DIGENETIC TREMATODES OF MARINE FISHES OF INDIA (SUPERFAMILY HEMIUROIDEA : FAMILIES LECITHASTERIDAE AND BUNOCOTYLIDAE)

This paper is based on 135 specimens on 47 slides. They belong to 9 species from 8 genera and 2 families of the superfamily Hemiuroidea Looss, 1899. The material was collected from the marine fishes of the Bay of Bengal (Bay of Bengal proper including Coromandel coast, Palk Bay and Gulf of Mannar) and Arabian Sea. It includes the description of a new species; two known species are reported for the fIrst time from India; some important synonymies have been suggested; Neotheleterum Gibson and Bray, 1979 is accepted; and some known species are reported with interesting remarks. The classification of Hemiuroidca as given by Gibson and Bray (1979) has been adopted here.


INTRODUCTION
This paper is based on 135 specimens on 47 slides. They belong to 9 species from 8 genera and 2 families of the superfamily Hemiuroidea Looss, 1899. The material was collected from the marine fishes of the Bay of Bengal (Bay of Bengal proper including Coromandel coast, Palk Bay and Gulf of Mannar) and Arabian Sea. It includes the description of a new species; two known species are reported for the fIrst time from India; some important synonymies have been suggested; Neotheleterum Gibson and Bray, 1979 is accepted; and some known species are reported with interesting remarks. The classification of Hemiuroidca as given by Gibson and Bray (1979) has been adopted here.

