It is very likely related to aromatase activity during the sexual differenciation period. Aromatase converts the androgen testosterone into estrogen estradiol. Therefore, it has a pivotal role in sexual differenciation. Its activity is modulated by temperature. Thus, temperature in itself can modulate the sex ratio of fish populations ! For example, in seabass Dicentrarchus labrax, when the water becomes warm, aromatase activity is downregulated and then the % of male within the population increases.

See this review: http://www.ncbi.nlm.nih.gov/pubmed/19289125

Hello, in certain reptiles the gender is determined environmentally by the temperature during egg-incubation. And in many hermaphroditic invertebrates sex ratio is determined also environmentally. Population density for example influences sex ratio - have a look if in your case there is also a correlation between water temperature and population density. I will have a look and suggest you a few artciles about the subject.

Dear Jonel

Reproduction is certainly a temperature dependent process. Especially in lower groups, bias in sex ratio has been reported from a number of taxa. I do not know if the crab species you are looking into has a temperature dependent distribution (production) of sexes, but there are literature that reported the phenomenon in other crustaceans. Further, there is the phenomenon of sex reversal in some crustaceans that is supposed to be dependent on abiotic parameters (including temperature) of their habitat.

Your observations are really interesting. But for concluding something out of this research, you need to accumulate a huge data set.

These are some literature that may be of your help:

1. Rigaud T. et al. (1997) The effect of temperature on the sex ratio of isopod Porcellinoides pruinosus: environmental sex determination or a by-product of cytoplasmic sex determination. Evolutionary Ecology, 11: 205-215.

2. http://plankt.oxfordjournals.org/content/31/9/1101.full.pdf+html

Let us know how things are coming up.

Best

Dola

Thank everyone for these very informative information and for giving articles related to my subject.

Dear Dola

I have already measured more than 8000 individuals of P. pelagicus from January to December. The parameters I measured was length and weight including their meristic characters which i will also include on the same paper for sex ratio.

Thanks,

Jonel

That is great Jonel. However it would be good if you keep tracking the trend even for a longer period. Keep updating the progress, we all are eager to know how things are coming up.

You are doing an interesting investigation. I would love to read your paper once it get published, kindly send a copy to me.

Good luck to you.

Hello Jonel, I was wondering if the correlation of the sex ratio with the water temperature is rather a correlation with the season and I also wonder whether your species may be hermaphrodite that alternate sex. for example, there are molluscs that alternate sex - and during the cold season only males are found while during the breeding season when the temperature rise the proportion of females rise. Why don't you make an experiment and check whether temperature influences the sex ratio and whether your species is hermaphrodite? Just keep artificial test populations with only males under two different temperature regimes (coled versus warm) one year round - or from one breeding season to the next - and contrast them with control populations with equal proportion of males and females with equal treatment. Have then a look what happen with the sex proportion.

Here is an article that i wrote. Although in this case I was testing whehter social factors were regulating sex in the species, the references inside and the methodology may serve you to set your experiment.

"Sex change in two Mediterranean species of Coralliophilidae (Mollusca: Gastropoda: Neogastropoda)

Alexandra Richter , Ángel A. Luque" you can download it from my page.

Best wishes.

Hi Jonal,

I would like to mention one taxonomic suggestion. Please identify the Portunus pelagicus species complex carefully as recently revision of the same species is made. I was doing identification wrong before I found out this paper.

http://rmbr.nus.edu.sg/rbz/biblio/58/58rbz199-237.pdf

Regarding your main post,, yes it is possible that either one of the sex might be sensitive to temperature. One more thing crabs are mostly demersal, so I suggest you to consider the depth from where samples were collected. In case samples were obtained from shallow water you can co-relate this observation with SST. However, it is interesting results you have got. You can try to get the breeding season of the P. pelagicus to relate increase or decrease in temperature with respect to spawning. Hope you will publish this observation soon. All the best.