Table of Contents
Last Updated: October 19, 2025
Estimated reading time: ~6 minutes
This guide provides a detailed summary of the 2011 doctoral thesis by Dr. Barrister Kumar Gupta, which offers a comprehensive look at fish trematode taxonomy. The research focuses on the parasites infecting freshwater fishes in India, which have significant economic and public health implications.
This thesis is a foundational piece of taxonomic work, identifying and describing 22 larval forms (metacercariae) and 16 adult trematodes. Below, we explore the key findings, newly described species, and the diagnostic features used for their identification.
- This research provides a taxonomic description of 22 metacercariae and 16 adult trematodes.
- Multiple new species (n. sp.) are described, including Neascus bhopalensis, Tetracotyle mauensis, and Bucephalus bhagalpurensis.
- First-time records in India were made for the metacercariae of Orchipedum (from fish) and Genarchopsis goppo.
- Key taxonomic differentiators include sucker ratios, shape of the holdfast organ, extension of vitellaria, and number of genital rudiments.
Introduction to Fish Trematodes and Their Impact
This section explains why the study of fish trematodes is a critical field in zoology and aquaculture.
Fish provides nutritious food and are important source of fresh animal proteins. However, almost all of them carry infections of adult trematodes or metacercariae. … In case of heavy infections, mortality is also caused, which in turn is a great loss to fish industry. (Gupta, 2011, p. 1)
Digenetic trematodes, or “flukes,” are parasitic flatworms with complex life cycles, often involving multiple hosts. Fish can serve as both intermediate hosts (hosting the larval metacercariae stage) or definitive hosts (hosting the adult fluke). This thesis investigates both forms.
The impact of these parasites is twofold. First, they damage the host fish, causing disease, reducing their food value, and leading to economic losses in fisheries (Gupta, 2011, p. 1). Second, some species can be zoonotic, meaning they “can also transfer infections to man when infected with trematodes larvae i.e. metacercariae” (Gupta, 2011, p. 1), typically through the consumption of raw or undercooked fish.
Student Note: Understanding the morphology of both larval and adult stages is essential for correctly identifying species and assessing their potential risk to fish populations and human health. Learn more about the digenetic trematode life cycle.
Metacercariae (Larval Forms) Discovered
The thesis identifies 22 distinct metacercariae, the encysted larval stage of flukes, including several new species from the Neascus and Tetracotyle groups.
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. (Gupta, 2011, p. 161)
The research provides detailed descriptions and taxonomic keys for these larval forms. The most significant findings are concentrated in the strigeid metacercariae groups Neascus and Tetracotyle.
The Genus Neascus
The thesis describes four new species of Neascus metacercariae. These are differentiated based on highly specific morphological features.
- Neascus bhopalensis n. sp.: Collected from the liver of Xenentodon cancila. It is “characterized by ratio of fore and hind body, absence of pharynx, ratio of suckers, position of hold fast organ, shape of hold fast gland and number of genital rudiments.” (Gupta, 2011, p. 161).
- Neascus dohrighatensis n. sp.: Found in the liver of Wallago attu. Its key features are the “ratio of fore and hind body, absence of pharynx and shape of holdfast organ and holdfast gland.” (Gupta, 2011, p. 161).
- Neascus kaisarbaghensis n. sp.: Collected from the cranium of Anabas testudineus. It is uniquely identified by its “intestinal caeca reaching upto posterior end of hind body, ratio of suckers and shape of hold fast organ and hold fast gland.” (Gupta, 2011, p. 162).
The Genus Tetracotyle
An impressive ten new species of Tetracotyle are described, highlighting the rich biodiversity of these parasites. Each is distinguished by subtle but consistent morphological differences.
- Tetracotyle bhopalensis n. sp.: Found in the gut of Channa punctatus. It is distinct for its “pre-equatorial ventral sucker, larger than oral sucker, and number of genital rudimentss.” (Gupta, 2011, p. 162).
- Tetracotyle allahabadensis n. sp.: Collected from Mastacembelus puncalus. This species is characterized by the “absence of pre-pharynx, short oesophagus, two genital rudiments and bowl-shaped hold fast organ.” (Gupta, 2011, p. 162).
