Are there more female octopuses than male?

monty;112982 said:
It looks like the abstract pretty much says it all, though, right?

I could imagine it being just an activation of some useful sexual characteristics, in the "why do men have nipples?" sense, or a throwback to a Cambrian hermaphrodite mollusc's genes being re-enabled. Very curious indeed. And quite possibly a Rosetta stone for "how is sex determined on cephalopods" research!

Grrr.. that abstract was pretty abstract. There's difference between intersexuality and actual sexual reassignment. I would like to read this paper to see if there was any environmental factors (i.e. hormones in the water, etc.). The genes for hermaphrodism are there, I would bet, buried in countless millenia of evolutionary pathways. Yes, cephs are usually gonochoristic and all, but more about these oddball males would be nice - at least to see if there is a reproductive effect here.

It seems more like the paper should focus on identifying and describing the pseudohermaphroditism rather than postulate on the distribution of the anomaly(?) across the entire population unless the sample size was really significant and covered the entire oceanographic range.

"Why do men have nipples?" - besides them being functional in rare cases of gynecomastia, plus that some species of male bats actually functionally lactate, its also because all vertebrate embryos are inherently female, but recieve the male "trigger" during development. You probably already knew that.

I can't imagine the sex being determined by temperature (great nod to Caretta by the way - I've worked with that species and I have a soft spot in my heart for sea turtles) in octos, but then again who knows?

- John
 
Fujisawas Sake;119018 said:
I can't imagine the sex being determined by temperature (great nod to Caretta by the way - I've worked with that species and I have a soft spot in my heart for sea turtles) in octos, but then again who knows? - John

If sex were temperature dependent, wouldn't we have seen a bunch of single-sex hatches in captivity?
 
Ramblings on deviation from primary 1:1 sex ratio

This is from my lecture on primary sex ratio and some circumstances that may cause it to deviate from 1:1.

Roy

IV. There are circumstances that will cause the primary sex ratio to vary from 1:1 investment. These are particularly instructive pointing out why the rule is so general. Let me give you five circumstances that will produce a shift in primary sex ratio.

A. Local Mate Competition. Suppose that two or more sons compete only among themselves for opportunities to mate. The mother would do better to put reproductive effort into producing daughters since one son can do all the mating necessary. This typically happens in species where there is little opportunity for dispersal outside of the family unit.

1. Acarophenox: viviparous mite. The female produces one son and about 20 daughters. The male mates with his sisters before they are even born from the brood pouch. (Note: This doesn't produce clones because females may occasionally mate after birth.)

2. Parasitoid Wasp, Nasonia vitripennis: females lay eggs in fly larvae. If only one female parasitizes a fly larvae, all daughters will be fertilized by sons. We would expect extreme local mate competition. Only 8% of brood is male. Remember, these are wasps and females can control sex of offspring by whether or not they fertilize the egg. If a second female lays eggs in same fly, she can detect the presence of eggs from another female and begins by laying more males, but then switches to females.

B. Local Resource Competition. In Galago, male biased investment in offspring. Why? As in many mammals, females disperse less than males. Daughters end up competing with mother and sisters for limited food (gum and fruit). Severe limitation so that usually only one female can survive to replace her mother and breed. Additional investment in daughters is wasted since the environment is pretty much saturated with breeding females, so it is better to make more sons. They have a chance of dispersing and each finding a breeding female.

In birds, helpers at the nest occur in some species. These are often males since the females are the sex that disperses. If males really can increase reproductive success, then more males should be produced. This appears to happen in a few species.

C. Maternal Condition. In the red deer studied by Clutton-Brock, males compete with one another to fertilize females. Bigger, stronger males do better. A mother's ability to nurse affects her ability to produce big sons. If she has lots of milk, she can produce larger offspring. A female's dominance status within the herd of females influences her ability to forage and thus her production of milk. Dominant females produce more sons. Subordinate females produce more daughters as would be predicted. We don't know the mechanism.

Some have tried to apply this same argument to human societies. Powerful clans should produce sons since they can take many wives. Weak families should produce daughters since a son would have little chance of taking a wife. A daughter has a better chance of reproducing.

