Differential Sexual Maturity Among Breeding Adults of Black Sea Turtle (Chelonia mydas agassizii) from Michoacan, Mexico

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work assessed the sexual maturity of breeding females and males of black sea turtles (Chelonia mydas agassizii) from the population of Michoacan, Mexico. These data provide concrete evidence of sexual maturity differences between genders in the black sea turtle population.It is useful for the protection of natural population of black sea turtles in the the eastern Pacific. Suggestions are as followed:

1 Estimate the age of black sea turtle might be depended on the growth rate and standard carapace lengths, but it is not the most accurate method. The author can estimate the age through mark-recapture study, and it is more accurate.

2 The author quoted the paper of Koch et al., (2007) published in Marine biology and Seminoff et al.,(2002) published in Copiea, and in the manuscript, it is said that the authors estimate that recruitment of juvenile black turtles (C. m. agassizii) from the pelagic phase occurs at an average body size of 40 cm SCL at an age of 10 years. From the above two papers, I can not find the information. The information might be inferred from the reference, “Nichols WJ (2003) Biology and conservation of sea turtles in Baja California, Mexico. PhD dissertation. University of Arizona, Tucson, pp 474”. or “Kamezaki, N.; Matsui, M. Geographic Variation in Skull Morphology of the Green Turtle, Chelonia mydas, with a Taxonomic Discussion. J. Herpetol. 1995, 29, 51”.

3 In the manuscript, after the turtle moved to the coastal habitats(feeding areas), they grow at an annual rate of 1.62 cm. From the paper of Koch et al., (2007) published in Marine biology(Reference 40), we can obtain this information, but from Reference 40, the relationship is not linear, the growth rate is not very constant. Furthermore, the range of data is from age 10 to age 28. It might not be accurate after the age is above 28.

4 The research team published a related paper, “Black Sea Turtle (Chelonia mydas agassizii) Life History in the Sanctuary of Colola Beach, Michoacan, Mexico” in Animals (Reference 21). In reference 21, the mean of SCL of nesting females was 77.9 cm (range = 64.2–93.4 cm; SD±5.31; n = 100 females). In this manuscript, the data was reported again (In Table 1). In reference 21, the minimum age at which female black turtles reach sexual maturity is 24.2 years.This is not consistant with the result of the manuscript. In reference 21, they calculate the age of sexual maturity using the mean growth rate (1.4 cm yr^-1) ,while in the manuscript, 1.6 cm yr^-1 was used.

Comments on the Quality of English Language

I have no special suggestions from the aspect of the quality of English language.

Author Response

Comments 1. Estimate the age of black sea turtle might be depended on the growth rate and standard carapace lengths, but it is not the most accurate method. The author can estimate the age through mark-recapture study, and it is more accurate.

Response 1: We agree with the comment, however, the average growth rate in breeding adults through mark-capture-recapture for this population was 0.53 cm similar to that obtained by Green (1993) in the Galapagos Islands, however, breeding adults once they reach sexual maturity the growth rate decreases, because individuals allocate part of the energy to reproduction. And the growth rate in juveniles is higher as reported by Koch et al., (2007) and Seminoff et al., (2002), which are growth rates estimated through the mark-capture-recapture method. We believe that the estimate of minimum sexual maturity for females and males reported in this work is correct because recruitment of hatchlings to the sea began in 1980 and the recovery of the population in Colola began in 2002, i.e. 22 years later. We consider that the increase in the number of nesting females is the result of conservation activities.

 

Comments 2. The author quoted the paper of Koch et al., (2007) published in Marine biology and Seminoff et al.,(2002) published in Copiea, and in the manuscript, it is said that the authors estimate that recruitment of juvenile black turtles (C. m. agassizii) from the pelagic phase occurs at an average body size of 40 cm SCL at an age of 10 years. From the above two papers, I can not find the information. The information might be inferred from the reference, “Nichols WJ (2003) Biology and conservation of sea turtles in Baja California, Mexico. PhD dissertation. University of Arizona, Tucson, pp 474”. or “Kamezaki, N.; Matsui, M. Geographic Variation in Skull Morphology of the Green Turtle, Chelonia mydas, with a Taxonomic Discussion. J. Herpetol. 1995, 29, 51”.

Response 2: In accordance with the comment, we have corrected the references to age and recruitment size.

