A Tale of Two Oithona (Apocyclops)

A Tale of Two Oithona (Apocyclops)

Postby JimWelsh » Wed Jun 09, 2010 1:43 am

I'm starting a new thread for the ID of the "A. tonsa" culture I got from Luis that clearly is NOT A. tonsa. The question is: What IS it?

WARNING: I'm going to let myself be long-winded in this post!

It looks VERY much like an Oithona culture I already have (from Adelaide). The question hanging thick in the air is, How did I end up with Oithona instead of A. tonsa? One theory (admittedly the most likely) is that I contaminated the A. tonsa culture with the Oithona I already had. Another theory is that they are a South American Oithona that was present in Luis' culture, and prevailed.

There are two reasons that I don't like the first theory: (1) I was very careful to keep the cultures separated, and (2) the visual appearance and behavior of the two cultures is noticeably different. Let me explain: For (1), the culture I got from Luis was kept in an erlenmeyer flask on a different counter about 5 feet away from Oithona culture I already had. As it grew and multiplied, I split it first into two flasks, then into three cultures: two flasks, and one 1/2 gallon fishbowl. The fishbowl eventually got split into two 5 Gallon tanks where I am now doing the Oxyrrhis marina experiment (one tank is the control, being fed live phyto, and the other is being fed just dead phyto, which feeds the O. marina). Meanwhile, I have two fishbowls and one flask with Luis' copepod culture still on that separate counter away from the Oithona. For (2), there are basically three visual differences between the two cultures: (a) the Oithona from Adelaide just looks larger, in general, (b) the Luis culture is more "active" or "excitable" in response to stimulus such as movement of the culture container or a sudden change in light, as when a flashlight is shined on it at night, and (c) the Luis culture tends to be negatively phototactic, and the Adelaide Oithona is more positively phototactic.

I took samples of both cultures to the lab where I work today. Usually, I ask the microbiologists to take pictures of my organisms for me, but today, instead of "giving me a fish", they "taught me how to fish". I got a lesson in using their microscopes, camera, and software, and I can now do this work for myself! As an aside, we can look forward to me providing lots of images and/or measurements of different copepod species at different developmental stages in the future.

So, my arguments above notwithstanding, I have to admit that I'm hard-pressed to tell the difference from the pictures, except for the size difference of the males (click on the pictures to see the whole image without scrolling).

Here are the images of the culture I got from Luis:

LuisAdultMaleSL.JPG


LuisAdultFemaleSL.JPG


LuisMaleGeniculate.JPG


Here are the images of the culture I got from Adelaide:

AdelaideAdultMaleSL.JPG


AdelaideAdultFemaleSL.JPG


AdelaideMaleGeniculate.JPG


The antennae of the males of both cultures are similarly geniculate -- it was hard to get a photo of this, because for some reason, the heat of the microscope's light tended to make the flexed antennae "relax". It was actually quite frustrating, as every time I found a representative male with flexed antennae, just about the time I was ready to take the picture, I would watch as they would relax back into a more normal posture!

I do notice that the Adelaide culture tend to be more slender in aspect, overall, and the Luis culture individuals tend to be a little more "broad" or "rotund". Aside from this, I'm hard pressed to point out any distinguishing characteristics between the two.

I found absolutely NO individuals in the Luis culture that looked anything like A. tonsa -- they were all this cyclopoid that we see here.

Looks like I still am in need of an A. tonsa culture! :roll:

BY THE WAY: I think what I've measured is what would be called "Standard Length" for a copepod, but I'm not sure. Is this Standard Length? Fork Length? To measure Total Length, would I need to measure all the way to the end of the caudal setae? If somebody can help me learn how to properly measure Standard Length and Total Length of a copepod, please enlighten me!
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Re: A Tale of Two Oithona

Postby Luis A M » Wed Jun 09, 2010 12:16 pm

Wow,pics are heading to perfection! :shock: It will be very nice if we can have a collection of different pelagic copepod species used in larviculture,so we can compare and guess an ID.
I have now two strains/species looking like Oithona.Formal ID is still being processed.
(EDITED CH).The other developed from a sample collected last March in Maldonado River,Uruguay.I believed that was Pseudodiaptomus richardi and so was labelled in your sample.The other sample was A.tonsa.
So a likely explanation is that the labels were at some point cross mixed,and the "Pseu" (actually Oithona) were considered to be A.tonsa,while the real A.tonsa vanished.
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Re: A Tale of Two Oithona

Postby Luis A M » Wed Jun 09, 2010 1:24 pm

The specialists working with these samples just confirmed that they are cyclopoids.
I know,we already knew that :roll: .But they have to disect the specimens and run the different parts thru tables and it takes time.
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Re: A Tale of Two Oithona

Postby spawner » Thu Jun 10, 2010 2:15 am

I don't think they are Oithona.
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Re: A Tale of Two Oithona

Postby JimWelsh » Thu Jun 10, 2010 2:22 am

spawner wrote:I don't think they are Oithona.


