Circadian Rhythm of Aggression in Crayfish

ResearchBlogging.orgLong-time readers of this blog remember that, some years ago, I did a nifty little study on the Influence of Light Cycle on Dominance Status and Aggression in Crayfish. The department has moved to a new building, the crayfish lab is gone, I am out of science, so chances of following up on that study are very low. And what we did was too small even for a Least Publishable Unit, so, in order to have the scientific community aware of our results, I posted them (with agreement from my co-authors) on my blog. So, although I myself am unlikely to continue studying the relationship between the circadian system and the aggressive behavior in crayfish, I am hoping others will.

And a paper just came out on exactly this topic - Circadian Regulation of Agonistic Behavior in Groups of Parthenogenetic Marbled Crayfish, Procambarus sp. by Abud J. Farca Luna, Joaquin I. Hurtado-Zavala, Thomas Reischig and Ralf Heinrich from the Institute for Zoology, University of Gottingen, Germany:

Crustaceans have frequently been used to study the neuroethology of both agonistic behavior and circadian rhythms, but whether their highly stereotyped and quantifiable agonistic activity is controlled by circadian pacemakers has, so far, not been investigated. Isolated marbled crayfish (Procambarus spec.) displayed rhythmic locomotor activity under 12-h light:12-h darkness (LD12:12) and rhythmicity persisted after switching to constant darkness (DD) for 8 days, suggesting the presence of endogenous circadian pacemakers. Isogenetic females of parthenogenetic marbled crayfish displayed all behavioral elements known from agonistic interactions of previously studied decapod species including the formation of hierarchies. Groups of marbled crafish displayed high frequencies of agonistic encounters during the 1st hour of their cohabitation, but with the formation of hierarchies agonistic activities were subsequently reduced to low levels. Group agonistic activity was entrained to periods of exactly 24 h under LD12:12, and peaks of agonistic activity coincided with light-to-dark and dark-to-light transitions. After switching to DD, enhanced agonistic activity was dispersed over periods of 8-to 10-h duration that were centered around the times corresponding with light-to-dark transitions during the preceding 3 days in LD12:12. During 4 days under DD agonistic activity remained rhythmic with an average circadian period of 24.83 ± 1.22 h in all crayfish groups tested. Only the most dominant crayfish that participated in more than half of all agonistic encounters within the group revealed clear endogenous rhythmicity in their agonistic behavior, whereas subordinate individuals, depending on their social rank, initiated only between 19.4% and 0.03% of all encounters in constant darkness and displayed no statistically significant rhythmicity. The results indicate that both locomotion and agonistic social interactions are rhythmic behaviors of marbled crayfish that are controlled by light-entrained endogenous pacemakers.

I think the best way for me to explain what they did in this study is to do a head-to-head comparison between our study and their study - it is striking how the two are complementary! On one hand, there is no overlap in methods at all (so no instance of scooping for sure), yet on the other, both studies came up with similar results, thus strengthening each other's findings. You may want to read my post for the introduction to the topic, as I explain there why studying aggression in crayfish is important and insightful, what was done to date, and what it all means, as well as the standard methodology in the field. So, let's see how the two studies are similar and how the two differ:

1) We were sure we used the Procambarus clarkii species. They are probably not exactly sure what species they had, so they denoted it as Procambarus sp., noting in the Discussion that it was certainly NOT the Procambarus clarkii, which makes sense as our animals were wild-caught in the USA and theirs in Germany. As both studies got similar results, this indicates that this is not a single-species phenomenon, but can be generalizable at least to other crayfish, if not broader to other crustaceans, arhtropods or all invertebrates.

2) We used only males in our study. They used only females. In crayfish, both sexes fight. It is nice, thus, to note that other aspects of the behavior are similar between sexes.

3) We used the term 'aggression'. They use the term 'agonistic behavior', which is scientese for 'aggression', invented to erase any hints of anthropomorphism. Not a bad strategy, generally, as assumed aggression in some other species has been later shown to be something else (e.g., homosexual behavior), but in crayfish it is most certainly aggression: they meet, they display, they fight, and if there is no place to escape, one often kills the other - there is no 'loving' going on there, for sure.

