Aquaculture 185 Ž2000. 191–196
www.elsevier.nlrlocateraqua-online
Marine leech žZeylanicobdella arugamensis/
infestation in cultured orange-spotted grouper,
Epinephelus coioides
Erlinda R. Cruz-Lacierda a,) , Joebert D. Toledo a ,
Josefa D. Tan-Fermin a , Eugene M. Burreson b
a
Southeast Asian Fisheries DeÕelopment Center, Aquaculture Department, Tigbauan 5021, Iloilo, Philippines
b
School of Marine Science, College of William and Mary, Virginia Institute of Marine Science, Gloucester
Point, VA 23062, USA
Accepted 9 November 1999
Abstract
Heavy infestation of a marine leech occurred among tank-reared juvenile and adult orangespotted grouper, Epinephelus coioides Hamilton, at SEAFDEC AQD, Philippines with a prevalence of 83% and 17%, respectively. The leeches were attached in large numbers on the fins,
lower jaw, under the operculum, eyes, and inside the mouth of the fish. The attachment and
feeding sites exhibited frayed fins, hemorrhages and swelling of the host’s skin. External and
internal features indicate that the leech is Zeylanicobdella arugamensis De Silva ŽHirudinea,
Piscicolidae.. The parasite can be effectively controlled using 50 ppm formalin bath treatment for
1 h. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Grouper; Marine leech; Zeylanicobdella arugamensis
1. Introduction
An extremely heavy infestation of a marine leech occurred among tank-reared
juvenile and adult orange-spotted grouper, Epinephelus coioides Hamilton, at SEAFDEC
Aquaculture Department in Iloilo, Philippines. The fish were being used for broodstock
development studies when the parasite infestation occurred. Subsequent observations of
)
Corresponding author.
E-mail address: [email protected] ŽE.R. Cruz-Lacierda..
0044-8486r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 0 4 4 - 8 4 8 6 Ž 9 9 . 0 0 3 5 6 - 7
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E.R. Cruz-Lacierda et al.r Aquaculture 185 (2000) 191–196
the same parasite were also recorded in grouper collected from the wild and from
earthen ponds.
This paper describes the disease outbreaks and a control measure is also presented.
2. Materials and methods
Twenty four Ž24. two-year-old Žmean BW, 1.0 kg; mean TL, 41 cm. juvenile and six
adult Žmean BW, 6.0 kg; mean TL, 66.5 cm. grouper were stocked in eight canvas and
one concrete tank, respectively. The juveniles were being used for experiments on
induction of sex inversion while the adults were being monitored for natural spawning.
Prior to the sex inversion experiment, the fish were reared in earthen ponds for two
years. The juveniles were then transferred to 10-ton, 4-m diameter canvas tanks for 4
months when the parasite infestation occurred. The adult fish were collected from the
wild and reared in a concrete tank Ž5 = 5 = 2 m. for more than 1 year prior to parasite
infestation. All fish were fed with fish-by-catch.
The tanks containing the juvenile fish were supplied with flow-through sand-filtered
water while 50–80% of the rearing water was changed at least three times a week for
the adult fish. Water temperature and salinity ranges recorded during the experiments
were 26–328C and 27–32 ppt, respectively. Mean water temperature and salinity for six
days prior to leech infestation were 288C and 22 ppt, respectively. Continuous heavy
rains were also noted a few days before the infestation making the incoming water
turbid.
Heavy infestation of the parasite was observed during regular sampling for experiments on sex inversion and natural spawning. The affected fish were anesthetized with
250 ppm 2-phenoxy-ethanol for 5 min to immobilize the fish. The parasites were then
removed manually by carefully rubbing the affected portion with a wet cloth and then
transferred to glass jars containing seawater. Many of the parasites could be removed by
this method. However, large numbers remained especially those attached on the corners
of the fins and the inner surface of the operculum.
The live parasites were observed microscopically and measurements were taken.
