INTRODUCTION

The study of fish parasites in the territory of what is now known as Bangladesh has a relatively short history, dating back to a few scattered records contained in the works of Thomas Southwell and colleagues, working at the first quarter of the 20^th Century in what was then known as British India (These are summarized in the series The Fauna of British India, including Ceylon and Burma - see for example, Southwell 1930).^[1] A few reports were made during the period following the separation of India and Pakistan in 1947, from the territory known as East Pakistan. However, most records date from the separation of the People's Republic of Bangladesh from Pakistan in 1971, and are mainly the result of the efforts of a few Bangladeshi scientists and their students (A.K.M. Bashirullah of the University of Dacca in the 1970s, and more recently, A.T.A. Ahmed and J. D'Silva of the University of Dhaka, and K.J. Chandra and M.B.R. Chowdhury of Bangladesh Agricultural University, Mymensingh).

In compiling this checklist, we have attempted to list only original reports appearing in the literature for each species. Previous listings of the parasites of fishes of Bangladesh are those of Ahmed (1979, 1981) for all helminths, Ahmed and Ezaz (1997) for the helminths of freshwater catfishes, and Chandra (1992b) for the Nematoda. A special problem was encountered with the papers of Ahmed (1981) and Ahmed and Ezaz (1997). Both papers included results of original research as well as information taken from the published literature. In both cases, it was not possible to completely distinguish records based on original findings from those derived from the published work of other scientists. In cataloguing these papers, all records have been entered.

In compiling this checklist, a large number the parasite taxa reported in the literature for Bangladesh were determined to be species inquirendae or nomina nuda. Also, many apparent misidentifications have been made. Although a detailed review of each species was beyond the scope of this study, we have noted those taxa that we believe are unlikely to occur in the waters of Bangladesh, in the hope that future workers will examine these taxonomic problems more closely.

To a large extent, the many problems posed by the literature for Bangladesh are probably due to the difficulty that local scientists have in accessing scientific literature. In many cases, scientists have apparently relied heavily on the Yamaguti volumes (Systema Helminthum) for species identification. New species have too often been established based on inadequate and inaccurate description, and/or insufficient material (a small number of specimens, or in dioceious forms, specimens of only one sex), often without critical comparisons with previously described taxa. As a result, although considerable effort has been expended on parasite surveys and taxonomic studies, it is still impossible to obtain an accurate picture of the parasite fauna of Bangladeshi fishes. This checklist must, therefore, be used with caution, both when attempting to identify parasites, and in zoogeographic analyses. We hope that this work will form the basis for the critical taxonomic study and revision that are needed, based on collection of new, properly prepared material, which will eventually lead to a more accurate picture of the parasite fauna of the fishes of Bangladesh.

Because Bangladesh is a deltic country and is subject to extensive flooding, it is possible for marine and euryhaline fishes to move far upstream, bringing with them much of their marine parasite faunas. Feeding by freshwater carnivorous fishes on marine or anadromous fishes may result in the temporary transfer of gastro-intestinal parasites ("pseudoparasitism" or accidental infection). In a number of cases, this appears to have resulted in typically marine helminth genera being reported from freshwater hosts.

In the literature dealing with the parasites of fishes of Bangladesh, there appear many incorrect spellings of parasite names, host names and species author's names, and incorrect attributions of dates of species authorship. Where erroneous spellings of parasite genus or species names have been consistently applied, these are noted using footnotes. Occasional typographical errors, misspellings of species authors' names, incorrect species attributions, and incorrect dates are not noted. Similarly, misspellings of host species names, with the few exceptions where these have been widely applied, have been corrected without comment using information obtained from FishBase (Froese and Pauly 2001).

The Parasite-Host List is a taxonomically arranged listing of all parasites reported from the fishes of Bangladesh. The higher classification used is as follows: for the Protista and Myxozoa, that of Lom and Dyková (1992); for the Trematoda, that of Gibson (1996); for the Monogenea, that of Boeger and Kritsky (1993); for the Cestoidea, that of Khalil et al. (1994); for the Nematoda, that of Anderson et al. (1974-1983) and Moravec (1998); for the Acanthocephala, that of Amin (1985, 1987); for the Copepoda and Branchiura, that of Kabata (1979, 1988); for the Isopoda, that of Rafi (1988); and for the Mollusca and Hirudinea, that used by McDonald and Margolis (1995). Other valuable references include the synopses of fish nematodes of the Indian subcontinent by Soota (1983) and Sood (1989).

