Table of Contents
Last Updated: October 19, 2025
Estimated reading time: ~6 minutes
This article provides a detailed summary of the 2011 doctoral thesis by Barrister Kumar Gupta on the taxonomy of parasitic worms infecting Indian freshwater fish. We will explore the key findings, methodologies, and the new species of metacercariae and adult trematodes of fishes identified in this comprehensive study.
- Study Scope: The research provides a taxonomic description of 22 metacercariae and 16 adult trematodes.
- New Species: Numerous new species (n. sp.) were identified, including Neascus bhopalensis and Allocreadium itwarensis.
- Methodology: Fish were collected from 2007-2011 across various Indian districts, and parasites were studied using standard staining and mounting techniques.
- Two-Part Focus: The work is divided into Part I (Metacercariae) and Part II (Adult Trematodes).
Metacercariae and Adult Trematodes of Fishes: A Taxonomic Summary
Reviewed and edited by the Professor of Zoology editorial team. Except for direct thesis quotes, all content is original work prepared for educational purposes.
Introduction: The Scope and Significance of Helminth Studies
This section outlines the research context, objectives, and the importance of studying trematode parasites in freshwater fish.
Fish provides nutritious food and are important source of fresh animal proteins. However, almost all of them carry infections of adult trematodes or metacercariae. They infect all the body parts and cause diseases thus reducing their food value.
The thesis builds upon a long history of helminth studies in India, focusing on trematodes, which have received significant scientific attention.The primary goal of Gupta’s work was to investigate and provide a detailed taxonomic description of these parasites in freshwater fish, as they pose a significant threat to the aquaculture industry and can even be transferred to humans. The study specifically focused on freshwater fish, as a colleague was already researching marine species. This research, conducted under the supervision of Prof. Nirupama Agrawal, systematically catalogs the parasites found.
Student Note: When studying parasitology, note the distinction between metacercariae (the larval stage, Part I of the thesis) and adult trematodes (the mature stage, Part II). This distinction is crucial for understanding parasite life cycles and pathology.
For more on parasitic adaptations, see our guide on Platyhelminthes parasitic adaptations.
Materials and Methods: Collecting and Identifying Parasites
This section details the practical methods used to collect fish, and then extract, preserve, and identify the trematode specimens.
Fish for the present work were collected from the water bodies of districts Aazamgarh, Allahabad, Ballia… and fish markets during 2007-2011. They were identified using fish base (Froese R., Pauly D. 2007).
The collection process was extensive, covering numerous districts in India.To find the parasites, researchers examined various organs, including visceral organs, body muscles, gills, liver, and bladders, under a dissecting microscope.Once collected, the worms were washed in normal saline and studied alive. For permanent slides, they were fixed in 70% alcohol under slight pressure, stained with Aceto-alum Carmine, dehydrated, cleared in Clove oil, and mounted in Canada Balsam.All measurements were taken with an oculometer, and drawings were made using a camera lucida attached to a microscope.
Exam Tip: The staining and mounting process (fixation, staining, dehydration, clearing, mounting) is a standard procedure in parasitology labs. You must know the purpose of each step, especially the use of Carmine stain for whole mounts and Canada Balsam as a permanent mounting medium.
Understanding these techniques is vital for practical exams. Learn more about histological techniques for parasite identification.
Key Findings Part I: New Species of Metacercariae
Part I of the thesis describes 22 metacercariae, including the identification of several new species (n. sp.) primarily from the genera Neascus and Tetracotyle.
Part -I deals with the description of 22 metacercariae. 1. Neascus bhopalensis n. sp. was collected from the liver of Xenentodon cancila (Ham), bought from Itwara fish market, Bhopal.
This section of the thesis is a classic example of taxonomic work. For each new species, the author provides a detailed morphological description, host, location (organ), and locality (place of collection). For instance, Neascus bhopalensis is characterized by specific body ratios, the absence of a pharynx, and the shape of its holdfast organ. Other new species, like Tetra cotyle allahabadensis from the gut of Misassembles pun Calus, are differentiated by features like the absence of a pre-pharynx and a bowl-shaped holdfast organ. The thesis also records the first-ever finding of Metacercaria of Ommatobrephus Mehra, 1928 in India.
Student Note: In taxonomy, a “new species” (n. sp.) is declared by comparing its morphology to all known species in the genus. The “Discussion” section for each species (e.g., [cite: 184-192, 273-286]) is where the author justifies this claim by highlighting differentiating characteristics.
Key Findings Part II: Adult Trematodes of Fishes
Part II of the thesis details the taxonomy of 16 adult trematodes, again identifying several new species from different genera like Bucephalus and Allocreadium.
Part-II deals with the description of 16 adult trematodes. I. Bucephalus bhagalpurensis n. sp. was collected from gut of Mystus tengra (Ham.) at River Saryu Bhagalpur….
Similar to the first part, this section provides detailed taxonomic descriptions for adult-stage parasites. The new species Bucephalus bhagalpurensis is characterized by the position of its pharynx, a short cirrus sac, and the extension of its vitellaria.Another new species, Allocreadium badatalabensis, collected from Heteropneustes fossilis, is distinguished by its bipartite vesicula seminalis and the specific position of its genital pore. This part of the thesis not only describes new species but also provides new locality records for known parasites like Bucephalopsis karvei [cite_start]and Phyllodistomum vachius.
Student Note: The cirrus sac and vesicula seminalis are components of the male reproductive system in trematodes. Their shape, size, and position relative to other organs (like the ventral sucker) are critical diagnostic features used in species-level identification.