Uh, care to elaborate at all (please!)? Not much for me to go on here...
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Re: A Tale of Two Oithona

Postby Luis A M » Thu Jun 10, 2010 2:11 pm

spawner wrote:I don't think they are Oithona.

It is a cyclopoid.
Few other marine pelagic cyclopoids other than Oithona exist.
Oithona is very common and cosmopolite.
(edited CH)
A definite ID is coming soon though.
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Re: A Tale of Two Oithona

Postby JimWelsh » Thu Jun 10, 2010 2:56 pm

(Edited CH)
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Re: A Tale of Two Oithona

Postby Luis A M » Fri Jun 11, 2010 8:31 pm

These Oithona are very prolific and very small,two good features! 8)
Oithona was one of Baensch,trio of success,with two paracalanids.
They are so small that even adult females with eggs pass thru the 200 mic screen. :shock: Yet all the naups are held in the 53 mic sieve.They are 90 mic long.
Amazing that they could feed on a 30 mic long flagellate! :shock:
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Re: A Tale of Two Oithona

Postby Luis A M » Sun Jun 13, 2010 11:59 am

JimWelsh wrote:
BY THE WAY: I think what I've measured is what would be called "Standard Length" for a copepod, but I'm not sure. Is this Standard Length? Fork Length? To measure Total Length, would I need to measure all the way to the end of the caudal setae? If somebody can help me learn how to properly measure Standard Length and Total Length of a copepod, please enlighten me!


Naups are measured whole,but adults are measured from the front end to the posterior side edge of the prosoma (metasoma).
This is because the tail (urosoma)can be damaged or bent in the preserved specimens;i.e. the same reason why the SL is taken in fishes.
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Re: A Tale of Two Oithona

Postby JimWelsh » Sun Jun 13, 2010 5:02 pm

To be clear: "Standard Length" of an adult copepod is the length of the prosome only, then?

What about "Total Length"? Is that what I measured in the images shown above, or would I have to include the caudal setae also?
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Re: A Tale of Two Oithona

Postby aomont » Sun Jun 13, 2010 6:14 pm

For taxonomic classification there may be a standard measurement.
That doesn't mean it is the same length we need to know to see if our larvae can eat it. ;)
What would be the worthy measurement for us to check ?
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Re: A Tale of Two Oithona

Postby Luis A M » Tue Jun 15, 2010 2:40 pm

Right,specialists need to refer to standard measures for comparative purposes,such as the length of the prososma or urosoma.
I confirmed that the total length of a copepod is measured from the front edge to the end of the branches of the furca,not including the setae.
For our practical purposes we must consider the total length and especially the width,which can be compared with the mouth gape of larval fish and points to the sieve mesh sizes we must use with them.

Both Oithona are under study now,but based in Jims´s pics,they find some difference between them in the width/length relation of the furca.They are focused now in the setae of the endop.of the maxilule :!: :shock:
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Re: A Tale of Two Oithona

Postby Luis A M » Thu Jun 17, 2010 11:14 pm

spawner wrote:I don't think they are Oithona.

This now comes as prophetic.Man,I am impressed! :shock:
Not Oithona,not even belonging to the Oithonidae family,because the swimming legs,P1 to P4 are biarticulated.Temptative ID from the Drs is Apocyclops panamensis(Marsh,1913).
Possibly both are strains of the same species,but some differences were found.Some males of one sample have shorter furcal branches,as can be seen in Jim´s pics.
A.panamensis exists in the western Atlantic,though it was found in Ivory Coast,possibly introduced.
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Re: A Tale of Two Oithona

Postby JimWelsh » Thu Jun 17, 2010 11:26 pm

Are you saying that both your copepod and the 2nd's were identified as Apocyclops?

(edited CH)

EDIT2: OK, now I'm getting a little confused (but what's new?) Googling Apocyclops panamensis, I see that it lives in fresh and brackish water, but I've been successfully culturing these copepods at full SW salinity. What gives?
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Re: A Tale of Two Oithona

Postby "Umm, fish?" » Fri Jun 18, 2010 10:36 am

Apocyclops panamensis appears to be suitable for intensive culture. Nauplii yields increased as stocking rates of wild-caught adults increased, with a peak of 17,872.5+-654.0 at an adult density of 5,120/L. In a closed system higher yields were possible. A yield of 36,800/L was obtained from a 6-day culture period when domesticated adults were stocked at 4,710/L. Maximum densities of ... 33,000 cyclopoid copepod Apocyclops royi nauplii per liter have been reported. Production trials with Acartia spp. have yielded up to 5,150 nauplii/L.


