Photographic Checklist, DNA Barcoding, and New Species of Sea Slugs and Snails from the Faafu Atoll, Maldives (Gastropoda: Heterobranchia and Vetigastropoda)^†

Round 1

Reviewer 1 Report

The article is very important to researchers.

1) I would suggest that table 1 be divided into several ones, make a table for each family, thereby the two left columns can be deleted, and replace one column with distribution information.

2) if possible, write a molecular diagnosis for each of the 6 new species

Author Response

> Thank you for the suggestions. We prefer to keep Table 1 as one table so that readers can retrieve all the information from the spreadsheet more easily, but we made the following changes to simplify the table as suggested: removed the first column; changed the reference style for numeric. The locality information can be found on Table S1.

> While the reviewer raises a valid argument, any statement about punctual molecular features of our newly described species would overshadow the molecular diversity among populations, and would likely not represent a true diagnosis. Because COI is variable even within species, and only one or few individuals of each species were sequenced, we believe a morphological diagnosis is informative enough at this stage to differentiate among species. Moreover, our molecular data is published on GenBank for future studies dealing with a wider taxon sampling.

Reviewer 2 Report

Dear editor,

CUNHA et al: Photographic checklist, DNA barcoding, and new species of sea slugs and snails from the Faafu Atoll, Maldives (Gastropoda: Heterobranchia and Vetigastropoda)

This paper describes diversity of two mollusk groups, of sea slugs and allies and of top-shells and allies, in two atolls in the Maldives. Authors found 105 species, half of which are new to the Maldives; and these include six new species. All species are both photo-recorded and analyzed by molecular tools.

This is a very good paper, novel in that it reveals how rich and diverse Pacific atolls are, way beyond what we knew of just two-three decades ago, and future papers concerning the diversities of tropical marine faunas shall surely cite it.

I strongly recommend that you publish this paper, once authors attend to an important point, concerning the description of the new species Facelina montana and Tergiposacca perspicua: For each of these species, for the benefit of future students of these groups, authors must state clearly: “this new species differs from the type species (or the nearest species) in that….”

Once authors attend to this minor yet important point, this very good paper should be published.

Author Response

> Thank you for your highlights on the strengths of the manuscript, and for the suggestion. We have included a clear statement on how the new species of Sakuraeolis and Tergiposacca differ from other congeneric species in the remarks section of each species description.

Reviewer 3 Report

This is an important study of high general interest in the field of marine malacology, especially since the checklist is complemented with extensive barcoding (COI), hence I recommend it for publishing. However, I would like to see more pictures on the new species that are being described, preferrably on separate figure sets with higher magnification, and showing other angles of the bodies. Even photos from side and below of the preserved types material could be useful if there are no photos on the living animal more than just from above. Any internal features from the feeding apparatus and reproductive organ would of course also strengthen the descriptions, if possible, but is not crucial. 

The paper would also benefit greatly if the supplementary would include tables with percentages of either matches or barcode gap distances, as these are used as basis in the discussion, on systematic relationships.

Minor spelling errors:

p.24, line 207 Stilliger should be Stiliger, same on p.32, line 581

p.33 , line 606 C. marmoreous should be C. marmoreus.

Supplementary

Fig. S2 header, Limenanandra should be Limenandra

Fig. S3 and S4 Martinov should be Martynov

For the Eubranchus doriae sequence, the species is named as Capellinia doriae in Molluscabase.

Author Response

> Thank you for your highlights on the strengths of the manuscript, and for the suggestions. We fixed the typos, replaced Eubranchus doriae with Capellinia doriae in the supplementary figure S3, and added two supplementary tables (S2 and S3) with BLAST results.

> The request for more images is a valid suggestion that would surely benefit the visualization of the described species. Nevertheless, due to changes in the soft tissue after preservation, especially for these small slugs, we believe that photos of the preserved specimens would be little informative as additional plates in the paper. The vouchers are available in the MCZ for further examination, and additional pictures from the live specimens with different angles can be found at the MCZ link provided in each species description (these will be available online once the paper is accepted for publication). In order to speed up taxonomy here we provide short but clear species descriptions with diagnostic remarks; anatomical dissections are out of the scope of this paper.

Reviewer 4 Report

This manuscript describes the diversity of Heterobranchia and Vetigastropoda in the Maldivian archipelago. The paper is of considerable interest as there is little previous work on this group of animals in that area, and there are no specific previous publications on the Vetigastropoda of the Maldives. The paper is well written and organised. In the Introduction section, perhaps the authors should elaborate more on the importance of realizing and providing faunistic lists, especially in light of the ongoing global change. The section of Materials and Methods was well illustrated and presented. The work was carried out comprehensively as the authors also refer to literature data. The Results section is well presented with the checklist and photographs. The descriptions of the animals are detailed. The Discussion section elaborates perfectly on the results obtained, providing details of the species found and comparisons with the related ones. In conclusion, I believe that this manuscript deserves publication.

Author Response

> Thank you for your highlights on the strengths of the manuscript, and for the suggestion. We opted to keep the Introduction focused on the literature that was more directly related, but we elaborate on the importance of faunistic surveys and the impacts of environmental change in the Discussion section (entire third paragraph and end of 2nd paragraph).