Table of Contents
Last Updated: October 28, 2025
Estimated reading time: ~7 minutes
Taxonomic studies form the bedrock of understanding biodiversity, including the often-overlooked world of parasites. Vijay Laxmi Tandon’s 1982 PhD thesis significantly contributed to the knowledge of helminth parasites in Indian fishes, with a particular emphasis on describing new species of digenetic trematodes.
- Focuses on the description of new digenetic trematode species from Indian fishes.
- Highlights key morphological features used for identifying new species in families like Paramphistomidae, Gyliauchenidae, and Acanthocolpidae.
- Illustrates the taxonomic process documented in the thesis.
- Provides specific examples of newly described trematodes and their fish hosts.
- Underscores the importance of systematic parasitology in fisheries and biodiversity research.
The Focus on Digenetic Trematodes
This section reiterates the primary group studied and its significance in fish parasitology, setting the stage for discussing specific taxonomic findings.
“But in the present study the morphology, distribution and host specificity of digenetic trematode parasites have been worked out.” (Tandon, 1982, p. 1)
Digenetic trematodes, commonly known as flukes, exhibit complex life cycles often involving multiple hosts, including fish as intermediate or final hosts. Their morphological diversity is vast, making taxonomic identification challenging yet essential. Tandon’s work concentrated on meticulously documenting these features – such as the structure of suckers, digestive system, reproductive organs (testes, ovary, cirrus sac, uterus), and vitellaria – to classify the collected specimens. This detailed morphological analysis allowed for the identification of known species within the Indian context and, crucially, the description of forms previously unknown to science.
Student Note: Digenetic trematodes are characterized by having at least two hosts in their life cycle and typically possess two main suckers (oral and ventral) for attachment. Variations in organ arrangement and morphology are key taxonomic characters.
Family Paramphistomidae: Helostomatis fotedari n.sp.
This section details the discovery and description of a new trematode species belonging to the family Paramphistomidae, found in a marine fish.
“Single specimen of this form was collected from the intestine of a marine fish Stromateus cinereus (Bleeker) from Arabian Sea, at Quilon, Kerala.” (Tandon, 1982, p. 90)
Tandon described Helostomatis fotedari n.sp. based on a single specimen. Key features included its elliptical, aspinose body (3.27 mm long), terminal oral sucker, distinct oral diverticula (claviform appendages), a large posterior sucker (0.70 mm diameter), and unequal, symmetrical testes located near the intestinal bifurcation. The genital pore was noted to be median, situated just behind the bifurcation of the oral diverticulum. Tandon distinguished this new species from previously known Helostomatis species based on the genital pore position and the specific extent of the vitellaria, which ran from behind the oral diverticula to slightly behind the intestinal caeca ends (Tandon, 1982, pp. 90, 92). The species was named in honor of Dr. D.N. Fotedar.
Exam Tip: When describing a new species, researchers compare its morphology against all existing species within the genus to highlight unique, distinguishing characteristics. Note features like sucker size/position, organ arrangement (testes symmetry/location), and vitellaria extent. Key Features of Helostomatis fotedari n.sp.
| Feature | Description (Tandon, 1982, pp. 90-92) |
|---|---|
| Host | Stromateus cinereus (Marine Fish) |
| Location | Intestine |
| Locality | Quilon, Kerala (Arabian Sea) |
| Body Shape | Elliptical, aspinose (3.27 x 1.38 mm) |
| Suckers | Oral (0.35×0.40 mm), Large Posterior (0.70 mm diam.) |
| Oral Diverticula | Present, claviform (0.35-0.45 mm long) |
| Testes | Spherical, symmetrical, unequal, near bifurcation |
| Genital Pore | Median, just behind oral diverticula bifurcation |
| Vitellaria | Follicular, from behind oral diverticula to behind caecal ends |
| Distinguishing Feature | Genital pore position & Vitellaria extent |
Family Gyliauchenidae: Gyliauchen indicum n.sp.
This section discusses another new species, Gyliauchen indicum, from the family Gyliauchenidae, highlighting its unique anatomical features.