- Tetracotyle varanasiensis n. sp.: Found in Macrognethus aculeatus. It has a very distinct feature: “a collar at anterior region of body, ratio of suckers… and number of genital rudiments.” (Gupta, 2011, p. 163).
- Tetracotyle trilobulata n. sp.: Named for its “trilobed holdfast organ” (Gupta, 2011, p. 48), this species was found in the liver of Mastacembelus armatus (Gupta, 2011, p. 163).
Other Metacercariae Records
Two major findings include the first-ever records of specific metacercariae in India.
- Metacercaria of Orchipedum Braun, 1901: Collected from the body cavity of Channa punctatus. This is significant as the “present specimen is the first record of the metacercaria from fish.” (Gupta, 2011, p. 164).
- Metacercaria of Genarchopsis goppo Ozaki, 1925: Found in the gut of Channa punctatus. This “appears to be first record of the metacercaria from India.” (Gupta, 2011, p. 164).
Exam Tip: When identifying Neascus or Tetracotyle species in a lab practical, the ratio of the suckers (oral vs. ventral), the shape of the holdfast organ, and the number of genital rudiments are the primary taxonomic characters to observe. See our detailed morphology of strigeid metacercariae.
Adult Trematodes Identified
This section details the 16 adult trematodes, many of which were also new to science.
Part-II deals with the description of 16 adult trematodes. 1. Bucephalus bhagalpurensis n. sp. was collected from gut of Mystus tengra (Ham.) at River Saryu Bhagalpur… (Gupta, 2011, p. 164)
The adult flukes were primarily found in the gut, body cavity, or gall bladder of their definitive fish hosts. Below are highlights of the new species (n. sp.) described.
New Species of Bucephalus and Allocreadium
- Bucephalus bhagalpurensis n. sp.: This new species is “characterized by position of pharynx, short cirrus sac and extension of vitellaria.” (Gupta, 2011, p. 164).
- Allocreadium itwarensis n. sp.: Collected from Mastacembalus puncalus. It is differentiated by “the ratio of suckers, position of receptaculum seminis, extension of vitelline follicles, shape and extension of cirrus sac and position of genital pore.” (Gupta, 2011, p. 165).
- Allocreadium badatalabensis n. sp.: Found in Heteropneustes fossilis. This species is uniquely identified by its “bipartite vesicula seminalis, position of genital pore, and extension of vitellaria and size of eggs.” (Gupta, 2011, p. 165).
Other New Species Described
The thesis also provides the first descriptions for several other adult flukes:
- Eucreadium madhubanensis n. sp.: From Eutropiicthys vacha, characterized by “the ratio of suckers, shape of gonads and extension of vitellaria.” (Gupta, 2011, p. 165).
- Rhynchocreadium dohrighatensis n. sp.: From Channa marulius, characterized by “ratio of suckers, ratio of testes and ovary and extension of vitellaria.” (Gupta, 2011, p. 165).
- Oudhia itwaraensis n. sp.: From Heteropneustes fossilis, characterized by “in ratio of suckers, extention of vitellaria and position of genital pore.” (Gupta, 2011, p. 166).
- Pleuragenoid madhubanensis n. sp.: From Ompok bimaculatus, characterized by “ratio of suckers, extension of cirrus and position of gonads and genital pore.” (Gupta, 2011, p. 166).
Student Note: For adult trematodes, taxonomic keys often rely on the relative positions of the gonads (testes and ovary), the extension of the vitellaria (yolk glands), and the structure of the cirrus sac. Guide to Bucephalid trematode anatomy.
Taxonomic Key Data Comparison
The thesis provides detailed measurements to differentiate species. The table below summarizes key measurements for Bucephalopsis linguiformis as found in this thesis compared to its original description by Chakrabarti and Baugh (1974).
| Organ Name | B. linguiformis (Chakrabarti and Baugh, 1974) | Present Specimens (Gupta, 2011) |
|---|---|---|
| Cyst | 0.22-0.30 mm x 0.18-0.24 mm | 0.25 – 0.30 mm x 0.08 – 0.10 mm |
| Body | 0.64-0.38 mm x 0.18-0.26 mm | 0.40 – 0.42 mm x 0.14 – 0.16 mm |
| Ap. sucker | 0.08 mm x 0.14 mm | 0.06 – 0.07 mm x 0.05 – 0.06 mm |
| Pharynx | 0.04 mm x 0.07 mm | 0.03 mm x 0.04 mm |
| Ovary | ? | 0.008 – 0.01 mm x 0.005 – 0.01 mm |
| Testes | 0.03-0.04 mm x 0.05-0.06 mm | 0.01 – 0.03 mm x 0.01 – 0.02 mm |
| Cirrus | 0.18 mm x 0.24 mm | 0.10 – 0.20 mm x 0.05 – 0.10 mm |
Table 1: Comparative morphometrics of Bucephalopsis linguiformis metacercariae as cited in Gupta (2011, p. 54).
