Fantastic Flatworms and Where to Find Them: Insights into Intertidal Polyclad Flatworm Distribution in Southeastern Australian Boulder Beaches

Round 1

Reviewer 1 Report

This is a welcome addition to knowledge of the distribution of polyclads in Australia, and it is especially important for contributing to knowledge of polyclads at higher latitudes.  
I am impressed that the authors properly identified the species using serial sectioning.

The title of the paper seems almost to allude to the comprehensive work that Leslie Newman and Lester Cannon did on polyclads of Australia and the western Pacific, but their papers are not mentioned.  Their book and video on "Fabulous Flatworms..." refers to several species in southeastern Australia:
Cestoplana australis,
Echinoplana celerrima,
Enantia sp.,
Myoramyxa pardalota,
Notoplana australis,
Pseudobiceros hancockanus,
Pseudoceros felis,
Pseudoceros gamblei,
Stylochus kimae,
S. meganae,
S. mcgrathi
(and maybe others; I did not check thoroughly).

To me, the statement on line 14, then, is misleading.  I would think, in any case, that what is known of polyclads in southeastern Australia should be mentioned.

The species named in the manuscript should be fully identified with authority the first time each is mentioned. (For example, "Echinoplana celerrima Haswell, 1907, occurred ..." on line 183.

line 21: "are discussed" is not appropriate for an abstract.  What, in brief, are these influences?

line 31 ff: It's already way too late---by at least 50, if not 150 years or more---to get a baseline view of polyclad distribution.  The ravages of anthropogenic change are already obvious, and your study reflects that.

line 38: spelling of "boulders," and you are not coining the term "boulder beaches"; you later cite Oak [32] as using that term 40 years ago.

line 59: Is it the research or the distribution that is poorly understood?

line 63: delete "of" in "data on of polyclads"

lines 73, 74: simply "diversity" (not "biodiversity")

line 81: hyphen also needed after "higher" (in "higher-wave-energy environments")

Fig. 1: Why are the sites marked with different colors?  I don't see those colors reflected elsewhere in the manuscript.  Two sets of markers overlap so much as to appear as one each.  Change the size of the markers or use arrows to better differentiate them.

line 91: should read "version of Oak (1984) [32]" or "version [32]".

Table 1: Change "Boulder size range" to "Grain size range". (Most of table is not about boulders.)

paragraph of line 100 ff: Were the turned boulders replaced in their formerly upright position (so as to minimize damage to under-rock biota)?

line 115: why is "the subset of" in this line?

line 121: delete "for" in "for for"

line 141: should "significance between" be "significant difference between"?

lines 156, 164: "emmeans" misspelled as "enmeans"

line 183, 185: delete "(E. celerrima)" and "(N. australis)". Use of the abbreviated form is understood.

Table 3: Add "Shelly" in front of "Eden" to relate it better to text;
    Ceratoplana falconeae is in Stylochoplanidae;
    "Notocomplana distincta" should be "Notoplana distincta" and is in the Notoplanidae;
    "Notoplana longiducta" should be "Notocomplana longiducta" and is in the Notocomplanidae;
    Replace "Pseudostylochidae" with Ilyplanidae (see Dittman et al., 2019);
    delete horizontal line at bottom of p. 7 and the 2 lines at top of p. 8;
    spelling is "Euryleptididae" (missing "id")

line 194: add comma after "Eden"

Fig. 4: explain why BottleGlass has two numbered entries in each section

line 225: Why is this heading a sentence when the other headings are not?
    As it reads, this paragraph contradicts p. 9, paragraph 1; make it clear that one is about mean numbers and the other about diversity

Fig. 6: Perhaps this is what the R package spits out, but the idea that you could graph negative numbers of individuals seems ridiculous.  Shouldn't you cut the graph off below 0 of the y-axis?  And shouldn't it be cut off to the left at 12.8 cm to match the x-axis label, "Boulder"; no boulder is smaller by definition in the Wentworth scale you show on p. 3.
The same applies to the Supplementary Figure.


line 239: "9 degrees of latitude" (not "9 latitudes")

line 241: "align with the phylogeny" makes little sense.  What do you mean? What were you expecting? (Note that no one has come up with a satisfactory phylogeny of polyclads with currently accepted methods.)

line 248: replace comma before "however" with semicolon; what follows is an independent clause.

lines 256 ff: Why is it not "despite human influence"? Why would anthropogenic perturbations lead to higher diversity? Very unlikely!

line 276 ff: Don't many polyclads feed on sessile organisms? So, of course, they could be expected to follow similar distributions.  This is why recording what organisms were on the rocks where the polyclads were collected is important.  These, I think, should be considered part of the substratum for the polyclads, not just rock.
If at all possible, it would be useful to report what sessile fauna the polyclads were found on.  