 

Comments 3. In the manuscript, after the turtle moved to the coastal habitats(feeding areas), they grow at an annual rate of 1.62 cm. From the paper of Koch et al., (2007) published in Marine biology(Reference 40), we can obtain this information, but from Reference 40, the relationship is not linear, the growth rate is not very constant. Furthermore, the range of data is from age 10 to age 28. It might not be accurate after the age is above 28.

Response 3: Agree with the comment. We agree that the relationship is not linear and the growth rate is not constant, therefore, we use the minimum recruitment age in this case 10 years, to make sure that it is the minimum recruitment size, the larger individuals could have been caught some time after their arrival at the feeding ground.

 

 

Comments 4. The research team published a related paper, “Black Sea Turtle (Chelonia mydas agassizii) Life History in the Sanctuary of Colola Beach, Michoacan, Mexico” in Animals (Reference 21). In reference 21, the mean of SCL of nesting females was 77.9 cm (range = 64.2–93.4 cm; SD±5.31; n = 100 females). In this manuscript, the data was reported again (In Table 1). In reference 21, the minimum age at which female black turtles reach sexual maturity is 24.2 years.This is not consistant with the result of the manuscript. In reference 21, they calculate the age of sexual maturity using the mean growth rate (1.4 cm yr-1) ,while in the manuscript, 1.6 cm yr-1 was used.

Response 4: We agree with the comment, in effect in the article referred to on the life history of black turtles in Michoacán, the estimation of sexual maturity was made considering a growth rate in juveniles, but the minimum size of the carapace curve length (CCL) of 60 cm was used, which resulted in a sexual maturity of 24.2 years.

 

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript reports on a study that evaluates the potential age at maturity of Chelonia mydas agassizii from the Colola Beach nesting area (and neighboring breeding areas). Such information can be vital in understanding the conservation of sea turtle populations. I have several suggestions to improve the manuscript which I outline below in the general order in which they appear in the manuscript.

 

Lines 19-20: This is not a complete sentence.

Lines 23-24: I would delete this sentence.

Lines 26-27: I would change “Differential sexual maturity” to “Differences in the age at sexual maturity”

Line 27: How do you know sexual maturity influences female carapace shape? This was not directly assessed in your study.

Lines 28-29: I would move this sentence earlier in the Abstract.

Introduction: The Introduction in general needs a great deal of work on the organization and flow. There are often almost random ideas thrown into the Introduction that disrupt the logical flow of ideas and distract the reader. In my more specific comments I provide some examples of where these are particularly obvious, but the authors should really go through the Introduction and focus it on the main ideas that are needed to tell your story, and eliminate any unnecessary tangents.

Line 47: Why limit this to “marine”? This is a more general rule and is not limited to marine environments.

Lines 49-52: It is not clear how this is connected to the surrounding paragraphs.

Lines 53-54: Isn’t this simply the definition of age of sexual maturity? What else would you be estimating for age at sexual maturity?

Line 56: What is “LongitudeSM”?

Lines 56-57: How is this sentence related to the rest of the paragraph?

Line 58: How does this first sentence fit in here? Also, wouldn’t you expect there to be variation in size among females since it simply reflects the age structure of the breeding females?

Lines 58-63: This sentence is very long and the ideas do not warrant inclusion in a single complex sentence. Break it into more than one sentence.

Lines 65-68: How does this paragraph fit into the surrounding paragraphs?

Line 70: Be precise in your use of Chelonia. If it is not italicized it implies turtles in general. If you are specifically referring to the genus then italicize the term.

Lines 70-73: Make it clear what species you are referring to here.

Lines 80-82: Why is this a separate paragraph? Seems like it should be included in the previous paragraph.

Figure 1: I’m not sure this figure is very useful as it currently exists. To be useful, there needs to be an inset that shows the location of this image in the context of Mexico and Central America.

Lines 117-118: There needs to be more details related to the capture of females. Did you measure all nesting females or just a subset? If just a subset was measured, how did you select that subset? Were females measured after depositing a nest?

Line 125: What does “reproductive segments” mean? It seems like it may simply mean you dealt with males and females separately. If so, just say that rather than using “reproductive segments”.

Lines 127-129: It is not clear what data were used to run these tests or why they are run.

Line 172: Why use the average size? It seems like this is not really appropriate to determine age at maturity. Instead it seems this would simply provide the average age of nesting females, which is interesting but does not address the question of age at sexual maturity.

Line 174: Won’t this differ among individuals? You are also assuming this is the same for males and females.

