Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Title: “Effects of selenite and selenate on the growth, nutrient composition, selenium species, and in vitro digestibility of mealworm Tenebrio molitor”

General comments:

This manuscript provides a systematic and well-designed investigation into the effects of selenite (Se⁴⁺) and selenate (Se⁶⁺) on the growth performance, nutrient composition, Se accumulation/speciation, and in vitro bioaccessibility of T. molitor larvae. The study addresses a timely topic at the intersection of insect-based nutrition, Se biofortification, and functional food development, and fits within the scope of Insects. The experimental approach and dataset are good, and the conclusions are generally supported by the results. Overall, the work represents a valuable contribution to the emerging literature on Se-enriched edible insects.

Strengths:

1. Comprehensive experimental scope:

• The study integrates growth performance, Se accumulation kinetics, nutrient composition, mineral profiling, Se speciation, and in vitro digestibility, providing a holistic assessment typically not achieved in a single study.
• Comparison of two inorganic Se forms across multiple concentrations and time points strengthens the ecological and nutritional relevance of the findings.

2. Strong evidence for biotransformation to organic Se:

• The demonstration that >79% of accumulated Se is present in organic forms, even at higher supplementation levels, is a strength.
• Identification of SeCys₂ as the dominant bioaccessible species following in vitro digestion is noteworthy and supports the premise that T. molitor can act as an effective bioreactor for nutritionally favorable Se forms.
• The use of HPLC-ICP-MS for Se speciation adds analytical rigor and credibility.

3. Nutritional and functional relevance:

• Observed increases in crude protein and polysaccharide content, coupled with reductions in crude fat, provide insights into how Se supplementation alters the nutritional profile of mealworms.
• The inclusion of in vitro gastrointestinal digestion enhances relevance for food and feed applications and aligns with current expectations for functional ingredient studies.

4. Clear data presentation and logical interpretation:

• Figures and tables are generally clear, organized, and support the narrative/discussion (e.g., growth trends, Se accumulation dynamics, and digestibility results).
• The discussion is thorough and appropriately contextualized within existing lit on Se toxicity, bioaccumulation, and insect metabolism.

 

Suggestions for Improvement:

These suggestions are intended to further strengthen clarity and impact rather than address major weaknesses:

1. Clarify practical Se fortification targets: While the dose-response trends are clear, a brief discussion linking the tested Se concentrations to practical feed or food fortification levels (and regulatory limits) would enhance applicability.
2. Mechanistic insight into nutrient shifts: The observed increases in protein and polysaccharide content and reductions in lipid content are interesting. A short mechanistic discussion (e.g., links to oxidative stress, energy or metabolic regulation under Se exposure) would add depth.
3. Molting and Se depuration: The proposed role of molting in Se elimination is reasonable and supported by literature. Noting whether molting events were observed or inferred during the experiment would improve transparency.
4. Language and minor editorial issues: The manuscript would benefit from English-language editing to correct minor grammatical issues and improve readability, particularly in the “Intro” and “Discussion”.

Recommendation:

Accept with minor revisions. The manuscript is scientifically and methodologically sound, and aligned with the aims/scope of Insects. The suggested revisions are minor and mostly focused on clarity, context, and presentation rather than experimental limitation.

 

Comments on the Quality of English Language

please see review letter 

Author Response

1. Clarify practical Se fortification targets: While the dose-response trends are clear, a brief discussion linking the tested Se concentrations to practical feed or food fortification levels (and regulatory limits) would enhance applicability.

[Yue SZ]: Thank you for this kind suggestion. We have checked carefully and added a brief discussion in Section “4.2. Se Accumulation Analysis in Mealworms” to explicitly link our tested selenium concentrations to practical feed fortification levels, enhancing the applicability of our findings.

The nutritional Se requirement for most animals is typically between 0.1-0.3 mg/kg of complete feed [56]. Consequently, mealworms from the lower-dose treatment group (Se5), when incorporated into feed formulations at a modest inclusion rate (e.g., 5-10%), could contribute to meeting the animal's dietary Se requirement. Se-enriched insects with a high Se concentration are a concentrated premix, and as such, must be diluted through blending with other feed ingredients in order to ensure that the final composite feed complies with the law. (see Page 16, Lines 708-714, in Revised Manuscript)

2. Mechanistic insight into nutrient shifts: The observed increases in protein and polysaccharide content and reductions in lipid content are interesting. A short mechanistic discussion (e.g., links to oxidative stress, energy or metabolic regulation under Se exposure) would add depth.

