New Species of Macellicephala McIntosh, 1885 (Annelida, Polynoidae), Associated with the Reef Stage of a Whale Fall^†

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is devoted to the description of a new species of polynoid polychaete, Macellicephala irisae sp. nov., from a deep-sea whale-fall ecosystem, which contributes to the understanding of biodiversity and successional stages of such habitats. The strength of the manuscript lies in its integrated approach, combining morphological (including SEM) and molecular phylogenetic (COI, 16S, 18S genes) analyses of individuals of the new species. The association of the new species with a cladorhizid sponge and the transition of the whale skeleton to the reef stage are discussed in detail. The work is clearly structured, with methods and results clearly presented. Photographs of live and fixed specimens, SEM images, drawings, and the phylogenetic tree are of high quality. At the same time, I have several technical and substantive comments, mainly concerning the description of the new species and the discussion of the results.

 

Abstract:

no comments

Introdaction:

no comments

Materials and methods:

1. It should be indicated how and in which part of the body the width of the animals was measured.

Results:

2. Lines 182,184,185,186. Following the museum numbers of specimens, some other numbers are given. Either an explanation of what these are should be provided, or they should be removed.
3. Line 183. The museum number of the paratype is missing.
4. Lines 184,185,186. The sizes of the specimens are given here; it would be better to place them in the species description under a specific section (e.g., “Measurements”). Moreover, it is unclear what body width the authors measured: body width including chaetae, or with parapodia but without chaetae, or without chaetae and parapodia? And in which part of the body was the width measured?
5. Lines 187-189. The last sentence of this section contains ecological information (location, depth, substrate, host). This should be moved to a specific section of the description – Ecology.
6. Lines 215-216. The authors state that the preserved elytra are extremely small. However, the size of the elytron in Figure 6 (if the scale is correct) is approximately 2.7 mm. For a polynoid of the size of Macellicephala irisae, these are rather large elytra that cover the dorsal surface. “Extremely small and spherical” probably refers to elytra that are regenerating after being lost during intraspecific conflicts. Many polynoids, especially symbionts, are territorial and lose elytra during intraspecific encounters, which then regenerate. Thus, the presence of such elytra may indicate territoriality in these polychaetes.
7. Lines 265-282. This section lacks a morphological comparison with the closest species of the genus.
8. Lines 279-282. Besides the hair‑like notochaetae, another unique feature of the species is the semilunar pockets on the neurochaetae, which support the authors' hypothesis that a new genus should be erected for this species. Similar pockets occur in some other, unrelated to Macellicephalinae, polychaete species, mainly symbiotic, e.g., Paradyte, Adyte, Subadyte, Echinophilia. These pockets may somehow be related to a symbiotic lifestyle, but their function is unclear.
9. Lines 322-323. The detailed morphological adaptations of polychaetes in general and polynoids in particular are primarily discussed in the paper of Martin and Britayev 1998.
10. Lines 315-325. To my knowledge, symbiotic species among Macellicephalinae were previously unknown. I recommend emphasizing this fact in the manuscript.

Comments for author File: Comments.pdf

Author Response

We are extremely grateful to the reviewer for very helpful comments, most of them have been incorporated in the revised version of the manuscript. See the reply to the specific points below.

Materials and methods:

1. It should be indicated how and in which part of the body the width of the animals was measured.

Response 1: Done.

Results:

2. Lines 182,184,185,186. Following the museum numbers of specimens, some other numbers are given. Either an explanation of what these are should be provided, or they should be removed.

RESPONSE 2:  These were the project numbers, but we have now deleted these.

3. Line 183. The museum number of the paratype is missing.

RESPONSE 3:  Not missing, it just has not been obtained yet. It is a common practice to add these at proof stages.

4. Lines 184,185,186. The sizes of the specimens are given here; it would be better to place them in the species description under a specific section (e.g., “Measurements”). Moreover, it is unclear what body width the authors measured: body width including chaetae, or with parapodia but without chaetae, or without chaetae and parapodia? And in which part of the body was the width measured?

