Text: Kingsley Wong
Images: Tin-Lun Wong, Kingsley Wong
“Aren’t animals beautiful people? ” As an alcohol-intoxicated writer gazed through glass walls into the lushly-vegetated fish tank, staring eye-to-eye with the crimson crustaceans housed within, that remark was a reference to a classical wildlife documentary. That titled “Animals are Beautiful People”, shot in Namibia, southwestern Africa and released in 1974, first revealed that intoxication was not quite a granted privilege of humans. Fruits of the marula tree are succulent and much favored, fresh or rotten. In the latter case where sugars in the fruits fermented, animals on these arid grasslands, baboons, giraffes, warthogs and elephants alike, indulge themselves with this tempting godsend, spending some tipsy evenings after a long, hot day.
DRUNKEN CRAYFISH:
so sloshed
and alike?
Why bother drunken crayfish?
For one to “get high”, in this case, means gaining exposure to alcohol (ethanol), itself a depressant (a substance that lowers neurotransmission levels) of the central nervous system, of vertebrates, including humans, and invertebrates alike. Among those spine-less folks, some, in term of clinical trials on responses after exposure to various substances, have been well studied: fruit flies, honey bees, and in the aquatic world, crayfish of various species. These woeful “lab rat” animals have some aspects in common: displaying obvious behaviours apparent to observing researchers, and in the case of crayfish, more notably that shrimp-like robust flap of the pleon (= abdomen, or the “tail”), bouncing instantly backwards, and the ability of righting itself from an upside-down position, thus reflecting physical conditions of that animal in trial.
Portraying those sloshed
Like some over-indulged humans, when exposed to alcohol, crayfish have also shown signs of getting drunk. For acute exposures (eg. 4.6% alc vol), activities can largely be divided into, initially, increased activity and excitability, shown by unresting jerking and twitching of those slender legs, agitated, frequently bouncing backward, perhaps experiencing times of happy, tipsy, then buzzed moments. After some prolonged periods the exhausted crustacean gives in, sedated, and lie sideways or on its back, unable to right itself to a normal position: simple “hammered”, flipping the flap-like swimming legs beneath the pleon in rhythm, perhaps just as lying on the floor blabbering Martian, wondering how him/herself got there in the first place.
According to brief experiments performed on our office crayfish, some adults of total lengths 5 to 6 cm, in alcohol baths of such concentrations, they stand more than two hours before collapsing, while afterward regaining sublimity shortly when transferred back to pristine, weed-laden freshwater. Act sober, rinse, and repeat? Pass, perhaps. As for crayfishes finding themselves in prolonged exposures (eg. for weeks) in lower concentrations (the “chronic treatment”), research has shown these individuals had their tolerance to alcohol enhanced, just as any old habitual drinkers in bars every now and then you find at the corners.
Sitting at a community bar, however, one would observe two extremes. Some in groups, prefer chitchatting and having fun, while others stay in solitude, indulging in one’s own starry night. Cannot readily tell whichever approach being more enjoyable, in the world of crayfish, however, research has recently shown tolerance of alcohol varies with social experiences, where loners can stand significantly longer, in comparison to those communal counterparts before showing “well-done” symptoms. In other words, those “sociable” individuals “get high” more readily given similar alcohol exposure.
While entertaining to tease less-then-sober crayfish retrieved from alcohol baths, scientists considered these implications further: while currently admitting premature to draw connections with behaviour of mammals, attempting to inspire explorations on possible connections between social experiences and tolerances to alcohol, abuse and addictions, and possible mediations.
Epilogue, and more on crayfish...
Some crayfish, having flamboyant colouration, made their way as pets in the aquarium. Ever come across a local aquarium store hawking those red crayfishes, dozens of those hapless beings cramped in a small container? For many freshwater crabs would combat and wither, to an unsalable condition. In contrast crayfish have been adapted, or evolved to dwell in high densities. When placed in an unfamiliar environment, individuals, big and small, initially combats, victors prevails and others escape, and the “sorting” process depends on size, sex, and physical conditions. Shortly after (eg. after one day), behaviour shifts from hard-boiled “cray-fight” and escaping, to approaching and retreating, and a hierarchy of dominance is formed. Those predominant individuals enjoy exclusive access to resources: shelter, food items and mates. Undeniable is that people living in a pre-defined social hierarchy: that rich and poor, and relevant social status. For the writer, perhaps having some hard time handling biochemical mechanisms (see Alcohol: trivial and transmigration in this issue), perhaps sitting blitzed beside the fish tank, attempting to convince those annoyed dull-reddish tenants “I am not drunk” in crayfish-ish, brings more than satisfaction. To himself, and rather possibly others, alike.
Suggested readings
Friedman, R. N., Bittner, G. D. & Blundon, J. A. 1988. Electrophysiological and bahavioral effects of ethanol on crayfish. Journal of Pharmacology and Experimental Therapeutics 246(1): 125–131.
Gherardi, F., Souty-Grosset, C., Vogt, G. Diéguez-Uribeondo, J. & Crandall, K. A. 2010. Infraorder Astacidea Latreille, 1802 p.p.: the freshwater crayfish. In: Treatise on Zoology, Anatomy, Taxonomy, Biology. The Crustacea, Decapoda 67. Brill, Leiden. pp. 269–423.
Herberholz, J., McCurdy, C. & Edwards, D. H. 2007. Direct benefits of social dominance in juvenile crayfish. Biological Bulletin 213: 21–27.
Issa, F. A., Adamson, D. J. & Edwards, D. H. 1999. Dominance hierarchy formation in juvenile crayfish Procambrus clarkii. Journal of Experimental Biology 202: 3497–3506.
Swierzbinski, M. E., Lazarchik, A. R. & Herberholz, J. 2017. Prior social experience affects the behavioral and neuron responses to acute alcohol in juvenile crayfish. Journal of Experimental Biology 220: 1516–1523.
Crayfish, as understood as freshwater “lobsters”, as distinct group (superfamilies Astacoidea and Parastacoidea) distinct from their distant relatives like the American lobster (Homarus americanus), are found in most freshwater habitats: in North America, Europe, Australia, Madagascar, and northern East Asia. While most of these animals are distributed in fairly restricted distributions and intolerant to disturbances and pollution, some, like the red crayfish Procambrus clarkii, native to southeastern North America, can be very hardy in adverse conditions, and become invasive species after introduced elsewhere.
In general these crustaceans are omnivores, consuming everything from detritus, plant fragments, to animal matter, predated or scavenged, picking food items by their pincers. Many of them dig burrows to dwell in, for temporary shelter or withstand season or prolonged drought. Along river banks, at bases of dams and artificial structures, or even river adjacent land, these weaken physical support and causes ground collapses.