An Overview of the Helminths of Moor Frog Rana arvalis Nilsson, 1842 (Amphibia: Anura) in the Volga Basin

Round 1

Reviewer 1 Report

• L. 14 – “over the past 40.” – check the manuscript for typos and phrasing issues.
• L. 36 – “fungi [12–14]” – please make sure that you cite the most appropriate references, i.e., either those that discovered the respective problem or those that are of the highest quality or those, which are the newest. In this case (and in some others), these conditions are not fulfilled.
• L. 36 – “and helminths [15–17]” – as this manuscript focuses on helminths, I would expect that the topic of helminth-caused pathologies of amphibians will be more developed in the Introduction.
• L. 43 – “the basin area” – better “catchment area”
• L. 50 – “data on helminths of moor frog remain scattered.” – please make sure that you provide an overview of helminths of the study species not only from the local perspective but also from the host species perspective that would not be limited to certain geographic areas only. In the other words, provide several sentences on a complete list of literature, which deals with helminths of the study species.
• The additional references may include Parasitology 7(1): 90, Acta Parasitologica Polonica. Warszawa 33(4): 267-272, Acta Parasitologica Polonica. Warszawa 33(2): 107-113, Parazitologiya. Akademiya Nauk SSSR. Leningrad 36(4): 304-309, and others.
• Table 2 – double-check the host cycles. For example, the definitive hosts of Tylodelphys excavata are frequently the birds of prey (e.g., Buteo buteo), Strigea sphaerula is typically found in corvids but may be present in other Passeriformes as well.
• The Results chapter does not contain any “results”. Instead, it contains only a list of helminths found in the study area. It is necessary to re-write the manuscript in a standard way, i.e., postulate the testable hypothesis/hypotheses or state at least some aims, describe the methods, including the more detailed specification of sampling sites, sampling efforts, diagnostic criteria used, describe the features of the species found, focus on what you found as new from the international point of view (you may mention what is of regional importance but this should not be the major focus of the manuscript). Quantify the findings. Analyze the species richness, abundance, alpha and beta diversity, etc.
• L. 448 – “The largest number of helminth species has been recorded in the moor frog from the Republic of Mordovia (25 species), the Samara region (24), and the Republic of Bashkortostan (22” – any such claims of differences would require appropriate statistical treatment. This treatment should reflect differences in sampling intensity.

Author Response

L. 14 – We have made corrections.
L. 36 – We have made corrections.
L. 36 – We only pointed out that amphibians are a helminthes disease. But we are not the subject of the entire manuscript.
L. 43 – The river basin is a common expression in the biological literature. The catchment area is usually used in geographical literature.
L. 50 – We have made corrections.
L. 448 – The intensity of sampling also affects the result. This is exactly what was stated in the original text. But we have made additional suggestions.

The data in the tables has been corrected.

The "Results" and "Discussion" sections have been reformatted. We moved the list of species to Appendix.

There are already a lot of References and adding additional ones will not change the manuscript.

Reviewer 2 Report

Dear Authors,

This is an intriguing and important study that combines all data on the helminth fauna of the moor frog.

While I support this paper for publication, I have several recommendations designed to help strengthen the study or its presentation. All of these are eminently feasible I suspect.

Some problems exist with citing of literature and the separate phrases:

52 – Gorkovskaya Oblast?

57 – the Volga River instead of the Volga river

57 – basin or drainage?

164 – Palaearctic instead Palearctic

203 – Why is it Pneumonoeces or not Haematoloechus?

Additionally, it is very good that you provide data on Russian literature, which is so insignificantly represented in foreign sources, but which in many respects are important for considering the problems of parasitology and remain without citation due to the language barrier.

Best regards,

Author Response

1. We have made all corrections to the manuscript.
2. 2. in 1902, Looss was forced to change the name of Haematoloechus to the new name Pneumonoeces, since the taxon was pre-occupied by Stal as early as 1874 for the name of one insect from the order Hemiptera. The database" Fauna europaea " has the name Haematoloechus. We have made corrections.

Round 2

Reviewer 1 Report

Despite there was some progress since the first manuscript version, I still consider the manuscript to be a "missed opportunity". The whole manuscript is still written as a faunistic report instead of a scientific paper. Some of the raised minor comments were reflected, whereas the major ones and some minor ones were not reflected or were reflected only partially. I now understand that the authors aim to keep the paper in line with the "faunistic" papers - therefore, the way how to improve it could be in providing at least more quantitative data instead of simple presence/absence data - intensities of infection, frequencies of infection, prevalence, etc. I also repeatedly call for the inclusion of the data obtained abroad in the Introduction/Discussion - compare your data to whatever was published on the study species not only in Russia but also abroad. Provide better coverage of helminth-caused pathologies of amphibians in the Introduction (again, including the references). I see the T. excavata host cycle updated (but without reference - you may cite, for example, Sitko, Parasitol. Int. 72 (2019): 101946); the S. sphaerula was not updated (see, e.g., Heneberg, Parasitol. Int. 67.6 (2018): 688-701), other species also need updates. The descriptions of helminths found were not addressed at all despite many of them are difficult to identify and providing detailed measurements and photographs would allow the readers (and the reviewers) to assess, whether the diagnoses were correct. Currently, we have no chance to check, whether the diagnoses were correct or not. The diversity data were not quantified as well, despite it was suggested. The requested statistical treatments were not performed.

