Bidenichthys okamotoi, a New Species of the Bythitidae (Ophidiiformes, Teleostei) from the Koko Seamount, Central North Pacific^†

Round 1

Reviewer 1 Report

The manuscript is well structured and well written. I only miss a barcoding analysis of the species. DNA barcoding is a tool that has successfully integrated and improved traditional morphological analysis in systematic studies of fishes. Obtaining the barcode for a new species can help in the correct identification of future records and in the knowledge of intra- and interspecific relationships.

Specific comments:

Abstract: As far as I know, the abstract does not support bibliographical references.

L.75: pectoral-fin rays 21-30 but in table 1 there is a specimen of B. capensis with 20 rays, so the range should be 20-30

L. 76: total gill rakers 18-27 but in table 1 there is a specimen of B. capensis with 13 gill rakers, so the range should be 13-27

L. 95: Bidenichthys okamotoi (in italics)

L. 219 and 220: I think “Distance from ventral fin insertion to anal fin origin” could be more adequate. The term “base” is mostly used for the fin bases.

L. 256: B. capensis (in italics)

L. 292: Add the symbol + in (12+27 vs 12+ 29–33)

L. 313-326: This paragraph is descriptive and should be moved to the Introduction section or to the material and methods in a "Study area" subsection.

L. 328: Eschmeyer, Abe & Nakano, 1979 but Eschmeyer, Abe & Nakano, 1978 in the references list

Figure 3: The letters A to I are in the figure caption but do not appear in the figure

Table 1: Prepectoral length and Prepelvic length should also be added

Table 1: The species key is based on pectoral fin peduncle lengths, but this character does not appear in the morphometric characters of Bidenichthys spp. Therefore, pectoral fin peduncle length and width should be added to the table 1.

Author Response

Response to reviewer 1.

 

We agree that barcoding is a tool that has successfully integrated and improved traditional morphological analysis in systematic studies of fishes. We also agree that a barcode of a new species can often help with the correct identification of future records. For studies of intra- and interspecific relationships more genetic markers than a barcode is usually needed. Unfortunately, we have no access to tissue samples from the specimens, that we have only seen in formalin preserved condition. Therefore – a barcode must await future sampling of fresh specimens.  

 

Specific comments

 

L.75: pectoral-fin rays 21-30 but in table 1 there is a specimen of

1. capensis with 20 rays, so the range should be 20-30

 

Done

 

 

1. 76: total gill rakers 18-27 but in table 1 there is a specimen of
2. capensis with 13 gill rakers, so the range should be 13-27

 

Done

 

1. 95: Bidenichthys okamotoi (in italics)

 

Done

 

1. 219 and 220: I think “Distance from ventral fin insertion to anal

fin origin” could be more adequate. The term “base” is mostly

used for the fin bases.

 

We agree – done

 

 

1. 256: B. capensis (in italics)

 

Done

 

 

 

1. 292: Add the symbol + in (12+27 vs 12+ 29–33)

 

Done

 

 

1. 313-326: This paragraph is descriptive and should be moved

to the Introduction section or to the material and methods in a

"Study area" subsection.

 

Ok – moved to Material and Methods – as a Study area subsection

 

1. 328: Eschmeyer, Abe & Nakano, 1979 but Eschmeyer, Abe &

Nakano, 1978 in the references list

 

Done

 

Figure 3: The letters A to I are in the figure caption but do not

appear in the figure

 

A new version of Figure 3 is un-loaded

 

 

Table 1: Prepectoral length and Prepelvic length should also be added

 

There is no tradition for these characters in recent Bythitid studies. Not added here.

 

 

Table 1: The species key is based on pectoral fin peduncle

lengths, but this character does not appear in the morphometric

characters of Bidenichthys spp. Therefore, pectoral fin peduncle

length and width should be added to the table 1.

 

We see the point, but since we do no longer have access to most of the studied specimens, adding to table 1 is very difficult. The character can be visual seen in figure 1. We have added the number of anal fin rays to the key, so that the ID is not relying only on the pectoral fin peduncle lengths.