MA TERIALS AND METHODS
The specimens were recovered alive from hosts and were studied in that condition rust. Later on, they were allowed to relaxe in normal saline. When completely relaxed, they were killed and fixed in AF A keeping them between glass slide and cover glass and applying a bit more pressure with the tip of a needle. After complete fixation, they were removed in AFA, washed in 70% alcohol to remove excess of AFA, and then stored in small glass vials in 70% alcohol. In the laboratory, these specimens were processed for staining, dehydration and final mounting. They were overstained with alcoholic Borax carmine. The overstained matcrial was then differentiated in acid alcohol to the desired shade of staining. They were then treated with ammonia alcohol to neutralise the traces of acid in the material. The specimens were then dehydrated with various grades of alcohol. After giving a slight touch in xylol, these specimens were submerged in a small pool of clove oil in cavity blocks for attaining transparency. They were then mounted on clean slides in Canada balsam and dried.
The specimens will be depositcd with the National Collections of the Zollogical Survey of India, Calcutta for registration. All measurements are in micrometres (Jlm) except otherwise stated. The diagrams have been made with the aid of a camera lucida.
No. of Specimens : 1, on slide; collected on 24. 1.1975. Discussion: Srivastava (1935 described this species from Allahabad (River Ganges) in the intestine of Clupea ilisha, a clupeid migratory fish. The present single specimen collected at Machhilipatnam (Bay of Bengal) from the stomach of an unidentified clupeid fish broadly agrees with Srivastava's description.
Discussion : Three species in the genus have been reported from India. They are A. breviformis Srivastava, 1939, A. bengalensis Srivastava, 1939(synonym of A. intermedius Manter, 1934 and A. orientalis Ahmad, 1981. Aponurus drepani n. sp. resembles A. breviformis in sucker width ratio and egg size, but differs from it in having a more anterior genital pore, a pars prostation curved and longer than the seminal vesicle and in the position and size of the seminal receptacle. From A. orientalis it differs in the prebifurcal position of the genital pore, in having a pars prostatica curved and longer than the seminal vesicle and in having mush smaller eggs (in A. orientalis the eggs are 30-35 x 17-19 Jlm). From all other species of the genus, the present form differs in one or more of the following characters: the sucker width ratio,·egg size, the position of the genital pore, the posterior extent of the uterus and the disposition of the testes.
Discussion : Manter .(1969) described this species from New Caledonia from Siganus sp., from Green Island and Moreton .Bay, Queensland, Australia from Siganus rivulatus, from Green Island, Qneesland, Australia from Abudefduf palmeri, and Green Island, Queensland, Australia from Micracanthus strigosus. As the species is reported for the frrst time from India, its full details have been provided above.
No. of Specimens : 3+5+10+3+3 respectively, tota124 on 7 slides Specimens deposited: Z. S. I. Reg. Nos. W 7598/1 to W 7604/1. Discussion : Yamaguti (1940) proposed the genus Trifoliovarium for specimens from the fish Acanthocepola limbata from Maisaki, Japan with T acanthocepolae as the type species. Its ovary was described as possessing three lobes, but later on the same author (1971) emended this in a foot note (p. 322) stating that the ovary actually has four lobes. Gibson and Bray (1979) confirmed this after examining the type material of T acanthocepolae. Bilqees (1973) described a second species T triacanthi, from the fish Triacanthus brevirostris from Karachi (Abrabian Sea), differentiating it from the type species mainly by the presence of a relatively larger ventral sucker (Sucker width mtio 1: 1.4), a shorter posterior extent of the seminal vesicle with respect to the ventral sucker, and a smaller egg size (32-39 x 17-20 J.1m) in the Japanese species and 20-25 x 11-13) J.1I11 in the Pakistani species). Gupta, V. and Ahmad (1976), obviously unaware of Bilqees' work, described T triacanthusi from the fish Triacanthus strigilifer from Pori (Bay of Bengal). The description of this species fully agrees with that of T triacanthi. Therefore, T triacanthusi is conspecific with T triacanthi. This synonymy has also been indicated by Gibson and Bray (1979). Gupta, A. N. and Sharma (1975) proposed that Cladolecithotrema Ichihara, 1970 is synonymous with Trifoliovarium Yamaguti, 1940, but Gibson and Bray (1979) do not agree with this synonymy and showed that the two genera are distinct The authr concurs with them.
All the above 9 specimens are mounted in lateral, ventrolateral or dorsolateral views due to the peduncle on which the ventral sucker is borne. This protuberance is retractile.
In partially or fully retraced condition, the edges of the ventral sucker are likely to be covered by portions of body parenchyma of the protuberance itself. This situation may be encountered in various conditions depending upon-the state of contraction of the peduncle. This explains the situation probably encountered by Yamaguti (1965) in Lobatovitelliovarium fusiforme and Srivastava and Sahai (1978) in Cryptodiscus indicus, and as such there is no special musculature associated with the ventral sucker; As regards the male duct, the ovoid seminal vesicle is continued as a short aglandular duct which then widens as it proceeds almost dorsoventrally. This wide pars prostatica is surrounded by a dense, compact layer of prostate' cells and opens into a large sucker-like genital atrium. It is very difficult to make out if an ejaculatory duct is differentiated at all. This difficulty arises due to the thick and compact layer of prostate cells. Most probably, neither is differentiated. A short metraterm is formed and opens into the sucker -like genital atrium separately, and thus no hennaphroditic duct is formed. This contradicts the opinion given by Gibson and Bray (1979) in parentheses on page 107. It is believed that materials of Manter (1961), Yamaguti (1965), Gupta A. N. andSharma (1972) and Srivastava and Sahai (1978) are similar to those reported here. Srivastava and Sahai (1978: p. 50), while. giving the generic diagnosis of Cryptodiscus, state that they are 'intestinal parasites of marne teleosts', whereas they have reported their genus from a cartilaginous fish Dasyatis urnak. While such cases are not uncommon, it seems to be an accidental host or the latter might have fed upon the teleost fish which serves as the normal host for this fluke under consideration. Furthermore, they (1978: p. 48, 50) have described Cryptodiscus indicus as the type species of thier genus Cryptodiscus, whereas in the abstract (p. 39) they have mentioned Cryptodiscus madrasensis as the type species.
Discussion : Full details of this species were reported by Hafeezullah and Dutta (1980) on the basis of specimens from Chiria Tapu, Andamans (vide Z. S. I. Reg. Nos. W 7272/1 to W 7274/1) in the genus Hysterolecithoides Yamaguti, 1934. Gibson andBray (1979) have given good reasons for considering it as the type species of a new genus Neotheletrum. The author is convinced by their reasoning and therefore concurs with them.
The details of the above specimens agree fairly well with the description of the species as given by Machida (1980) from the same species of host from Ki Peninsula, Japan. However, as this is the fIrst record from India and the second from the world, full details are provided here.
Testes two, 358-500 long, 508-875 wide, transversely oval, tandem, posterior to acetabulum, inmiddle-third of body, separated by coils of uterus. Seminal vesicle long, narrow, tubular and coild anterior to testes. Pars prostatica long, narrow and curved posterior to ventral suker, surrounded by well -developed prostatic gland cells. Aglandular part of pars prostatic straight entering into sinus-sac in preacetabular region. Sinus-sac oval, muscular, containing muscular and coiled hermaphroditic duct, opening just behind caecal bifurcation into shallow genital atrium. Genital cone or sinus organ absent.
Ovary 508-1016 long, 192-383 wide, kidney-shaped or transversely elongate, situated in anterior part of posterior-third of body, post-testicular. Blind seminal vesicle present, antero-dorsal to and shorter than ovary. Vitellariam compact, two separate masses, transversely elongate, parallel to each other, postovarian. Mehlis' gland well developed, situated between ovary and anterior viteline mass. Post-vitelline region of body filled with coils of uterus, anteriorly forming metraterm entering sinus-sac along with aglandular pars prostatica to form hermaphroditic duct, whose anterior part is funnelshaped. Eggs 30-43 x 10-14 J.1In.
Discussion : Although the present specimens agree well with the description ~f Neopisthadena habei Machida, 1980, they do not agree to have papillae along the border of the oval opening. Similarly, the semicircular fold behind acetabulum in Machida's species is not present in the present material. As such, these two structures do not seem to form important parts of generic'diagnosis of Neopisthadens Machida, 1980. and Bunocotylidae Dollfus, 1950 in the superfamily Hemiuroidea Looss, 1899. Of these species, Aponurus dr.epani is new to science. Hysterolecithoides sigani Manter, 1969 and Neopisthadena habei Machida, 1980 are reported for the first time from India. Lecithaster indicus Srivastava, 1935, Trifoliovarium triacanthi Bilqees, 1973, Prolecitha obesa Manter, 1961 and NeotheleterumJrontilatum (Manter, 1969) are reported and commented' upon. Cryptodiscus Srivastava and Sahai, 1978 and Trifoliovarium triacanthusi Gupta, V and Ahmad, 1976 are considered new synonyms of Prolecitha Manter, 1961 and