Cannibal shrimp

(Warning: This posting will wander some.)

It started with a story in New Scientist (online 11/17/11, in print 11/19/11): Chelsea Whyte’s:

Cannibal shrimp shows its romantic side

In order: (1) the interpretation and accenting of cannibal shrimp; (2) the tale of the cannibal shrimp (no linguistics to speak of here); (3) cleaner shrimp; (4) CRSs and their potential for cannibalism; (5) CRS shrimp and other instances of RAS syndrome; (6) orphan initialisms.

(1) The interpretation and accenting of cannibal shrimp. When I read the headline, I took cannibal shrimp to be a type name (like tiger shrimp, fairy shrimp, snapping shrimp, and pink shrimp), and so to be forestressed, accented on its first element: cánnibal shrìmp. But it turns out that cannibal shrimp is to be understood with predicative cannibal (‘shrimp that is a cannibal’), so it’s afterstressed: cànnibal shrímp. (Accenting in composite expressions is complex but not chaotic; there are generalizations, but also subgeneralizations and idiosyncrasies.)

(2) The tale of the cannibal shrimp. What goes on in coral reefs and aquaria? Nasty things at night:

Species: Lysmata amboinensis
Habitat: coral reefs in the Indian and Pacific, striking in the night

Cannibalistic and willing to fight to the bitter end under the cover of darkness: Lysmata amboinensis shrimp have a brutally romantic side. They are so hell-bent on living in pairs that when placed in groups of three or four, they attack their peers until just one couple remains alive.

These hermaphrodite cleaner shrimps start out as males and develop female reproductive organs as they grow. They can mate as a female only in the few hours after moulting their exoskeleton, but can then mate as males even while they are incubating eggs. Despite all this gender-bending prowess, however, there is one thing they cannot do: self-fertilise. Both male and female they may be, but they still need a mate to mate.

The bright orange shrimp, which have bold red and white go-faster stripes on their backs, wouldn’t normally encounter many of their kind as they move around the reefs where they live. Mostly, they just hang out on their own, occasionally pairing up to mate. If they do happen across others, they might ignore each other or sit quietly together as the afternoon sun streams through the water from above. But as soon as the sun sinks and the water goes dark, the seemingly calm crustaceans turn into killers.

Moonlit massacre

At just 6 centimetres long, L. amboinensis has a Napoleon complex to go with its size.

It scavenges parasites and dead tissue off the backs of larger fish, and faces intense competition for food resources. As a result, L. amboinensis is aggressive to the point of killing off other shrimp that threaten their livelihood.

In a study at the University of Basel in Switzerland, Janine Wong placed groups of three or four shrimps together in tanks, fed them regularly, and observed them for 42 days. During the day, the shrimps sat quietly in the tanks, mostly ignoring each other.

But at night, infrared cameras captured a very different scene. “The shrimp started to go crazy and chase one individual until they had killed it,” Wong says. “They are also cannibalistic, so they were eating the dead individual in the morning.” The murderous rampages always happened just after the victim had moulted its exoskeleton, when the crustaceans are at their most vulnerable.

Killing patterns depended on how many shrimp were in a tank, but always left one couple alive. With three shrimp in one tank, the smallest one usually got the chop, simultaneously attacked by the pair of larger animals.

In tanks with four shrimp, the shrimp that moulted first died first. The largest of the remaining trio then turned on the smallest.

The shrimp would fight to the death even when they had plenty of food, suggesting that the serial killing had nothing to do with resources and everything to do with living in pairs. “Their behaviour is sort of hardwired,” says Wong.

Fickle monogamy

“It’s surprising to find social monogamy in hermaphrodites,” she adds, explaining that in most hermaphroditic species, cheating is common because having more mating partners increases the chances of reproducing.

Though the experiments always resulted in only one pair of shrimps surviving in each tank, Wong says that an interloper could cause the happy couple to split up. Partnerships only last as long as they are the best thing on offer for both. If another, larger shrimp were to enter the tank, the smaller of the existing pair would not survive its next moulting.

A photo:

and some Wikipedian details:

Lysmata amboinensis, the northern cleaner shrimp, scarlet cleaner shrimp, skunk cleaner shrimp or Pacific cleaner shrimp, is an omnivorous shrimp species, which will generally scavenge and eat parasites and dead tissue. L. amboinensis is naturally part of the reef ecosystem, and is widespread in the Red Sea and tropical Indo-Pacific.

It has been observed that fish with parasites may come to “cleaning stations” in the reef. Certain species of fish and several types of cleaner shrimp may assist the fish in large numbers and even go inside the mouth (and then to the gill cavity) without being eaten.

Many species of Lysmata, including L. amboinesis, are safe and beneficial in salt water tanks since they will (as indicated by their common name) clean both the tank and occasionally other fish within the tank.

L. amboinensis will normally moult every 3–8 weeks.

(3) Cleaner shrimp. I found this fascinating, but there’s not much of linguistic interest in there, though we do learn that L. amboinensis is a subtype of cleaner shrimp (cleaner shrimp as a type name will, of course, be forestressed).