RESPONSE 4:  Thank you for this suggestion. We have now created the section “Measurements” and standardized the presentation of the data.

5. Lines 187-189. The last sentence of this section contains ecological information (location, depth, substrate, host). This should be moved to a specific section of the description – Ecology.

RESPONSE 5:  This is a descriptive information of sampling site and belongs to the “Material examined” section. This is a common practice.

6. Lines 215-216. The authors state that the preserved elytra are extremely small. However, the size of the elytron in Figure 6 (if the scale is correct) is approximately 2.7 mm. For a polynoid of the size of Macellicephala irisae, these are rather large elytra that cover the dorsal surface. “Extremely small and spherical” probably refers to elytra that are regenerating after being lost during intraspecific conflicts. Many polynoids, especially symbionts, are territorial and lose elytra during intraspecific encounters, which then regenerate. Thus, the presence of such elytra may indicate territoriality in these polychaetes.

RESPONSE 6:  The elytron is extremely small as is obvious in Fig. 3E, F, however we are grateful to the reviewer for catching the error in the scale bar of Fig. 6, which has now been corrected.

We appreciate the interesting input about the potential territoriality, although reference to the published work would be appreciated. We understand this observation is most likely from the shallow water polynoids, however the reduced size of elytra is likely a deep-water adaptation and has been previously reported in some deep-water species, although rarely as elytra are commonly lost.

7. Lines 265-282. This section lacks a morphological comparison with the closest species of the genus.

RESPONSE 7:  No, it does not (see also reply to the point 8 below). The new species possess several unique features, none of them shared with the previously known species of Macellicephala, hence the dilemma about the erection of a new genus, as discussed in the text.

8. Lines 279-282. Besides the hair‑like notochaetae, another unique feature of the species is the semilunar pockets on the neurochaetae, which support the authors' hypothesis that a new genus should be erected for this species. Similar pockets occur in some other, unrelated to Macellicephalinae, polychaete species, mainly symbiotic, e.g., Paradyte, Adyte, Subadyte, Echinophilia. These pockets may somehow be related to a symbiotic lifestyle, but their function is unclear.

RESPONSE 8:  Notochaetae, small head, neurochaetae with semi-lunar pockets, body papillae are cited throughout manuscript. However, we agree, that in this section it could have been made more obvious. We have now rephrased the text as follow:

“The very small head, neurochaetae with semi-lunar pockets, and body surface with papillae and filamentous notochaetae make this new species taxonomically unique and different from all known Macellicephala species.”

The emphasis on the chaetae was given as chaetal morphology was considered the most reliable character for genus-level diagnoses (e.g., in the genus Abyssarya).

Thank you for pointing the presence of semi-lunar pockets in other symbiotic polychaetes.

We have now expanded the discussion with the following text based on the information above:

“Such pockets have been previously reported in symbiotic polynoid in genera such asParadyte, Adyte, Subadyte, Echinophilia, although their function remains unknown”.

9. Lines 322-323. The detailed morphological adaptations of polychaetes in general and polynoids in particular are primarily discussed in the paper of Martin and Britayev 1998.

Response 9: We are already citing this source. Reference no. 49.

10. Lines 315-325. To my knowledge, symbiotic species among Macellicephalinae were previously unknown. I recommend emphasizing this fact in the manuscript.

RESPONSE 10:  Thank you for this suggestion. We have now added the following text:

“Nevertheless, this observation represents the first reported instance of a symbiotic relationship within Macellicephala, although it has been previously reported in the closely related genus Abyssarya (Bonifácio and Menot 2019).”

Reviewer 2 Report

Comments and Suggestions for Authors

Review of the MS by Lenka Neal, Helena Wiklund, Craig Randall Smith, Angela Benn, Kirsty Kemp, Thomas G. Dahlgren, and Adrian G. Glover, titled "New species of Macellicephala McIntosh, 1885 (Annelida, Polynoidae) associated with the reef-stage of a whale-fall."

