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Surface ultrastructure of the adult and juvenile stages of the trematode Astiotrema impletum (Looss, 1899) Looss 1900 (incertae sedis) from the Nile puffer, Tetraodon lineatus Linnaeus, 1758

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08 juin 2021
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Fig. 1

Scanning electron micrographs (SEM) of adult Astiotrema impletum.A – Ventral view of whole body. B – Distribution of sensory papillae around oral sucker and mouth. C – Different shapes of sensory papillae on oral sucker. D – Randomly distributed papillae on naked tegument surrounding ventral sucker. E – Solitary knob-like ciliated papillae and grouped papillae in vicinity of ventral sucker. Abbreviations: ccp – conical ciliated papillae; cnp – conical non-ciliated papillae; ecp – embedded ciliated papillae; enp – embedded non-ciliated papillae; eo – excretory opening; go – genital opening; kcp – knob-like ciliated papillae; mo – mouth opening; os – oral sucker; vs – ventral sucker; arrowheads indicate sensory papillae.
Scanning electron micrographs (SEM) of adult Astiotrema impletum.A – Ventral view of whole body. B – Distribution of sensory papillae around oral sucker and mouth. C – Different shapes of sensory papillae on oral sucker. D – Randomly distributed papillae on naked tegument surrounding ventral sucker. E – Solitary knob-like ciliated papillae and grouped papillae in vicinity of ventral sucker. Abbreviations: ccp – conical ciliated papillae; cnp – conical non-ciliated papillae; ecp – embedded ciliated papillae; enp – embedded non-ciliated papillae; eo – excretory opening; go – genital opening; kcp – knob-like ciliated papillae; mo – mouth opening; os – oral sucker; vs – ventral sucker; arrowheads indicate sensory papillae.

Fig. 2

SEM of ventral surface of adult A. impletum.A – Naked area around and anterior ventral sucker. B – Tegumental spines of anterior ventro -lateral surface of body, just posterior to oral sucker. C – Tegumental spines on the ventro- lateral part, at level of ventral sucker, are long and pointed. D – Tegumental spines on the ventro -lateral part, at level of third quarter of body are smaller, fewer and more corrugated or with parallel surface ridges. E – Cytoplasmic processes on tegument of posterior end have a vermiculate, brain-like velvety appearance. F – Excretory opening is slightly shifted towards ventral surface. Abbreviations: eo – excretory opening; na – naked area in front of ventral sucker; vs – ventral sucker.
SEM of ventral surface of adult A. impletum.A – Naked area around and anterior ventral sucker. B – Tegumental spines of anterior ventro -lateral surface of body, just posterior to oral sucker. C – Tegumental spines on the ventro- lateral part, at level of ventral sucker, are long and pointed. D – Tegumental spines on the ventro -lateral part, at level of third quarter of body are smaller, fewer and more corrugated or with parallel surface ridges. E – Cytoplasmic processes on tegument of posterior end have a vermiculate, brain-like velvety appearance. F – Excretory opening is slightly shifted towards ventral surface. Abbreviations: eo – excretory opening; na – naked area in front of ventral sucker; vs – ventral sucker.

Fig. 3

SEM of juvenile Astiotrema impletum.A – Ventral view of whole body. B – Distribution of sensory papillae on and around oral sucker. C – Genital opening. D - Ventral sucker surrounded by a number of randomly distributed sensory papillae. E – Tegumental spines on anterior ventro -lateral side of body, just posterior to oral sucker. Note pocket-like tegument covering bases of spines. F – Tegumental spines on ventro -lateral surface of body at level of ventral sucker. The spines are small in size and with parallel surface ridges or corrugated. G – Cytoplasmic processes of tegument display a fine granulated or small cobblestone-like appearance on the posterior end of body. Abbreviations: go – genital opening; mo – mouth opening; os – oral sucker; vs – ventral sucker; arrowheads indicate sensory papillae.
SEM of juvenile Astiotrema impletum.A – Ventral view of whole body. B – Distribution of sensory papillae on and around oral sucker. C – Genital opening. D - Ventral sucker surrounded by a number of randomly distributed sensory papillae. E – Tegumental spines on anterior ventro -lateral side of body, just posterior to oral sucker. Note pocket-like tegument covering bases of spines. F – Tegumental spines on ventro -lateral surface of body at level of ventral sucker. The spines are small in size and with parallel surface ridges or corrugated. G – Cytoplasmic processes of tegument display a fine granulated or small cobblestone-like appearance on the posterior end of body. Abbreviations: go – genital opening; mo – mouth opening; os – oral sucker; vs – ventral sucker; arrowheads indicate sensory papillae.

Statistical parameters of dimensions and indices of the adult and juvenile Astiotrema impletum (Looss, 1899) Looss 1900 from the Nile puffer fish Tetraodon lineatus Linnaeus, 1758 in Egypt_ (Metric characters are in mm_)

Morphological Adult Juvenile
parameters Mean SD n SE Mean SD n SE
Total body length 2 0.3860 8 0.1367 1.19 0.1400 8 0.0574
Maximum width 0.5 0.1455 8 0.0515 0.46 0.0770 8 0.0315
Oral sucker length 0.27 0.0489 8 0.0122 0.24 0.0200 8 0.0083
Oral sucker width 0.34 0.1132 8 0.0128 0.27 0.0340 8 0.0173
Ventral sucker length 0.16 0.0351 8 0.0132 0.15 0.0270 7 0.0097
Ventral sucker width 0.18 0.0348 8 0.0131 0.15 0.0320 7 0.0114
Ant. testis length 0.27 0.0443 8 0.0156 0.13 0.0450 6 0.0183
Ant. testis width 0.23 0.0512 8 0.0181 0.12 0.0400 6 0.0166
Post. testis length 0.34 0.0504 8 0.0178 0.15 0.0640 6 0.0264
Post. testis width 0.27 0.0296 8 0.0104 0.13 0.0650 6 0.0265
Cirrus sac length 0.32 0.0977 7 0.0369 0.12 0.0400 3 0.0233
Ovary length 0.16 0.0349 8 0.0123 - - - -
Ovary width 0.18 0.0370 8 0.0130 - - - -
Egg length 0.040 0.0055 8 0.0021 - - - -
Egg width 0.0124 0.0028 8 0.0012 - - - -

Significant differences between Astiotrema impletum described in this study and the trematode recorded by Hamada (2002)_

Feature Present Study Hamada (2002)
Host Fahaka, Nile Pufferfish Tetraodon lineatus Tetraodontiformes Tetradontidae White Tilapia Orechromis niloticus Perciformes Cichlidae
Oral sucker much larger than ventral sucker. yes no
Ventral sucker found in the anterior quarter of the worm. no yes
Ventral sucker surrounded by numerous spines no yes
Ventral sucker with sensory papillae and tend to be in four clusters. yes No, papillae absent.
Tegumental area between the oral and ventral suckers. Square-shaped and has relatively small spines directed posterolaterally and arranged in parallel rows. Rectangular and naked.