Shrimp is the most consumed seafood in the United States, and it is also one of the most frequently mislabeled. Published surveys put U.S. shrimp substitution rates at roughly 20–35%, and premium species are a favorite target. A new study in Food Chemistry: Molecular Sciences from Samuel Kwawukume, Nethraja Kandula, Leqi Cui and Prashant Singh at Florida State University tackles one of the clearest examples: royal red shrimp (Pleoticus robustus) being swapped for the cheaper, look-alike Argentine red shrimp (Pleoticus muelleri). Their answer is a fast, sequencing-free DNA test that pairs RNase H2-dependent PCR (rhPCR) with a lateral flow strip readout, and the strips used for detection were supplied by Attogene.
Why Royal Red Shrimp Is a Fraud Target
Royal reds are a deep-water, wild-caught U.S. species with a distinctive sweet flavor. They require specialized gear to harvest and are scarce: U.S. landings were just 81 metric tons in 2024, a tiny fraction of the hundreds of thousands of tons of shrimp the country imports each year. That combination of high price and low supply makes them a natural target for substitution. Argentine red shrimp share the same genus and similar coloring, and once the shrimp are peeled, cooked or frozen, telling them apart by eye is effectively impossible.
DNA barcoding of the COI gene is the regulatory gold standard for species identification, but it needs a sequencing lab, specialized staff and one to three days per result. That turnaround limits how useful it is for inspectors and quality-control teams who need answers the same day.
How the Test Works
The team designed two species-specific primer sets targeting short regions of the COI gene that differ between royal red, Argentine red and other commonly traded shrimp. The key to telling such closely related species apart is rhPCR. Each primer carries a single internal RNA base and a blocked 3′ end, so it cannot extend until the RNase H2 enzyme cleaves it, and that cleavage only happens when the primer matches its target perfectly. Mismatched templates from other species are simply not amplified.
The forward primers are labeled with FAM and the reverse primers with biotin, so every amplicon carries both tags. Instead of running a gel, the PCR product is added to running buffer and a lateral flow dipstick is dipped in. If target DNA is present, the labeled amplicon is captured at the test line and a visible red band appears in about five minutes. A control line confirms the strip worked.
Sample preparation is deliberately simple. A toothpick-sized piece of tissue is heat-lysed in a commercial crude extraction reagent for 30 minutes, spun down and diluted, with no column purification. The crude lysates actually gave higher DNA yields than a standard spin-column kit, with comparable purity.
Key Results
- 100% sensitivity and specificity. Against 65 DNA-barcoded shrimp spanning seven commercial species (royal red, Argentine red, Atlantic white, Pacific white, brown, pink and tiger shrimp), both assays matched the barcoding result every time, with no false positives or false negatives.
- Detection down to 0.01 ng/µL of crude DNA for both species, more than enough for identifying a single-species shrimp sample.
- Works on cooked product. Cooked retail samples still produced readable, if fainter, test lines.
- Consistent visual reads. Three lab staff independently scored a blinded set of 20 strips and agreed on every one.
- About 150 minutes for 20 samples, start to finish, using only a standard thermocycler. The strips, buffer and extraction reagent are all stable at room temperature.
60% of “Royal Reds” Weren’t
The real-world test came from 20 blinded samples sold as royal red shrimp, collected from boats, grocery stores and seafood markets by the Alabama Department of Agriculture and Industries’ Food Safety Division. Only 8 were confirmed as royal red. Six were Argentine red shrimp, and the remaining six matched neither species. In other words, 60% of the product labeled royal red was something else. The authors note that broader geographic and seasonal sampling would be needed to estimate a national rate, but the result fits a long line of reports of royal red mislabeling in U.S. retail.
Why It Matters
The authors see state departments of agriculture, FDA field labs, enforcement agencies and seafood quality-control teams as the main users: anyone with a thermocycler who needs a species call the same day rather than waiting days for sequencing. The trade-off is clear. The test gives a yes/no answer for a specific species instead of a full DNA sequence, but it does so far faster and with far less equipment. The team plans to combine both assays into a single multiplex test, and the same design approach has already been applied to Atlantic white shrimp, Pacific white shrimp and red snapper.
Nucleic acid lateral flow is a simple swap for gel electrophoresis in any PCR, LAMP or RPA workflow that uses FAM- and biotin-labeled primers. Explore Attogene’s Universal Lateral Flow Assay Kit (anti-FAM/FITC-Gold), the Universal Lateral Flow Assay Kit (Strep-Gold), and our FAM/biotin NALFIA control DNA, or contact our team to discuss a custom species-identification or food-authenticity assay.
Frequently Asked Questions
What is rhPCR?
RNase H2-dependent PCR uses primers that contain one RNA base and a blocked 3′ end. The RNase H2 enzyme only cleaves, and so activates, a primer that is perfectly bound to its target. This sharply reduces amplification from closely related, mismatched sequences, which makes it well suited to telling apart species in the same genus.
How does lateral flow read a PCR result?
When PCR uses one primer labeled with FAM and the other with biotin, every amplicon carries both tags. On the strip, gold particles bind one tag and a capture line binds the other, so only a dual-labeled amplicon forms a visible test line. Unused primers cannot bridge the two, so they do not give a signal.
Does this replace DNA barcoding?
Not entirely. Barcoding identifies any species from its sequence, while this test answers whether a specific species is present. For routine screening of products labeled as a particular species, a targeted rhPCR–lateral flow test is much faster and cheaper, and barcoding remains available for confirmation or for identifying an unknown substitute.
Reference: Kwawukume S, Kandula N, Cui L, Singh P. A rapid rhPCR–lateral flow assay for authenticating royal red and Argentine red shrimp in the U.S. seafood supply chain. Food Chemistry: Molecular Sciences 13 (2026) 100434. https://doi.org/10.1016/j.fochms.2026.100434 (open access, CC BY-NC 4.0).
