Hi guys, I'm just a reefer who has been working on L. amboinensis for my studies. With regards to L. amboinensis I can only say they are much much harder to culture compared to L. debelius. I got L. debelius to settle even though I neglected them rather badly during their first 2 weeks of life. They did'nt seem to need any settlement cue and apparently they seem to be more voracious feeders compared to L. amboinensis.
I have done some preliminary work on early nutrition for L. amboinensis. Comparing the results with another study performed by another student before me seems to indicate that zoea I larvae of L. amboinensis rely and benefit more on Tetraselmis chuii than L. debelius. Tetraselmis chuii concentrations should be maintained around 50000 cells per mL. Rotifers don't appear to be neccessary and Artemia nauplii will be readily consumed (maintain around 3-5 artemia nauplii per mL).
L. debelius does not seem to need any settlement cue. For L. amboinensis I have tried the following settlement cues: Fish, coralline liverock, adults, settlement substrate. None worked. I have read up on coralline (GABA) and this settlement cue seems to apply only to sedentary organisms like corals, etc. For crustaceans which retain their mobility after settlement I doubt coralline derivatives will aid settlement.
The interesting thing about L. amboinensis larvae is that they can easily reach 5-10X the mass of L. debelius larvae. Even though they appear to be ready to settle, they tend to die off once they reach 1cm and above in total length. From the growth I have observed in an upwelling system (Zoea VII reached around 17 days), the possibility of them settling at 42 days (According to Waikiki aquarium) does not seem to be impossible. The larvae easily reach close to 1cm by 42 days and any larval duration exceeding that is probably due to mark-time molting attributed by delayed metamorphosis. Delayed metamorphosis either results in spontaneous settlement or mass mortality. Mass mortality for L. amboinensis larvae is not surprising as the large larvae might incur some detrimental metabolic costs by delaying metamorphosis.
As for how long larvae can survive, it depends on how fast they develop. Scientific reported larval durations range from 58-140 days for L. amboinensis. Such a large range is probably caused by many factors like larval quality, larval nutrition, zoea I starvation, etc etc. Larvae raised in rectangular tanks/beakers will develop much slower than those raised in upwelling and hence they can have much much longer larval lifespans. For instance I have raised a handful of L. amboinensis larvae in small beakers solely on newly hatched Artemia nauplii up to 50-63 days. However, none developed past zoea VII. Zoea VII is normally reached below 20 days so you can imagine how long they can delay development. As such, it is impossible to raise these larvae to settlement on Artemia nauplii alone. Best to supplement their diets with other foods (finely chopped prawns, squid, mussels and even crab eggs) or even on-grown enriched Artemia (I used all this for L. debelius and amboinensis). I might try chopped polychaetes next time.
As whether settlement is due to nutrition or settlement cue, the answer might be to dump a batch of laboratory-raised late-stage larvae into floating sea cages to see if settlement occurs.
Just my 2 cents~