Kakapo Parrots of New Zealand. This is a nocturnal, flightless parrot that is extremely threatened. There are only 83 birds left. They have a lek breeding system where male Kakapos clear a display arena and call for females. There is strong competition and a lot of reproductive skew with the biggest males getting the most copulations. In a situation such as this, sex allocation theory predicts that fit females should produce sons; small, low weight females should produce daughters. However, conservationists had intervened and were feeding the kakapo females trying to get them to reproduce more. Typically, female kakapos only breed every few years when the Rimu trees bear fruit. If the females reach a weight over 1.5 kg, they breed. The thinking was that if the females were fed and brought to reproductive weight, they might reproduce more often. Unfortunately, because of this, the fed females were producing more young, but they were 70% males – not a good way to make more kakapos. Beginning five years ago, the fat females were put on a diet and all females were kept just over 1.5 kg. It worked. The sex ratio came back slightly in favor of females. Provisioning still occurs, but only after the eggs are laid and the sex ratio determined.

D. Population Sex Ratio. When the population sex ratio deviates from 1:1, an individual that could engage in a compensatory shift would be favored. In Polistes, when queens die, the colony can still produce some males (unfertilized eggs) in the hope that they will reproduce. Since this happens frequently, queen right colonies produce slightly more queens to compensate for this over production of males.

In white-tailed deer, if males are scarce, females produce more males. If males are common, they produce more females. This is determined by how long it is after ovulation that a female is fertilized. If the female is mated within 24 hrs, 14% of the offspring are male. If she mates after 96 hrs, 80% are male.

E. Population Growth. If a species periodically experiences opportunities for population explosion, might favor more females because this will favor more rapid growth. This happens in wood lemmings. Primary sex ratio is 3:1 female. Species is diploid. Female is XX, Male is XY, but there is a second kind of X, X*. XX* is female, but X*Y is also female because genes on X* suppress the effects of the Y. Also, genes on X* prevent the formation of Y eggs. The result is that X*Y produce only daughters. If X and X* are in equal frequency, only 1/4 of the individuals will be XY and thus male.
 
I wonder if the apparent skew towards females showing up in the pet trade could be related to seasonality of the location of different sexes. I have noticed in in some of my collection sites for O. rubescens that during certain parts of the year (summer and fall) about 90% of the octopuses I collect will be male, while during the winter and spring many more will be female (about 80%). If there were people collecting these octopuses for the pet trade, and if they were only collecting during certain seasons (perhaps avoiding the harsh weather during the Salish Sea winter) they may conclude the population is dominated by males.
 
Great post for Ive been thinking about this in relation to cuttlefish.

In every batch of Bandensis that I have raised from eggs, I always had many more males then females. This was also the case for Rich. I believe Cuttlegirl also had 2 males and a single female. All these were raised from wild caught eggs. However, the eggs had time to develop in our systems. Im curious to know if this is coincidence, relates to temperature, thier ability to develop hunting skills, or some other factor. There are often runts in the litter that die younger probably from starvation. Perhaps these are all females?

Knowing the answer to this question would be very helpful for future breeding attempts.
Any thoughts?
 
That's interesting.

Hmm.... Well, the problem is that in animals such as Cephalopods, being that they are exclusively marine and lay their eggs in clusters with all eggs exposed to roughly the same conditions, the idea that temp. would be a determining factor somehow doesn't seem to compute. It is possible though.

Maybe Tao is on to something here... Maybe the situation is based on a temporal issue; i.e. the studies being done only during certain times of the year, or perhaps environmental condition shifts resulting in a new halocline or thermocline which in turn affect the development of larvae in their egg...

By the way, this is off topic and off kilter a bit, but what is it called when a change occurs in the egg? I mean, with mammals its called "in utero", but with egg layers (YES, I'm talking to you too, Platypus and Echidna!) is it referred to "in ovo"? Or "in eggo" ? Or how about Spanish "en huevo"?

:smile: Just me being odd, but back to the original question...

What about territoriality among males and females?