“Five specimens of this form were collected from the intestine of a marine fish Engraulis hemiltoni (Cuv.& Val.) from Bay of Bengal, at Puri, Orissa.” (Tandon, 1982, p. 94)
Tandon identified Gyliauchen indicum n.sp. based on five specimens. This species was characterized by a crescent-shaped body (2.11-3.40 mm long), a terminal oral sucker with diverticula, a long coiled oesophagus with a muscular bulb, and intestinal caeca extending only up to the gonads. The ventral sucker was ventro-terminal or subterminal. Distinctive reproductive features included obliquely tandem or symmetrical testes in the posterior body, a large pyriform genital atrium, and vitellaria extending from anterior to the oesophageal bulb up to slightly posterior to the intestinal bifurcation. Tandon differentiated G. indicum from related species like G. papillatus and G. ozakii based on the limited extent of the intestinal caeca (not reaching gonads), the absence of oesophageal glands, the extent of the external seminal vesicle (not reaching gonads), and the relative position of the ovary and testes (Tandon, 1982, pp. 94, 96, 97).
Student Note: Pay attention to the digestive system variations (oesophagus length, presence of bulb, caecal extent) and the structure/position of the terminal reproductive organs (genital atrium, seminal vesicle) as these are often critical for genus and species identification in trematodes.
Family Acanthocolpidae: Three New Species
This section focuses on the family Acanthocolpidae, where Tandon described three new species, A. thapari, A. caranxi, and A. srivastavi, from different marine fish hosts.
“The new form differs from all these forms in having vitellaria confluent anterior to ovary.” (Tandon, 1982, p. 119, regarding A. thapari) … “The new form differs from all these forms in having genital pore on lateral side at the middle of pharynx.” (Tandon, 1982, p. 122, regarding A. caranxi) … “The new form differs from all the known species of the genus Acanthocolpus Iühe, 1901, in the extension of vitellaria from hind end of ventral sucker upto posterior end of body.” (Tandon, 1982, p. 126, regarding A. srivastavi)
Tandon’s work significantly expanded the knowledge of the Acanthocolpidae family in India by describing three new species. Acanthocolpus thapari n.sp., found in Glyphidodon bengalensis from Puri, was distinguished primarily by its vitellaria being confluent anterior to the ovary and its long cirrus sac extending more than half the body length (Tandon, 1982, pp. 117, 119). Acanthocolpus caranxi n.sp., from Caranx kalla also from Puri, was characterized by the unique position of its genital pore, located laterally at the mid-level of the pharynx (Tandon, 1982, pp. 120, 122). Acanthocolpus srivastavi n.sp., collected from Serranus leopardus at Pondicherry, was identified based on the extensive distribution of its vitellaria, running from the hind end of the ventral sucker all the way to the posterior end of the body (Tandon, 1982, pp. 123, 126). All three species shared features like an elongated, spinose body, simple intestinal caeca reaching the posterior end, a tubular excretory bladder, and tandem or obliquely tandem testes, but differed in these specific key characteristics, host species, and precise organ locations/extensions.
Exam Tip: Within a single genus, new species are often differentiated by subtle but consistent differences in features like genital pore position, extent of vitellaria or cirrus sac, sucker ratios, and internal organ arrangement relative to body landmarks. Comparison of New *Acanthocolpus* Species (Tandon, 1982)
| Feature | A. thapari n.sp. (pp. 117-119) | A. caranxi n.sp. (pp. 120-122) | A. srivastavi n.sp. (pp. 123-126) |
|---|---|---|---|
| Host | Glyphidodon bengalensis | Caranx kalla | Serranus leopardus |
| Genital Pore | Lateral to ventral sucker | Lateral, at mid-pharynx level | Median, pre-acetabular |
| Cirrus Sac Extent | > 1/2 body length | ~ 1/2 body length | ~ 1/2 body length |
| Vitellaria Extent | Mid-cirrus pouch to hind end | Mid-body to hind end | Hind end of ventral sucker to hind end |
| Vitellaria Confluence | Anterior to ovary & Post-testicular | Post-testicular only | Anterior to vesicula seminalis & Post-testicular |
Author: Vijay Laxmi Tandon, M.Sc., Department of Zoology, University of Lucknow, India (as of 1982).
This article provides a summary based on selected sections of a 1982 PhD thesis. For definitive taxonomic details and current classifications, refer to peer-reviewed scientific literature and databases.
Reviewed and edited by the Professor of Zoology editorial team. Except for direct thesis quotes, all content is original work prepared for educational purposes.
