Diversity of Cryptofaunal Nematode Assemblages along the Jardines de La Reina Coral Reef, Southern Cuba

Round 1

Reviewer 1 Report

This is an interesting and well-written manuscript that will certainly be in demand among specialists.

A few key notes:

- line 67. I strongly disagree with the statement about the components of diversity. I ask the authors not to confuse the concepts of “components” and “scales”, and to pay attention to the terms “species richness” and “evenness”, “structure” and “composition” of communities (for example, Magguran, 1988, 2004).

- section 4.3. The authors do not have any facts about the hydrodynamics of the studied water area, no comparisons of areas with different hydrodynamics. All arguments in this section are not supported by any results.

- Unfortunately, the entire list of discovered species is not available for analysis; only 14 typical ones are presented. But even this list is somewhat surprising in the attribution of all individuals to specific known species. Moreover, many species were originally described from very remote water areas (Japanese islands, the eastern coast of Africa, etc.). This is a rather unexpected result, which requires at least a detailed discussion.

Again, this is a well-done manuscript and the comments I have made do not detract from its quality. I will be glad to read the final version of this interesting work.

Author Response

Reviewer 1

This is an interesting and well-written manuscript that will certainly be in demand among specialists.

R/ Thank you very much for your opinion. Please, find below a detailed response to your comments.

A few key notes:

- line 67. I strongly disagree with the statement about the components of diversity. I ask the authors not to confuse the concepts of “components” and “scales”, and to pay attention to the terms “species richness” and “evenness”, “structure” and “composition” of communities (for example, Magguran, 1988, 2004).

R/ We partially agree. We think that concepts and definitions of related-diversity terms are debatable. For instance, Magurran (2021) treats richness and beta-diversity as facets; for the same properties, Whittaker et al. (2001) used the terms inventory and differentiation diversity. It is not in our spirit to discuss different approaches and terminology. Therefore, we modified our statement to make it softer. Now, it is as follows: “We analyze two facets of diversity: richness and β-diversity”.

We note that our terminology reflects the state of art and agrees with seminal studies about diversity [references 18 to 24 in the text].

Two references cited above:

Magurran, A. E. (2021). Measuring biological diversity. Current Biology, 31(19), R1174–R1177. https://doi.org/10.1016/j.cub.2021.07.049

Whittaker, R. J., Willis, K. J., & Field, R. (2001). Scale and species richness: towards a general, hierarchical theory of species diversity. Journal of Biogeography, 28, 453–470.

- section 4.3. The authors do not have any facts about the hydrodynamics of the studied water area, no comparisons of areas with different hydrodynamics. All arguments in this section are not supported by any results.

R/ We agree that we do not have direct measurements of water flows, but we can propose reasonable hypothesis and explanations of the observed patterns. We removed the term “hydrodynamics” from the section’s title. We also modified the text as follows: “We hypothesized that the moderate rareness is related to the effects of chronic stress by hydrodynamics on the nematode assemblages. This hypothesis is also supported by the similar morphology…”

The second paragraph within this section pointed to the overarching effects of hydrodynamics on coral reef fauna. Then, we added at the end of this paragraph the following sentence: “We highlight the necessity of an experimental approach to relate small-scale water flows with meiofauna resuspension rate in the different features of the reef bottom (e.g., coral heads, epilithic algal matrix).”

- Unfortunately, the entire list of discovered species is not available for analysis; only 14 typical ones are presented. But even this list is somewhat surprising in the attribution of all individuals to specific known species. Moreover, many species were originally described from very remote water areas (Japanese islands, the eastern coast of Africa, etc.). This is a rather unexpected result, which requires at least a detailed discussion.

R/ We appreciate very much this comment that moved our attention to the important issue of the solidity of the identifications. First, we regret that the species list was not available for revision. We put the supplementary materials Fig S1 and table S2 at the end of the manuscript. But the Excel matrix with the primary data (table S1) was too large to insert within the text file. We will upload separately into the system, hoping it be available for checking it.

Second, figure 6 included only the most abundant species, if we included all the species (70) the heat map is too cluttered, and the visual pattern is lost. Therefore, we left the original format but changed a few names (see below).

Third, regarding the species names. It is common to find cosmopolitan species of nematodes, which are often the most abundant in the samples. If these species are truly cosmopolitan or cryptic species is subject of debate currently and demands molecular data (discussions about this issue in Decraemer et al. 2001, Boeckner et al. 2009, Bik et al. 2010). However, we rechecked the identification and made a few changes in a conservative spirit. We noted that the change of names indicated below does not affect the diversity patterns described in the paper since they are still well differentiated morphospecies.