4) The sizes of animals were an order of magnitude different between the two studies. Their crayfish weighed around 1-2g while ours were 20-40g in body mass. This may be due to species differences, but is more likely due to age - they used juveniles while we used adults. Again, it is nice to see that results in different age groups are comparable.

5) We did not measure general locomotor activity of our animals in isolation. We, with proper caveats, used aggressive behavior of paired animals as a proxy for general locomotor activity, and were straightforward about it - we measured aggressive behavior alone in a highly un-natural setup. As Page and Larimer (1972) have done these studies before, we did not feel the need to replicate those with our animals.

The new study, however, did monitor gross locomotor activity of isolated crayfish. Their results, confirming what Page and Larimer found out, demonstrate once again that activity rhythms are a poor marker of the underlying circadian pacemaker (which is why Terry Page later focused on the rhythm of electrical activity of the eye, electroretinogram - ERR - in subsequent studies) in crayfish. Powerful statistics tease out rhythmicity in most individuals, but this is not a rhythm I would use if I wanted to do more complex studies, e.g., analysis of entrainment to exotic LD cycles or to build and interpret a Phase-Response Curve. Just look at their representative example (and you know this is their best):

i-8e437d3be0bcb086a2d40950b68bc6aa-crayfish image 1.JPG

You can barely make out the rhythm even in the light-dark cycle (white-gray portion of the actograph) and the rhythms in constant darkness (solid gray) are even less well defined - thus only statistical analysis (bottom) can discover rhythms in such records. The stats reveal a peak of activity in the early night and a smaller peak of activity at dawn, similarly to what Page and Larimer found in their study, and similar to what we saw during our experiments.

6) They used an arena of a much larger size than ours. We did it on purpose - we wanted to 'force' the animals to fight as much as possible by putting them in tight quarters where they cannot avoid each other, as we were interested in physiology and wanted it intensified so we could get clearly measurable (if exaggerated) results. Their study is, thus, more ecologically relevant, but one always has to deal with pros and cons in such decisions: more realistic vs. more powerful. They chose realism, we chose power. Together, the two approaches reinforce and complement each other.

7) As I explained in my old post - there are two methodological approaches in this line of research:

Two standard experimental practices are used in the study of aggression in crustaceans. In one, two or more individuals are placed together in an aquarium and left there for a long period of time (days to weeks). After the initial aggressive encounters, the social status of an individual can be deduced from its control of resources, like food, shelter and mates.

In the other paradigm, two individuals are allowed to fight for a brief period of time (less than an hour), after which they are isolated again and re-tested the next day at the same time of day.

They used the first method. We modified the second one (testing repeatedly, every 3 hours over 24 hours, instead of just once a day).

What they did was place 6 individuals in the aquarium, a couple of hours before lights-off, then monitor their aggressive behavior over several days. What they found, similar to us, is that the most intense fights resulting in a stable social hierarchy occur in the early portion of the night:

i-54f70f2e789d1d1bacae36e45a4acf07-crayfish image 2.JPG

Once the social hierarchy is established on that first night, the levels of aggression drop significantly, and occasional bouts of fights happen at all times, with perhaps a slight increase at the times of light switches: both off and on. Released into constant darkness, the pattern continues, with the most dominant individual initiating aggressive encounters a little more often during light-transitions then between them. The other five animals had no remaining rhythm of agonistic behavior: they just responded to attacks by the Numero Uno when necessary.

In our study we tried to artificially elevate the levels of aggression by repeatedly re-isolating and re-meeting two animals at a time. And even with that protocol, we saw the most intense fights at early night, and most conclusive fights, i.e., those that resulted in stable social hierarchy, also occuring at early nights, while the activity at other time of the day or night were much lower.

8) The goals of two studies differed as well, i.e., we asked somewhat different questions.

