The body of 1-day-old fluke was flat and leaf-shape pointed posteriorly. The oral sucker, circular and wide open, was subterminal at anterior end of the body. The acetabulum was median at anterior two-fifths of the body (Fig. 1A). The lip of oral sucker appeared velvety and wrinkled cytoplasmic processes, and was devoid of tegumental spines. Unciliated sensory papillae swelled with wrinkled surface (Type II papillae), 14 in number, located equidistantly on the lip of oral sucker. Sensory papillae bulbous with the tegument wrinkled at base and smooth at apex and with a short cilium (Type I papillae) ornamented densely around the oral sucker and sparsely over the body surface. The Type I papillae were found on inner surface of the oral sucker. Anterior apex was devoid of tegumental spines and appeared cytoplasmic processes corrugated. On anterior outskirts of the oral sucker Type I papillae intercalated Type II papillae, looks supplementing the later ones (Fig. 1B). Surface of the acetabulum was covered with worm-like cytoplasmic processes arranged radially. The acetabulum was encircled with two circles, inner and outer, of Type II papillae. Of the outer circle, six Type II papillae located equidistantly along outer margin of the acetabulum. Of inner circle, 5-6 Type II papillae sat on anterior two-thirds of the lip (Fig. 1C). Type I papillae, 3-5 in number, were found on lateral rim of the acetabulum. Genital pore opened distantly postero-median to the acetabulum, revealing general feature of the ventral surface. On dorsal surface, Type I papillae aligned bilaterally symmetrical (Fig. 1D) and became more distant posteriorly.

The body surface, from anterior to posterior ends, was beset with tegumental spines, spade-like anteriorly and peg-like posteriorly (Figs. 1E, 1F). The tegumental spines were deployed concentric to the oral sucker on anterior half of the body. Posterior end of the body notched in V-shape with an excretory pore. Cytoplasmic processes was cobblestone-like on anterior half of the body and became slightly finer posteriorly (Figs. 1E, 1F).

In 3-day-old flukes, cytoplasmic processes on anterior apex devoid of tegumental spine were velvety. On the body surface, the cytoplasmic processes differentiated into transient shapes from cobblestones to velvet between tegumental spines.

In 5-day-old flukes, the body got thicker and paremchymatous, and bulged out like a hip in posterior half. From half of the observed flukes, sperms ejaculated from the genital pore found on the ventral surface. Type I papillae concentrated on the anterior apex while very rare all over the body surface. On margin of the oral sucker, two grouped form of 2-3 Type I papillae located bilaterally symmetrically. Type II papillae got prominent contour on the lip of oral sucker (Fig. 2A). The acetabulum became thinner and less stout compared to the oral sucker. One grouped form of two Type I papillae was found anterior margin of the acetabulum. Genital opening revealed protruded as a mound devoid of tegumental spines, posterior to the acetabulum (Fig. 2B). Excretory pore, extruded buttock-like, with spine-free Y-shape area on posterior end of ventral surface. Around the excretory pore sensory papillae were not found. Tegumental spines on posterior half of the body retained its peg-like shape and density. Cytoplasmic processes were differentiated into velvety ones on the entire body surface.

In 7-day-old flukes, the surface structure retained generally as in the 5-day-old flukes. Anterior body armored heavily with tegumental spines and reduced loosely to the end of body. Tegumental spines got bigger and stouter than those of juvenile flukes. The spines revealed spade-shape with broader base on anterior body surface (Fig. 2C) and narrowed posteriorly to peg-like ones with a pointed-tip (Fig. 2D). The tegumental spines on the middle part of the ventrolateral surface of the body were wider than those on the dorsal surface. Cytoplasmic processes developed into fine velvety processes over the body surface (Figs. 2C, 2D). The swollen dome of Type II papillae, on the oral sucker and acetabulum, appeared strawberry-like covered with fine velvety cytoplasmic processes (Fig. 2C). Type I papillae elevated with spiraling tegument or with concentric circles; looked like a fried egg at top view (Figs. 2C, 2D).

In 14-day-old flukes, maximum width of the body was observed at posterior one-third level, just after the acetabulum. Whole surface featured similar to that of 7-day-old flukes. Posterior end of the body protruded out like a turret, centered with an excretory pore. Around the excretory pore was free from tegumental spines. At central part of the lip of oral sucker was spaced devoid of sensory papillae and tegumental spine, where cytoplasmic processes were wrinkled longitudinally. On anterior margin, transient to the apex, of the oral sucker, 3-4 Type I papillae intercalated the Type II papillae. On anterior surface, ventral and dorsal, of the body, some Type I papillae emerged very close, so seemed to form a grouped form.

In 28-day-old flukes, whole surface retained ultrastructure similar to that of 14-day-old flukes. The tegumental spines on posterior half of the body were decreased in their size and density. The acetabulum was wrinkled radially and equal size to the oral sucker. One Type II papilla on anterior center of outer circle flanked a Type I papilla. On the body surface, Type I papillae were most prominent observed yet, and aligned symmetrical bilaterally (Fig. 2E). Of the type I papillae, smooth dome based on 2-3 encircling rings supported with velvety cytoplasmic processes of adjacent surface. On the posteriormost surface, the tegumental spines reduced to minute in size and sparse in density. The cytoplasmic processes were finer on posterior surface by 1/2-1/3 than those on anterior surface of the body (Fig. 2F).