[Yue SZ]: Thank you very much for this kind suggestion. Combined with your valuable comments, we have slightly expanded the discussion (in Section “4.3. Effects of Se Addition on Nutrient Components”) regarding the observed changes in protein, polysaccharide, and lipid content, to add depth to the interpretation.

The observed alterations in the composition of crude protein, crude polysaccharide, and crude fat in T. molitor in response to varying concentrations of inorganic Se exposure may be attributable to the stress induced by high concentrations of chemicals, which subsequently led to the re-regulation of energy and metabolic processes, as evidenced by changes in amino acid content [57]. (see Page 16, Lines 743-748, in Revised Manuscript)

3. Molting and Se depuration: The proposed role of molting in Se elimination is reasonable and supported by literature. Noting whether molting events were observed or inferred during the experiment would improve transparency.

[Yue SZ]: Thank you very much for this kind suggestion. As is well documented, Tenebrio molitor undergoes a moulting process approximately once per week. The duration of the experiment was 28 days within the present study, a period during which T. molitor may undergo three to four molts. During the course of the experiment, it was observed that all of the treatments resulted in molting of T. molitor. Furthermore, an attempt was made to collect and detect the selenium content in the larval moult. It was intended that the selenium content data from the larval moult should be incorporated into the supplementary materials. Unfortunately, the larval moult is so light in weight, and the quantity collected was minimal. This renders it impossible to quantify the moult with any degree of accuracy. While the presence of selenium is discernible, precise quantification of its concentration remains challenging. Consequently, we have cited documents that have undergone rigorous testing to substantiate the presence of selenium in larval moult. Besides, we added a concise exposition in Section “3.2. Total Se Concentration and BAF_Se”), to improve transparency:

……, and molting was observed in all treatments. (see Page 7, Lines 394-395, in Revised Manuscript)

4. Language and minor editorial issues: The manuscript would benefit from English-language editing to correct minor grammatical issues and improve readability, particularly in the “Intro” and “Discussion”.

[Yue SZ]: I would like to express my sincere gratitude for this thoughtful suggestion. Following the receipt of your valuable comments, the manuscript under review was subjected to a thorough English language editing process, with particular attention being paid to the Introduction and Discussion sections. This editing process was undertaken with the aim of correcting minor grammatical issues and enhancing the overall readability of the text.

 

Recommendation:

Accept with minor revisions. The manuscript is scientifically and methodologically sound, and aligned with the aims/scope of Insects. The suggested revisions are minor and mostly focused on clarity, context, and presentation rather than experimental limitation.

[Yue SZ]: I would like to express my sincere gratitude for your supplementary constructive suggestions and for your overall positive recommendation of "Accept with minor revisions." We are truly grateful for your meticulous analysis, which has elucidated specific areas that merit enhancement in terms of clarity and impact. I would like to express my gratitude once more for the time you have dedicated to this matter and for your invaluable recommendations. We anticipate the opportunity to submit a revised manuscript that has fully incorporated your suggestions.

Reviewer 2 Report

Comments and Suggestions for Authors

In this paper, the authors investigate the effects of selenite and selenate on the growth, nutrient composition, selenium speciation, and in vitro digestibility of the mealworm, Tenebrio molitor. The experimental concept is both interesting and highly relevant, addressing an important goal for the future utilization of edible insects. The results are robust, and the authors present a comprehensive dataset that supports further implementation in this field. The findings represent a relatively novel and significant approach to the rearing and utilization of edible insects. Therefore, I recommend that the manuscript be accepted for publication.

Author Response

Comments: In this paper, the authors investigate the effects of selenite and selenate on the growth, nutrient composition, selenium speciation, and in vitro digestibility of the mealworm, Tenebrio molitor. The experimental concept is both interesting and highly relevant, addressing an important goal for the future utilization of edible insects. The results are robust, and the authors present a comprehensive dataset that supports further implementation in this field. The findings represent a relatively novel and significant approach to the rearing and utilization of edible insects. Therefore, I recommend that the manuscript be accepted for publication.

Response: Thank you very much for your time and thoughtful review of our manuscript. We sincerely appreciate your positive and encouraging comments. We are delighted that you found the experimental concept interesting and highly relevant, the results robust, and the dataset comprehensive for supporting further implementation in this field. It is particularly gratifying to know that you consider our findings to represent a novel and significant approach to the rearing and utilisation of edible insects. We are very grateful for your recommendation to accept the manuscript for publication. Thank you again for your valuable feedback and support, and we look forward to your review of our next manuscript.