Later,

This suggests that during a 4-day production cycle, it was possible for some of the nauplii to reach maturity and reproduce, thus increasing the total number of females (mature and immature)....


From Cheng-Sheng Lee, Patricia J. O'Bryen, and Nancy H. Marcus, Copepods in Aquaculture, p. 165. http://www.amazon.com/Copepods-Aquaculture-Nancy-H-Marcus/dp/0813800668
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Re: A Tale of Two Oithona

Postby Luis A M » Fri Jun 18, 2010 2:42 pm

Amazing, Andy! :shock:
I have the book at home,will check it later.
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Re: A Tale of Two Oithona

Postby ladygator » Fri Jun 18, 2010 3:43 pm

(edited CH)

I have been so busy at my new job at the Smithsonian Marine Research Station I haven't had a chance to take a look at it again.

I would love to get some from you, Luis, so I can pick their legs off and document the species.

You said yours came from Uruguay?

It is possible they are the same species, but there are a ton of cryptic copepods and the only way to distinguish is to consult an expert in that taxa or to do a detailed analysis on the legs and antennae.

I am now set up to do that, so if you want to send a preserved batch my way, I'd love to compare.

(edited CH)
(edited CH)

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Re: A Tale of Two Oithona

Postby Clownfish75 » Sun Jun 20, 2010 10:44 pm

This thread has been reposted and unlocked by myself.

I have edited it any deviation off topic will be removed.

Thanks

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Re: A Tale of Two Oithona

Postby spawner » Sun Jun 20, 2010 11:04 pm

Luis A M wrote:
spawner wrote:I don't think they are Oithona.

This now comes as prophetic.Man,I am impressed! :shock:


An educated guess. Apocyclops is the easiest of the family to culture, well of those culture thus far. It's a good group to work with.

http://www3.interscience.wiley.com/jour ... 1&SRETRY=0

http://www.ingentaconnect.com/content/b ... awler=true

Farhadian, Omidvar (2006) Culture of a Planktonic Cyclopoid, Apocyclops Dengizicus (Lepeshkin, 1900) and Its Suitability as Live Feed for the Postlarvae of Giant Black Tiger Shrimp, Penaeus Monodon Fabricus (1798). PhD thesis, Universiti Putra Malaysia.

Most impressive is that it lives on some green algae. This and Pseudodiaptomus are the easiest to culture. Both genera could be invasive so it would be best if farms kept local species.
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Re: A Tale of Two Oithona

Postby Luis A M » Mon Jun 21, 2010 4:17 pm

I checked the book and indeed Apocyclops (panamensis,royi) seems a very convenient copepod genus.They are small,and extremely hardy and prolific.
And they also seem very common and widespread.A very promising larval food. 8)
Jim,you should add the correct name to the tittle. :wink:
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Re: A Tale of Two Oithona

Postby JimWelsh » Mon Jun 21, 2010 4:20 pm

How 'bout we just start a new topic? :wink: :wink:
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Re: A Tale of Two Oithona

Postby Luis A M » Mon Jun 21, 2010 4:36 pm

I don´t think so.This thread is one of the most valuable in recent times,both as academic,pictorial and as an introduction to a new promising larval food.This is an asset of MOFIB and shouldn´t be deprived of anything other than the off topic posts or sentences.
I expect the editor has taken this line in consideration.
Of course we can start new threads dealing with the culture or practical use of this amazing new copepod.
This thread is ripe,anyway, and few things remain to be said,like the end results of the ongoing taxonomic study,or additional bibliography found about this genus.
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Re: A Tale of Two Oithona (Apocyclops?)

Postby JimWelsh » Mon Jun 21, 2010 4:39 pm

Title edited.
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Re: A Tale of Two Oithona (Apocyclops?)

Postby "Umm, fish?" » Tue Jun 22, 2010 4:40 pm

Okay, new culture. Day 1. Nice culture! Very dense. Thanks, Jim!

[mg]http://www.ummfish.com/Vid00005311.jpg[/img]
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Re: A Tale of Two Oithona (Apocyclops?)

Postby "Umm, fish?" » Tue Jun 22, 2010 5:06 pm

Another of the copepodid, with scale. Each hash = 10 microns.

[mg]http://www.ummfish.com/copepodid_with_scale.jpg[/img]
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