Ascaridoid Nematodes Infection in Anadromous Fish Coilia nasus from Yangtze River

Round 1

Reviewer 1 Report

- Line 16 and 276 and other places: spelling of the families Anisakidae and Raphidascarididae should be corrected.

- Line 31:  According to the articles below, life cycle of aquatic/marine ascaridoid involves marine mammals, birds, reptiles, amphibians and predatory fish and elasmobranchs as definitive hosts. Please update your statement.

Journal of Helminthology 1979, 53, 265-282.

Journal of Helminthology 2017, 91, 613-624.

Parasitology Research, 2019.  118, 2159–2168.

-Line 32: Please note the information about the intermediate hosts is outdated. Birds and sea-snakes also have been found as the intermediate hosts. Please see this articles:

Transactions of the Royal Society of South Australia, 1942,  66, 66-70.

Parasitol Int, 2017, 66, 837-840.

-Lines 34 to 37: There appears to be a confusion in the definition of anisakidosis and its causative agents, which may include all anisakids rather than solely Anisakis spp. I recommend referring to the following papers for a comprehensive understanding of the distinction between anisakidosis and anisakiasis. In your article, it is suggested to use the term "anisakidosis" and refer to the causative agents as "anisakids." Additionally, consider including Hysterothylacium spp. as mentioned in the cited papers. However, it is crucial to explicitly state in the Introduction the scope of your discussion, specifying what is included and excluded.

Parasitology Research, 2023, 122, 1733–1745.

Parasitology Research, 2021, 120, 3007–3033.

-Line 38: The initial mention of the fish host must include the name of the authority.

- Lines 66 to 70: Please provide details of the approval, including the number and the date.

- Lines 71 to 79: The authors exclusively utilised visual examination for parasite collection. While this method is commonly employed, it has inherent limitations that need to be acknowledged, especially concerning the aims and scope of this study. The most comprehensive approaches involve either digestion or incubation methods, allowing for the emergence and collection of all parasites from the fish tissues.

 Please see these articles:

For Digestion method see: Canadian Journal of Fisheries and Aquatic Sciences, 1986, 43, 1312-1317.

For Incubation method see: International Journal of Food Microbiology, 2016, 227, 13-16.

It is noteworthy that the use of one of these methods is crucial for the emergence of Contracaecum larvae. Authors may also be interested in reading the first paragraph of the materials and methods in this article: Journal of Helminthology, 2017, 92, 216-222.

This paper reports that using visual examination no parasite was found. It was only after employing the incubation method that parasites were found in examined fish:

Marine and Freshwater Research 2023, DOI: https://doi.org/10.1071/MF23095

Please address these considerations in the Discussion section. This limitation is of significant importance for the manuscript since it implies that the mean intensity and abundance could potentially be higher in C. nasus. Additionally, this limitation suggests that other members of Anisakidae, such as Contracaecum, might still be present in C. nasus, but due to the constraints of the study, they were not detected.

- Lines 81 and 82: What criteria were employed to select this specific number of specimens from 16 individual fish? It is essential to explore the basis for this choice and discuss the limitations it poses to the study. Could this selection method have overlooked potential diversity in ascaridoid findings? This aspect should also be addressed in the Discussion.

- Line 98: Why some words are capital letters?

- Sections: 3.1 and 3.2: Another limitation of the study is the amalgamation of all diverse parasites into a single analysis. Conducting analyses for each taxon separately could yield significantly different and more informative results. If separate analyses for each taxon were not feasible, this constraint should also be acknowledged as a limitation in the Discussion.

- Line 175: Please change anisakids to ascaridoids.

- Line 176 and 177: Please present the taxa found consistently with the information provided in Table 2. You can phrase it as follows: "There were seven anisakid nematodes, closely related to the following taxa in GenBank:"

- Table 2: In addition to the number of individual sequenced, it is important to include what was the total number of specimens belonging to that particular taxon.

- Table 2: The authors noted that for certain taxa, more than one specimen has been sequenced, but the GenBank accession numbers for these sequences have not been provided. It is essential to include these accession numbers for clarity.

- Results: Regarding the two taxa reported here, Hysterothylacium fabri and Hysterothylacium aduncum, I would like to encourage the authors to review and consider the findings presented in this article: Journal of Fish Disease, 2018, 41, 1463-1475. The authors of that study sequenced specimens across various developmental stages, conducting both morphological and genetic examinations, and provided museum voucher specimens, providing a reliable reference sequence for these taxa. It would be valuable to assess how closely or distantly your specimens align with those in the aforementioned study.

- Line 234 to 239: Based on your results, could you elucidate the likely origin of the infection? Is it predominantly associated with marine, estuarine, or freshwater environments? Additionally, please take into consideration the limitations highlighted in the earlier comments.

- Line 242: Without including the age factor, it is challenging to draw definitive conclusions about the relationship between length and infection. To make a meaningful assessment of the length-infection relationship, it is essential to compare lengths within the same age group. For more information you may see some similar studies such as:

Dis Aquat Organ 2016,  120, 69-75.