For all the species (except one) in fig. 6, we have at least five males. Males are the “gold standard” to identify morphologically marine nematode species because occurrence of reproductive structures (spicules and gubernaculum). Therefore, we had good material for identification.

For the species without a male (Actinonema longicaudatum), we were conservative and put it as sp. Other three species (Perepsilonema ritae, Leptepsilonema richardi, and Draconema ophicephalum) had males, but because the taxonomic difficulty of that genera and the distance of the type localities, we decided to be conservative as well and changed them to sp.

Five species in the figure 6 have been reported previously from Cuban waters based on extensive samplings in coral reef habitats (e.g., Pérez-García et al. 2020). These seem to be true cosmopolitan species because they have been reported from many places in the World: Desmodora pontica, Euchromadora vulgaris, Croconema cinctum, Chromadora brevipapillata, and Euchromadora gaulica.

Other three species are reported for the Gulf of Mexico and/or west Atlantic Ocean, and our identification was solid as well: Spilophorella paradoxa, Euchromadora gaulica, Acanthonchus cobbi and Zalonema vicentei.

For the less abundant species (in table S2), we were conservative since the beginning, and many species were named using cf. to indicate that identification was not 100% proof-of-bullet because subtle variation in morphology (e.g., body size) or regular/bad quality of specimens.

The reference cited above:

Bik, H. M., Thomas, W. K., Lunt, D. H., & Lambshead, P. J. D. (2010). Low endemism, continued deep-shallow interchanges, and evidence for cosmopolitan distributions in free-living marine nematodes (order Enoplida). BMC Evolutionary Biology, 10, 389. https://doi.org/10.1186/1471-2148-10-389

Boeckner, M. J., Sharma, J., & Proctor, H. C. (2009). Revisiting the meiofauna paradox: dispersal and colonization of nematodes and other meiofaunal organisms in low- and high-energy environments. Hydrobiologia, 624, 91–106. https://doi.org/10.1007/s10750-008-9669-5

Decraemer, W., Gourbault, N. E., & Helléouet, M. N. (2001). Cosmopolitanism among nematodes: Examples from Epsilonematidae. Vie et Milieu, 51(1–2), 11–19.

Pérez-García, J. A., Ruiz-Abierno, A., & Armenteros, M. (2020). A checklist of aquatic nematodes from Cuban Archipelago. Zootaxa, 4731(3), 301–320. https://doi.org/10.11646/zootaxa.4731.3.1

Again, this is a well-done manuscript and the comments I have made do not detract from its quality. I will be glad to read the final version of this interesting work.

R/ Thank you again for your comments, they are very welcome.

Reviewer 2 Report

This is a solid work with clear results. Nematode assemblages of coral communities are characterized in terms of taxonomic and functional diversity by several ways.

The only remark concerns methods of sampling. What kinds of material were sampled for meiofauna – sediment between corals? Abundant cryptofauna incliding nematodes dwells also cavities, crevices and tunnels inside calcareous parts and fragments of corals. Does the fauna inside coral parts differ from that of coral sand between corals? For record of the coral cryptofauna, the coral parts should be further atomized. Therefore, I ask to explain the way of extraction of meiofauna in detail, which substrate was treated, sediment between corals, surface of dead parts oа corals, interior of corals, maybe also algae, sponges, etc.

Author Response

Reviewer 2

This is a solid work with clear results. Nematode assemblages of coral communities are characterized in terms of taxonomic and functional diversity by several ways.

R/ Thank you very much for your time revising our manuscript. We address your remarks below.

• The only remark concerns methods of sampling. What kinds of material were sampled for meiofauna – sediment between corals? Abundant cryptofauna incliding nematodes dwells also cavities, crevices and tunnels inside calcareous parts and fragments of corals. Does the fauna inside coral parts differ from that of coral sand between corals? For record of the coral cryptofauna, the coral parts should be further atomized. Therefore, I ask to explain the way of extraction of meiofauna in detail, which substrate was treated, sediment between corals, surface of dead parts oа corals, interior of corals, maybe also algae, sponges, etc.

R/ We agree with your remark. We added several sentences in Material and Methods to clarify and describe more in detail the nature of the collected material. The added sentences were as follows:

“Specifically, we sampled the epilithic algal matrix, that is the mixture of detritus, sand grains and turf-forming algae covering the hard bottom of the reef. We did not collect large pieces of coral (dead or alive), nor sediment accumulated on the bottom.”

“This method collected the cryptofauna living mostly on the epilithic algal matrix but may also include cryptofauna associated to other invertebrates found within the PVC frame (e.g., sponges, gorgonians, or even small corals).”   

We note that the last section of discussion was already devoted to the sampling methods given the importance of this issue and the lack of a standard procedure to collect meiofauna in coral reefs.