Comparative study of helminth parasites in Mastacembelus armatus ( Lacepede , 1800 ) and Macrognathus pancalus ( Hamilton , 1822 ) collected from fish market of Savar , Dhaka

Mastacembalus aramtus and Macrognathus pancalus are very much popular and delicious fish in Bangladesh and commonly known as salbaim and guchi baim respectively. According to IUCN Bangladesh (2015), though the M. pancalus is least concern but, the M. armatus is endangered in Bangladesh and their abundance are not satisfactory. Beyond the various biological and ecological factors, parasites of fish constitute one of the major problems to fish health. For proper culture and management of fish as well as to keep fish well in their natural habitat, it is essential to control the fish parasites.

Several works has been carried out by Khan & Yaseen (1969), Anon (1974), Ahmed & Saha (1983), Banarjee & Chandra (1993) and Khanum & Parveen (1997) on the above mentioned fish.However, the recent studies on the stated fish are very much limited.Therefore the present study was undertaken to comparative evaluation of the present status of prevalence and intensity of helminth parasite of Mastacembalus aramtus and Macrognathus pancalus with emphasis on sex, organal and length wise distribution.
A total of 160 of each Mastacembelus armatus and Macrognathus pancalus were collected from a savar bus stand fish market (23 o 50´57.57Nand 90 o 15´30.08 o E ) of Savar Upazila, Dhaka at each month during the October 2016 to May 2017.Collected fishes were immediately brought to the laboratory and their outer surface like skin, fins and tail were examined with the help of hand lens and dissecting microscope for parasites.Sexes were determined according to their body color, bulged-out bellies, genital pore and internal gonad.The total length of each fishes was recorded with the help of a centimeter scale.
To collect the helminth parasite, fishes were dissected and different organs of fish like gill, body cavity, liver, stomach and intestine were collected and kept in separate petridishes containing saline solution (0.75%).Thereafter, collected parasites were kept in 70% ethylalcohol.Then the parasites were mounted temporarily in lactophenol to clear the cuticle of the parasites.Whole mount of parasites were carried out by passing through graded alcohol and stained in borax carmine.Thereafter, dehydrated in xylena and finally mounted in canada balsam for their microscopic study.Parasites were identified according to Yamaguti (1958Yamaguti ( , 1959Yamaguti ( , 1961Yamaguti ( and 1963)).Finally, according to Margolis et al. (1982), prevalence and intensity of occurrence of each species of identified helminth parasite were determined.
In present study a total of 160 Mastacembelus armatus and Macrognathus pancalus of each species were studied.It was observed that both prevalence and intensity of parasite was higher in M. armatus than M. pancalus (Table 1).Again, male of both host species showed higher prevalence (86.04% and 69.62%) compare to female (41.89% and 29.63%).However, female of both host species exhibited higher intensity than that of male (Table 1).According to Aloo et al. (2004), the main reason for the differences in parasitic load with sex is physiological.In this study, higher percentage of infection in male compare to female agrees with the work reported by Oniye et al. (2004), Khanum et al. (2008) and Kamrujjaman & Ferdous (2009) but disagrees with the reported work of Sultana & Salam (2015) and Ayanda (2009).Ahmed (2002) found 11 and 2 species of helminth parasites from M. armatus and M. pancalus respectively.Khanum et al. (2011) recorded 7 species of helminthes in Macrognathus aculatus.On the other hand 7 species of helminth parasite was reported in M. armatus by Malsawmtluangi & Lalramliana (2016).So, the present finding was higher than the previous record may be due to adverse environmental factors of host species suggested to more intensive study.Again, infestation of helminth parasites was higher in M. armatus than the M. pancalus.Former was heavily infected may be due to their voracious feeding habit.This species forages at night on benthic insect larvae, worms and some submerged plant material thus making them more susceptible to helminth infections (Rainboth, 1996).
Again, trematode showed highest prevalence (28.12% and 21.25%) in both host fishes ( M. armatus and M. pancalus respectively) which was followed by cestodes (15.62% and 13.12%), nematodes (11.87% and 9.37%) and acanthocephalans (10% and 5.62%) ( The main factors determining the variety of parasite fauna as well as the intensity and incidence of infection depends on the diet, lifespan, mobility of the host throughout its life including the variety of habitats it encounters, its population density and the size attained, large hosts provide more habitats suitable for parasites than do small ones ( Polanski, 1961).The results showed that maximum prevalence of parasite were recorded from intestine (40.62%) and stomach (23.12%) in M. aramtus and M. puncalus respectively (Table 3).However, highest intensity was in body cavity (6.11%) and liver (3.83%) in M. aramtus and M. puncalus respectively.On the other hand, minimum prevalence (1.25%) and intensity (1.00) were observed in gill in both host fishes.Khanum et al. (2011); Khanum et al. (2015) and Sultana & Salam (2015) stated highest prevalence and intensity of parasites in the intestine followed by stomach in Macrognathus aculeatus, Clarias batrachus and Channa punctatus respectively.Whereas, Khanum & Parveen (1997) were found maximum in the stomach followed by intestine in Macrognathus aculeatus and M. armatus.Fish parasites like other vertebrates, feed either on the digested contents of the host in the alimentary canal or the hosts own tissues (Marcov, 1946).The intestine and stomach seems to be a favorite site for helminth parasites as because of their thick cuticular body covering of the parasites are well adapted to their hosts.Besides, they possess a complete or partially complete alimentary canal and thereby can absorb digest the undigested food materials from the stomach of the host (Khanum et al., 2011).This later findings were also similar with the present findings.Age and habitat of the host plays vital role in the differences of prevalence (Bashirullah, 1973).Present study revealed that studied fishes harbor significant number of helminth parasites more especially trematodes.To confirm the recorded species as well as biology of parasites, intermediate hosts, behavior of host and most essentially seasonal variation of parasite should be examined.

Table 4 . Prevalence and intensity of helminth parasites in different length group of M. aramtus and M. puncalus
*NE=Number Examine, NI=Number infected, NPC=Number of parasite collected.