The Impact of Low Temperatures on the Hatching Success of Eurytemora pacifica (Copepoda, Calanoida) Resting Eggs

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors studied the effect of low temperatures on the survival of Eueytemora pacifica, which is an important candidate to use as food for aquatic animals. The author has established reliable experiments and statistical tests and proposed the interesting results for storing resting eggs for aquaculture purposes.  However, there are minor points that, if added, would make this paper more complete as the following: 

Line 76 : exemine ---- > examine

Figure 4 : please cited this figure in the text. In addition, the results showed less hatching succession in the control experiments than in the experimental experiments at both temperatures. Please elaborate this point, probably in the discussion part.

Figure 6 : please put the scale bar of figure6a, 6c in the pictures

Author Response

Please see the attachment.

We appreciate the time and effort in reviewing our manuscript and sending us your comments. We revised a problem with some writing expressions. Again, thank you for allowing us to strengthen our manuscript with your valuable comments and queries. We have worked hard to incorporate your feedback and hope that these revisions persuade you to accept our submission.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors This study analized the  Eurytemora pacifica  resting eggs  hatching depending on different low temperatures during different time periods. During the study was discovered that exposure more than 6 months at –5°C, and more than 2 months at –20°C lead to negatively impacts hatching success. What is also interesting the authors found that the freezing of eggs even ameliorates the hatching success after one month, probably due to the freeze biocide effect on the eggs microbiota. Additionally they identified two distinct types of Eurytemora pacifica eggs differed morphologically: from sediments and from egg sacs. The paper is well written, interesting for readers and describes actual topic especially in terms of climate changing and the recent use of the species nauplii as living food in aquaculture. Few smal remarks wich I would like to give: In lines 274-276: disclose what limitation is being discussed  The limitation I see in this paper is the unreliability of species identification based on eggs, although the authors write that there are distinctive features for the species under study. Even considering that all those that hatched and grew to adulthood were Eurytemora pacifica, it is theoretically possible that other species did not hatch. This issue could be resolved using genetics, but this is another separate paper and I do not think that this will be a reason for rejecting the article. Although, perhaps, it is worth describing this limitation in the article.

Author Response

Please see the attachment.

We appreciate the time and effort in reviewing our manuscript and sending us your comments. We revised a problem with some writing expressions. Again, thank you for allowing us to strengthen our manuscript with your valuable comments and queries. We have worked hard to incorporate your feedback and hope that these revisions persuade you to accept our submission.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript ID: water-3174884

Title: The impact of low temperature on the hatching success of Eurytemora pacifica (Copepoda, Calanoida) resting eggs

Authors: Seo Yeol Choi et al.

 

Since the discovery of marine copepod resting eggs for the first time in the late 1960s (although freshwater copepod resting eggs were reported much earlier in 1902 by Valentin Hächer), their physioecological studies have been conducted by many workers.  Such studies include investigations on the effects of environmental factors on the induction, maintenance, and revival of egg dormancy, because the resting egg production is a seasonal event closely associated with the seasonal dynamics of the planktonic populations.  The aim of this study, however, is much more practical rather than scientific comprehension to reveal the diapausing mechanism of the resting eggs of Eurytemora pacifica.  The authors intend to use them to produce nauplii as live food for larval fish in aquaculture.  To determine appropriate storage temperatures and periods, they examined the hatching ability of the resting eggs by placing them at two freezing temperatures (-5 and -20ºC) for various periods up to 12 months.

I must mention that the authors’ experimental design was loose because only two temperatures were examined.  To reveal a clear-cut critical temperature for the storage, experiments should have been conducted at least at 4 different temperatures, such as the freezing point (ca. -1ºC), -5, -10 and -20ºC.  In addition, it is also necessary to reveal the mechanisms for causing the mortality of eggs stored at -20ºC, perhaps by employing a chemohistological technique.

Another problem is the inclusion of two potentially different types of eggs (Figure 6) in the Discussion.  It is odd to state this in the Discussion, as there is no explanation about the eggs from the female carrying egg sac in the Materials and Methods.  Therefore, this is not a part of this study; the sentences of L282-288 should be deleted.

Comments on the Quality of English Language

no

Author Response

Please see the attachment.

We appreciate the time and effort in reviewing our manuscript and sending us your comments. We revised a problem with some writing expressions. Again, thank you for allowing us to strengthen our manuscript with your valuable comments and queries. We have worked hard to incorporate your feedback and hope that these revisions persuade you to accept our submission.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

It has been modified and is worth publishing in this form.