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Thank you for your perseverance; I am happy to move this into production and look forward to seeing the published version.
[# PeerJ Staff Note - this decision was reviewed and approved by Anastazia Banaszak, a PeerJ Section Editor covering this Section #]
[# PeerJ Staff Note: Although the Academic and Section Editors are happy to accept your article as being scientifically sound, a final check of the manuscript shows that it would benefit from further English editing. Therefore, please identify necessary edits and address these while in proof stage. #]
You are almost there, but again, the single event and overstatement of your findings misrepresents your work. Please check carefully, and be honest and clear in your evaluation of your results.
For the most part, the authors have sufficiently addressed Reviewer #1's comments. However, a few small but important issues still need to be addressed.
On the whole, I think this work represents an important new locality record, clarified taxonomically by genetic data. However, this work also only represents a single collecting event of 12 Calcinus specimens, all with Palythoa. The lack of this species at other sites suggests that its presence is rare, and that is important too. Nevertheless, this putative facultative association is supported by a single event and the authors do not make this clear in their abstract and fail to emphasize it in their discussion.
To this point, the author's have now misrepresented and over-stated their interpretation of the FLMNH collection records.
Their abstract states:
"...potential association of C. vachoni with . . . Palythoa . . . based on our on-site observation and a public collection database of Calcinus species"
However, none of these FLMNH collections records show any association of Calcinus with Palythoa and the records also do not make a strong case for any kind of association of Calcinus with any reef organisms. That is, I believe most of the 50+ FLMNH collection records of C. vachoni that are "associated" with Pocillopora, were collected during events that targeted only DEAD coral heads (you may want to confirm s with FLMNH staff that these were DEAD coral heads). However, these records do suggest that Calcinus occupies a reef environment, but that is about it I think. The authors need to revise their comments regarding these collection records.
If the authors can revise these minor issues, this manuscript should be acceptable for publication.
Sufficiently addressed
See previous comments
I have heard back from two reviewers now on your work. While one recommends accept, the other reviewer still has many comments and questions that remain to be addressed, many substantial, with regards to your experiment and your conclusions.
As well, as an expert on Zoantharia and Palythoa, I note you have called the zoantharian as "Palythoa mutuki" yet the recent paper by your group recovered sequences close to both "Palythoa mutuki" and "Palythoa aff. mutuki" - these are likely two species as shown by Mizuyama et al. 2018 (PeerJ). Your text does not reflect this at all in this paper.
Species identities of both the crab and its host must be done as best you can given the information at hand, and I wish you to very carefully consider both the reviewer and my comments. Failure to do so will result in likely rejection in the next round of review. If you have questions on Palythoa please ask me any time.
Thus, based on the sum of my concerns and the reviewer's comments, my decision is again "Major revisions". Please note that it is likely I will send a revised version out for re-review.
While I believe the authors have made an honest effort at revising their manuscript, there are still critical issues that prevent me from recommending this manuscript for publication in PeerJ. Primarily, I believe the authors have not done a sufficient job addressing reviewers concerns regarding how they evaluated and reported a facultative association among this hermit crab and Palythoa. As it stands, there work includes important details on a new locality record that extends the distribution of Calcinus vachoni and, using genetic data, puts it within a phylogenetic context of a previously identified species complex. These are important results.
However, the authors argument for putative facultative symbiotic association is overstated and insufficiently supported by their own findings. To review, they found 12 hermit crabs at one site that seemed to be associated with Palythoa. They surveyed 11 other sites and found Palythoa at just one site, but no hermit crabs at any of the 11 sites. Where are their replicates? This is one observation of a putative association. I encourage the authors to look at the collection records of FLMNH (http://specifyportal.flmnh.ufl.edu/iz/). If they search these collection records they will find ~ 80 records of Calcinus vachoni, of which ~45 are associated with collection from Pocillipora heads (I am not sure if these were dead or alive coral heads). I encourage the authors to check other collection records, but this quick search suggests that on the aggregate this species is likely not a typical facultative symbiont of Palythoa across the Pacific. In Korea? Maybe. But one collection event does not strongly support this.
