Lysmata amboinensis larva

[Luis A M]

Well,I´m playing again this crazy game,but I think I´m improving.
I have a new batch at Z7 with decent survival,so I expect at least to document some more stages.
The good thing is that they reached Z7 in 18 days.Like a clockwork,they molted and changed stages every three days.There were no "marking time molts"ie. molts where the same stage is repeated.
So at least up to Z7 we can expect a molt and a new stage every 3 days as per the formula (stage-1)x3=age in days.
If things could keep like that,we would have a Z12 at 33 days and a settled shrimp at 36,about the same peppermints take.
Unfortunately things change after Z7.It´s like a video game where we are moved to a new,difficult and unknown level.After Z7,larvae take several months to settle and usually die in the meantime.The mechanisms they use to stretch for so long their larval development could be one or more of the following:a- the infamous "time marking"which is related to larval distress,so not clear how natural this is;b-longer inter-molting periods and c-more,undescribed larval stages.
I will watch carefully this "second level"of larval development and try to describe and document new stages here.Some day we will have pictured the whole series

[spawner]

Luis,

It's "Mark-time molting"

This next level is a lot more fun than the previous, but the one after that is the real killer

[Luis A M]

Originally posted by spawner
Luis,

It's "Mark-time molting"

This next level is a lot more fun than the previous, but the one after that is the real killer

Perhaps a combination of the three?(a-b-c)

You think mark-time molting under natural conditions does occur physiologically?(as a normal,healthy process)

When does this awful killer level start?(hope that will be the last?)

[Luis A M]

Bummer!.They started to disappear. Welcome to level 2,I miss level 1
There suddenly were about 40,next day 20.Then I discovered lots of hydroids
in the larval tank,that I can´t imagine how they came.I suspect hydroids are the culprits,based on previous experiences.
Yesterday I moved all remaining larvae into a clean tank,but they were only 11! May be some will keep going,but I´m afraid this is a no win run
Andy,tell us about level 3!.How could it be worse?

[FuEl]

Level 3 = die in the process of metamorphosis or shortly after settlement?

[Luis A M]

The 11 larvae moved to a clean tank are still fine.
Interestingly,all the three proposed mechanisms explaining the very long larval life of this shrimp seem to be working here.Between the 7th zoea (Z7) where all the legs develop and the stage where pleopods (swimmerettes)show, I found some new stages.
While many of the larval structures show slight though definite changes,the feature one must look to follow these stages is the development of the antenna called flagellum of A2,and it´s relation with the basal plate,called the scale.

So following are the observed stages:

Z7-day 18.Flagellum is a short blunt bud.

Z8-day 26.Flagellum is longer and slender with two apical setae (hairs in the tip).Reaches the point in the scale where setae start,about 1/4 the length of the scale.

Z9-day 33.Flagellum almost reaches half of the scale.

Z10-day 36.Flagellum reaches the fork of A1,the antennula,or almost the total length of the scale.Pleopod buds show but only of the 3rd and 4th pairs.

Of course I must repeat these observations many times and document them with pictures.And find and describe new stages.This is not a formal academic description,of course.Just a practical,hobbyist oriented staging key to monitor the long larval development of this shrimp.As long as they help me by staying alive,that is!

[Luis A M]

Ten larvae remain
A new stage was found:

Z11-day 37.Flagellum is now longer than scale.All five pairs of pleopod buds are now present.3º and 4º pairs are more developed than the others.
This level of development is reached by the 8th zoea in peppermint shrimps. See how this species has more stages,possibly related with the extra long larval phase.

[spawner]

I would not call these stages but maybe instars Luis. Your going to see a lot of strange developmental features and some are going to be varible between larvae of the same instar. Best if you use instar or molt number and the number of days. At zoea 10 these guys have a very long flagellum and well developed pleopods.

[Luis A M]

Originally posted by spawner
I would not call these stages but maybe instars Luis. Your going to see a lot of strange developmental features and some are going to be varible between larvae of the same instar. Best if you use instar or molt number and the number of days. At zoea 10 these guys have a very long flagellum and well developed pleopods.

"Instar" and "Stage" are in the literature often used as synonims.But the current trend ( see Anger) is to use "instar" as a "molting cycle"or "numerical stage".And morphologically distinguishable instars are considered "stages" and given a roman number:zoea I,zoea II,etc.
So,to put it simple,everytime a larva molts,it becomes a new instar.If the new instar has some morphological (anatomical) change it is also a new stage.In larvae,different instars represent also different stages.
Not so if a new instar is larger albeit identical to the previous one,as might happen in "time marking" then we have more instars than stages.This is why I think we must use "stage"to describe morphologically different instars.

Of course Andy,these are only preliminary observations which I have to confirm or correct with many further observations.I am watching carefully and documenting with pics that will be posted here,with the aim of showing all the life story of larval L.amboinensis.But at a hobbyist level,and using means any other hobbyist can repeat.I don´t kill or dissect larvae for precise descriptions,just watch living larvae.

The interesting thing is that stages Z1 to Z7 are virtually identical in peppermints like L.boggessi that take about one month to settle and L.amboinensis that need over four months.Only afterwards things change.
I found three more stages between Z7 and the pleopod buds stage (Z8 in boggessi and Z11 in amboinensis).Now I will check the pleopod development stages until settlement ,Z9-11 in boggessi and perhaps some more in amboinensis.