Our study was designed to provide some background answers that would tell us if a particular hypothesis is worth testing: winning a fight elevates serotonin in the nervous system; elevated serotonin correlated with the hightened aggression in subsequent fights, more likely leading to subsequent victories; crayfish signal dominance status to each other via urine; melatonin is a metabolic product of serotonin; melatonin is produced only during the night with a very sharp and high peak at the beginning of the night; if there is more serotonin in the nervous system, there should be more melatonin in the urine; perhaps melatonin may be the signature molecule in the urine indicating social status.

In order to see if this line of thinking is worth pursuing, we needed to see, first, if the most aggressive bouts happen in the early night and if the most decisive fights (those that lead to stable hiararchy) happen in the early night. This is what we found, indicating that our hypothesis is worth testing in the future.

They asked a different set of questions:

Is there a circadian rhythm of locomotor activity? They found: Yes.
Is there a circadian rhythm of aggression? They found: Yes.
Do the patterns of general activity and aggressive activity correlate with each other? They found: Yes.
Does the aggression rhythm persist in constant darkness conditions? They found: Yes.
Do all individuals show circadian rhythm of aggression? They found: No. Only the most dominant individual does. The others just defend themselves when attacked.
Is there social entrainment in crayfish, i.e., do they entrain their rhythms to each other in constant conditions? They found: No. All of them just keep following their own inherent circadian periods and drift apart after a while.
Is there a pattern of temporal competitive exclusion, i.e., do submissive individuals shift their activity patterns so as not to have to meet The Badassest One? They found: No. All of them just keep following their own inherent circadian periods.

So, a nice study overall, the first publication I know of that attempts to connect the literature on circadian rhythms in crayfish to the literature on aggressive behavior in crayfish.


If you Google 'crayfish+circadian+agonistic' one of the top ten hits is my post (also found here and here). That is the regular Google Web Search. These posts are #one and #two in Google Blogsearch, but do not appear in Google News or Google Scholar.

That post is also reporting on the only previous study on circadian rhythms of agonistic behavior in crayfish. There is a lot of literature on crayfish, on agonistic behavior in crayfish, on circadian rhythms in crayfish, etc., but none putting it all together: is there a circadian rhythm of agonistic behavior in crayfish? The only exception is my blog post. With data. Nice data, but not enough even for a Least Publishable Unit. Some time ago I thought about contacting my co-authors and putting this on Nature Precedings so it gets a DOI, but decided against it - I kinda wanted to use it as "bait", to see if anyone will ever cite it, and as a teaching tool about citing blog posts in manuscripts.

This post of mine was cited in a review paper and this post was cited in an Editorial. And that's just me. So, citing blogs is not such a new thing any more.

National Library of Medicine even made some kind of "official rules for citing blogs" which are incredibly misguided and stupid (and were not changed despite some of us, including myself, contacting them and explaining why their rules are stupid - I got a seemingly polite response telling me pretty much that my opinion does not matter). Anyway, how can anyone make such things 'official' when each journal has its own reference formatting rules? If you decide to cite a blog post, you can pretty much use your own brain and put together a citation in a format that makes sense.

The thing is, citing blogs is a pretty new thing, and many people are going to be uneasy about it, or ignorant of the ability and appropriateness to cite blogs, or just so unaware of blogs they would not even know that relevant information can be found on them and subsequently cited. So, if you see that a new paper did not cite your paper with relevant information in it, you can get rightfully angry, but if you see that a new paper did not cite your blog post with relevant information in it, you just shrug your shoulders and hope that one day people will learn....

One of the usual reasons given for not citing blog posts is that they are not peer-reviewed. Which is not true. First, if the post contained errors, readers would point them out in the comments. That is the first layer of peer review. Then, the authors of the manuscript found and read a blog post, evaluated its accuracy and relevance and CHOSE to use it as a reference. That is the second layer of peer-review. Then, the people who review the manuscript will also check the references and, if there is a problem with the cited blog post, they will point this out to the editor. This is the third layer of peer-review. How much more peer-review can one ask for?

