OF THE INDIAN SPECIES OF TREMATODE GENUS PHILOPHTHALMUS LOOSS , 1899 PARASITES IN THE CONJUNCTIVA OF BIRD ' S EYE

INTRODUCTION Aquatic, terrestrial and arboreal birds are found to harbour in their conjunctival sac, various species of trematodes, belonging to the genus Philophthalmus Looss, 1899. More than thirty species have been described so far from various zoo-geographical region of the world. As many as fifteen species have been described or recorded so far from dove, pigeon, duck, fowl, vulture, eagle and kingfisher from India. We obtained six specimens belonging to above mentioned genus from conjunctiva of three Black Drongo (Dicrurus adsimilis), constituting a new host record and showing some interesting variation of characters of taxonomic importance. A review of the species of the genus Philophthalmus described from India forms the subject matter of present communication.


INTRODUCTION
Aquatic, terrestrial and arboreal birds are found to harbour in their conjunctival sac, various species of trematodes, belonging to the genus Philophthalmus Looss, 1899.More than thirty species have been described so far from various zoo-geographical region of the world.As many as fifteen species have been described or recorded so far from dove, pigeon, duck, fowl, vulture, eagle and kingfisher from India.
We obtained six specimens belonging to above mentioned genus from conjunctiva of three Black Drongo (Dicrurus adsimilis), constituting a new host record and showing some interesting variation of characters of taxonomic importance.A review of the species of the genus Philophthalmus described from India forms the subject matter of present communication.

MATERIAL AND METHOD
Six specimens were recovered from eye of Black Drongo (Dicrurus adsimilis) shot at Sikkim.These were stained in Borax carmine.Drawings were made with camera lucida.All the measurements used in this paper are in millimeters.Testes tandem in last quarter of body, large, unequal, slightly lobate with smooth margins.Anterior testis larger or smaller than posterior one.Anterior one 0.475 -0.675 x 0.7 -0.925 and posterior one 0.425 -0.625 x 0.725 -0.925.Vasa efferentia distinct.Cirrus sac long, club-shaped, 1.325 -1.5 in length, placed on the right side of the ventral sucker and extending posteriorly from the level of the intestinal bifurcation, may extend upto or behind the ventral sucker.Oval vesicula seminalis occupies the broad basal part of the cirrus sac, leads through a short narrow tubular part into the ductus ejaculatorious.
Long ejaculatory duct, traverses the whole narrow part of the cirrus sac and ultimately terminates into a short eversible cirrus.Genital pore sub-median, on the right side of the caecal arch.
Globular ovary, situated in front of the anterior testis, median or sinistral in position, 0.2 -0.25 x 0.22 -0.275, partly covered on the ventral side by uterine coils.Tubular extra and intra caecal vitellaria mostly lateral, extends from the level of the posterior end of currus sac upto the level of ovary where they tum inwards, crossing the caeca dorsally, intruding into intercaecal field.In some places the vitellaria have a beaded appearence due to agglomeration of yolk cells.Narrow transverse vitelline ducts appear as prolongations of tubular vitellaria and they meet behind the ovary to form a vitelline reservoir, Laurer's canal is present.The complex lies slightly to the left of the median line, close to the postero lateral boarder of ovary and is partly masked by the initial coils of uterus.Receptaculum seminis uterinum present.Utrine coils occupy almost the whole space between anterior testis and cirrus sac, extending laterally into extracaecal field and posteriorly at the sides of testes.Muscular metraterm, wide, near the posterior end of cirrus sac, but distally it narrows and runs straight along cirrus sac to open outside by genital pore.Mature eggs are rather elongated, thin walled, broadened at one end; measures 0.074 x 0.033.These eggs contain fully developed miracidia which have two closely apposed cup-shaped eyes.Some of the miracidia are seen lying free in uterus which are possibly released from the eggs during flattening and fixing.Each micacidium is found to contain a well developed sporocyst, often packed with germ cells and germ balls.
Excretory pore is terminal.Excretory bladder appears 'T' -shaped with short transverse limbs from the ends of which arises lateral cornua.