Some were fixed in 10% buffered formalin and processed for histological examination
or preserved in alcohol-formalin-acetic acid ŽAFA. and stored in 70% ethyl alcohol.
Serial transverse sections were cut at 5 mm for determination of internal anatomy.
A mini-bioassay was conducted to determine control measures against the parasite.
The leeches Ž n s 10rtreatment. were exposed to 0 Ž100% freshwater., 15 and 30 ppt
Žcontrol. seawater and 50, 100 and 200 ppm formalin in glass petri plates. The parasites
were observed under the stereo microscope every 30 min for 4 h.
3. Results
Twenty Ž20. out of 24 juvenile fish Ž83%. and one out of six adult fish Ž17%. were
infested by the leech. The parasites were attached in heavy patches Žseveral hundreds. in
E.R. Cruz-Lacierda et al.r Aquaculture 185 (2000) 191–196
193
pectoral, ventral, anal, and caudal fins ŽFig. 1.. Large numbers of the leeches were also
found in the skin folds behind the lower jaw, under the operculum, eyes, and inside the
mouth. The affected fish showed frayed fins, hemorrhages and swollen areas on the
parasite’s attachment and feeding sites ŽFig. 2..
Microscopic examination of the live brownish-black parasites revealed an elongated
and cylindrical body narrowing at both ends with oral and caudal suckers ŽFig. 3a..
Total length ranged from 8–12 mm including the suckers. The oval-shaped oral sucker
ŽFig. 3b. measured 0.5–0.6 = 0.3–0.5 mm and contained a pair of eyes located dorsally
at the lower portion of the sucker. The discoid-shaped caudal sucker ŽFig. 3c. measured
1.0–1.2 mm in diameter and its width was equal or wider than the maximum width of
the body.
From the microscopic examination of live and preserved specimens and the histological sections, the parasites were confirmed as Zeylanicobdella arugamensis De Silva
ŽHirudinea, Piscicolidae..
The leech was also observed in pond-cultured grouper Žmean BW, 40 g., collected
and acclimatized Ž27–288C, 29–31 ppt. in 600-l fiberglass tanks for one month for a
feeding experiment ŽP. Eusebio, personal communication. with a prevalence of 25% and
mean intensity of 4. The leeches were observed in the jaw and corners of the fins. The
affected fish were found aggregated near the aeration source and mortalities occurred.
The fish also showed heavy infestation of monogeneans Ž Pseudorhabdosynochus sp..
and didymozoid trematodes in the gills. The leech was also observed in grouper
fingerlings ŽBW, 3–58 g. collected from the wild for transport experiment ŽE. Coniza,
Fig. 1. Adult E. coioides infested with Z. arugamensis Žarrows.. Bar s 4.5 cm.
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E.R. Cruz-Lacierda et al.r Aquaculture 185 (2000) 191–196
Fig. 2. Caudal fin of adult E. coioides infested with Z. arugamensis. The attachment and feeding sites of the
parasite are hemorrhagic and swollen Žarrows.. Bar s 0.6 cm.
personal communication. with a prevalence of 30% and mean intensity of 2. The leech
in both observations was confirmed as Z. arugamensis.
Fig. 3. Z. arugamensis: Ža. entire specimen, dorsal view, bar s1 mm; Žb. oral sucker, dorsal view, bar s 0.25
mm; Žc. caudal sucker, dorsal view, bar s 0.5 mm.
E.R. Cruz-Lacierda et al.r Aquaculture 185 (2000) 191–196
195
Results of the bioassay showed that all treated leeches died after 1 h exposure to 0
ppt seawater Ž100% freshwater. and 50–200 ppm formalin. Those exposed to 15 and 30
ppt seawater were still active even after 4 h.
For treatment, fish with remaining attached parasites were treated with 50 ppm
formalin bath for 1 h. The fish were supplied with ample aeration during the treatment
period and observed closely. At the end of the treatment period, most of the parasites
were found detached from the fish and seen at the bottom of the tank. The 50 ppm
formalin, however, did not have an adverse effect on the treated fish.