The Parasite-Host List contains information for all parasite species reported from the fishes of Bangladesh. For each parasite, the currently recognized scientific name, including authors and dates, and any synonyms under which original records appeared, are given. This is followed by the environment in which the parasite normally completes its life cycle, indicated as fresh water (F), brackish water (B) or marine (M). As the life cycles of Bangladeshi fish parasites are for the most part unknown, this information is drawn primarily from non-Bangladeshi sources or from information on collection locality and/or host biology. The Location gives the site of infection where the parasite is normally found in or on the host. Under Hosts, the hosts are listed alphabetically by their currently recognized scientific names. In parentheses, following each host name, are given the numbers for the references (Records) reporting the parasite from the host in question. The distribution (Dist.) provides a summary of the reported distribution of the parasite in Bangladesh, and is given alphabetically by major administrative unit (Barisal, Chittagong, Dhaka, Khulna, Rajshahi and Sylhet Divisions), and for the Bay of Bengal.^[2] In many cases, accurate information on distribution is lacking, due to imprecise collection information being provided by authors; in those cases where no information is given, the distribution is simply indicated as Bangladesh. Unless otherwise indicated by the authors(s), fishes examined for parasites that were obtained from local markets are considered to have originated from the division in which the market was located. However, readers should be aware that fish obtained from markets in larger cities, such as Dhaka, may well have originated from other divisions or from the Bay of Bengal. Under Records are given the numbered individual references containing the parasite records, each followed by detailed information on the locality (ies) (administrative divisions) to which they pertain. Under Remarks are given comments on various aspects, such as synonymies, pathogenicity, life cycles, zoonotic importance and introductions. More specific notations on individual records are given as footnotes.

The Host-Parasite List is organized phylogenetically following the classification of fishes given by in the on-line Catalog of Fishes by W.N. Eschmeyer (Eschmeyer 2001), with the genera and species within individual families arranged alphabetically. Information on the scientific and common names, status and environment of fishes was obtained from the species database of FishBase (Froese and Pauly 2001). For each host, the following information is given: the currently recognized scientific name, including species author(s), followed by any synonyms under which original parasite records were made, the FishBase recognized English common name, the Bengali common name (where available), the host's Status in Bangladesh (native or exotic), and its typical Environment (fresh water, brackish water, marine). This is followed by a listing of the parasites reported for the host in question, arranged by higher taxon and listed alphabetically. Following each parasite name, the distribution is summarized by administrative division. Records that involve possible parasite misidentifications are indicated by a question mark preceding the parasite's name. Finally, where appropriate, Remarks and footnotes are included to provide information on such topics as host taxonomy, distribution and introductions. An additional useful reference is Freshwater Fishes of Bangladesh (Rahman 1989).

Under References are listed all the papers containing the records, as well as other works cited in the text. A short Supplementary References lists some additional articles dealing with Bangladeshi fisheries parasitology but not containing any original reports. Not included in this checklist are unpublished records of fish parasites contained in the many post-graduate (M.Sc. and Ph.D.) theses produced in Bangladesh. A Parasite Index and a Host Index complete the volume.

The parasite fauna of the fishes of Bangladesh is poorly known. To date, a total of 147 named species of parasites (not including 20 nomina nuda), (1 Protozoa, 1 Myxozoa, 55 Trematoda, 6 Monogenea, 23 Cestoda, 40 Nematoda, 17 Acanthocephala, 1 Hirudinea, 1 Branchiura, 1 Copepoda and 1 Isopoda) have been reported. Contained in this checklist are records for parasites from a total of 85 fish species. As over 500 species of fish occur in the country^[3], there remain many years of basic systematic and survey work to be conducted before the parasite fauna of Bangladeshi fishes will be thoroughly documented.

We would like to thank a number of colleagues who kindly provided critical comments on sections of the manuscript, key references, and/or taxonomic advice. These include T.E. McDonald (Monogenea, Isopoda), D.I. Gibson and R.A. Bray (Trematoda), J.S. Mackiewicz (Caryophyllidae), J.N. Caira (Tetraphyllidea), I. Beveridge (Trypanorh-yncha) and F. Moravec (Nematoda). The assistance of Drs R.P. Subasinghe, S.E. McGladdery, D.J. Marcogliese, D.I. Gibson and K.J. Chandra in obtaining essential literature is gratefully acknowledged. We especially thank Dr. R.P. Subasinghe (Food and Agriculture Organization of the United Nations, Rome), for arranging publication of this volume.

J. Richard Arthur
Sparwood, Canada

Abu Tweb A. Ahmed
Dhaka, Bangladesh