Author Response

The authors of the manuscript made the following edits to the text and tables at the suggestion of one of the reviewers:

 1. A new paragraph has been added to the introduction, which briefly describes a wide range of helminthic pathologies in amphibians of different generations: from changes at the cellular and tissue level to skeletal anomalies and deviant behavioral reactions. The presented information is provided with new references to 8 studies by foreign and Russian authors.

2. A new paragraph on the study of helminths of the moor frog in the countries of Europe, as well as the states of the former USSR (Belarus), has been added. The information is provided with new references to 26 studies by 23 foreign authors from 8 modern and former countries.

3. The life cycles of individual trematode species of the families Strigeidae and Diplostomidae are clarified. New groups of final hosts have been added to the tables. The information is provided with new references to the studies of 3 foreign authors.

4. A description of laboratory methods for fixing, coloring and manufacturing helminth preparations has been added in the part “Materials and methods”.

5. The introduction of new references in the text and tables of the manuscript led to the changes in the part with references. Thus, it was changed.

One of the honorable reviewers pointed out that information about the helminths of amphibians in Russia is poorly represented in foreign sources. The reasons should not be discussed. However, Russian data may expand the understanding of the distribution of amphibian helminths both in Europe and in Eurasia. Moreover, the Volga River basin is the largest in Europe. Any parasitological study has its own initial, basic stage. It consists of a description of the fauna of the host parasites in a particular part of the habitat. After that, it is possible to move on to the next stage of research: population study, biocenotic study, etc. As it was indicated in the manuscript, information about the helminths of Rana arvalis from Russia was published for the first and last time in Europe in the summary of Vojtkova, Roca (1994, 1996) and at that time was already outdated. The data were based on data from the book K. M. Ryzhikov et al. (1980), which refers to the study of the 60-70s of the XX century. That is why our primary goal was to combine disparate data from different authors and our own materials for a new presentation. We believe that the presence of extensive tables is quite illustrative for such a study and fully reveals our topic. This is how most faunal studies look, including the most recent ones that we read while searching for the necessary references. This opinion is shared by other reviewers with whom we have collaborated in a series of past papers on Rana temporaria (Acta Parasitologica, 2014), Bufo bufo (Nature Environment and Pollution Technology, 2016), Pelophylax lessonae (Nusantara Biosciences, 2018, 2019; Journal MVZ Cordoba, 2019). It seems that the detailed measurements, index calculations, photographs that the reviewer mentions are the data for the next stage of research. But in this faunal context, in our opinion, they will lead to an excess of information, semantic overload and an increase in the already long manuscript.

Round 3

Reviewer 1 Report

All raised comments were addressed to a sufficient extent.

Author Response

The authors of the manuscript made the following edits to the text and tables at the suggestion of one of the reviewers:

1. A new paragraph has been added to the introduction, which briefly describes a wide range of helminthic pathologies in amphibians of different generations: from changes at the cellular and tissue level to skeletal anomalies and deviant behavioral reactions. The presented information is provided with new references to 8 studies by foreign and Russian authors.
2. A new paragraph on the study of helminths of the moor frog in the countries of Europe, as well as the states of the former USSR (Belarus), has been added. The information is provided with new references to 26 studies by 23 foreign authors from 8 modern and former countries.
3. The life cycles of individual trematode species of the families Strigeidae and Diplostomidae are clarified. New groups of final hosts have been added to the tables. The information is provided with new references to the studies of 3 foreign authors.
4. A description of laboratory methods for fixing, coloring and manufacturing helminth preparations has been added in the part “Materials and methods”.
5. The introduction of new references in the text and tables of the manuscript led to the changes in the part with references. Thus, it was changed.
6.  

One of the honorable reviewers pointed out that information about the helminths of amphibians in Russia is poorly represented in foreign sources. The reasons should not be discussed. However, Russian data may expand the understanding of the distribution of amphibian helminths both in Europe and in Eurasia. Moreover, the Volga River basin is the largest in Europe. Any parasitological study has its own initial, basic stage. It consists of a description of the fauna of the host parasites in a particular part of the habitat. After that, it is possible to move on to the next stage of research: population study, biocenotic study, etc. As it was indicated in the manuscript, information about the helminths of Rana arvalis from Russia was published for the first and last time in Europe in the summary of Vojtkova, Roca (1994, 1996) and at that time was already outdated. The data were based on data from the book K. M. Ryzhikov et al. (1980), which refers to the study of the 60-70s of the XX century. That is why our primary goal was to combine disparate data from different authors and our own materials for a new presentation. We believe that the presence of extensive tables is quite illustrative for such a study and fully reveals our topic. This is how most faunal studies look, including the most recent ones that we read while searching for the necessary references. This opinion is shared by other reviewers with whom we have collaborated in a series of past papers on Rana temporaria (Acta Parasitologica, 2014), Bufo bufo (Nature Environment and Pollution Technology, 2016), Pelophylax lessonae (Nusantara Biosciences, 2018, 2019; Journal MVZ Cordoba, 2019). It seems that the detailed measurements, index calculations, photographs that the reviewer mentions are the data for the next stage of research. But in this faunal context, in our opinion, they will lead to an excess of information, semantic overload and an increase in the already long manuscript.