DISCUSSION
Looss, 1899 established the genus Philophthalmus with the species P palpebrarum (Fig. 3) collected from Corvus cornix and Milvus parasiticus from Egypt.Subsequently more than thirty species were added to this genus from Europe, Asia, Africa and America from various aquatic and terrestrial bird's eye.
Fifteen species under the genera Philophthalmus have been described so far from India.List of the species along with their host and feeding habit is given in Table 1, to indicate the wide range of the ecological habitats of the hosts in which the species of this genus have established.Skrjabin, 1947 proposed two subgenera, Phi/ophthalmus, for the species with distinctly few isolated large vitelline follicles and Tubolecithalmus for those species, not having widely separated follicles but singular tubular or closely placed innumerable follicles.He included P. nocturnus Looss, 1907; P. gralli Mathis et Leger, 1910; P. nyrocae Yamaguti, 1934 andP. muraschikinzewi Tretikowa, 1946 in the later subgenus.This, apparently sound basis, proposed by Skrjabin for splitting the species in two subgenera, seems to very much well conceived.All the Indian species so far described have apparently tubular or closely placed small vitelline follicles.Subsequently Karyakarte, 1967 found Philophthamids, possessing both the follicular and tubular vitellaria and proposed a third subgenus Mixophthalmus for his species P. chrysommae.
Ching, 1960 studied the developmental stages of P. gralli Mathis et Leger, 1910 in various hosts such as chickens, ducks, rats and rabbits in Hawaii and noted morphological variations in respect of many characters of taxonomic importance.He suggested closer similarity between P. in die us laiswal and Singh, 1954 (Fig. 7); p. oeculare Wu, 1938 and P. mirzai laiswal and Singh, 1954 (Fig. 8) with P. nocturnus Looss, 1907.He stated that for specific identification in the genus Philophthalmus series of specimens have to be studied since great variations of characters are very common feature.Prokash and Pandey, 1968 after detail observation considered all the Indian species such as P. indicus laiswal and Singh, 1954; P. aquilla laiswal, 1955; P. lucknowensis Baugh, 1962 (Fig. 10) and P. halcyon; Baugh, 1963 (Fig. 9) as synonym of P. mirzai.Even about the validity of P. mirzai, they opined that, "A truely valid status, distinct from P. nocturnus, would need a detailed scrutiny of the specimens described under the genus."Subsequently many species were added to this genus.Srivastava and Pan de, 1971;Varghese and Sundaram, 1975;and Mehra, 1980 on the otherhand considered P. mirzai as synonym of P. grail; Mathis et Leger, 1910. Mehra, 1980 further listed P. (Mixophthalmus) chrysommae Karyakarte, 1967 (Fig. 11) as synonym of P. gralli.Srivastava, 1982 also considered P. grail; as the only valid species and considered P. (P.) problematicus Tubangui, 1932 of Karyakarte, 1967; P. (P.) columbae Karyakarte, 1968 and P. (P.) acridotheres Karyakarte, 1969 as synonym of P. gralli.Murty, 1966Murty, , 1967 initiated life history studies on some specimens of this genus from India.Swarnakumari and Madhavi, 1992 studied the life hostory stages of Philophthalmus cercariae, obntained from naturally infected snail Thiara tuberculata at Vishakhapatnam, AndhraPradesh.
They infected Leghorn Chickens with the cercariae and recovered 721 flukes from the eyes of 50 chickens.They observed after detail study and analysing allometric growth that "P.nocturnus stands close to P. gralli both in growth pattern and in the details of the development of adult form metacercariae.The similarities are also reflected in the morpholoogy of the adults of the two species.Hence the detailed study of the biology and the host-parasite relationship of the two species may disclose P. grail; to be synonym with P. nocturnus (Fig. 2).
It may be noted here that most of the Indian species have been described on the basis of few specimens only.Evaluations of various characters relied upon for differentiating species, reveals that the following characters are to be taken into account for correct diagnosis.
Ratio of suckers, length and breadth, nature of vitellaria whether tubular or follicular; extension of vitellaria is a variable character as it is found to vary as per the stage of maturity.Extension of cirrus is also an important character.In some species cirrus sac extends further below to acetabulum or not crossing even half to the length of the acetablum.Uterine coils appear to be variable to a great extent, possibly depending upon the stage of maturity.Shape and the size of the vesicula seminalis, recepticulum seminis uterinum, are also much variable.Position of the genital pore may be a dependable character, provided observed in large number of specimens.
Thus on the basis of our study along with observations of Murthy, 1966Murthy, , 1967;;Prokash and Pandey, 1968;Swarnakumari and Madhavi, 1992, we consider P. gralli as synonym of P. no cturn us.
Distinguishing characters of the species P. anatinus Sugimoto, 1928, P. (L) alii Karyakarte, 1971 (Fig. 12) and P. peter; Sreekumaran and Peter 1973 subsequently recorded from India are well within the wide range of variations in P. nocturnus.As such they are also considered as synonymous with P. nocturnus.
Thus in our opinion P. nocturnus stands as the specific trematode parasites of eye, found in different species of birds throughout Indian subcontinent.

SUMMARY
Taxonomic status of all the Indian species under the genera Philophthalmus described and recorded so far from India have been revaluated.Critical studies on the extent of variation in respect of genital pore, nature & distribution of vitellaria, genital complex etc., have been made.It has been inferred that Philophthalmus nocturnus Looss, 1907 is the only valid species under the genus Philophthalmus in Indian subcontinent.

Table 1 .
Host Prasite list and feeding behaviour of hosts of Ph ilophthalmus sp.described from India.