Molting

[technoshaman]

Just wondering if anyone has any idea on the frequency of molting on O.Scyllarus in particular. I have had mine for about 5 weeks and she arrived missing one dactyl and one damaged. I've been trying to take really good care of the critter and now she finally molted and regrew most of the missing dactyl and the damaged one. I have had the photoperiod a little shorter in that tank the past week and haven't been able to watch as much as I'd like so sometime over this weekend it happened. Are there any environmental cues or does it just depend on growth?

Also I'm curious on iodine supplementation. It's a small tank (5 gallons) and I change about 1/2 gallon a week. In my experience normal water changes seem to provide adequate levels of iodine in my reef tanks since my cleaners molt constantly with no issues to date. The shell either was buried or hidden in her burrow or she consumed it - no trace to be found.

Also I have heard various things about O.Scyllarus having some kind of particular problem with their appendages atrophying due to lack of use? Should I be feeding it some hard shelled food occasionally? Currently for a staple it's been krill , sometimes calamari or mussel and the occasional ghost shrimp. Other than the initial shipping injury it's been doing very well and per Dr. Caldwell's advice I have a very dark PVC tube in the substrate she constructed her burrow around - this molt losing a lot of the reddish - orange color and darkening to green towards the tail region now. Does this mean I actually have a male?

Sorry a million questions but these creatures fascinate me. I spend more time watching my mantis than I do all my other tanks combined!

 

[Gonodactylus]

Molt frequency in O. scyllarus depends on size (age), food, reproduction, social environment, physical condition and can be synchronize by external cues.

Size. Juveniles will molt every 2-4 weeks, very large animals every 4-6 months. The standard 11 cm O.s. usually molts every 2-3 months.

Food. Feeding an animal all the food it can handle will accelerate molting - perhaps even half the interval between molts. Depriving it of food will slow the rate, but even an animal barely getting enough to eat will molt every 6 months or so. It may get smaller, but the molt is necessary for maintenance of the cuticle and apodemes.

Reproduction. Females will not molt and lay eggs at the same time. If they lay eggs, they skip a molt cycle. We don't know if reproduction has any effect on male O.s, but in Neogonodactylus bredini which has highly synchronized reproduction, mature males wait until after females have mated and laid eggs before they molt.

Social environment. There is some evidence of synchronized molting in the field and certainly in our large holding tanks where we keep 6 to 8 adult O.s., they seem to molt at the same time. However, I can't honestly say if this is due to external cues or signals from the other stomatopods. Other stomatopods that live in monogamous pairs such as Lysiosquillina do molt at the same time.

Physical condition. The loss of the raptorial appendages will accelerate the molt if the animal can get enough food. In a study that we did on another species, loss of one or two walking legs or one raptorial appendage did not accelerate molting, but losing both raptorial appendages did. There was a cost in that growth was reduced and reproduction was delayed. If you think about it, this makes sense. An animal with one functioning raptorial appendage can feed and defend itself, so why incur more risk molting than necessary. With no rapts, the animals only hope is to regenerate them and this requires molting.

Obvioiusly, other factors such as disease, temperature, etc. can also have an impact.

We track the growth of our animals by measuring the lenght of the carapace (down the midline) without the rostrum. Since this piece of cuticle is shread in one piece and is flat, it is easy to measure. You can also measure the new cuticle on the intact animal or wait until the next molt. Growth rates typically are in the 5 - 7% range, but are higher for very small animals.

Roy

 

[technoshaman]

RE: Molting

Dr. Caldwell, thanks so much that is exactly the kind of information I was looking for. Fascinating about the synchronized molting in groups. The idea that they might possibly modify the cycle if their dactyls are lost is interesting and may have been applicable here.

When you talk about using the length of the carapace as a measurement are you measuring the actual specimen or the recently discarded molt? And I am familiar with where the rostrum would be located on most species of shrimp but I don't see anything like that on my mantis - the typical sawtooth type protrusion near the center of the head. Are there any good print books or periodicals that have an overview of stomatopod anatomy that you could reccomend? I've read a lot google found but they are pretty fragmentary or I am not looking in the right place.

Thanks again for he information!

 

[Gonodactylus]

The nice thing about using the carapace for growth measurements is that you can measure either the molted exoskeleton or the intact cuticle. Often times the first part of the molt skin eaten is the soft carapace. However, if you can retrieve it, you can measure it and the intact on and get a reliable estimate of how much the animal grew during that molt.

The rostrum is the shield shaped flap directly behind the eyes. Shape varies according to species (it is often one of the most useful diagnostic characters). It is hinged while the carapace is fixed. If you look at your O.S., it should be fairly easy to see. In a 12 cm animal, it will be about a half a centimeter wide and 3 mm long.

Roy