ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Thursday, June 13, 1996 TAG: 9606130048
SECTION: VIRGINIA PAGE: C-3 EDITION: METRO
DATELINE: GLOUCESTER POINT
SOURCE: Associated Press
Eight years ago biologist J. Emmett Duffy came across some tiny tropical shrimp with unconventional living arrangements - a single female in a dense colony of dozens of males.
When Duffy, a professor at Virginia Institute of Marine Science, got around to taking a closer look, what had struck him as odd turned out to be significant. The sole female takes care of all reproduction, he found, while the males work together to raise the young and protect the colony from invaders. This sort of arrangement is familiar in social insects.
The behavior he discovered in these tiny shrimp is called ``eusociality.'' Eusociality refers to animal behavior characterized by specialization of tasks, such as cooperative care of the young. Fifteen years ago, it also was found in a mammal, the naked mole rat of southern Africa.
But Duffy's shrimp - a previously unknown species of snapping shrimp named Synalpheus regalis - mark the first time the behavior has been found in a marine animal. The VIMS scientist's findings were published last week in Nature magazine., where an accompanying editorial hailed them as a ``remarkable discovery'' that would advance our understanding of animal behavior.
Duffy and his shrimp also drew attention outside of scientific circles after the Nature article. The Washington Post, Dallas Morning News, National Public Radio and the Discovery Channel were among those that called before he returned to his shrimp research in Central America over the weekend.
What is interesting to biologists about this shrimp is that Duffy's shrimp provide a twist on eusociality with the males being the workers. Except for termites, hive workers are nonreproducing females. The males, called drones, serve only for reproduction and do not work.
Eusociality also raises the evolutionary question: In a world where animals evolve by looking out for No.1, why would any organism, such as Duffy's male snapping shrimp, forgo its own reproduction to help another?
``The more situations like this that we have, the easier it is to say, `OK, what do these different species share in common that leads to eusociality?''' Duffy said.
What almost all known eusocial animals have in common is that they live in some sort of cavity, like hives or burrows. Duffy's species of snapping shrimp live inside the hollow, catacombed bodies of living marine sponges. Not only do the sponges provide shelter, but, as they filter sea water to feed themselves they draw in all the nourishment the shrimp need.
There are only so many sponges to go around, however. Duffy said evolution favored these shrimp because they found a way to live cooperatively in a single sponge, rather than striking out on their own.
``It makes sense to stay at home and care for the family,'' Duffy said.
The family could include more than 300 shrimp, all male except for the ``queen'' of the colony. At half an inch long, the queen shrimp is roughly twice as large as a mature male. If she dies, one of the largest males in the colony will simply turn into a female, Duffy said he speculates.
The female produces nearly all of a colony's offspring, meaning most of the shrimp are each other's brothers or uncles. It is likely the female mates with a single male, though Duffy couldn't figure out which one.
``There's not an obvious king, so to speak,'' Duffy said.
The main job of rank-and-file males is to protect the colony using the larger of their two claws, which make the snapping sound for which they are named. Duffy confirmed this by repeatedly introducing another species of snapping shrimp to a colony in a laboratory.
``The results were dramatic,'' Duffy wrote. ``Contact between a resident and a `foreign' intruder generally resulted in an intense battle, with both individuals repeatedly snapping at one another with their major chelae [claws]. This continued sporadically until the intruder was killed.
``In two of 10 experimental runs, two residents together gripped the vanquished intruder's carcass and dragged it out of the chamber,'' Duffy said.
Snapping shrimp are distant cousins of the larger species that make up our shrimp cocktails and seafood salads. They are almost exclusively limited to the tropics.
Duffy doesn't expect his discovery to prompt a run on snapping-shrimp research. For starters, it takes a trained eye to tell one species of snapping shrimp from another, and only a handful of scientists in the world have it.
``It's hard to tell them apart,'' Duffy said. ``They're sort of a pain to work with.''
LENGTH: Medium: 83 linesby CNB