BLACKPOOL SEA LIFE CENTRE ATLANTIC NURSE SHARKS GOITRE 95

nemesis in a more enlightened way. The Shark Experience informs the visitor about some of the many threats facing sharks today, such as fin-netting, over- fishing and pollution. The human impact on shark populations is made dramati- cally clear by a comparison of statistics which show 228 000 shark fatalities for each human shark attack victim. The need for further studies and an active commit- ment to the conservation of sharks is, we hope, clearly illustrated and emphasized in the Marine World Africa USA’s Shark Experience.

We have not conducted any research on whether the conservation message was being received by our visitors, although, in the past, we have collected data which clearly indicate that the retention of information about an exhibit animal is significantly higher the closer the viewer is to the animal and the more exciting the experience. We do know that the exhibit is extremely popular; in the year of its opening a total of 1 900 000 visitors was recorded, a 29% increase in attendance over the previous year.

ACKNOWLEDGEMENTS

In addition to the authors the Marine World Africa USA Shark Team included Chris Baldwin, Vice President of Construction & Development, Fred Beiner, Director of Landscape, Anne Monk, Edu- cation Director, Marsha Englehrecht, Curator of Sharks, Ed Comer, Curator of Fishes, Beverley Diplock, Coordinator, to all of whom we express our thanks.

CONSTRUCTION DETAILS

Architecture and life-support system design & engineering: Enartec, Inc., 4542 Ruffner Street, San Diego, CA 92111-2216, USA. Life support-system computerization: Southern Elec- tric Internation, Inc., San Diego, CA, USA. Filters fabrication: Stark Aquatic Systems, Seattle, WA, USA. Acrylic tunnel and windows: Reynolds Polymer Tech- nology, Inc., 607 Hollingsworth Street, Grand Junc- tion, CO 81506, USA. Artificial rock and coral designlfabriciation: David L. Manwarren Corporation, 1957 E. Cedar Street, Ontario, CA 91761, USA. Discovery Gallery exhibitry fabrication: Color 2000, 570 Jessie Street, San Francisco, CA 94103, USA. Life-size shark model fabrication: California Crea- tions, PO Box 1307, Port Hueneme, CA 93044, USA. Moving walkway fabrication: Montgomery Elevator Co., 10950 Bigge Street, San Leandro, CA 94577, USA.

Manuscript submitted 18 November 1994

Int. Zoo Yb. (1995) 34: 95-98 0 The Zoological Society of London

Treatment of goitre in Atlantic Nurse sharks

at the Blackpool Sea Life Centre Ginglymostoma cirratum

NICHOLAS LLOYD Blackpool Sea Life Centre, Golden Mile, Blackpool FYI 5AA, Great Britain

Six Nurse sharks Ging[ymosfoma cirratum main- tained in a heated natural sea-water pool at Black- pool Sea Life Centre showed signs of goitre within 16 months. As well as increasing the percentage of water changes from 2-3% to 12% per week, the Centre investigated a number of possible treatments for the affected animals and instituted a successful

regime of additional potassium iodide given in cap- sule form in the feed.

vertebrates have a thyroid gland, sit- uated in the ventral neck region some- where between the lower jaw and the

96 AQUARIUMS

heart, which is responsible for the pro- duction of the only iodinated hormones in vertebrate physiology. The thyroid gland of elasmobranchs, lungfish and parrot fish is structurally different to that of other fish because it is a single bilobed structure encased in a fibrous capsule of connective tissue. The function of the thyroid is the selective uptake of iodine from the blood- stream and, starting from the amino acid L-tyrosine, the synthesis, intermediate storage and release of iodinated hor- mones. Thyroid hormones influence growth and maturation and have regula- tory roles in energy metabolism.

When iodine is missing or in a depleted state, the thyroid gland can develop into a swelling or struma, commonly called a goitre. Left in an iodine depleted state the tissue may develop into a tumour of the gland and eventually into a malignant tumour that produces relapsing metastasis in other organs (Straub, 1993).

In fishes goitre has been regularly described since the beginning of the cen- tury. In bony fishes, it can be macro- scopically discerned by a slight to large swelling of the pharyngeal region below the gills. In sharks it is much more obvious as a roundish swelling under the lower jaw in the flat throat area. The cells within the struma have been known to become 300-800 times their normal size and can sometimes prevent the animal from feeding.