This is a highly interesting and substantial work describing a species of annelid worm new to science, found in association with carnivorous sponges that have colonized the bones (specifically, the scapula) of a whale.

Overall, the MS provides a detailed description of a taxon new to science belonging to the genus Macellicephala (Polynoidae) (I agree with the authors' decision not to erect a new genus). The MS is well-illustrated and is suitable for publication following minor revisions.

 

Comments:

1)         Judging by the description and diagnosis of the new Macellicephala species, the sole distinguishing character appears to be the presence of very fine notopodial chaetae that form a tangled mass or tuft (is this perhaps an artifact?). Are there truly no other differences distinguishing it from previously described species? A more comprehensive comparative analysis would be highly beneficial.

2)         Comments regarding the illustrations:

A) The drawing of the anterior end of the body (Fig. 3C) is too small, making it difficult to compare with the corresponding photograph (Fig. 3B).

B) The SEM images are very small and of poor quality. In Fig. 5B, it is impossible to distinguish the ciliary pads that randomly cover the dorsal surface of the worm (they appear instead to be papillae). In Fig. 5E, it is impossible to discern the morphology of the tips of the notopodial chaetae. Fig. 5C suffers from very low contrast.

C) Incidentally, the figure references within the descriptive text are mixed up. For example, the text refers to the ciliary tufts on the lateral and dorsal body surfaces as being shown in Fig. 5A, whereas in reality, they are depicted in Fig. 5B. Furthermore, it appears that Figures 5C and 5B should share the same scale, yet they differ significantly (10 and 50 microns).

Following minor revisions, the MS may be accepted for publication.

Author Response

We thank the reviewer for their review. Here is the response to the specific comments.

1. Judging by the description and diagnosis of the new Macellicephala species, the sole distinguishing character appears to be the presence of very fine notopodial chaetae that form a tangled mass or tuft (is this perhaps an artifact?). Are there truly no other differences distinguishing it from previously described species? A more comprehensive comparative analysis would be highly beneficial.

RESPONSE 1:  This point has been already addressed in reply to Reviewer 1 (point 8).

 Comments regarding the illustrations:

A) The drawing of the anterior end of the body (Fig. 3C) is too small, making it difficult to compare with the corresponding photograph (Fig. 3B).

RESPONSE:  OK. We have created the plate in the portrait and enlarged the images.

B) The SEM images are very small and of poor quality. In Fig. 5B, it is impossible to distinguish the ciliary pads that randomly cover the dorsal surface of the worm (they appear instead to be papillae).

RESPONSE:  The entire surface of the body is clearly papillated and we (and reviewers 1) feel there is nothing difficult to see. There may be confusion about the terminology – at no point have we observed “ciliary pads”. However, in the earlier version of the MS, the term “cilia” was used and later changed to “papillae”. However, not consistently, so as a result in four instances the text still contained the expression “cilia”, which has now been changed for “papillae”. Nevertheless, there is nothing wrong with the images.

Comment: In Fig. 5E, it is impossible to discern the morphology of the tips of the notopodial chaetae.

RESPONSE:  We disagree; they are obvious.  To accommodate the reviewer, we have now added Fig. 5F. to make it even more obvious.

Comment: Fig. 5C suffers from very low contrast. RESPONSE:  Corrected.

Comment: C) Incidentally, the figure references within the descriptive text are mixed up. For example, the text refers to the ciliary tufts on the lateral and dorsal body surfaces as being shown in Fig. 5A, whereas in reality, they are depicted in Fig. 5B.

RESPONSE:  This is incorrect, papillae are shown in Fig. 5A. (as well as in Fig 5B, with the reference to the parapodia as cited appropriately in the text).

Comment: Furthermore, it appears that Figures 5C and 5B should share the same scale, yet they differ significantly (10 and 50 microns).