Line 179: This seems like a questionable way to estimate age at sexual maturity, or at the very least it is probably a relatively weak estimate. One of the weaknesses is that you are assuming all turtles grow at the same rate, especially assuming males and females grow at the same rate.

Lines 181-185: I found this paragraph hard to understand. It is not very clear.

Lines 196-198: This is methods and should appear there.

Lines 205-207: It is not clear why the absolute difference is important. You should also provide some measurement of variation in those means.

Line 208: Don’t focus the sentence on the statistical test, focus it on the result of the test.

Line 227: The figure does not actually show differences between males and females. It shows the distribution of SCL in males and females. In addition, you need to explain what the box plots are showing.

Lines 231-233: This belongs in the methods.

Lines 233-235: This is misleading. “Average” implies the average size or age at which they mature; however, this is not what you are actually reporting. You are reporting how long it takes turtles to reach the average size in the population (also gives the average age of individuals in the population).

Lines 241-242: How do you know this You need to clearly say how you came to this conclusion and what evidence you used to specifically test this.

Lines 269-272: First, you need to explicitly state that you are assuming that males and females grow at the same rate when they are juveniles. Second, this seems like circular reasoning to me. They are both calculated using the same formula and data so it is not surprising that you got the results you did.

Lines 271-272: The values for SCL and CCL are both from females so doesn’t seem to be the right values to support the sentence.

Lines 277 & 280: I would avoid the use of “prefer” or “preferring”. The turtles are not making a conscious decision. Also, this again assumes males and females grow at the same rate.

Lines 287-297: I think this is overly speculative. You provide no specific data to show that this is true.

Lines 298-307: You don’t have evidence that directly addresses this.

Lines 313-315: You would have to do a much more detailed morphometric analysis to show this.

Comments on the Quality of English Language

The main issue, also outlined in the comments for the authors, is the organization of the Introduction. 

Author Response

Lines 19-20: This is not a complete sentence.

Response 1: Corrected

 

Lines 23-24: I would delete this sentence.

Response: Corrected

 

Lines 26-27: I would change “Differential sexual maturity” to “Differences in the age at sexual maturity”

Response: Corrected the change

 

Line 27: How do you know sexual maturity influences female carapace shape? This was not directly assessed in your study.

Response: We believe that the small size of males has modified the small size of females.

 

Lines 28-29: I would move this sentence earlier in the Abstract.

Response: Corrected

 

Introduction: The Introduction in general needs a great deal of work on the organization and flow. There are often almost random ideas thrown into the Introduction that disrupt the logical flow of ideas and distract the reader. In my more specific comments, I provide some examples of where these are particularly obvious, but the authors should really go through the Introduction and focus it on the main ideas that are needed to tell your story, and eliminate any unnecessary tangents.

Response: The comments were addressed

 

Line 47: Why limit this to “marine”? This is a more general rule and is not limited to marine environments.

Response: Corrected

Lines 49-52: It is not clear how this is connected to the surrounding paragraphs.

Response: Corrected

 

Lines 53-54: Isn’t this simply the definition of age of sexual maturity? What else would you be estimating for age at sexual maturity?

Response: Corrected

 

Line 56: What is “LongitudeSM”?

Response: Corrected

 

Lines 56-57: How is this sentence related to the rest of the paragraph?

Response: Corrected

 

Line 58: How does this first sentence fit in here? Also, wouldn’t you expect there to be variation in size among females since it simply reflects the age structure of the breeding females?

Response: Corrected

 

Lines 58-63: This sentence is very long and the ideas do not warrant inclusion in a single complex sentence. Break it into more than one sentence.

Response: Corrected

 

Lines 65-68: How does this paragraph fit into the surrounding paragraphs?

Response: Corrected

 

Line 70: Be precise in your use of Chelonia. If it is not italicized it implies turtles in general. If you are specifically referring to the genus then italicize the term.

Response: Corrected

Lines 70-73: Make it clear what species you are referring to here.

Response: Corrected

 

Lines 80-82: Why is this a separate paragraph? Seems like it should be included in the previous paragraph.

Response: Corrected

 

Figure 1: I’m not sure this figure is very useful as it currently exists. To be useful, there needs to be an inset that shows the location of this image in the context of Mexico and Central America.

Response: Corrected

 

Lines 117-118: There needs to be more details related to the capture of females. Did you measure all nesting females or just a subset? If just a subset was measured, how did you select that subset? Were females measured after depositing a nest?