SUBJECT HISTORY In September 1993 six Atlantic Nurse sharks Ginglymostoma cirratum, which had been housed at the Blackpool Sea Life Centre for up to three years and weighed about 50-60 kg each, were showing an advanced state of goitre. Two of the animals, obtained in June 1990, had been maintained in a 500 000 litre display tank, two were acquired from private aquariums in 1992 and two, received as juveniles in summer 1992, were moved from a 1000 litre to the 500 000 litre dis- play tank in 1993. The water for the

aquarium system was taken direct from the Irish Sea and heated to a constant 22°C. All six animals were eventually housed together in the 500 000 litre dis- play tank.

Within 16 months of arrival at the Centre, all six sharks had started to show a swelling under the throat region and an iodine deficiency was diagnosed. The animals were given a kelp supplement with their daily feed (three to four 2 g tab- lets per day, 1-2-2-9 mg iodine per tablet) but over the following 18 months the swellings continued to increase in size.

Because an untreated goitre may develop into a tumour in the long term a study of the animals’ case history was made to ascertain the cause of the defi- ciency and potential remedies.

Goitre disease results from impaired thyroid function and the diminished pro- duction of thyroid hormones. Iodine defi- ciency is a primary cause of the disease, however other causative factors, such as water quality and the stress levels of the animals should also be considered.

The goitre swellings in the six Nurse sharks were c. 60 mm in diameter and raised c. 20 mm from the skin surface, forming distinct lumps. Water analysis showed that the amount of iodine present in the water in the aquarium system was 0.01 mg/litre (Table 1) compared with 0.06mg/litre in fresh samples from the Irish Sea. While a short-term fast-acting remedy was of utmost importance, it was

IRISH SEA TROPICAL SYSTEM

Ammonia mgllitre 0.2 0.8 Nitrate mgllitre < 1 < 1 Nitrite mgllitre <0.1 <O.I Iodine mg/litre 0.06 0.01

Total dissolved solids YO 3.18 3.61 Salinity as g/litre NaCl 28.5 33.5

Table 1. Comparison of water direct from the Irish Sea and the heated sea water in use in the tropical aquarium system at the Blackpool Sea Life Centre.

BLACKPOOI. SEA LIFE CENTRE ATLANTIC NlJRSE SHARKS GOITRE 97

apparent that water management was also in need of upgrading if long-term preven- tion was to be achieved.

It was necessary to establish a basis for iodine uptake. The National Aquarium in Baltimore had achieved success in the treatment of goitre with a supplement for sharks and rays which provided 6 mg of iodine per kg of fish body weight per week. This information formed the basis for all the calculations made in investi- gating potential remedies available in the United Kingdom.

Sources of natural iodine compounds were investigated, including kelp and kelp extracts, but kelp was found to be lacking in the levels of iodine required for sharks of the size of those needing treatment. Potassium iodide (KI) was found to be a sufficiently concentrated compound to bring the amount of available iodine to acceptable levels and trials began on three of the six animals in the 500 000 litre dis- play tank. The other three specimens remained on display but received no treat- ment. At the same time water changes in the display tank were increased from 2-3% per week to 12% per week in order to start the long-term prevention regime.

We considered three main methods of increasing the amounts of iodine available to the treated animals: (1) instituting greater water changes to replenish depleted water, a long-term process which could take up to a year to bring iodine levels back to normal; (2) mixing an iodine solution into the sea water to bring the environmental levels back to accept- able quantities; (3) incorporating iodine into the diet.

WATER CHANGES On reviewing records of the water- management regime and analysing the water in the system, it was concluded that although ammonia, nitrite and nitrate levels were within acceptable parameters, trace elements had dropped beyond acceptable limits (Table 1). If the goitre had been caused by a gradual increase in

concentration of ammonia and nitrogen waste in the pool then increased water changes may have reduced these levels.

Although the percentage of water change was increased in September 1993, the effect upon the goitre would be limited until normal levels of iodine could be established over a long period.

ADDITION OF IODINE TO THE WATER It is possible to introduce iodine into depleted sea water. Potassium iodide can be introduced to sea water at any level. If the remedy is needed quickly, Uchida & Abe (1986) suggest levels of 0.1 mgllitre, almost twice the level found in natural sea water. Introducing this amount every two weeks should ensure that the iodine in the water does not drop below natural levels.