 

 

Thanks a lot for a careful review.

Reviewer 2 Report

This is a great paper, and well written.

I have made a few suggestions to smooth out some of the language. there are a few places where the sentences are too long & recommend breaking them up.

I have also added a few suggestions around 1) the putative distributions and causes/origins, and 2) the depth ranges of the species which I feel need addressing.

Comments for author File: Comments.pdf

Author Response

A file is attached

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper is very well written and takes in account numerous features to describe the new species Bidenichthys okamotoi.

Unfortunately it completely lacks molecular study of the specimens, that is by now of fundamental importance to create a valid dataset in the definition of a new species. The authors should consider to use metabarcoding procedures to be sure of genetic distance of their specimens from already described species. It would be better to sequence the entire mitochondrial genome. 

The authors should consider to use appropriate terms about "otoliths". Three pairs of otoliths (three on each side), known as the sagitta, lapillus, and asteriscus are present in teleost fishes. The authors described only sagitta, so it is my suggestion to change otoliths in "sagittal otolith" or "sagitta". Appropriate terms can be found in "D’Iglio, C., Albano, M., Famulari, S., Savoca, S., Panarello, G., Di Paola, D., Perdichizzi, A., Rinelli, P., Lanteri, G., Spanò, N., Capillo, G. Intra- and interspecific variability among congeneric Pagellus otoliths (2021) Scientific Reports, 11 (1), art. no. 16315". In this last paper the authors used R shape analyses to detect differences among sagittal otoliths; it would be a good idea to perform this analyses on  Bidenichthys okamotoi sagittal otoliths. 

For what concerning references in the text, it would be checked. In fact, all references are in the wrong format; e.g. ....Barnard (1934)[1]... line 30. 

All the best regards

The reviewer 

Author Response

Response to reviewer 3.

We agree that barcoding is a tool that has successfully integrated and improved traditional morphological analysis in systematic studies of fishes. We also agree that a barcode of a new species can often help with the correct identification of future records. For studies of intra- and interspecific relationships more genetic markers than a barcode is usually needed. The entire mitogenome is a good idea. Unfortunately, we have no access to tissue samples from the specimens, that we have only seen in formalin preserved condition. Therefore – a barcode must await future sampling of fresh specimens.  

 

Instead of molecular work that was not possible, we have expanded the morphological part, with the use of a high-quality CT scan and sagittal otolith analysis. We are not in doubt that this is a new species and we think it is still ok to describe new species without molecular data.

 

Reviewer 3 requested that ‘sagittal otolith’ rather than ‘otolith’ should be used for the description. It is true that we only describe sagittal otoliths. The reason for that is that sagittal otoliths show by far the most diversity and diagnostic value. In the very large body of morphological otolith research, the term ‘otolith’ is usually used as synonym of ‘sagittal otolith’ unless when describing other otoliths such as the ‘lapillus’ or ‘asteriscus’. However, we are aware that not all readers are familiar with this usage, and therefore changed to ‘sagittal otolith’ in the subheading for the description for clarity.

Reviewer 3 further suggests whether it could be useful to include R shape analysis of the sagittal otoliths and gives reference to a recent paper in that respect. R shape analysis is a new technique occasionally used for otoliths when dealing with very similar morphologies across species or in the presence of very large sample sizes for a statistic approach. Both is not the case here. Bidenichthys species are generally rare, and even more so are the otoliths extracted from them. Also, the differentiation of the various species is very clear with otolith morphology and does not require such technologies at all. The way the otoliths are described follows a well-established standard for nearly 150 years now and we strongly recommend to keep it like that.

 

Thanks a lot for a careful review.

Reviewer 4 Report

No suggastion for authors

Author Response

Thanks a lot for your positive review. 

Round 2

Reviewer 3 Report

Thanks for your responses. 

Author Response

We are uncertain if further changes/ corrections was requested from this reviewer. Please specify if this is the case.