General Morphology of a Neascus Metacercaria
This thesis identifies several new Neascus species. The diagram below illustrates the general body plan for this type of strigeid metacercaria, highlighting the key features used in identification.
The morphology of these larval flukes is highly adapted. The body is typically divided into an anterior Forebody, which contains the suckers and a specialized Holdfast Organ for attachment, and a smaller posterior Hindbody, which contains the Genital Rudiments. The shape of the holdfast organ and its associated gland, along with the number and arrangement of the undeveloped genital masses, are critical for distinguishing one species from another.
Multiple Choice Questions (MCQs)
- What was a key feature used to characterize the new species Neascus bhopalensis?
- A) Presence of a large pharynx
- B) Absence of a pharynx and ratio of suckers
- C) Three ventral suckers
- D) Spines on the hindbody
- The new species Tetracotyle varanasiensis was noted for what unique feature?
- A) A collar at the anterior region
- B) A bifurcated hindbody
- C) Absence of a ventral sucker
- D) A spinose oral sucker
- Allocreadium badatalabensis n. sp. was distinguished by which feature?
- A) A single large testis
- B) A bipartite vesicula seminalis
- C) Vitellaria limited to the forebody
- D) Absence of an oral sucker
Frequently Asked Questions (FAQs)
What is a metacercaria? A: A metacercaria is the encysted larval stage of a digenetic trematode (fluke). It is often found in the tissues of an intermediate host, like a fish.
What is a “holdfast organ”? A: It is a specialized adhesive organ, distinct from the ventral sucker, used by strigeid trematodes to attach firmly to the host’s intestinal lining.
What does “n. sp.” mean in taxonomy? A: “n. sp.” is an abbreviation for species nova, Latin for “new species.” It indicates the author is formally describing this species for the first time.
Why is fish trematode taxonomy important? A: It helps scientists understand parasite biodiversity, fish health, and potential risks to the aquaculture industry and human (zoonotic) health.
What is vitellaria? A: The vitellaria (or vitelline glands) are yolk glands in trematodes. Their shape, size, and extension (how far they spread in the body) are key identification features.
Lab / Practical Note
Lab Protocol for Trematode Preparation: When collecting trematodes, immediately wash them in normal saline. For fixation and permanent mounting, fix the worms in 70% alcohol under slight coverslip pressure. This prevents curling and ensures a flat specimen for morphological study. Staining with Aqueous Aceto-alum Carmine, followed by dehydration in alcohol grades and clearing in Clove oil, yields excellent differentiation of internal organs for taxonomy (Gupta, 2011, p. 3).
About the Researcher: This work was completed by Barrister Kumar Gupta as part of his doctoral thesis, supervised by Prof. Nirupama Agrawal (Ph.D., D.Sc.), at the Department of Zoology, University of Lucknow.
Reviewed and edited by the Professor of Zoology editorial team. Except for direct thesis quotes, all content is original work prepared for educational purposes.
Disclaimer: This article summarizes a specific academic thesis for educational use. It does not replace formal peer-review or serve as a definitive diagnostic tool for fish pathology.
Further Reading & External Links
Primary Source: Gupta, Barrister Kumar. (2011). ON SOME METACERCARIAE AND ADULT TREMATODES OF FISHES. Thesis submitted for the award of degree of Doctor of Philosophy in Zoology at the University of Lucknow, Lucknow. Supervised by Prof. Nirupama Agrawal. Excerpts and data primarily sourced from the Introduction (pp. 1-2), Material and Methods (p. 3), Table (p. 54), and Summary (pp. 161-166).
Discover more from Professor Of Zoology
Subscribe to get the latest posts sent to your email.