I checked my 10 remaining larvae.I have one Z11,one Z10,four Z9 and four Z8

[Luis A M]

Originally posted by Luis A M
Bummer!.They started to disappear. Welcome to level 2,I miss level 1
There suddenly were about 40,next day 20.Then I discovered lots of hydroids
in the larval tank,that I can´t imagine how they came.I suspect hydroids are the culprits,based on previous experiences.
Yesterday I moved all remaining larvae into a clean tank,but they were only 11! May be some will keep going,but I´m afraid this is a no win run
Andy,tell us about level 3!.How could it be worse?

The ten remaining larvae were doing reasonably well until one day they were 7,then 5 and now freaking three!.There is where I found hydroids had taken again the tank! .I imagine they kill the larvae when they are just molted.
Again moved them to a clean tank and look fine so far.They are 1cm long at 60 days.But they have to grow to 2cm at 120 days before settlement,according to other folks experiences.But with only three larvae my odds are faint.
Nevertheless,the zoea show advanced development.A2 (antenna)reaches half the branches of A1 (antennule).Pleopods are biramous (two branched) and with 5-7 setae (hairs) at the tip.
I agree with Andy here and I won´t call stages based in only three individuals,and I might have missed some in between stages.But I will keep detailed development records of them,as long as they survive.
As I say ,this is a masochist game

[Kmiec123]

Originally posted by Luis A M
,this is a masochist game

I hear That!!!

Kill one your a Murderer,

Kill many your a conqueror,

Kill them all...Your a God!

Not saying I'm a god, but I understand this.

Carl

[Elmo18]

Hi Luis! Oh my....let's keep this going!

Your efforts are applauded..

Best,
Ilham

[Luis A M]

Thanks.I could document with pics the development of the antenna in each of the new found stages,but have been unable to upload them so far,something wrong with the format

[FuEl]

Hi Luis, great efforts so far. I experienced the same mark-time moulting after zoea VII is reached. Perhaps you might want to rear the remaining 3 individually. If they all settle out fine after doing that you might be onto something. Perhaps the larvae inhibit each other's growth somehow.

[Luis A M]

See my previous "update"post.My point (which needs confirmation)is that there were (at least in this case) no marking time molts after Z7 as it is said,but three "new"stages,Z8,Z9 and Z10 before the pleopod buds stage.I promise pics...

[purplehaze]

Originally posted by Luis A M
See my previous "update"post.My point (which needs confirmation)is that there were (at least in this case) no marking time molts after Z7 as it is said,but three "new"stages,Z8,Z9 and Z10 before the pleopod buds stage.I promise pics...

Hi Luis,

So you are saying that the pleopod buds only appear in ZXI

[spawner]

I don't think that Luis is trying to put a number on the stages that would agree with morphological development patterns. More a guide for what is normally seen.

[Luis A M]

85th. day.The three larvae were growing fine and reached 15 mm and today two died.I found again some incipient hydroid growth.Somehow the UV was shut down
Once more I moved the lone survivor to a clean tank and it´s doing great.
Antenna A2 is almost as long as A1.Pleopods are fully developed,with setae,about 40,all around them.Seems like the last larval stage and matches the 120 days larva description in Wunsch´s monography.And yet it should have to grow to 20 mm.
Will this larva make it?.Probably not.Or perhaps this will be the one?.While it lasts,I´ll hold my breath every morning until I find it swimming around.And all that fuzz about a bug the size of a mosquito!(well,a large mosquito)
You see why I call it a masochist game?

[FuEl]

Originally posted by Luis A M
You see why I call it a masochist game?

Only those who have attempted would understand.

[purplehaze]

Are you just feeding BBS?

[Luis A M]

Originally posted by purplehaze
Are you just feeding BBS?

BBS plus Otohime

[Kmiec123]

Luis, Do you have any other animals in the tanks with the larva? I was just thinking since I read that shrimp eat detritus that maybe in addition to a phyto mixture Thalasiosira weissflogii, Tetraselmis, Rotifers, etc.. adding some snails to feed off the glass and bottom eating benifical algae should have some tasty detritus(tasty for shrimp larva that is) Just a thought....hope this helps. I have no experience with this, just thinking out loud.....Carl

[Luis A M]

Originally posted by Kmiec123
Luis, Do you have any other animals in the tanks with the larva? I was just thinking since I read that shrimp eat detritus that maybe in addition to a phyto mixture Thalasiosira weissflogii, Tetraselmis, Rotifers, etc.. adding some snails to feed off the glass and bottom eating benifical algae should have some tasty detritus(tasty for shrimp larva that is) Just a thought....hope this helps. I have no experience with this, just thinking out loud.....Carl

The only (unwelcome ) other animals that show are darned hydroids.
Larvae do feed on many items as you point,and I tried many diets in the past.I´m now pretty happy with this food and focus in an environment as clean and bacteria free as possible.

[Luis A M]

I could upload the pics.This series shows the development of the antenna (flagellum of A2) which is the feature that best defines the new stages I will document here.

This is a close view of the head of the 7th Zoea.The bud of the antenna can be seen between A1,the antennula and A2,the scale.

[Luis A M]

In the 8th zoea,the antenna reaches the first setae(hairs) of the scale.