With regard to their “ex situ observations” the authors put 7 hermit crabs into one tank and cared for them until they all died (by two months). There were no replicates (i.e., multiple tanks), no controls (e.g., non-symbiotic hermit crabs), and no trials with a putative host. Palythoa can be kept in aquaria, and very simple short-term (multi-day) presence absence trials would be easily done, and could be informative. Any number of things could have led to the demise of 7 crabs in one tank and no results of this event should be taken as evidence for, or against a facultative association. Any future submission of this manuscript should leave out all mention of these “ex situ observations”.
In the future, if the authors do want to pursue “ex situ” experiments, I recommend they look at the experimental design provided in Hay et al. (1989; reference provided below). This is an exciting topic, understudied, and easily done with appropriate access to specimens.
Hay, M. E., Pawlik, J. R., Duffy, J. E., & Fenical, W. (1989). Seaweed-herbivore-predator interactions: host-plant specialization reduces predation on small herbivores. Oecologia, 418-427.
see previous comments
see previous comments
The authors should be aware that Calcinidae is no longer considered a valid family following Poore & Ahyong (2023) and this is reflected on WoRMS (reference and link below). Thus any text regarding this family should be amended to reflect its current inclusion in Diogenidae.
Poore, G. C., & Ahyong, S. T. (2023). MARINE DECAPOD CRUSTACEA: A Guide to Families and Genera of the World. CSIRO PUBLISHING.
https://www.marinespecies.org/aphia.php?p=taxdetails&id=1515001
Regarding Line 54-57 (*.docx).
Reviewer 1 asked the authors to correct and clarify their description of Calcinus species as facultative symbionts (as it is reported in existing literature). Unfortunately, the revised text is now both vague (making no statement of what coral reef organisms Calcinus typically associate with) and overstated (no matter the host, Calcinus has not been demonstrated to be “one of the major facultative symbionts” of any organism). The sentence is also grammatically incorrect and awkward. It should be split into multiple sentences.
Regarding *.docx file Lines 194-211:
Was a new detailed species-level diagnosis needed? That is, was this diagnosis notably different than previously published diagnoses for the species? If not, then a reference to previous work is more appropriate, especially since you also briefly describe the most important diagnostic traits on Lines 170-171. Since this is a species complex, detailed description of your specimens might be helpful, especially if your specimens demonstrate any intraspecific variation (to each other or the entire spp. complex). But the text would need to be rewritten with this purpose in mind.
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I have heard back from two reviewers, both of whom have offered substantial comments that require a considerable amount of work; hence my decision of major revisions. Personally, as an expert on zoantharians, I can also agree that Palythoa is not a "soft coral" and can also direct you to literature on Palythoa (even from Jeju) if needed. Please revise your work very carefully, and consult with me if needed.
[# PeerJ Staff Note: Please ensure that all review and editorial comments are addressed in a response letter and any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate. #]
This manuscript is mostly very well structured and well written. They do a good job of citing the relevant literature. However, they do a poor job at several points of framing their work within the context of the past studies they cite (below, I discussed this further).
This manuscript successfully:
1) provides a new geographic record extending the range of Calcinus vachoni into S. Korean waters.
2) provide CO1 genetic data to confirm which genetic lineage of C. vachoni these specimens belong to (lineages previously delineated by Malay & Paulay, 2010).
3) provides limited evidence supporting an association with the soft coral Palythoa aff. mutuki
However, the authors make a number of claims in their abstract that are not novel and may even be misleading when viewed in the context of previous work (Malay & Paulay, 2010). That is, counter to what this abstract suggests is novel:
-Malay & Paulay, 2010 have already conducted a much more thorough phylogenetic analysis of Calcinus using multiple loci and including C. vachoni.
- They already demonstrated the monophyly of Calcinus and many of its sub-lineages
- They already explicitly and more thoroughly discussed species and species complex boundaries.