And all of that ignores that book chapters, books, popular magazine articles and even newspaper articles are regularly cited, not to mention the ubiqutous "personal communication". But blogs have a bad rep, because dinosaur corporate curmudgeon journalists think that Drudge and Powerline are blogs - the best blogs, actually - and thus write idiotic articles about the bad quality of blogs and other similar nonsense. Well, if you thought Powerline is the best blog (as Time did, quite intentionally, in order to smear all of the blogosphere by equating it with the very worst right-wing blathering idiotic website that happens to use a blogging software), you would have a low of opinion of blogs, too, wouldn't you?

But what about one's inability to detect relevant blog posts, as opposed to research papers to cite? Well, Google it. Google loves blogs and puts them high up in searches. If you are doing research, you are likely to regularly search your keywords not just on MedLine or Web Of Science, but also on Google, in which case the relevant blog posts will pop right up. So, there is no excuse there.

Now, let me make it clear that I do not blame the authors of this new study - I don't know them, I really like their paper, and I understand that this is a new world in which citing blogs is such a novelty that most people are not even aware of the possibility. I am not at all angry at not getting my blog post cited by them, although I think that citing it would have strengthened their paper significantly. I just hope that this blog post you are reading right now will help spread the awareness that citing blogs is OK. Do it if you come upon a citable post yourself. Let's change the world, one citation at the time.


A. J. Farca Luna, J. I. Hurtado-Zavala, T. Reischig, R. Heinrich (2009). Circadian Regulation of Agonistic Behavior in Groups of Parthenogenetic Marbled Crayfish, Procambarus sp. Journal of Biological Rhythms, 24 (1), 64-72 DOI: 10.1177/0748730408328933

Hughes, Amy, Zivkovic, Bora and Grossfeld, Robert, Influence of Light Cycle on Dominance Status and Aggression in Crayfish (April 6, 2006), A Blog Around The Clock;

Page,Terry L. and Larimer, James L. (1972), Entrainment of the circadian locomotor activity rhythm in crayfish: The role of the eyes and caudal photoreceptor, Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology, Volume 78, Number 2: 107 - 120


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I have found an abundant biofilm of ammonia oxidizing bacteria (AOB) on marine lobsters. I presume that crayfish have the same, and that the biofilm is sustained by NH3 leaking through their shell, perhaps done to maintain a high pH and prevent the shell from dissolving (other shelled creatures release NH3 too, such as snails).

A common feature of crayfish aggression is to spray urine on their opponent. I suspect that NH3 in that urine forms NO/NOx from the ammonia oxidizing biofilm which signals the protein and energy status of the spraying crayfish. If so, then aggression should be able to be manipulated by changing the surface biofilm.

Incidentally, the ammonia monooxygenase (AMO) enzyme of ammonia oxidizing bacteria is inhibited by light. I suspect that that plays a role in circadian rhythms, low light causes high NO levels; high light causes low NO levels. AOB use NO as a quorum sensing compound to switch from biofilm phenotype to planktonic phenotype (on NO becoming low). I suspect that is part of the normal life-cycle, low NO during the day (from light) and the biofilm becomes planktonic and disperse. High NO at night and the biofilm gets thicker.

Acetylene irreversibly inhibits AMO at ppm levels as do many other compounds (i.e. alkyl benzene sulfonate detergents are toxic at ppm levels). I suspect that an effect of xenobiotic compounds on AOB biofilms is to mimic the effects of light causing low NO. That may cause the biofilm to depopulate, leaving the niche open for heterotrophic organisms to expand, express quorum sensing compounds and cause infection. I suspect that is what causes lobster shell disease, inhibition of AMO via atrazine, detergents or other xenobiotic compounds.

NO regulates steroid synthesis (and other P450 reactions). Disrupting an AOB biofilm will cause endocrine disruption (because the NO from the biofilm is part of the normal regulation of basal NO/NOx).

In humans sleep is a high NO state. Inhibiting NOS inhibits sleep.

If you are doing research, you are likely to regularly search your keywords not just on MedLine or Web Of Science, but also on Google, in which case the relevant blog posts will pop right up. So, there is no excuse there.