4. Discussion
This paper is the first documented report of marine leech infestation in cultured
grouper in the Philippines with grouper as a new host record for Z. arugamensis.
Zeylanicobdella arugamensis have been observed to infest a number of brackishwater
and marine fishes in Sri Lanka, Malay Peninsula off Singapore, and India ŽDe Silva,
1963; De Silva and Fernando, 1965; Sanjeeva Raj et al., 1977.. This leech is also
common in Indonesia and along the coast of Queensland, Australia ŽBurreson, unpublished data.. Bondad-Reantaso Ž1992. reported Piscicola sp. in grouper from Luzon
Island, Philippines. Leong and Wong Ž1988. reported an unidentified leech from grouper
cultured in floating cages in Malaysia with a prevalence of 0.4%. The checklist of
parasites of fishes of the Philippines did not show any record on the occurrence of Z.
arugamensis ŽArthur and Lumanlan-Mayo, 1997.. However, the heavy infestation by
this leech found in the present study is very unusual ŽBurreson, unpublished data..
The pathology of leech infestations has been reviewed in marine fish by Rohde
Ž1984. and in fish cultured in the tropics by Kabata Ž1985.. Hemorrhages and swelling
of affected areas have been reported in yellow fin bream, Acanthopagrus australis and
Atlantic cod, Gadus morhua ŽKhan, 1982; Roubal, 1986.. In the present study, hemorrhages and swelling on the attachment and feeding sites of the leech have been observed.
The importance of leeches as vectors of pathogens and as parasites of fish have been
reviewed by Burreson Ž1995.. It would be appropriate to look at possible viruses and
blood parasites associated with heavy infestation of leech in grouper.
Despite the heavy infestation in juvenile fish, no mortality occurred among the
affected individuals. However, the adult fish died three days after the parasite infestation. This can be attributed to the extremely heavy leech infestation with the consequent
loss of large amount of blood, the probable secondary effects of multiple feeding
wounds, and the loss of appetite of the affected fish. Mortality has been recorded in
Pacific salmon Ž Oncorhynchus spp.. with extremely heavy infestations by leech ŽKhan,
1982.. The mortalities in grouper fingerlings caught from the wild and grow-out ponds,
however, can be attributed to transport stress and the combined effects of multiple
parasite infestations, respectively.
The epizootic outbreaks of Z. arugamensis in the present study are probably
attributable to environmental factors such as high turbidity level of the incoming water.
The incoming rearing water was turbid brought about by continuous heavy rains for
several days before the infestation. The leeches in adult and juvenile fish were not
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E.R. Cruz-Lacierda et al.r Aquaculture 185 (2000) 191–196
evident one week prior to infestation. Thus, an effective and good filtering system for
the water intake may prevent the entry of leeches in culture facilities. The average
salinity of the rearing water six days before the outbreak was 22 ppt, indicating that Z.
arugamensis can tolerate brackishwater conditions.
The 50-ppm formalin bath treatment for 1 h proved to be effective in controlling the
leech. The use of freshwater to control the parasite may also be effective but has limited
applications in strictly marine species, such as E. coioides. These methods will remove
leeches from the fish, but if the leeches have deposited cocoons in the culture facilities,
then the total elimination of the parasite may be difficult. Cocoons are very resistant to
chemical treatment ŽBurreson, 1995.. Fish that have been treated can quickly become
re-infected as leeches hatch from cocoons present in the tank or pond. Fish should be
examined carefully for leeches prior to stocking to prevent parasite infestation. Cocoons
can also be eliminated by thorough drying of culture facilities.
Acknowledgements
We appreciate the technical assistance of the Staff of Fish Health and Breeding
Sections of SEAFDEC AQD. Catherine T. Tamse acted as our personal courier and Mila
Castanos
˜ edited an early draft of the manuscript.
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