Key Takeaways
- Tandon’s 1982 thesis focused heavily on the taxonomic description of digenetic trematodes from Indian fishes.
- Detailed morphological analysis using standard parasitological techniques enabled the identification of new species.
- Helostomatis fotedari n.sp. (Paramphistomidae) was described from Stromateus cinereus, distinguished by genital pore position and vitellaria extent.
- Gyliauchen indicum n.sp. (Gyliauchenidae) from Engraulis hamiltoni was characterized by short intestinal caeca and specific reproductive anatomy.
- Three new species of Acanthocolpus (Acanthocolpidae) were described: A. thapari, A. caranxi, and A. srivastavi, differentiated by features like genital pore location, vitellaria distribution and confluence, and cirrus sac length.
- Taxonomic keys provided in the thesis aid in the identification of species within genera like Helostomatis and Gyliauchen.
- Such descriptive taxonomic work is fundamental for understanding parasite biodiversity and host associations.
Multiple Choice Questions (MCQs)
- Helostomatis fotedari n.sp. was primarily distinguished from other species in its genus by:
- A) Body shape and sizeB) Number of testesC) Genital pore position and vitellaria extentD) Host species only
Explanation: Tandon explicitly states that H. fotedari differs from other known forms in the genus by the location of the genital pore (just behind oral diverticula bifurcation) and the extent of the vitellaria (Tandon, 1982, p. 92). - A key morphological feature used to differentiate *Gyliauchen indicum* n.sp. was:
- A) The presence of spines on the body
- B) The intestinal caeca extending only up to the gonads
- C) Having only one testis
- D) The absence of an oral sucker
Explanation: The description notes the intestinal caeca extend up to the gonads, and the discussion contrasts this with other species where they might extend further (Tandon, 1982, pp. 94, 97). - Which feature uniquely characterized Acanthocolpus caranxi n.sp. among the Acanthocolpidae described?
- A) Vitellaria confluent anterior to the ovaryB) Genital pore located laterally at the mid-level of the pharynxC) Vitellaria extending from the ventral sucker to the posterior endD) Non-pedunculate ventral sucker
Explanation: The discussion for A. caranxi explicitly mentions its distinction lies in the unique position of the genital pore relative to the pharynx (Tandon, 1982, p. 122).
Frequently Asked Questions (FAQs)
- What does ‘n.sp.’ mean after a species name?
‘n.sp.’ stands for nova species, Latin for “new species,” indicating the species is being formally described for the first time in that publication. - What is a ‘type species’?
The type species is the species used to define or anchor a genus when it was first established. - What are vitellaria in trematodes?
Vitellaria (or vitelline glands) are glands that produce yolk cells, which contribute nutrients and shell material to the eggs. - What is a cirrus sac?
The cirrus sac is a muscular pouch containing the terminal male reproductive organs (like seminal vesicle, prostate cells, ejaculatory duct, cirrus) in many trematodes. - Where were most of the new marine species described from?
Many of the new marine species mentioned (G. indicum,A. thapari, A. caranxi) were collected from Puri, Orissa, on the Bay of Bengal coast. - Why is naming species after people common?
Naming species after mentors, colleagues, or respected scientists (patronyms) is a common practice in taxonomy to honor their contributions to the field.
Lab / Practical Note
For accurate trematode identification, precise measurement of organs and structures is vital. Use a calibrated ocular micrometer. Record ranges (min-max) if multiple specimens are available. Pay close attention to relative organ positions (e.g., pre-acetabular, post-testicular) and the extent of features like vitellaria or uterine coils relative to body zones or organs. Consistency in terminology (e.g., using Yamaguti’s classification terms) is important for comparative studies.
External Links for further study
Sources & Citation
Primary Source: Tandon, Vijay Laxmi. (1982). Studies on Helminth Parasites of Indian Fishes [PhD Thesis Excerpt, selected pages 1, 90-98, 117-126]. Department of Zoology, University of Lucknow, Lucknow, India. Supervisor: Dr. S. P. Gupta.
Note: This analysis is based solely on the provided PDF excerpt. Full context requires the complete thesis. Page numbers refer to the internal numbering within the supplied pages. Modern taxonomic classifications may differ from those used in 1982.
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