57% comprising of Ergasilus (0.41%),

Piscinodinium (23.13%), Eustrogylides (4.08%) and

Neobenedenia (0.95%). E. fimbriata had a total prevalence

of 20.82% comprising of Piscinodinium (18.23%) and

unidentified worm (2.59%). This relationship is shown in

Table 5 and Fig. 3.

Prevalence of Parasites with respect to size of fish Glochida was discovered to be more prominent in larger

sized C. nigrodigitatus while Gyrodactylus was found to

infest fish of different sizes but with an increased

prevalence in larger species of C. nigrodigitatus,

Eustrongylides and Neobenedenia was found in matured

S.melanotheron, Piscinodinium was found to affect S.

melanotheron and E. fimbriata irrespective of their size.

This relationship is represented in Table 6 and Fig. 4.

DISCUSSION

This study recorded a parasitic prevalence of 45.6% from

all infected specimens, C. nigrodigitatus recorded the

highest prevalence of parasitic infection with 50.16%. This

agrees with the finding of Olorin and Somorin (2006) which

recorded the highest parasitic burden in C. nigrodogitatus

which was found to be infected with the metacerceria of the

trematode (Clinostomum tilapiae) and the adult of the

acanthocephalan (Neochinorynchus rutili). S.

melanotheron had the highest number of parasite diversity

with four different families of parasite, Ergasilidae

(Ergasilus sp), Capsilidae (Neobenedenia mellari),

Oodinidae (Piscinodinium pillulare) and

Dioctophymatidae (Eustrongylides sp).

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Table 4: The species of parasites identified from specimens and the part of fish they were found

Fish Site of infection Family of parasite Specie of parasite

S. melanotheron Gill Ergasillidae Ergasilus sp.

S. melanotheron Gill Dioctophymatidae Eustrongylides sp.

C. nigrodigitatus Gill and skin Unionidae Glochida (Anodonta grandis)

C. nigrodigitatus Skin Gyrodactylidae Gyrodactylus arcuatus

C. nigrodigitatus Skin Gyrodactylidae Gyrodactylus derjavini

E. fimbriata Gill Oodinidae Piscinodinium pillulare

S. melanotheron Skin Capsalidae Neobenedenia mellari

S. melanotheron Gill Oodinidae Piscinodinium pillulare

E. fimbriata Gill Unidentified worm

Figure 1: Map showing the sampling sites in Lagos lagoon

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Figure 2: Prevalence (%) of parasite from all infected specimens of S. melanotheron, C. nigrodigitatus and E. fimbriata

Figure 3: Prevalence of parasite with respect to species

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Figure 4: Prevalence of parasite with respect to size of fishes

PLATE 1a: (A) Slide of Eusrongylides sp. from gill infected of S. melanotheron. (Mg x60), (B) Slide of Neobenedenia mellari

from skin of infected S. melanotheron (Mg x60), (C) Slide of Piscinodinium pillulare from gill of infected E. fimbriata (Mg x60),

(D) Slide of Ergasilus sp. from gill of infected S. melanotheron (Mg x60),

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PLATE 1b: (E) Slide of Gyrodactylus derjavini from skin of infected C. nigrodigitatus (Mg x60), (F) Slide of Glohida (Anodota

grandis) from gill of infected C. nigrodigitatus (Mg x60).

Chen (1973) and Wang et al. (1997) reported the larvae of

Eustrongylides from the fish species of the families

Engraulidae, Cyprinidae, Siluridae, Bagridae, Channidae

and Percichthyidae. The prevalence of parasitic infections

corresponds with fish length which also in turn corresponds

to fish size and age as reported by Lagler et al. (1979), with

exceptions from Piscinodinium sp. Poulin, (2000) stated

that larger fish have more internal and external space for

parasite establishment and therefore tend to have heavier

infestations. This study recorded similar case of higher

prevalence of parasitic infestation in agreement with the

work of Omeji, et al., (2010) who reported higher rate of

protozoan parasites in bigger C. gariepinus and

Heterobranchus longifilis than the smaller ones. Emere and

Egbe (2006) reported higher rate of protozoan parasites in

bigger Synodontis clarias than the smaller ones an

indication that parasites infest fish based on the size and the

surface area. Gyrodactylus show an increase in prevalence

with respect to size to a certain level then declines in this

study, these results are in accordance with those of Ramollo

et al (2006), who reported that the prevalence and intensity

of infestation generally increased with the host’s size, up to

a certain point and then declined. The prevalence of

gyrodactylus in the fish species could be as a result of the

fact that gyrodactylus are host specific (Marcogliese and

Price, 1997). Combination of factors, such as infection rate,

survival, reproduction, population growth and virulence,

determine host optimality (King and Cable, 2007). Parasite

infection rate from all specimen was generally low and this

could be attributed to several factors which include:

temperature, salinity, season (raining or dry), this is in line

with Ramollo (2008), which reported that good biological

indicators are sensitive to environmental alterations so that

changes in their numbers can be used as warning of

deteriorating conditions before the majority of less

sensitive organisms are seriously affected. In the same vein,

Vidya and Sukumar (2002) noted that potential factors

determining the transmission of parasites include

environmental conditions (affect the viability and behavior

of parasites) and feeding, movement and defecation

patterns of the host (determine the parasites encountered).

In the wild it is difficult to isolate and quantify the effects

of any single factor on parasitized fish population

dynamics. However, studies of fish in captivity or under

culture conditions have provided much information about

the effects of parasites on fish survival. From this study

parasite infestation was known to cause swelling in the

gills, rotting of fin and loss of scale. It was reported by Cruz

– Lacierda (2001) that Glochidia destroy the gills and

disrupt the respiratory function of the gill. Nematollahi et

al. (2013) also reported that parasites are among the

important factors responsible for weight loss, disruption of

reproduction or impotency blindness, abnormal behavior,

epithelial lesions, deformities of gills and other symptoms

that ultimately lead to economic loss in fish industry.

Evidences suggest that parasites can act as severe

pathogens, causing direct mortality or rendering the fish

more vulnerable to predators (Kunz and Pung, 2004).

Parasites are a natural component of the environment and

may be viewed as an indicator of the relative health of an

ecosystem. The majority of species of parasites present on

and within fish are not hazardous to human and those which

are hazardous tend to have complex life-cycles which

involve more than one type of host for development.

Eustrongylides is known to affect birds that feed on infected

fish and they cause a condition known as Eustrongylidosis

(Franson and Custer, 1994). Humans who consumed raw or

under-cooked fish that carry the larval stages of

Eustrongylides have experienced gastritis or inflammation

of the stomach and intestinal perforation requiring surgical

removal of worms (Measures, 1988).

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CONCLUSION

Parasites are a natural component of the environment and

may be viewed as an indicator of the relative health of an

ecosystem. The majority of species of parasites present on

and within fish are not hazardous to human and those which

are hazardous tend to have complex life-cycles which

involve more than one type of host for development.

Humans who consumed raw or under-cooked fish that carry

the larval stages of Eustrongylides have experienced

gastritis or inflammation of the stomach and intestinal

perforation requiring surgical removal of worms.

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