Learn more about the general body plan of these parasites in our overview of trematode anatomy.
Summary of Selected New Species Described
The following table summarizes the key details for a selection of the new species (n. sp.) identified in Gupta’s 2011 thesis.
Table 1: Selection of new trematode species from Gupta (2011) [cite: 98-166, 1622-1690].
| New Species Name | Part | Host Fish | Location in Host | Collection Locality |
|---|---|---|---|---|
| Neascus bhopalensis n. sp. | I: Metacercaria | Xenentodon cancila | Liver | Bhopal |
| Neascus dohrighatensis n. sp. | I: Metacercaria | Wallago attu | Liver | Dohrighath |
| Tetracotyle bhopalensis n. sp. | I: Metacercaria | Channa punctatus | Gut | Bhopal |
| Tetracotyle allahabadensis n. sp. | I: Metacercaria | Mastacembelus puncalus | Gut | Allahabad |
| Bucephalus bhagalpurensis n. sp. | II: Adult | Mystus tengra | Gut | Bhagalpur |
| Allocreadium itwarensis n. sp. | II: Adult | Mastacembelus puncalus | Gut | Bhopal |
| Allocreadium badatalabensis n. sp. | II: Adult | Heteropneustes fossilis | Gut | Bhopal |
| Haplorchoides varanasiensis n. sp. | II: Adult | Eutropicthes vacha | Gut | Varanasi |
Key Takeaways
- Taxonomic Contribution: This thesis is a significant work of descriptive taxonomy, formally describing 22 larval and 16 adult trematode species.
- Host-Parasite Records: The study established new host and locality records for several known parasites, such as Bucephalopsis karvei in Kanpur and Banaras.
- Pathological Importance: The work underscores the high prevalence of parasitic infections in commercially important freshwater fish, which can reduce their food value and cause economic loss.
- First Records: The thesis documents the first record of the metacercaria of Ommatobrephus and Genarchopsis goppo from India.
Review Quiz: Test Your Knowledge
Multiple Choice Questions
- According to the thesis, which two genera were the primary focus for the new species of metacercariae described?
- (a) Bucephalus and Allocreadium(b) Neascus and Tetracotyle(c) Ommatobrephus and Genarchopsis(d) Phyllodistomum and Opisthorchis
- What standard histological procedure was used to prepare the trematodes for microscopic study?
- (a) Frozen sectioning and H&E staining(b) Gram staining and oil immersion(c) Fixation in alcohol, staining with Aceto-alum Carmine, and mounting in Canada Balsam(d) DNA extraction and PCR amplification
- The new adult species Allocreadium badatalabensis n. sp. was characterized by what specific morphological feature?
- (a) Absence of a pharynx(b) A bowl-shaped holdfast organ(c) Bipartite vesicula seminalis(d) A circlet of 16-24 spines
Frequently Asked Questions (FAQs)
Who was the author of this thesis?
The thesis was submitted by Barrister Kumar Gupta for the degree of Doctor of Philosophy in Zoology at the University of Lucknow.
What is a metacercaria?
A metacercaria is the encysted larval stage of a digenetic trematode. is the stage that typically infects the second intermediate host (like a fish) and waits to be eaten by the final host.
Where were the fish collected for this study?
Fish were collected from various fish markets and water bodies across India, including districts like Bhopal, Lucknow, Varanasi, Allahabad, and Gorakhpur, between 2007 and 2011.
What is a “holdfast organ”?
A holdfast organ (or tribocytic organ) is a specialized adhesive structure, characteristic of strigeid trematodes (like Neascus and Tetracotyle), used to attach firmly to the host’s intestinal lining.
Why is this research important for fisheries?
Heavy infections of these parasites can cause disease and mortality in fish, reducing their food value and leading to significant losses for the fish industry.
Lab & Practical Note
When performing a parasite survey, as described in this thesis, thoroughness is key. Do not just examine the gut. Parasites, especially larval stages like metacercariae, can be found in almost any tissue.The methods list examining “body muscles, scales, fins, eye, nasal organ, gills, gall bladder, liver, air bladder, and urinary bladder”. Always use a dissecting microscope and tease tissues apart in a saline solution to locate encysted forms.
About the Researcher
Barrister Kumar Gupta, M.Sc., conducted this research as a doctoral candidate in the Department of Zoology at the University of Lucknow, under the supervision of Prof. Nirupama Agrawal.
This post is an educational summary of a publicly available thesis. This content is for informational purposes only and does not constitute professional veterinary or medical advice.
Primary Source (Thesis)
- Title: On some metacercariae and adult trematodes of fishes
- Author: Gupta, Barrister Kumar
- Supervisor: Prof. Nirupama Agrawal
- Institution: University of Lucknow, Lucknow
- Year: 2011
- Excerpt Pages Used: 1, 3, 5-7, 11-12, 14-19, 21-22, 25-26, 28-29, 31-32, 34-35, 37-38, 40-41, 43-44, 46-47, 49-50, 52-53, 55-56, 58-59, 61-62, 64, 66, 68-69, 71-72, 74-75, 77-78, 80-81, 83-84, 86, 88-89, 91-92, 94-95, 97-101, 103-104, 106-107, 109-110, 112-113, 115-116, 118, 120-121, 123-124, 127-128, 130, 134, 161-166, 176-181.
Note: All content, unless cited as a direct quote with a page number, is original explanatory text written by the Professor of Zoology editorial team based on the findings within this thesis.
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