Portunidae identificationAndhra Pradesh — field & lab guide

Last Updated: 09 October 2025

Estimated Reading Time: ~8 minutes

This practical primer translates the thesis’ Portunidae findings into a student-friendly ID key, habitat checklist, and lab workflow tailored for the Andhra Pradesh coast.

• Key takeaway: Portunidae were among the most frequently recorded families on the Andhra coast — learn the fastest morphological cues to separate common genera and prepare for lab-based confirmation. 0
• Field-to-lab workflow: Sampling → measurement → preservation → preliminary ID → selective molecular confirmation (if needed).
• Practical exam tip: Draw the male 1st pleopod and swimmeret — many species keys hinge on these features. 2

Introduction

Why focus on Portunidae identification Andhra Pradesh? Swimming crabs (Portunidae) include commercially important species and dominate many coastal trawl samples in the Bay of Bengal surveys. Understanding their diagnostic morphology helps in fisheries reporting, biodiversity assessments and exam answering. 3

This post condenses the thesis’ methods and species notes into quick reference keys, short quotes with exact page citations, lab/practical instructions and exam-ready pointers — all drawn from the uploaded thesis.

Why this topic is best: Students often face identification questions on Portunidae in practical exams and field courses; the thesis provides species-level observations and measurement protocols that directly support such training. 4

Quick field diagnostics — Portunidae at a glance

Plain-English summary: Portunids are typically dorsoventrally flattened, with paddle-like last pereiopods (swimmerets) and a carapace bearing distinct anterolateral teeth.

“The maximum crab species were recorded belonging to family Portunidae and Xanthidae.” (p. 157). 5

Explanation: In the thesis, Portunidae occurrence was high across trawl samples — useful to know when inspecting bycatch. Look first for flattened fifth pereiopods (swimming paddles) and a broad, often granulated carapace. 6

Exam tip: Sketch the paddle-shaped last leg and label it “5th pereiopod — natatory” for quick marks.

Step-by-step field-to-lab workflow

Plain-English summary: Follow a reproducible chain: sample → record → preserve → label → preliminary ID.

“Sampling was done … from June 2014 to May 2018.” (p. 20). 7

Explanation: Use 10-kg trawl subsamples for biodiversity snapshots; record GPS station, date, substrate, and water salinity if available. Measure carapace width (CW) and length (CL) with vernier calipers and note sex (male — presence of 1st pleopod). Preserve voucher specimens in 70% ethanol after initial fixation as described in methods.

Lab note: Avoid formalin for samples destined for DNA — use 95% ethanol for molecular vouchering. Mark labels with durable ink and include specimen code, station, date and collector initials.

Identification key (practical, quick-reference)

Plain-English summary: Use a stepwise morphological approach from general family traits to genus-level characters.

1. Step 1 — confirm Portunidae: last pair of legs flattened into paddles; carapace usually wider than long.
2. Step 2 — check anterolateral teeth: Number and shape of carapace teeth narrow down to Portunus, Thalamita, Charybdis. 9
3. Step 3 — cheliped & ambulatory leg proportions: Robust chelae with particular fingers point to Scylla vs Portunus. 10
4. Step 4 — male 1st pleopod: Shape (curved/spear-like or simple) confirms species-level separation in keys. Draw and photograph at 10×. 11

Student note: For Portunus pelagicus look for four antero-lateral teeth and a distinct hexagonal carapace outline; for Thalamita inspect marginal spines close to the antero-lateral angle.

Common Portunidae species from the thesis (students must know)

• Scylla serrata — large mud crab, strong chelae, mangrove/estuarine habitats. 13
• Portunus pelagicus — swimmer crab, sandy bottoms, commercial interest. 14
• Thalamita crenata — smaller porter, carapace teeth distinct near anterolateral margin. 15

Molecular confirmation — when to sequence

Plain-English summary: Use COI/16S barcoding for damaged specimens, cryptic species or unexpected records.

“Molecular taxonomy of two brachyuran crab species were identified for barcoding, confirmation was done in BLAST.” (p. 176). 16

Explanation: The thesis applied molecular confirmation selectively. For coursework: preserve a small pereiopod muscle in 95% ethanol and request COI sequencing; interpret % identity with caution (<97% may indicate misidentification or novel record). 17

Lab exercise idea: Students compare morphological ID vs BLAST result for 5 unknown Portunidae vouchers and write a short report on discrepancies.

Visuals & infographic suggestions

Suggested diagrams:

1. Portunidae ID plate: dorsal carapace views of Portunus pelagicus, Thalamita crenata and Scylla serrata with labelled anterolateral teeth, swimmeret and 1st pleopod. Caption: “Key morphological characters for Portunidae identification.”
2. Field workflow infographic: stepwise boxes: Sample → Measure (CW/CL) → Preserve (95% EtOH for DNA) → Label → Preliminary ID → Optional sequencing.

Key takeaways

• Confirm Portunidae by checking the paddle-like 5th pereiopod and broad carapace. 18
• Use a stepwise key: anterolateral teeth → cheliped form → male 1st pleopod → molecular backup.
• Preserve for purpose: 95% ethanol for DNA; 70% ethanol for morphology vouchers. 20

MCQs — quick check

1. Q: Which feature is diagnostic for Portunidae?
   A: Flattened (paddle-like) 5th pereiopods. Explanation: Portunids are adapted for swimming; last legs are natatory. 21
2. Q: Best preservative for DNA barcoding?
   A: 95% ethanol. Explanation: Formalin degrades DNA; the thesis used ethanol for molecular samples.

FAQs

Q: How many Portunidae species were reported in the thesis? A: The thesis lists several Portunidae species among the 46 brachyurans recorded; see the species list in results. 23 Q: Is molecular work essential for all specimens? A: No — morphology suffices for many specimens; molecular confirmation was used selectively for ambiguous cases. 24 Q: Which measurement is essential in practical exams? A: Carapace width (CW) and male 1st pleopod shape — draw both.

Conclusion

This compact guide gives you the essentials to tackle Portunidae identification Andhra Pradesh in fieldwork, lab practical’s and exams — from the decisive paddle-shaped leg to preservation and selective barcoding. Use the workflow and drawing exercises in your next practical class.

EEAT, sources & credits

Author Bio: Researcher Ponnada Vijaya Kumar, M.Sc., M.Phil (Andhra University).

Reviewed and edited by: Professor of Zoology editorial team.

“Reviewed and edited by the Professor of Zoology editorial team. Except for direct thesis quotes, all content is original work prepared for educational purposes.”

Source & Citations

Thesis Title: Studies on the diversity and systematics of brachyuran crabs (Crustacea; Decapoda) off Andhra Pradesh coast, Bay of Bengal, India.
Researcher: Ponnada Vijaya Kumar. Guide: Prof. D.E. Babu. University: Andhra University, Visakhapatnam. Year: 2019. 26

Excerpt page numbers used: p.20 (sampling), p.157 (family results), p.16–17 & p.176 (molecular notes), p.11 (methods/preservation).

Disclaimer: All thesis quotes remain the intellectual property of the original author. Professor of Zoology claims no credit or ownership. If you need the original PDF for academic purposes, contact us through our official channel.