Response: Corrected

 

Line 125: What does “reproductive segments” mean? It seems like it may simply mean you dealt with males and females separately. If so, just say that rather than using “reproductive segments”.

Response: Corrected, we refer to females and males.

Lines 127-129: It is not clear what data were used to run these tests or why they are run. Response: Corrected, we use carapace length data

Line 172: Why use the average size? It seems like this is not really appropriate to determine age at maturity. Instead it seems this would simply provide the average age of nesting females, which is interesting but does not address the question of age at sexual maturity.

Response: We agree with the comment.

 

Line 174: Won’t this differ among individuals? You are also assuming this is the same for males and females.

Response: We agree with the comment.

 

Line 179: This seems like a questionable way to estimate age at sexual maturity, or at the very least it is probably a relatively weak estimate. One of the weaknesses is that you are assuming all turtles grow at the same rate, especially assuming males and females grow at the same rate.

Response: We agree with the comment, however, there is no standardised estimate of age at sexual maturity.

 

Lines 181-185: I found this paragraph hard to understand. It is not very clear.

Response: Corrected

 

Lines 196-198: This is methods and should appear there.

Response: Corrected

 

Lines 205-207: It is not clear why the absolute difference is important. You should also provide some measurement of variation in those means.

Response: Corrected

 

Line 208: Don’t focus the sentence on the statistical test, focus it on the result of the test.

Response: Corrected

 

Line 227: The figure does not actually show differences between males and females. It shows the distribution of SCL in males and females. In addition, you need to explain what the box plots are showing.

Response: Corrected

 

Lines 231-233: This belongs in the methods.

Response: Corrected

 

Lines 233-235: This is misleading. “Average” implies the average size or age at which they mature; however, this is not what you are actually reporting. You are reporting how long it takes turtles to reach the average size in the population (also gives the average age of individuals in the population).

Response: We agree with the comment.

 

Lines 241-242: How do you know this You need to clearly say how you came to this conclusion and what evidence you used to specifically test this.

Response: Corrected

 

Lines 269-272: First, you need to explicitly state that you are assuming that males and females grow at the same rate when they are juveniles. Second, this seems like circular reasoning to me. They are both calculated using the same formula and data so it is not surprising that you got the results you did.

Response: We assume that males and females have the same growth rate because they are juveniles and have an omnivorous diet.

 

Lines 271-272: The values for SCL and CCL are both from females so doesn’t seem to be the right values to support the sentence.

Response: Corrected

 

Lines 277 & 280: I would avoid the use of “prefer” or “preferring”. The turtles are not making a conscious decision. Also, this again assumes males and females grow at the same rate.

Response: Corrected

 

Lines 287-297: I think this is overly speculative. You provide no specific data to show that this is true.

Response: This may be speculative, however, we have evidence to support these conclusions.

 

Lines 298-307: You don’t have evidence that directly addresses this.

Response: Corrected

 

Lines 313-315: You would have to do a much more detailed morphometric analysis to show this.

Response: Corrected

 

 

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

I have carefully reviewed your manuscript and have a few minor suggestions related to phrasing and formatting to enhance readability and consistency. These are small adjustments that do not affect the scientific content of the manuscript.

Please let me know if you have any questions or if there is anything else I can assist with. I appreciate the opportunity to review your work and look forward to seeing the final version.

All the best

Comments for author File: Comments.pdf

Author Response

The reviewer's comment 3 was addressed.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have improved the manuscript, and answerd the questions well. I have no other suggestions.

Author Response

The authors are grateful for your contributions to improve this manuscript.

Thank you very much.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made many of the changes I suggested. However, the main problems of the manuscript still remain. The authors still insist on saying the average CL of individuals in the populations give the average age at maturity. As outlined in my previous review this is NOT correct - it may give the average age of reproducing females but that is not the same as the average age at maturity. In addition, the whole shape of the female carapace issue is still not well supported nor is the link to the age at maturity - it is probably just a difference in growth trajectories and morphometric relationships in the two sexes that are not directly related to age at maturity.

Comments on the Quality of English Language

The manuscript would benefit from improving the flow and connections among ideas. In several places ideas are put forth with very little connection to the surrounding material. In many cases it seems that these issues I raised in my earlier review have not been satisifactorily addressed.

Author Response

The authors considered the reviewer's suggestions and have changed the estimate of sexual maturity referring to the average size for females and males.

Author Response File: Author Response.pdf