I wonder, because it seems like so many people describe their octopuses laying eggs, it seems like the population is dominated by females. Is their any evidence of this in the progeny, or is it just a coincidence.

Interesting question, but you also have to ask whether females are more likely to be captured as wild caught octopuses than males.

I remember reading a few years ago that female octopuses are more likely to crawl into pots, but I've also heard the opposite. I wonder whether any research has been done in this area.

Nancy

I've heard that female nautiluses supposedly comprise 75% of the population, can't remember where I heard it, but that could also be a trapping bias. Interesting question..

In the Tropic Shale of Southern Utah you only find the female dimorph of Metoicoceras geslinianum, yet in New Mexico the ratio is about 1:1, biogeographical bias?

You also have to keep in mind that not many people will write to report about their octopus NOT laying eggs. :wink: Baited pots might be more likely to attract gravid females when they are in their food binging period right before laying.

Could it have something to do with temperature? For example, in Caretta caretta, if the temperature of incubation is ~24-26 C the egg will most likely be male, if the temperature of incubation is ~32-34 C the egg will most likely be female, in between those 2 temperatures is neutral and usually results in a 1:1 ratio. Is this the case with octo eggs? If this is the case, could climate change have anything to do with a higher population of female octos?

Could it have something to do with temperature? For example, in Caretta caretta, if the temperature of incubation is ~24-26 C the egg will most likely be male, if the temperature of incubation is ~32-34 C the egg will most likely be female, in between those 2 temperatures is neutral and usually results in a 1:1 ratio. Is this the case with octo eggs? If this is the case, could climate change have anything to do with a higher population of female octos?

I've been trying to figure out what drives sex determination in cephalopods, and as far as I've been able to tell, it's not known. There are no species of cephs that ever change sex or hermaphrodites, so a genetic determination seems likely, but hardly proven... temperature would certainly be a factor to look at in any studies. One more reason we need an octopus genome project (and a cuttlefish genome project, and a squid genome project, and a nautilus genome project, and especially vampyroteuthis/argonaut/spirula genome projects!)

Good discussion. Some of my thoughts.

I would guess that female octopus are just more likely to be caught than their male counterparts. Many are caught already at the end of their life and the pot would be an enticing den, while males would be more active at this point and probably fall victim to predation. I would think that the sex ratios in the wild are fairly balanced given that most octopus will die shortly after mating. There would be no advantage to having more males than females, or the reverse. Although, sperm competition has been noted in cuttlefish so perhaps more males exist in the wild??? I would not believe there to be more females based on anecdotal evidence.

The nautilus statement sounds intriguing. Perhaps in that case, the fact that nautilus have much slower maturity rates than other cephalopods and are able to reproduce more than once, having more females would allow the greatest chance for population expand.

Greg

Great comments, but I'm confused by this part:

I would think that the sex ratios in the wild are fairly balanced given that most octopus will die shortly after mating. There would be no advantage to having more males than females, or the reverse. Although, sperm competition has been noted in cuttlefish so perhaps more males exist in the wild???

I think I'm missing something here... since most male octos (AFAIK all except argonauta, where the hectocotylus breaks off during mating, and I don't know if it is regrown, but even if it is, it's hight cost) can mate numerous times once they reach maturity, even with immature females that can store spermatophores for months, doesn't the "die shortly after mating" argument only apply if the male can't roam a lot looking for multiple mates?

It seems like, looking at large numbers of animals, most have a pretty even sex ratio, which certainly seems good for the whole population (if you believe in group selection) in that it keeps the gene pool shuffled. This would seem to apply to most cephs, and pretty much most animals, but there's certainly a number of exceptions... I know lion pride structure is one male and many females, but I don't know if that's maintained by an uneven birth sex ratio, or of males kill each other off, or there are just a lot of wandering unattached males. Similarly with deer and pinnipeds, IIRC, at least deer when it's OK for the locals to shoot bucks but not does... I wonder if anyone's done genetic diversity studies of deer populations comparing "hunting allowed" and "no hunting" (like national parks)?

What I'm getting at is that there seem to be more exceptions than rules in terms of looking at the diversity in animals in sex ratio's impact on reproductive strategy, so "there would be no advantage" doesn't seem to show obvious universal rules in animals that are easier to sex by observation...

I'd almost say sex ratio and reproductive strategy seems to have different selective advantage or disadvantage based on context, and is often neutral enough that animals have drifted into a diverse set of strategies. And it seems like cephs have a fairly wide variety of strategies, ranging from the single event schooling mating behavior followed by egg-laying and death common in shallow-water squids like Loligo and seen in Sepia apama to the more spread-over-time we see in captive bandensis to Nautilus laying eggs over years, to most octopus having a fairly long window for females to mate and store sperm, but then having a single brooding event just before senescence (except for chierchiae) to Steve's reconstruction of Architeuthis having infrequent encounters (squids passing in the night) needing extensive sperm storage rather like octopuses.

I'm not meaning this to be a counter-argument, more of a brain-dump of things I'm finding confusing, interesting, or both in this discussion...

Excellent input so far, it seems I learn more on these boards then i did in BIO 430 (marino bio)!

There are no species of cephs that ever change sex or hermaphrodites....

Mark, Henk Hoving published a VERY interesting paper on hermaphrodite (I recall male and female structures, but not sure if fully functional) squid off South Africa. Brain is too exhausted to recall the details, but it came out last year in 'Reviews in Fish Biology and Fisheries' (I think the title was). Tomorrow I'll cite more, with literature at hand.

Mark, Henk Hoving published a VERY interesting paper on hermaphrodite (I recall male and female structures, but not sure if fully functional) squid off South Africa. Brain is too exhausted to recall the details, but it came out last year in 'Reviews in Fish Biology and Fisheries' (I think the title was). Tomorrow I'll cite more, with literature at hand.

Fascinating! I suppose that's what I get for pretending there are any rules without exceptions in biology... I wonder if this is a reversion to an earlier evolutionary state (I know hermaphrodite non-ceph molluscs aren't too unusual) or something that developed on its own.

It's interesting that if we pot for an octopus (for the aquarium) 9 times out of 10 we'll get a male, if we want a female (not terribly likely, they're more strongly nocturnal than the males! Not good in a display animal) we have to dredge! this is for P. cordiformis.

J

Here (http://www.blackwell-synergy.com/doi/abs/10.1111/j.1469-7998.2006.00093.x) tiz

fooey, I don't have full-text access to that one. It looks like the abstract pretty much says it all, though, right?

This actually is starting to sound familiar, I wonder if you've mentioned it before and I'd forgotten. It's certainly interesting, and I wonder what its evolutionary implications are... 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!

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

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?

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:

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" (http://medical.merriam-webster.com/medical/in%20ovo) appears to be right. I was thinking the same thing regarding that "cuttles learning in ovo" reference.

I still prefer "In eggo". :lol:

I would like to know more about the intermediates... That sounds cool.

Mmmm, Eggo (http://en.wikipedia.org/wiki/Eggo). Can't get them in NZ. :cry:

Mmmm, Eggo (http://en.wikipedia.org/wiki/Eggo). Can't get them in NZ. :cry:

what about potato waffles?

wow. are a lot of the people on tonmo marine biologists or just hardcore enthusiests? you guys have an insane knowledge of cephs

Yes and Yes :smile:

<-- enthusiast

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.

wow. are a lot of the people on tonmo marine biologists or just hardcore enthusiests? you guys have an insane knowledge of cephs

No, not a marine biologist, but still quite insane, thank you.

yea i know a lot of aquarium enthusiests, but you guys know freakin EVERYTHING i could ever hope to know about cephs.