Search Results - (Author, Cooperation:S. H. Gruber)

2013-02-16

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; *Conservation of Natural Resources ; *Sharks

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

The swimming speed of seven large juvenile lemon sharks Negaprion brevirostris following attachment of an external speed-sensing ultrasonic transmitter was significantly higher during the first 18 h after release compared to the average swimming speed obtained 〉48 h after release. The external speed-sensing transmitter can be used to monitor the voluntary swimming speed of large fishes in the field, but data during the first 24 h period should be excluded from analysis of natural speeds, at least from species similar in behaviour to N. brevirostris.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Young lemon sharks, Negaprion brevirostris, were kept under controlled conditions in an aquarium and fed blue runner, Caranx crysos, at different ration levels. The relationship between feeding rate and growth rate was best described by a von Bertalanffy growth curve, which predicted a maximum growth rate of 140 kJ kg−1 day−1 (0·66% b.w. day−1), a maintenance ration of 199 kJ kg−1 day−1 (1·06% b.w. day−1), and losses due to starvation of -236kJ kg−1 day−1 (1·11% b.w. day−1). The relationship between gross conversion efficiency (K1) and feeding rate was also examined. K1 ranged from - 64 to 25% and did not drop at high ration levels. Activity levels of both starved sharks and sharks fed at maintenance were not significantly different (0·2 body lengths s−1). K1 values generated from both laboratory and field data suggest that young lemon sharks can convert food to new tissue as efficiently as teleosts.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Six scarecrow toadfish Opsanus phobetron were found in the stomachs of five juvenile lemon sharks Negaprion brevirostris, and subsequent sampling yielded 29 O. phobetron specimens from mangroves (45% of toadfish), conch shells (28%), and seagrass beds (25%) around Bimini, Bahamas during the winter. The presence of large numbers of scarecrow toadfish including mature females, when the water temperature was 〉22° C, suggests that this is a successful breeding tropical population and not a glacial relict.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Multilocus genotypes using nine DNA microsatellite loci provided an effective and permanent individual identification mark for lemon sharks Negaprion brevirostris, the first example of genetic tagging for any elasmobranch species. The double-tagging provided by micro-satellites afforded a means to determine passive integrated transponder (PIT) tag shed rate in lemon sharks. Of 388 sharks that were recaptured, 47 (12.1%) had shed their PIT tag.

Electronic Resource

1365-2761

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Medicine

Abstract Healthy lemon sharks, Negaprion brevirostris (Poey), were inoculated with Vibrio carchariae and V. damsela, two vibrios known to cause disease in other shark species. Vibrio damsela was not recovered from the inoculated sharks; V. carchariae infected the healthy lemon sharks, but did not produce clinically observable disease. However, histological evaluation revealed active splenic and hepatic disease with Gram-negative bacteria found in association with mononuclear cells. When the experiment was repeated with a physiologically compromised lemon shark, V. carchariae was lethal for the test animal, but V. damsela was again cleared. Vibrio carchariae was also isolated from skin lesions of a lemon shark infested with monogeneans (Dermophthirius nigrellii). Histological evidence indicated that this shark died of protozoan infection. Thus, lemon sharks are susceptible to infection with V. carchariae which can cause subclinical disease in otherwise healthy specimens. We suggest that D. nigrellii may act as a vector of V. carchariae and that stress plays a role in the clinical manifestation of this disease.

Electronic Resource

1432-136X

Springer Online Journal Archives 1860-2000

Biology

Medicine

Summary Polyethylene cannulae were implanted in pre- and post-branchial blood vessels allowing nonstressful blood sampling over a variety of activity ranges in an active tropical elasmobranch, the lemon shark (Negaprion brevirostris). TheP 50 was found to be 11.8 Torr at 24°C and pH of 7.7. A Bohr shift of −0.36 was also found. BloodP o 2 and oxygen content were measured during rest, routine swimming, and exercise in unanesthetized, free swimming juveniles. Under all conditions venous oxygen levels were low with venousP o 2 of 7.1±2.7 Torr, and venous oxygen content ( $$C\bar v_{O_2 } $$ ) of 0.56±0.4 vol%. However, a large variability was found in arterial blood measurements. ArterialP o 2 ranged from 7 to 80 Torr, while arterial oxygen content (Cao 2) varied from 1.6 vol% to 6.8 vol% among ten experimental animals. A significant increase in arterialP o 2, oxygen content, and hematocrit was noted during increased activity. Since the venous system provides little or no oxygen reserve, increased oxygen extraction from the blood ( $$Ca_{O_{_2 } } - C\bar v_{O_2 } $$ ) appears to be met by an increase inCao 2 rather than a decrease in $$C\bar v_{O_2 } $$ . Mechanisms to accomplish this may include increasing hematocrit and vacular gill shunts.

Electronic Resource