sh atteredarms

Are youl col,lcerned witl.r the health of vour" touch tank critters?

he University of Georgia Marine Education Centerand Aquarium operates an education facility andpublic aquarium year-round on Skidaway Island near

Savannah, Georgia. Each year thousands of K-5th gradersparticipate in a two-hour program, which includes learningabout and handling our touch tank animals. The menageriethat is presented to students often includes Luidia clathrata,the slender sea stat which is common along the beaches ofGeorgia. Because Luidia feeds well in captiviry and is notusually perceived as a threatened species, it is a very suitabletouch tank animal for younger students to study.

About 860lo of individuals in a wild population of Luidiaexperience arm loss (Lawrence and Dehn 1979), so it is nosurprise that our touch tank animals are in varying states ofrepair when they are first caught. However, even without afull complement of arms, our sea stars feed well.

\7e wanted to understand the human handling effects onsea stars as they relate to the health of the animals used inour programs. Each sea star can receive daily "attention' fromup to 60 pairs of hands during a 30-minute span. If handled

too often, sea stars that reside in touch tanks have beenknown to fall apart in one's hands.

How much stress are we putting on our touch tank animalsby handling them, and how can we quantif' that stress? If asea star previously had 3.5 arms, for example, how longwould it take to regenerate the arms under continual han-dling compared to animals in a similar state of repair thatwere not handled at all? We make the assumotion that themeasured regeneration rates of non-handled sea srars repre-sent "normal" regrowth. \7e also assume that stress (i.e. han-dling) interferes with the "normal" regeneration rate. Thus,we hypothesize that the regeneration rates of sea star arms innon-handled sea stars will be greater compared to the regen-eration rates ofhandled sea stars.

Sea stars collected in Wassaw Sound by our research vessel,the Sea Dawg, were acclimated to an indoor flow-throughtouch tank system for 81 days. During this time, they werefed fish every Monday, \Tednesday and Friday. Once accli-mated, the sea stars underwent minor surgery. \7e cut two

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Sea Stars continued jiom p. 9

adjacent arms offeach sea star for the purpose of measuringarm regenerat ion rares in our exper iment.

Our experimental design consisted of 32 sea stars in all: 16controls (non-handled) and 16 "handled" treatments. Eachsea star was contained in a separate compartment of theflow-through tank, and fed normally during the three-weekexperiment. The controls were only handled during armlength measurement once per week. The 16 "handled" seastars received the daily treatment we call the "Flip and Dip":Volunteers removed each sea star from the water, flipped theanimal over in their hands every 30 seconds, then dipped itinto the saltwater for five seconds to rehydrate. This proce-dure was repeated for five minutes. By doing so, we hopedto produce the same kind of stressful situation that the seastars experience during the handling portion of our touchtank programs. At the week's end, every arm of each sea starwas measured and recorded.

What we found was not a shock. During the first weekneither the handled nor the control sea stars regenerated newarm tips. Wound healing was observed, however.Organisms began to regenerate new arm tips during week 2.At the end of this week, the average length of the regeneratedarm tips of the control animals measured 2.6 mm.Individuals in the control treatment had grown slightly morecompared to those in the handled treatment (average regen-erated arm length of 2.3 mm); however, this difference wasnot significant (T-test, P<0.13). At the conclusion of theexperiment (week 3), the control organisms' average regener-ated arm length measured 5.5 mm. This was one millimetermore than the handled treatment (average regenerated armlength of 4.5 mm). Statistical analysis showed a highly sig-nificant difference between the length of the arm tips of con-trol and handled organisms for total growth in three weeks(T-test, P < 0.00). Growth of the organisms, defined as theaverage increase in length of regenerated arm tips from weekto week, also showed a significant difference from week 2 to3 for control and handled treatments (T-test, P < 0.00).Control organisms grew 0.8 mm more on average than seastars in the handled trearmenr.

After concluding the experiment, we continued to feed allexperimental animals, but did not touch them for an addi-tional 20 days. After 20 days all sea stars were measuredagain. Surprisingly, the control group had an average regen-erated arm length of 6.61 mm, and the handied sea stars hadan average regenerated arm length of 3.34 mm. Is this adelayed stress response? How long, if ever, would it take forthe control and handled groups to have equal regenerationrates? We weren't able to find out this time, but the researchcontinues. 'We have, however, learned how to best rotate seastars in order to promote rather than inhibit arm regenera-tion. 'We now rotate the sea stars out of the touch tank afterone week of handling and place them into a retirementhome. After one month we may use them again. As in allresearch, this study has generated further questions regarding

ways to keep our animals healthy. 'We hope this reportencourages further research projects on the rotation of touchtank animals.

Lawrence, J.M. and P.F. Dehn, 1979. Biological characteristics of Luidia

clathrata (Echinodermata: Asteroidea) from Tampa Bay and the shallow

waters of the Gulf of Mexico. Florida Science. 42; 9 - 13. $

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