The few survivors entered a semidormant cyst-hibernation to emerge in six years as small (about three meters long) sandworms. Of these, only a few avoided their larger brothers and pre-spice water pockets to emerge into maturity as the giant shai-hulud.
An important point to note here is that an organism basically hand-sized (limited mass) grows and changes into a three-meter-long sandworm. That's probably why FH added "semi-dormant": the metamorphosing sandtrout-worm is absorbing mass in some way, from some source...maybe sandplankton? (I'm assuming here that FH at least was more familiar with the concept of the Conservation of Matter than his son or the other hack, so this is necessary.)
I think I suggested somewhere that more than one sandtrout might enter the cyst since it's pointed out in CoD
that the sandtrout are haploid, having only one set of chromosomes. Two joining together would give them a full set.
Maybe when a worm becomes too old and approaches death, it's body naturally begins to reorganize itself into sandtrout and the dying worm seeks out a water source for them? If that is correct, then drowning a mature but not decrepit worm would simply kill it, leaving no sandtrout, because it hadn't begun to form them yet. (Was the worm killed in the House books described as old? I forget. If not, here's something else they've probably gotten wrong.)
Leto is, of course, a special case: originally a human encased in sandtrout. The majority of the mass of his body is probably something created by the sandtrout that make up his outer layer. Or, since we know that sandtrout do propagate, maybe the growing worm part of him is composed of new sandtrout generated by the outer layer and undergoing the worm metamorphosis in some weird variation as a result of the human-sandtrout symbiotic environment?
It would be nice to come up with a coherent picture of all of this before they try to establish something silly in Letotard of Dung
I think from the quote chigger provided above one sandtrout equals one worm. Note it says "The few survivors
entered a semidormant cyst-hibernation to emerge in six years as small (about three meters long) sandworms
." Plural. So we can say with some degree of certainty that the few survivors don't all combine to form a
worm. Perhaps they pair up as chigger suggests; but they can't all combine into one worm because it clearly states a plural outcome.
As far as being haploid, chigger's proposition certainly is a logical alternative. However, algae also have a haploid life cycle and it doesn't work in quite the same way as a combination of gametes does in most animals. Individual starts out as a diploidzygote. The zygote goes through a meisosis and then develops into haploid spores. Meiosis produces four cells from each zygote and these four cells can be like spores (or some other structure depending on the actual organism--I believe, don't quote me, it works a little different between algae and some fungi). The four cells would then go through mitosis and become the organism. What's important here is that in this example, its asexual
Perhaps a sandtrout enters into the cyst state, and at that time meisosis occurs within the organism itself to produce two gametes. Those combine within the cyst state and mitosis begins to form a new organism--a sandworm. This would require some sort of mutation for the chronosomal code to be different, because the four haploid cells would combine to form an organism identical the original. Remember in plants meiosis results in the formation of haploid cells that can divide vegetatively without undergoing fertilization. In this scenario, in fact, its possible that the sand plankton start out as the diploidzygote, and eventually split into the haploid which would theoretically create two sandtrout.
Incidently, addressing your earlier question SC, in the House series Rabban's sandworm distintegrates, but the "reamers of dune" explain it off on the FAQ like such:
FAQ: In the prequels when Rabban kills a worm it disintegrates completely, but in the DUNE classic, Kynes says that every worm segment has a life of its own and that, barring atomics, no explosive can destroy a worm completely.
Their absurd answer: The original novels establish that when an ancient worm is close to death it prepares to fission and disintegrate. Rabban's worm was very old and near its reproductive-death stage. It broke apart into separate ring segments, according to the worms' reproductive cycle, as established by Frank Herbert.
I don't recall it turning into sandtrout.