RESPONSE:  This is incorrect. Parapodia (Fig. 5B) are much larger structures than the chaetae (Fig. 5C). Of course, the scale bars must be of different size. We do not understand this comment.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript titled "New species of Macellicephala McIntosh, 1885 (Annelida, Polynoidae) associated with the reef-stage of a whale-fall" described a new species of Macellicephala that associated with a cladorhizid sponge in whale-fall site. The discovery of the new species provides further evidence for the specialized fauna inhabitating the reef stage whale-fall. The morphological descriptions are detailed and well-illustrated. The manuscript can be accepted after the authors address the following comments:
P76 "Two newly described species at the time "  do you mean "at the same time"?
P79 "report on" remove "on" 
P81 "specimens may potentially represent two species" change to "the nominal species B. guaymasensis may potentially consist of two sympatrical species"?
P89 There appears to be an extra space after "more".
P108 Better to write the full name of SEM: scanning electron microscopy (SEM)
P111 it is fine to use SEM here. 
P112 Why is a new paragraph started here?
P136 an extra space after "with".?
P154 Table 1, Please add a collumn of "References" of these sequences. Besides, There are several sequences of Macellicephala in Hiley et al. 2024. Why were these sequences not included here?
Hiley, A.S.; Mongiardino, K.N.; Rouse, G.W. Phylogenetics of Lepidonotopodini (Macellicephalinae, Polynoidae, Annelida) and comparative mitogenomics of shallow-water vs. deep-sea scaleworms (Aphroditiformia). Biology 2024, 13, 979. 
P171 What is the display threshold for ML?
P172 There is no "/" in the figure
P180 Have the new spcies name been registered in ZooBank?
P183 Why there are specimens with museum deposit numbers while others not?
P312 The author mentioned that "The cladorhizid host reported here may belong to one of those species or potentially 
P288 Genetics. Would a genetic distance analysis of COI or 16S help detect the threshold between species and genera?
represent a new species". So does the cladorhizid host  belongs to one of the genera mentioned in Line 310? Was the new species collected from the same species of cladorhizid host?
P337 remove still 
P338 It is a bit confusing here by saying "associations between Macellicephala and cladorhizid sponges have been observed at the Santa Catalina whale-fall site." Isn't the new species the first record associated with cladorhizid sponges at the Santa Catalina whale-fall site?

Author Response

We are always grateful to reviewers for their time and helpful suggestions. Here are our responses to their specific comments.

P76 "Two newly described species at the time "  do you mean "at the same time"?

Response: We mean “at the time of work of Pettibone (1993)….” (this should be obvious from the context).

79 "report on" remove "on" 

RESPONSE:  The only incidence of “report on” in the entire text is in the references [31] where it is part of the title, so we are not sure what is the reviewer referring to.

P81 "specimens may potentially represent two species" change to "the nominal species B. guaymasensis may potentially consist of two sympatrical species"?

RESPONSE:  OK. We changed the text as suggested by the reviewer.

P89 There appears to be an extra space after "more".

RESPONSE:  OK. Removed.

P108 Better to write the full name of SEM: scanning electron microscopy (SEM)

RESPONSE:  The explanation of the abbreviation was already given earlier in the text, so abbreviation is fine to use here.
P111 it is fine to use SEM here. 

P112 Why is a new paragraph started here?

RESPONSE:  Because it deals with a different part of the molecular work (analysis vs PCR).

P136 an extra space after "with".?

RESPONSE:  OK, corrected.

P154 Table 1, Please add a collumn of "References" of these sequences.

Response: Not really needed as the accession numbers are there, follow those to get the reference. To include the references would make the table much larger.

Comment: Besides, there are several sequences of Macellicephala in Hiley et al. 2024. Why were these sequences not included here? Hiley, A.S.; Mongiardino, K.N.; Rouse, G.W. Phylogenetics of Lepidonotopodini (Macellicephalinae, Polynoidae, Annelida) and comparative mitogenomics of shallow-water vs. deep-sea scaleworms (Aphroditiformia). Biology 2024, 13, 979. 

Response: We only used sequences with proper species names on Genbank in our tree, to compare with other described Macellicephala species.

P171 What is the display threshold for ML?