Parasitology Research, 2018 17, 3327-3331.

- Line 248 to 249: It is crucial to highlight a significant limitation here. There might be some variation overlooked if the authors did not treat each different nematode separately, combining them as a single entity.

- Line 253 and elsewhere: cecum or caeca?

- Line 259: How was the determination of severe damage reached without conducting histopathology? This statement needs to be revised.

- Lines 279 and 280: It is essential to discuss the reasons why these larvae were not detected in your study despite being found in previous research. Is it possible that the prevalence and infection rate were so high that infected fish died, leading to no observations in your study? This absence of observation could potentially signify a severe impact on the population. Notably, Eustrongylides, in particular, has been identified as lethal in both fish and birds, according to these studies:

Marine and Freshwater Research. 1974. 25 (1), 105–120.

Rambaut, A., 2014. FigTree v1.4.2, a Graphical Viewer

Eolophus, 2018, 2, 33-36.

Food and Waterborne Parasitology,2023,  e00189.

- Lines 286 and 290: These statements are intriguing, and I recommend that the authors read the following articles and consider their implications in the present study. In nearby waters in Japan and Australia, there has been a decline in the population of marine ascaridoids (see: Parasitol Res 2021, 120, 1605-1615; Int J Food Microbiol DOI: https://doi.org/10.1016/j.ijfoodmicro.2019.108306; Int J Food Microbiol DOI: 10.1016/j.ijfoodmicro.2018.03.007). This decline has been attributed to lower populations of zooplanktons and crustacea (see: Parasitol Res 2021, 120, 3007–3033).

- Lines 291 to 298: I recommend authors read and reflect on this article here:

Journal of Helminthology 2017, 92, 81-89.

Dis Aquat Organ 2016,  120, 69-75.

few minor typos that have been mentioned in the comments.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

I have completed a thorough review of the manuscript titled "Ascaridoid nematodes infection in anadromous fish Coilia nasus from Yangtze River" and believe that it requires significant revisions for improvement. Firstly, while the authors mention that species were identified based on morphological and molecular data, there is a lack of detailed morphological information and molecular analysis in the text.

To enhance the manuscript, I suggest the following revisions:

1. Molecular Analysis: Please provide a detailed description of the molecular analysis process, including the methodology and results. Additionally, I recommend including a phylogenetic analysis to elucidate the evolutionary relationships among the nematode species studied.

2. Morphological Observations: Develop detailed descriptions of morphological characteristics observed in the nematode species. Furthermore, incorporate figures or drawings to support these morphological observations for better clarity and understanding.

3. Material Deposition: Please specify where the materials supporting this research have been deposited for reference and future studies.

4. Graphs and Figures: Merge redundant information presented in graphs 5 and 6, and retain only one of them for clarity and conciseness. Consider removing figures 1 to 4 if they do not significantly contribute to the understanding of the research findings. Additionally, prioritize the presentation of Figure 10 as the first figure in the manuscript.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

I have had the opportunity to review the manuscript entitled "Ascaridoid Nematodes Infection in Anadromous Fish Coilia nasus from Yangtze River" by Qingjie Zhou et al. Overall, I find the work to be well-written and the results obtained are intriguing from both a parasitological and ecological perspective.

The study sheds light on the infection of ascaridoid nematodes in anadromous fish species, particularly Coilia nasus, from the Yangtze River. This research contributes significantly to our understanding of parasite ecology in aquatic ecosystems. The authors have effectively highlighted the prevalence and impact of these infections on the host population, which is crucial for both ecological and fisheries management perspectives.

One suggestion for improvement is regarding the terminology usage throughout the manuscript. While discussing parasites, terms such as "ascaridoid" and "Anisakidae" are central. However, I noticed occasional spelling errors or inconsistencies in their usage. I recommend that the authors carefully review the text to ensure consistency and accuracy in the usage of such terminology.

Furthermore, the ecological implications of parasitic infections, as mentioned in the manuscript, are particularly noteworthy. I suggest that the authors emphasize the role of parasites as ecological indicators even more prominently. By integrating relevant literature, such as the work by Palomba et al. (2023) in Parasitology, the authors can strengthen the ecological narrative of their study.

In summary, this manuscript presents valuable insights into the parasitological and ecological aspects of ascaridoid nematode infections in Coilia nasus from the Yangtze River. With minor revisions to improve terminology consistency and further emphasis on the ecological implications of parasitic infections, this work has the potential to make a significant contribution to the field.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

After reading the answers to my inquiries, I believe it is appropriate for the work to be accepted for publication. I congratulate the authors on the improvement in the manuscript.

Author Response

Thank you for your help. We appreciate the time and effort that you and the reviewers dedicated to providing feedback on our manuscript, and are grateful for the insightful comments on and valuable improvements to our paper.