While I routinely search MedLine (actually, PubMed) for research purposes, I usually only "resort" to Google when I am trying to find some specific information that I cannot find in PubMed. So I can easily see being remiss in not citing a relevant blog posting. You can teach an old dog new tricks, but it takes a while.

By Guy Plunkett (not verified) on 02 Feb 2009 #permalink

They are probably not exactly sure what species they had, so they denoted it as Procambarus sp., noting in the Discussion that it was certainly NOT the Procambarus clarkii, which makes sense as our animals were wild-caught in the USA and theirs in Germany.

The problem isn't that they didn't know what species they have -- they have Marmorkrebs, also known as marbled crayfish. The problem is that there isn't a formal description of this species for several reasons, not the least of which is that it's not clear if it can be considered a distinct species! I've blogged about this here. The German animals would probably not wild-caught. There are no known "wild" populations of Marmorkrebs (though they have been introduced into ecosystems).

Their crayfish weighed around 1-2g while ours were 20-40g in body mass. This may be due to species differences, but is more likely due to age - they used juveniles while we used adults.

Almost certainly correct. Marmorkrebs don't seem to get quite as large as P. clarkii, and they are more lightly built, but adult Marmorkrebs are certainly much bigger than a few grams!

Can crayfish eat a whole human? I saw that implied in a movie recently (unfortunately, the actual process was left to our imaginations). I thought that they can bite, but eat a whole human? Sorry for the stupid question, but I am 1)exploiting the brotherly privilege (since I claim Bora as my only brother) and 2) trying to inject some popular culture into science. Just for fun (and to advance popularization of science of course)

By Marko Zivkovic (not verified) on 02 Feb 2009 #permalink

In Japanese movies, everything is possible, of course ;-)

I guess if there was a LOT of crayfish, and the human sat very, very still, and they are given months of free time to do so, I guess they could eat a human - but would they enjoy it?

I seem to remember from my youth, crayfish from a pond consuming an animal down to the bone. The animal was at the water line and was either trapped or dead.

It is my understanding that crayfish will eat just about anything including other crayfish.

They don't really bite, they tear off pieces and then consume those.

Corrrection, not a Japanese movie but RockenRolla directed by Guy Ritchie. The bad guy likes to feed people to American crayfish that have eaten all their British brethren in the river Thames after being introduced there. He is finally himself bound and lowered into Thames with the implication that he will be eaten and that this will be relatively quick. And he also earlier on gives a little lecture on crayfish and how they started eating each other after they finished off the natives. I want reliable scientific opinion on this.


I think we need to do an experiment! The movie has already provided the experimental protocol. Volunteers?

I remember a while back you posted a series of questions about how blogs could be used to report scientific results. It's great to see how this process of open source science is working out to build up our foundation of knowledge. Hat tip to you sir. I have just linked to this post over at The Primate Diaries.

Demand and Letter motivation
Dear Doctor

I am asking for a post Doc position in your laboratory.
I have just finished (October 07 2008) my doctoral thesis under the co-direction of Professor Ali OUAROUR (Laboratory of Biology and Health Department of Biology of the Faculty of Science of the University Abdelmalek Essaadi de Tétouan, Morocco) and Dr. Patrick VUILLEZ (Institut of Cellular and Integrative Neurosciences, department of Neurobiology of the Rhythms, Strasbourg, France). My studies of thesis and my multi-field diploma of 3rd cycle enabled me to acquire knowledge and competences of many techniques such as the development of wheel running locomotor activity recordings of rodents in the lab of Tetouan, analysis of rhythmic data obtained, immunocytochemistry on brain and retina sections, detection of the expression of ARNm by in situ hybridization, quantification of labeling, RT-PCR for the synthesis of the DNAc and the probes thereafter.

I strongly wish to invest myself in a laboratory in neurobilogy of the rythmes.
Your laboratory as well as the techniques to consider will allow me a very active participation and an implication in a new laboratory and of discovering a very interesting formation.

For more information, please see my CV and the abstract of my thesis in this files.

