NOTE Gelsleichter et a!.: Evaluation of oxytetracycline in Ginglymostoma erratum 
625 
regimes. After an acclimation period of two weeks, 
all animals were sexed, measured (stretched total 
length; STL), weighed, and tagged with rototags for 
individual identification. Sharks were divided into two 
groups: an OTC group (re-5; mean STL (±SE)=62.6 ± 
3.62 cm; mean weight (±SE)=1.7 ±0.36 kg) and a con- 
trol (CO) group (re=4; mean STL=51.2 ±2.09 cm; mean 
weight = 0.9 ± 0.10 kg). All nine animals were injected 
in the lateral musculature with an elasmobranch 
Ringer’s solution vehicle {Forster et al., 1972) which, 
for the OTC group, contained OTC at a dosage level of 
25 mg/kg body weight (BW). Following the injections, 
all nurse sharks were returned to the experimental 
tanks for captive maintenance over a 7-month period. 
During the experimental period, all sharks were 
measured, weighed, and examined for external le- 
sions on a monthly basis. In addition, the general 
condition of all sharks was evaluated and recorded 
in terms of behavioral abnormalities or signs of dis- 
tress. All animals were fed three times per week ad 
libitum with Atlantic thread herring, Polydactylus 
oligodon, or sardine, Sardinella aurita. 
Toxicity of OTC on nurse shark growth was evalu- 
ated by comparing the mean growth rate (%BW/d) of 
control and OTC -injected G. cirratum. In addition, 
blood samples were obtained from all specimens at 
the end of the experimental period and subjected to 
white blood cell (WBC) and serologic parameter 
analyses. Afterwards, all remaining specimens were 
anesthetized with 1 g/L tricaine methanesulfonate 
(MS-222) and sacrificed by severing the spinal cord. 
Necropsies were performed for all specimens to as- 
sess general animal health. 
Results 
All nurse sharks survived the experimental period 
without any apparent behavioral complications. All 
grew in length (Fig. 1A) and weight (Fig. IB) while 
exposed to identical temperature fluctuations (Fig. 
1C). No significant differences in growth rates be- 
tween control and OTC groups were observed (f-test, 
P<0.05, Table 1). 
Observations on serum chemistry 
also indicated little difference be- 
tween groups, except that both lac- 
tate dehydrogenase (LDH) and as- 
partate aminotransferase (AST) were 
significantly greater in OTC-injected 
animals (f-test, P< 0.05, Table 2). Dif- 
ferential WBC counts indicated no 
significant difference between control 
and OTC groups (f-test, P<0.05; Table 
3). Both serologic and hematologic 
Month 
Figure 1 
Mean monthly growth (± SE) in (A) length 
and (B) weight for nurse sharks in the OTC 
(•, n= 5) and control (■, n= 4) groups; (C) 
shows the monthly temperature ranges and 
midpoints in the experimental tanks. 
Table 
1 
Growth rates (expressed as %BW/d) of nurse sharks in the control and oxyte- 
tracycline-treated (OTC) groups. Body weights (BW) are in kg. 
Group 
n 
Initial BW 
Mean ± SE) 
Final BW 
(Mean ± SE) 
Growth rate 
(Mean ± SE) 
Control 
4 
0.88 ± 0.10 
2.52 ± 0.29 
0.91 ± 0.11 
OTC 
5 
1.70 ± 0.38 
4.64 ± 0.73 
0.79 ± 0.11 