Response: Figure legend rewritten to make it clearer: Only values of 95 and over are labelled in the tree as we ran UltraFast Bootstraps.

P172 There is no "/" in the figure

Response: We have changed in the figure legend so that it says **, -* and *- without the / and been even clearer in the text there.

P180 Have the new species name been registered in ZooBank?

Response: It will be upon the acceptance of the MS. Why introduce formal species name prior to the acceptance of the manuscript? These numbers can be added at the proof stages.

P183 Why there are specimens with museum deposit numbers while others not?

Response: SEM specimen was not access yet, the number can be added even at the proof stage, a common practice. That’s why there is a place holder marked “XXXX”.

P312 The author mentioned that "The cladorhizid host reported here may belong to one of those species or potentially represent a new species". So does the cladorhizid host  belongs to one of the genera mentioned in Line 310? Was the new species collected from the same species of cladorhizid host?

Response: The cladorhizid host – we have no specimen, only the image. No further identification is possible. The specimens were imaged on the host in situ, the same ROV box contained all specimens examined here.

P288 Genetics. Would a genetic distance analysis of COI or 16S help detect the threshold between species and genera?

Response: No, as genera are constructed on different basis. Within vs. between species distances are interesting when the species are closely related, but there are no threshold limits between genera.

P337 remove still 

Response: OK, done.

P338 It is a bit confusing here by saying "associations between Macellicephala and cladorhizid sponges have been observed at the Santa Catalina whale-fall site." Isn't the new species the first record associated with cladorhizid sponges at the Santa Catalina whale-fall site?

RESPONSE:  Yes, that’s why this section is titled “Conclusions”.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I have two small remaining comments:

1. I recommend placing the "Measurements" section after the species description.

2. Reference 49 at the end of the last sentence — "Such pockets have been previously reported in symbiotic polynoids in genera such as Paradyte, Adyte, Subadyte, Echinophilia, although their function remains unknown [49]" — is not appropriate. It should be replaced, for example, with the work by Pettibone (1969) and/or Barnich et al. (2004).

• Pettibone, M.H. 1969b. Review of some species referred to Scalisetosus McIntosh (Polychaeta, Polynoidae). Proceedings of the Biological Society of Washington, 82: 1–30.

• Barnich, R., Fiege, D. & Sun, R. 2004. Polychaeta (Annelida) of Hainan Island, South China Sea. Part III. Aphroditoidea. Species Diversity, 9: 285–329.

     

Author Response

We are immensely thankful to the reviewer for a very thorough review of our manuscript. Please find our replies below.

1. I recommend placing the "Measurements" section after the species description.

Response: We are happy to do so, but usually the measurements are reported early in the description. They provide an important context for the species description. If there is no strong view on this, we prefer to keep this section where it is.

2. Reference 49 at the end of the last sentence — "Such pockets have been previously reported in symbiotic polynoids in genera such as Paradyte, Adyte and Subadyte although their function remains unknown [49]"— is not appropriate. It should be replaced, for example, with the work by Pettibone (1969) and/or Barnich et al. (2004).

Response: Thank you for pointing this out. We have checked these references and we have now removed the citation [49] and replaced it with the two citations suggested by the reviewer. The following publications have been added to the refences list as [55,56]

55. Pettibone, M.H. Review of some species referred to ScalisetosusMcIntosh (Polychaeta, Polynoidae). Proc. Biol. Soc. Wash. 1996, 82, 1–30.

56. Barnich, R., Fiege, D.; Sun, R. Polychaeta (Annelida) of Hainan Island, South China Sea. Part III. Aphroditoidea. Species Divers. 2004, 9, 285–329.

Additional and/or unprompted changes:

• The missing NHM registration # has now been added: NHMUK.ANEA 2026.701
• The species has now been registered at ZooBank and the following identifier has been added: urn:lsid:zoobank.org:pub:9EA4AAC7-07F8-4ADD-AD54-09A37BD17F2A
• We have added the missing initial “G.” to the 6^th author
• Acknowledgment section - the name Iris Stowe has been removed