The 1st reference you can contact is: Patrick Vuillez, Institute for Cellular and Integrative Neurosciences, Department of Neurobiology of Rhythms, CNRS-University of Strasbourg, 5 rue Blaise Pascal, 67084, Strasbourg, France.

The 2nd reference you can contact is Prof. Ali OUAROUR, Laboratory of Biology and Health, department of Biology of the Faculty of Science of the University Abdelmalek Essaadi of Tetouan, B.P. 2121, Tetouan, Morocco.
FAX : 0021239994500 ; TEL : 0021266 27 73 13, e-mail :

The 3rd reference you can contact is Dr. Paul Pevet, Head of the âFederative Institute in Research in Neurosciences of Strasbourgâ 5 rue Blaise Pascal, 67084, Strasbourg, France.
(33) 3 88 45 66 05 (secretary) (33)3 88 45 66 08. (33) 3 88 61 29 08
E-mail :

Thank you for your attention

Mohamed LAHMAM
Adress France
Département de Neurobiologie des Rythmes
INCI, Institut des Neurosciences Cellulaires et Intégratives
5, rue Blaise Pascal
67084 Strasbourg France
Tél. (33) (0)
Fax. (33) (0)
Adress Maroc Université Abdelmalek Esaadi
faculté des sciences de tetouan
Departement de Biologie
Laboratoire de Physiologie Animal
B-P:2121 M'hannech II
Tetouan 93002
Tél. mobile 00 212 665 086 843

Curriculum Vitae

Last name : LAHMAM
First name : Mohamed
Date of birth : 10.13.1978 (October 13, 1978)
Nationality : Moroccan
Permanent address : 161 Casablanca street, Farah residence n°19 Tétouan, Morrocco
E-mail :

Phone number. :( +212) 065 08 68 43 in Morocco, (+33) 643 640 925 in French

Circadian and seasonal rhythms

Biology cells

Molecular biology
In situ hybridation

Stereotaxic on rodents

Behavior technical
Locomotors activity of wheel

Statistics and Informatics
Microsoft office

Technical capture and navigation on ground

07.01.2004 - 07.10.2008: Ph.D. student position between the laboratory of Biology and Health Department of Biology of the Faculty of Science of the University Abdelmalek Essaadi Tétouan (Morocco) and the Department of neurobiology of the rhythms (ex-UMR 7518) INCI Institut of cellular and integrative Neurosciences Strasbourg. The PhD thesis defense done at 7th of October 2008. doctoral thesis under the theme Daily Behavioral Rhythmicity and Organization of the Suprachiasmatic Nuclei and the retina in Lemniscomys barbarus Rodent : demonstration of the Diurnality and reproduction seasonality.

2001-2003: Diploma of the Superior Studies Deepened in Biotechnology, Food and Health, in the faculty of the Sciences of Tétouan.

1999-2001: Mastery Of Sciences and Techniques (MST), specialty " Alimentary Technology" at the Faculty of the Sciences and Techniques in Béni-Mellal.

1997-1999: DEUG in Biology to the Faculty of the Sciences and Techniques in Béni-Mellal.

1996-1997: Baccalaureate in Experimental Sciences, Academy of Béni-Mellal.


Practicum 3 years between 2004 and 2008 to the laboratory of neurobiology of the rhythms (UMR 7518) 12, street of the university F-67000 Strasbourg framed by the Prof. P. VEUILLEZ and under the direction of the Dr. Paul PEVET, Director of the Federative institute of the neurosciences, Strasbourg. Theme of the practicum" Survey of the distribution of the innervations neuropeptidergiques of the suprachiasmatiques nucleus among a small mammal of north Africa Lemniscomys barbarus (survey immunohistochemistry and in situ hybridation) ".

01/01/2003 at 31/05/2003: Practicum to the laboratory of Biology Applied to the Faculty of the Sciences and Techniques of Tangiers under the theme" Ionization Effect on the conservation of the dates Jihel variety: physico-chemical and biochemical survey and technological quality ".

01/01/2003 at 31/05/2003: Practicum to the food technology laboratory to the ionization station at Boukhalef (Tangiers - Morocco).