line 292: replace "lack" with "low"

line 309: replace "report these data" with "substantiate this trend"

line 331: replace comma before "however" with semicolon; what follows is an independent clause.
Replace "alimentary" with "dietary"

line 336: ?? "the second" and "the latter" have no precedents.

line 343: Echinoplana celerrima has been reported outside the Mediterranean:
Gammoudi M, Bulnes V, Kurt G (2021) The polyclad fauna (Platyhelminthes, Rhabditophora) of the Sinop Peninsula (Black Sea, Turkey) with the description of a new species of Cryptocelis Lang, 1884.    Mediterranean Marine Science, 22(1), 141-156.  [doi: 10.12681/mms.24666]

line 369: delete comma
line 370: replace "does" with "do"  (subject is plural)
line 372: delete colon; change "continuing" to "continuous"(?).

lines 389, 392,403: delete colons; they are not needed after headings.
Why aren't the sources of funding in Acknowledgements listed in the Funding section?

I'm neither an ecologist nor a statistician, but it seems to me that the statistical tests on such a paucity of data are overreach: the total number of species is only 15, 8 of which occurred as 1 individual at just 1 each of the 9 sites; 5 of the 9 sites had just 1 species other than the almost ubiquitous and probably invasive species Echinoplana celerrima; just 2 species, E. celerrima and N. australis, account for 70% of the collections.  Can statistical tests showing 3 significant digits be taken seriously?  A simple table like Table 3 with an added row showing totals of number of species at each site would tell the whole story---no statistics needed.

The discussion seems repetitious.  It could be simplified.

Author Response

we have responded to all the comments provided by Reviewer 1 in the attached table

Author Response File: Author Response.docx

Reviewer 2 Report

The authors of the manuscript “Fantastic flatworms and where to find them: insights into intertidial polyclad flatworm distribution in southeastern Australian boulder beaches” have presented an interesting work in which they assess the diversity of polyclad flatworms in boulder beaches across the southeast Australian coast. By doing so, they have significantly increased the knowledge on this group in this area. They have also shed light on how this specific type of beaches helps in the maintenance of biodiversity. This work is well done and contains a nice discussion.

I only have a couple of comments about the species identification in this study:

1) I understand that the sectioning was a great deal of work. Dozens of specimens were collected, fixed for morphological study, cut, and inspected. In my experience, this is a tremendous amount of work. Please confirm that this process was performed for each specimen collected. After sectioning, the copulatory apparatus must be reconstructed from the sections to assign the specimens to their species, which is a painstaking process. Please explain in the Material & Methods section how the specimens were assigned to their respective species; Was it after the complete reconstruction of the copulatory apparatus?

2) There are a number of unidentified species in the study (i.e. Planocera sp., Stylochus sp., Eurylepta sp., Enchiridium sp., and Pseudoceros sp.). Considering that the sectioning was made for all the specimens, why were these specimens not assigned to a known species? Was it because they were new? Without copulatory apparatus? Please explain in the manuscript. On the other hand, 6 specimens were assigned to Stylochus sp., was there any confidence in assigning all 6 specimens to the same ‘unknown’ species? Based on which characteristics? Or were these specimens different from each other?

Very minor comments:

- Abstract and Introduction first line is exactly the same. Please change one of them.
- Line 63. it seems that either ‘on’ or ‘of’ should no be there.
- Line 95. Although it might be obvious, please explain in the manuscript what the different numbers in the scale of the Baardseth’s wave exposure index mean: 0 less exposed and 9 more exposed?

Author Response

we have replied to all comments by reviewer 2 in the attached table.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors,

In your study, you presented methods for identifying flatworm hotspots by assessing the diversity and total abundance of flatworms on pebbly beaches along the south-eastern Australian coast. The research methods were well described and the results were well presented.

However, the following must be done:

1. State: All three sites are more likely to be affected by anthropogenic perturbations than other sites sampled due to their proximity to major cities, making this diversity an interesting phenomenon leading to speculation as to whether polyclad flatworms in more disturbed areas have an advantage over other species in under-rock assemblages. Unfortunately, we were unable to directly assess this concept in the present study.

-          - What advantage do you mean? Numerical value or advantage of this type of worm?

2. State: A higher number of flatworms occurred under rock sizes of medium boulders to coarse cobble, even though a diversity of other rock size classes occurred on the beaches sampled. We also observed that more flatworms occurred under larger rock size classes at more protected beaches.

- Why, what do you think? Is the protected beach favorable for their habitat?

3. State: Larger boulders could also provide better protection against potential predators.

- Is that all? What are the potential predators?

4.   State: Further research needs to be done to determine if there is a trend in the abundance       of flatworms and those in other communities under rocks at higher latitudes or if there is a seasonal influence.

- Of course, this needs to be done in order to define the influence of these factors on the existence of flatworms.

5. Completely redo the Сonclusion. Namely, it should be stated briefly what was done in this manuscript.

Best regards

Author Response

we have responded to all the comments of reviewer 3 in the attached table.

Author Response File: Author Response.docx