Or - and this one's for you, Monty - genetics? What determines Cephalopod sex in the embryo? Not the obvious answer, but the actual trigger mechanisms between X and Y and/or even prezygotic factors, such as factors during meiosis?

*shudders* Oooooh... Its so good to be back. :lol:
 
Fujisawas Sake;119092 said:
That's interesting.

Hmm.... Well, the problem is that in animals such as Cephalopods, being that they are exclusively marine and lay their eggs in clusters with all eggs exposed to roughly the same conditions, the idea that temp. would be a determining factor somehow doesn't seem to compute. It is possible though.

Maybe Tao is on to something here... Maybe the situation is based on a temporal issue; i.e. the studies being done only during certain times of the year, or perhaps environmental condition shifts resulting in a new halocline or thermocline which in turn affect the development of larvae in their egg...

By the way, this is off topic and off kilter a bit, but what is it called when a change occurs in the egg? I mean, with mammals its called "in utero", but with egg layers (YES, I'm talking to you too, Platypus and Echidna!) is it referred to "in ovo"? Or "in eggo" ? Or how about Spanish "en huevo"?

:smile: Just me being odd, but back to the original question...

What about territoriality among males and females?

Or - and this one's for you, Monty - genetics? What determines Cephalopod sex in the embryo? Not the obvious answer, but the actual trigger mechanisms between X and Y and/or even prezygotic factors, such as factors during meiosis?

*shudders* Oooooh... Its so good to be back. :lol:

As far as I've been able to tell (and I've tried) no one knows how sex determination is controlled in cephs at all. In fact, I even asked PZ Myers if he knows, and he's also tried to find out and failed, so it may just not be known. Last time I mentioned this, Steve pointed out that there's a squid guy in South Africa (I think) who found a squid species that has male, female, and sort of "intermediate"-- I think they're males that have some female parts that aren't used, if I remember right. I'll look for the paper, but I'm in the process of rebuilding a crashed hard disk from an old backup, so my files are in a lot of disarray today.

Something I only found out recently is that squids (and I think all or at least most cephs) are syncytial in early development. This is weird, because most molluscs aren't, but drosophila and a few other weirdos are, and the belief is that the ancestral state wasn't, so it's not clear if this is some sort of convergent evolution or what... the ancestral state is believed to be "type 1" embryogenesis where cell fates are locked in, but cells divide normally, vs. "type 2" like us where cell fates are more context-dependent, and squids, fruit flies, and a few others are "type 3" which pretty much means "extra weird," and it's not really well-studied whether cephs are similar to drosophila in early development in ways other than being syncytial protostomes.

Anyway, genetic control of sex in cephs seems to be a very wide-open area for research. Since it's uncommon to see weird intermediate sex cases, the squids above being an exception, I'd think it would be locked in very early in development, so if there's some environmental factor like temperature, I'd expect it to only be important early. But, that's clearly just a mildly-educated guess, of the sort that's likely to get me in trouble...
 
p.s. "in ovo" appears to be right. I was thinking the same thing regarding that "cuttles learning in ovo" reference.
 
and waffles, apparently.

I'm not a marine biologist, but I play one on the internet. (But I didn't stay in a holiday inn express last night, so don't take me too seriously!)

There are quite a few people who either have or will have soon impressive marine biology degrees, faculty positions, and professional aquarist jobs, but some of the most knowledgeable people also don't have any official credentials. I'm perhaps in a weird category, because although I don't have any kind of biology degree, I've been in an environment where I could take or sit in on biology classes and lectures and I've had access to some serious biology library resources and a lot of friends studying biology, so I can fake it so well I sometimes can play with the big kids. :roll: But one of the many things I like about TONMO is that we've got a range that goes from "interested novice" to "university professor" and we manage to mostly keep things balanced between "serious academic discussions about open research questions" and "no question is too naive, don't be shy." Sometimes both in the same post.
 
well i guess i found the right site then. i actually got recommended to this forum by my friends uncle. he's kept octos for years. a few months ago i was at a barbecue at his house and i got to check out his 5 set ups. i definately dont have the cash to get what he has, but it definately sparked my interest. glad i found a good info resource.
 

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