However, the danger of introducing iodine artificially into marine water is that the potassium iodide will be solvated. Unfortunately, the solvation can be affected by temperature changes, owing to the unstable nature of the iodine and water, which could cause the immediate and total release of the iodine which, at such concentrations, could prove lethal to the animals.

ADDITION OF IODINE TO DIET Iodine is insoluble within the digestive system of animals but can be absorbed into the gut in compounds such as potas- sium iodide and calcium iodide. High levels of iodine are also found in certain algae which have also been successfully incorporated into diets to treat goitre.

Four types of product available for feeding in the United Kingdom were considered.

Kelp tablets Iodine levels in kelp tablets vary with the kelp harvested and can range between 1.2 and 2-9 mg iodine per 2 g tablet. Working on the basis of a die- tary requirement of 6 mg of iodine per kg of fish body weight per week, the amount of kelp needed in tablet form would not be practical.

98 AQUARIUMS

Aqueous extract of algae CLMO1, a product obtained from a cosmetic manu- facturer, is also a natural extract of kelp. Although levels of iodine were 7.5-8.5 g per litre, higher than in the tablet form, the amount required for the size of fish was still too great for its use to be a prac- tical proposition.

WEEKS '!h REDUCTION

1-6 nil 7 5 8 10 9 20 10-1 1 50 12-13 65 14 75

Multivit tablets The multivitamin tablet used successfully at the National Aquarium in Baltimore has a high level of iodine and has been used successfully in cases of goitre. We considered its use but found other products more readily available.

Iodine salts Potassium iodide has been used successfully in the treatment of goitre in humans. Being in a salt form it can be fed as a supplement and absorbed easily by the sharks. The correct calculated dose was encased in a gelatine capsule (size 00) so that the animals could not taste the compound.

RESULTS Treatment using KI started on 10November 1993. The three sharks received 1.2 g of KI per week for 12 weeks. The dosage was the equivalent of three feeds per week with doses of 40 mg KU60 kg but was administered once a week for practical reasons.

During the first six weeks of treatment no change was apparent but at eight weeks a slight reduction was noticeable and by ten weeks the swelling had reduced by c. 50%. At 12 weeks there was a further 15% reduction (Table 2).

An identical course of treatment was then given to the other three sharks with similar results.

Because we had no previous experience of this regime or knowledge of possible side effects, the sharks were observed closely, but throughout the trials their swimming behaviour, appetites and gen- eral appearance were all within normal parameters.

Table 2. The average reduction in swelling seen in Nurse sharks Ginglymostoma cirratum treated with KI.

The treatment is now an on-going pro- cess and the swellings on all six Nurse sharks have been reduced by c. 75-85%. This study illustrates the need the need for further research into the levels of iodine required to sustain healthy production of thyroid hormones.

ACKNOWLEDGEMENTS

My sincerest thanks to Rod Haynes of Sea Life Cen- tres for his encouragement and advice in compiling this document. To Boots Pharmaceutical for their professional advice and help in locating the iodine compounds and to Blackpool Sea Life Centre for the freedom of resources in pursuit of a remedy to the goitre problem.

PRODUCTS MENTIONED IN THE TEXT

CLMOl: extract of algae, manufactured by Jan Dekker (UK) Ltd, Liss, Hants., Great Britain. Gelatine capsules: manufactured by Thornton & Ross, Huddersfield, Yorks., Great Britain. Kelp tablets: manufactured by Nature's Aid, Lan- caster, Lancs., Great Britain. Multivit tablets: shark and ray vitamin supplement, manufactured by Purina Mills, Inc., Test Diets Divi- sion, 505 North 4th Street, PO Box 548, Richmond, IN 47375, USA. Potassium iodide: manufactured by Thornton & Ross, Huddersfield, Yorks., Great Britain.

REFERENCES STRAUB, J. 0. (1993): First results of goitre treatment in aquarium kept sharks using algal extract. 3rd International Aquarium Congress: April 25-29th, 1993. Abstracts. UCHIDA, H. & ABE, Y. (1986): The prevention of goitre in captive sharks. Int. Zoo Yb. 2 6 59-61.

Manuscript submitted 28 November 1994