- They have already demonstrated that C. vachoni is subdivided into three well-supported haplogroups (although, here the authors have provided improved sampling to confirm this!)
The authors need to do a better job in their abstract (and the rest of their manuscript) of not overstating their analyses and results. They are specifically investigating C. vachoni, and that is important. They are not doing a thorough reanalysis of the group, and they need to heavily revise their manuscript to reflect this.
Taxon sampling of Molecular data: The authors need to do a better job of explaining why they chose the taxon sampling they did. Malay & Paulay (2010) generated relevant CO1 data (and other loci) for nearly all species of Calcinus (>40 spp.). Here the authors have only sampled 9 species (including 3 lineages of C. vachoni). The rational answer seems to be that they are only trying to place the Korean specimens within the 3 MOTU/ESUs Calcinus vachoni species complex identified by Malay & Paulay (2010). This is great! Run with this! Explain this! Last, their outgroup is a brachyuran crab (i.e., belongs to an entirely different infraorder). This is strange. They need to explain this choice. These are quick analyses to run, so it would not be unreasonable to suggest they rerun these with a more appropriate outgrip. Pick a few from Malay & Paulay (2010).
Regarding their “ex situ experiments”, the authors need to explain why they did not try to run these with Palythoa present in the tanks. I am not sure what to conclude from any of these observations. I think they are implying that the crabs all died because Palythoa was not present. However, I do not think there is evidence enough to suggest that these crabs are obligate commensal species, so it seems less compelling to argue that their demise was due to absence of a host. I remain respectfully skeptical that we can make any inference from these lab observations.
See previous comments
Line 53: "where a symbiotic association of the hermit crabs with soft corals is generally reported"
Is this true? Can you provide more details or references? Malay & Paulay (2010) indicate that many Calcinus species are "facultative coral associates" frequently found within branching corals. I assumed they were referring to scleractinian/stony corals. Please clarify.
Table 1: the legend indicates ** are sequences pulled from Genbank, while the table lists these with *. This needs to be fixed. However, I generally dislike the use of * for these designations and encourage the authors to just bold their new sequences and drop use of * entirely (including in your phylogenetic tree. But, it is up to them.
The manuscript by Jung and Park reported Calcinus hermit crabs for the first time from Korea, with notes of ecological association with Palythoa aff. mutuki. In general, this manuscript is well written and nicely illustrated. However, several issues should be clearly addressed when revising the manuscript.
Line 66-: How did you identify co-occurring Palythoa species? Identification of Palythoa species is usually difficult by morphological data (see Mizuyama et al. 2018 PeerJ). As associated Palythoa speices may affect the occurrence of Calcinus vachoni, the authors need to identify correctly for this Palythoa species. Please consider performing phylogenetic analyses for this Palythoa species (with ITS marker) to confirm.
Line 108: How did you choose these 12 sites? The authors need to provide more details on this sentence.
Line 219-224: Does this mean that you could not find both C. vachoni and co-occurring P. aff. mutuki in other 11 sites? Do you find any P. aff. mutuki without C. vachoni? I suggest that the authors need to explain more detail on each site. Also, I would delete this sentence “tide level, substrate composition, seawater inflow, and other abiotic environmental factors”, as you did not measure any of those factors.
Line 231-235: Since the authors did not perform any controlled experiments in the aquarium (with Palythoa aff. mutuki vs. without P. aff. mutuki), it is hard to tell that the presence/absence of P. aff. mutuki affects to the survival of C. vachoni. I suggest that the authors need to mention about this.
Line 62-64: “Soft coral” is usually used for a member of Alcyonacea (Octocorallia), and “colonial anemone” is sometimes used for Zoantharia (Hexacorallia). I suggest that the author correct this terminology in the manuscript.
Line 53-55: I think the authors need to explain more details on the sentence “hermit crabs with soft corals is generally reported”. What kind of soft corals are often associated with Calcinus species?
Line 184-185: What does BP mean?
Figure 1: It is hard to find Calcinus vachoni in this figure. I suggest that the authors use arrow or something to highlight them.
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