02/04/2001 at 31/05/2001: Practicum to Lesieur-Crystal society under the theme" Contribution to the setting up of a HACCP system on the level of the production line within Lesieur-Crystal" society (Casablanca - Morocco).

July 2000: Practicum to the cannery of fish (Espadon). Agadir (Morocco).

02/06/1998 at 12/07/1998: Practicum to the Sweet Refinery of the Tadla (SUBM). Béni-Mellal (Morocco).

Juillet, 2000: Agent of service to the laboratory of control of the production line to the sweet refinery of the Tadla. (SUBM). Béni-Mellal (Morocco).

Research activities and publications

M. Lahmam, A. El Mârabet, A. Ouarour, P. Pévet, E. Challet and P. Vuillez (2008). Daily behavioural rhythmicity and organization of the suprachiasmatic nuclei in a diurnal rodent, Lemniscomys barbarus. Chronobiology international 25(6):882-904.

C. Bobu, M. Lahmam, P. Vuillez, A. Ouarour and D. Hicks (2008). Photoreceptor organisation and phenotypic characterization in retinas of two diurnal rodent species: Potential use as experimental animal models for human vision research. Vision Research 48(3):424-32.

A. OUAROUR, M. LAHMAM et A. EL MâRABET. Lemniscomys barbarus, a diurnal micro mammal and seasonality of reproduction. 4rd days Nationales of the Biodiversity, Tétouan, les 26-27 Octobre 2007.

M. Lahmam, A. Ouarour, P. Pévet et P. Vuillez. Rythmicité journalière et saisonnière chez un rongeur diurne : Lemniscomys barbarus. 39rd Congrès of Chronobiology Francophone Society, Paris french, 19-21 septembre 2007.

M. Lahmam, A. Ouarour, A. El Mârabet, P. Pévet, E. Challet et P. Vuillez. Activité locomotrice circadienne et neuroanatomie des noyaux suprachiasmatiques dâun rongeur diurne, Lemniscomys barbarus, en fonction de la photopériode. 1st scientific reunion on GDRI-Neuro (Groupement of international research in neurosciences, Rabat 29-30 novembre 2007, Mohammed V-Agdal University, Faculty of the des sciences.

M. Lahmam, A.El Mârabet, A. Ouarour, P. Pévet and P.Vuillez. Lemniscomys barbarus, a diurnal photoperiodic rodent: a new model for studying neurobiology of rhythms. Cadi Ayyad University, Moroccan Association of Neurosciences, 2nd Mediterranean Conference of Neurosciences, Marrakech, Morocco, 13-15 December 2006.

Application au 14th IBRO/ISN Africas Neuroscience School in Neurochemistry on âMechanisms of neurotransmission in normal and brain diseasesâ, December 6 - 11, 2006, Rabat, Maroc.

M. LAHMAM, A. OUAROUR, P. VUILLEZ, N. LAKHDAR-GHAZAL et P. PEVET ; Les Neuropeptides des noyaux suprachiasmatiques chez un petit mammifère du Rif Lemniscomys barbarus : rôles dans le fonctionnement de lâHorloge biologique, IXèmes days of scientific research of Abdelmalek Essaâdi University, 22 Décembre 2005 in Faculty of Sciences B.P. 2121 Mhannech 2, Tétouan (Morocco).

Participation of NEUREX (Neuroscience network in Europe 3 federation of research (Strasbourg, Freiburg, Basel) in brain sciences. 18-19-20 Novembre 2005 Freiburg, Germany.

-ïM. LAHMAM and F. SAYAH " Ionization effect on the conservation of the dates Jihel variety: physico-chemical and biochemical survey and technological quality." Memory of DESA, June 13, 2003.

-ï Participation at the 5th national scientific day ; Tangier (December 2002).

-ï Participation at the 3rd national congress of genetic& molecular Biology, Tangier, Morocco ( November 2003)

--ïM. LAHMAM and F. SAYAH."Ionization effect on the conservation of the dates Jihel variety: physico-chemical and biochemical survey and quality technological" international Convention of Biochemistry, May 3-6, 2004 at the faculty of the Sciences. Semlalias, Marrakech (Morocco).