(4) CRSs and their potential for cannibalism. It then occurred to me to wonder if there was a type of shrimp known as cannibal shrimp. Apparently not, though my search took me to a CRS site (CRS is an initialism for crystal red shrimp), where a worried shrimp fancier was concerned that his CRSs were behaving like L. amboinensis:

So I have this CRS tank for about 9 months. When the light turned on this morning, i saw my shrimps were eating a dead shrimp. There was an empty shell next to them too. I have been noticing some shrimps are missing, so i guess this is not the first one. My question is, what went wrong? Do you think it molded and then got jumped by others? Or am I not feeding them enough? I always feed them twice a week, but since my shrimps have been breeding, so maybe i should feed a bit more… Also, can i just let them eat the dead shrimp or the dead body will course problems?

(Linguistic points here: discourse-introducing so; the spelling molded for molted; the spelling course for cause.)

Reassurance from another enthusiast on this site:

crs allways will eat a dead one but never kill one. They have no way to kill! What probbably happened is it died from molting and then was eating. Trust me, no crs has ever killed another one to eat it!

(More interesting spellings, especially eating for eaten.)

A CRS photo:

And some Wikipedian details:

Caridina is a genus of freshwater atyid shrimps. They are widely found in tropical or subtropical water currents in Asia, Oceania and Africa. They are filter-feeders, collector-gatherers and omnivorous scavengers.

… The popular “Crystal Red” (red and white striped) are hybrids or mutants of a shrimp from this genus, probably Caridina serrata.

(5) CRS shrimp and RAS syndrome. I have been pluralizing CRS as CRSs, but you can see that some CRS fanciers treat the initialism as having a zero plural, presumably because shrimp does. For these people, CRS is understood as simply a briefer way of writing (or saying) crystal red shrimp.

But not for everyone. You can find a fair number of references to CRS shrimp, like this one:

CRS Shrimp Tank Journal (link)

Now we’re in the world of “RAS syndrome”. From the Wikipedia entry for redundancy in linguistics:

A subset of tautology is RAS syndrome in which one of the words represented by an acronym [or initialism] is then repeated outside the acronym: “ATM machine”, “HIV virus”, “PIN number” and “RAID array”. These phases expand to “automated teller machine machine”, “human immunodeficiency virus virus”, “personal identification number number”, and “redundant array of independent disks array”, respectively. “RAS syndrome” is itself a tongue-in-cheek example of the RAS syndrome in action; it expands to “Redundant Acronym Syndrome syndrome”.

RAS examples are a prime target of peevers. People collect them — here’s one inventory, under the alternative name RAP phrases (“Redundant acronym phrase phrases”), and there are more — and bemoan the stupidity of those who use them.

(6) Orphan initialisms. But let me say a few words in defense of this usage. People who say (and write) “PIN number”, “ATM machine”, and (for that matter) “CRS shrimp” are treating what were historically alphabetic abbreviations (acronyms and initialisms) in them as “orphans”, no longer associated with their historical sources; see the Wikipedia page on orphan initialisms (actually, taking in both orphan initialisms like ATM and orphan acronyms like PIN), which links to my 2006 posting on orphans.

Things like AT&T, KFC, and SRI no longer “stand for” anything — each one is just a string of letters, with a referent for the whole string. In these cases the company or institution in question consciously decided to orphan the initialism, but I don’t see why orphaning can’t happen spontaneously. Certainly, it would be folly to insist that history is destiny, in this case or any other.

So, for many people (I am one), ATM machine and PIN number are now species + genus constructions, like Nautilus machine and Erdös number. And as someone not in the aquarium world, I would be very much inclined to opt for CRS shrimp rather than CRS, since CRS shrimp seems clearer to me; I’d be inclined to view a CRS as a truncation of a CRS shrimp, in the same way that I’d view a Nautilus as a truncation of a Nautilus machine and my Erdös as a truncation of my Erdös number — entirely understandable given the right context, but shorthand for the full, clearer expression.

4 Responses to “Cannibal shrimp”

  1. inyazserg Says:

    Hello, Professor! May I ask you a question? How do you call the words written with capitalized letters:
    “CANNIBAL shrimp, MONKEY business, CHICKEN soup” –
    I suppose some of them do not have adjective form, and there is no `s to show the state of being possessed (i.e. those are not possessive forms). Composite expressions?

    • arnold zwicky Says:

      “Composites” include two-part nominals of many types: second element is N, first usually N or Adj. There are many different types of N + N and Adj + N composites.

      The examples you cite (with accent on the first element) are all N + N composites, but of different types.

      Some discussion here.

  2. The Ridger Says:

    I too would say CRS shrimp. (I used to say ATM machine, but now say ATM.) SALT Talks is another (though many people think the T is Treaty, it wasn’t originally), helped by there being SALT I, SALT II, etc… Interestingly, I see people do say “CR shrimp”, though PI number and AT machine are unknown to me – and the existence of pi and the preposition “at” make Googling problematic!

    I imagine that as the acronym grows more opaque, the use of the noun becomes more motivated.

  3. The Ridger Says:

    I think my last sentence is poorly expressed. What I meant to say was, the less people understand what the acronym means, the more they’re inclined to include the noun. Back when ATMs were new, the noun felt needed. Now everyone knows what one is, so the acronym (whether people know the M means “machine” or not) can stand on its own.

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