Prickly Pear Cladodes as an Alternative Source of Water in Small- and Medium-Scale Yellow Mealworm Rearing

Round 1

Reviewer 1 Report

This is a very interesting and appealing research where authors are proposing a new water supply for edible insects that is sustainable. The experiment design is right, the results are correctly presented and in general the writing is also correct, although sometimes information is excessive or repeated. I strongly recommend the publication of this manuscript, it only needs some small adjustments that I will explain next.

Introduction

Please provide some additional references in the fifth paragraph (lines 45-19).

I think the paragraph in lines 82-93 is not needed, nor the previous one (lines 79-81). The introduction is already too long, and you do not need to explain how good the OFI is, you only need to demonstrate that it is good for feeding the larvae, and that Italy is one of the main producers in Europe.

The way the aims are written look somewhat odd. I think it would be better to say that you are comparing the performance of OFI and the selected fresh VMs in terms of dehydration in the rearing chamber, selection of TLMs, palatability after 6 days and the larval weight gain and survival.

Materials and Methods

Figure 1 is not mentioned in the main text.

Keep the days-old format to tell the age of larvae, as in line 131.

I do not understand what you mean in lines 165-166 (“to verify that adding VMs with a higher water content results in a greater weight gain of the TMLs”). Did you test different water contents? According to what you said in section 2.2, the three VMs had a similar water content.

In my opinion, the information given in lines 169-172 is part of the problem you are trying to solve, so it should be placed in the introduction.

Results

All three paragraphs from line 194 to line 214 can be merged in a single one, only highlighting the main results and the significant differences specially at the end.

Data from figure 3 is already shown in table 3, so I recommend removing figure 3.

Lines 251-253 are not necessary, you already said that in the methods section. Actually, you do not have to repeat the methods in every subsection of the results (e.g., lines 268-269, lines 273-274 and 284-286 in section 3.3, but please revise in all sections).

Please do not show the results in bullet points (lines 288-294), just write it in a fluent way.

Please provide the units in table 3 (I guess it is number of larvae).

You did not say in methods section that you were going to calculate the moisture of fresh vs stored vegetables in the thermobalance.

Lines 325-326, “This confirms that the amount of water supplied to the larvae by the wet supplement influences their weight gain”. Not necessarily. There are other nutrients that might explain the weight gain. You should do a different experiment to confirm that. Please remove that sentence.

Discussion

Since you are providing the equivalents of carrots in water, it would be interesting to see how much TM rearers would be saving if using OFI.

I do not feel paragraph in lines 345-351 is necessary. You can keep the main idea in a sentence, but there is no point in discussing the results of other researches non related to your own.

You do not need to mention again figures and tables in this section, nor the methods (e.g., lines 375-377, “At this end, we tested the palatability of “fresh” and 6-day-old matrices under standard rearing conditions (“stored”) to verify if larvae eat the VMs even 6 days after feeding”).

Lines 393-395: ok, but maybe there are other articles evaluating this species (or other similar cactacea) for rearing insects. And you could also discuss the use of OFI for rearing other insects.

Paragraphs in lines 396-409 are not necessary.

Conclusions

This section is too long, you can summarize all that in a single paragraph. Actually, I think the first paragraph might be enough.

I have found only a few small mistakes, it just needs a thorough read.

Author Response

Please, see the attached file

Author Response File: Author Response.pdf

Reviewer 2 Report

Title:

ok.

Abstract:

·         The abstract section of the manuscript needs some revisions to improve clarity and conciseness. While it provides a general overview of the study, it could benefit from restructuring and refining certain sentences to enhance readability and ensure that the main points are effectively conveyed.

·         Additionally, it would be helpful to include more specific information about the study design, key findings, and their implications. I recommend revisiting the abstract with these suggestions in mind to ensure that it accurately represents the research and engages readers right from the start.

Introduction

·         In sentence 28, it would be helpful to specify the timeframe for the projected increase in the population to over 9 billion. Adding "by 2050" or another relevant year will provide a clearer sense of urgency (with reference).

·         Sentence 31 states that livestock is responsible for most of the greenhouse gas (GHG) emissions in the food system. It would be beneficial to include a reference or cite specific studies to support this claim and demonstrate the magnitude of the issue.

·         Defend the advantages of OFI with reference.

·         Sentence 98, where the objective of the article is mentioned, it would be useful to specify the geographical scope or target region for the evaluation of Opuntia ficus-indica (OFI) as a replacement for common water-supplying vegetable matrices. Clarifying the geographic focus will help readers understand the relevance and applicability of the findings.

Materials and Methods

·         In sentence 106, it is mentioned that OFI cladodes were collected in the ENEA - Trisaia research center, while other tested VMs were purchased from local retail suppliers. It would be helpful to provide more specific information about the characteristics of the OFI cladodes, such as their size, maturity, or any pre-processing steps, to ensure the consistency and reproducibility of the experiments.

·         In sentence 110, it states that the TMLs (yellow mealworm larvae) were reared under standard conditions of temperature, relative humidity, and photoperiod. It would be beneficial to defend the rearing method with some already published methods.

·         Sentence 111 mentions the standard diet of the larvae, consisting of bran and zootechnical yeast. It would be useful to provide the composition of the standard diet, including the percentage of each component, to provide a comprehensive understanding of the larvae's nutritional intake.

·         In section 2.1, where the dehydration test of some VMs is described, it would be helpful to defend the methodology with citations.

·         In section 2.2, where the choice test by TMLs is explained, it would be helpful to provide environmental conditions details during the larvae's choice test observations were recorded and whether any behavioral observations were made during the test

·         In section 2.5, where the statistical analyses are mentioned, it would be helpful to specify the sample size or the number of replicates used for each experiment. This will provide a clearer understanding of the statistical power and reliability of the results.

·         It would be beneficial to provide a reference or citation for the statistical analysis software used (GraphPad Prism version 8) to ensure transparency and reproducibility of the statistical methods.

Results

·         In Figure 3, which displays the percentage distribution of the larvae on the three VMs, it would be beneficial to provide error bars or any other indication of variability to represent the uncertainty or variability in the data

·         In Figure 4, check the error bar again.

Discussion

·         To provide a better context for the study, it would be beneficial to briefly summarize the main objectives and hypotheses at the beginning of the discussion.

·         When discussing the need for supplementing the TM's dry diet with a water-supplying vegetable matrix, it would be helpful to highlight the importance of water in the TM's diet and its role in their growth and development. Emphasize the significance of finding sustainable and cost-effective alternatives for water supplementation.

·         Discuss the potential economic and practical benefits of using OFI as a sustainable alternative for water supplementation in TM rearing. Consider factors such as cost-effectiveness, ease of availability, reduced labor and energy costs, and potential implications for large-scale TM production.

·         Highlight the novelty of using OFI as a water-supplying vegetable matrix in TM rearing. Discuss the lack of existing literature on this topic and the significance of the current study in introducing and evaluating this alternative.

General comments

The manuscript presents a well-executed study investigating the use of OFI as a water source in TM rearing. The findings support the feasibility and sustainability of using OFI as an alternative to other VMs. With some minor improvements in addressing limitations and ecological considerations, the manuscript would be even stronger. Overall, it provides valuable insights for researchers and practitioners interested in optimizing water supplementation strategies in TM rearing.

Careful proofreading is required. 

Author Response

Please, see the attached file

Author Response File: Author Response.pdf