-ï Participation at the 4rd international congress African Association of Physiological Sciences, Abdelmalek Essaadi University, Faculty of science Tetouan-Tangier, Morocco (21-26 November 2004).


Reading Writing Spoken

-French G G G
-Spanish C R R
-English C R R
-Arabic G G G

R = regular , C = correctly, G = Good


Maîtrise of the Windows environment, Word, Excel and PowerPoint.
Navigation in Internet.

15/03/03: Member of the committee of organization of the" scientific day on the biologic struggle" organized by the Moroccan association of the Researchers in Biology and the faculty of the sciences of Tétouan.

November 22-26 2004 Member of the committee of organization of the 4th international convention of physiology organized by the association African of the Sciences Physiological AAPS; Abdelmalek Essaâdi University, Tétouan (Morocco).

1997: Driver's license: B category.

Abstract of my thesis

This work is the first description neuroanatomical and characterization of the daily and seasonal rythmicity of Lemniscomys barbarus, a rodent captured in the north of Morocco.
The diurnality and the phenotypical main features of the operation of the circadian clock of this species were determined by recordings of the locomotor activity of wheel under various conditions of illumination.
Wheel-running activity was recorded in Lemniscomys barbarus exposed to different lighting conditions. This rodent shows rhythmic locomotor activity under natural twilightlight/dark (LD) as well as squared-LD cycles. A mean of 77% of the activity occurred during the light phase. Under different controlled photoperiods, the quantity of daily locomotor activity was relatively stable except for a lower level in the shortest photoperiod tested (LD 06:18). The duration of the active phase tended to increase with the duration of the light phase, especially in the longer photoperiods. Whatever the lighting conditions, Lemniscomys barbarus started running before lights-on and stopped after lights-off. The phase angle of activity offset relative to lights-off was stable in each squared-photoperiod, whereas the phase angle of activity onset relative to lights-on was significantly the highest under the shortest photoperiods. Recording of activity under constant lighting conditions showed that the daily rhythm of locomotor activity is fundamentally circadian. The endogenous period was slightly,24 h (mean=23.8 h) in permanent darkness and .24 h (mean=24.5 h) in continuous light. Re-entrainment of the locomotor activity rhythm after a 6 h phase advance or delay requires only four days on average. Moreover, the phase-responses curve to a 30 min light pulse (200 lux) in Lemniscomys barbarus kept in constant dark reveals large phase shifts according to circadian times (CT). With CT0 being defined as the onset of daily activity, maximum phase delay and advance shifts were observed at CT11= - 5.7h and CT21=+4.9h). Interestingly, the phase-response curve to light did not show any dead zone. Immunohistochemical staining of the suprachiasmatic nuclei indicates that arginine vasopressin-immunoreactive cell bodies and fibers delimited a dorsal subregion that extends laterally and medially.The ventral subregion is rich in vasoactive intestinal peptide-immunoreactive neurons overlapping a smaller area containing gastrin-releasing peptide-expressing cells and receives numerous fibers labeled with neuropeptide Y antibody. The results of this study clearly demonstrate that Lemniscomys barbarus is a diurnal species highly sensitive to the shifting effects of light. Overall, this rodent can be considered a new and interesting model for circadian rhythm neurobiology.
Besides, the relation established between the state of gonads and the expression of the AVP in the lateral septum, which is involved in the nervous control of the appearance of the episodes of hypothermia in certain hamsters, seems to be no existing in Lemniscomys barbarus.
The number of AVP cells and NPY innervations are more important in short photoperiod than in long photoperiod in the SCN. On the other hand, the vasopressinergic innervation of the lateral septum by the BNST do not seem to present of seasonal variation.
The characteristics of Lemniscomys barbarus position it like a new very promising model of studies in neurobiology of the daily and seasonal rhythms. Its diurnality in particular makes it very gravitational for research to human applications.

By mohamedlahmam (not verified) on 08 Apr 2009 #permalink