|dc.description.abstract||The sensitivity of four New Zealand freshwater fish species to 99.5% pure pentachlorophenol was studied. For one part of the study, four early life stages of smelt (Retropinna retropinna), inanga (Galaxias maculatus), koaro (Galaxias brevipinnis), and common bully (Gobiomorphus cotidianus) were exposed to pentachlorophenol, and the acute and sublethal responses were compared to those of the reference species rainbow trout (Oncorhynchus mykiss).
Analysis of the acute exposures enabled the determination of 25 LC50 values for the various life stages and fish species examined. In addition, an in depth examination of post-exposure mortality allowed the determination of an additional 16 LC50 values. The acute sensitivities of early life stages of native fish to pentachlorophenol did not differ appreciably when compared to those of rainbow trout. In fact, there was a larger variation between the different life stages within a species, than there was between species. The 48 hour LC50 for pentachlorophenol varied between 31 and 389 ppb (smelt), 30 and 1034 ppb (inanga), 78 and 1043 ppb (koaro), 92 and 191 ppb (common bully), and 77 and 910 ppb (rainbow trout). The larval stages of all fish species examined were more sensitive to acute pentachlorophenol exposure than embryonic stages.
The sublethal parameters of the early life stages that were studied included: growth, the induction of cranial, axial, eye and other deformities, swimming performance, successful hatching rate, time-to-hatch, post-exposure mortality and heart rate. Sublethal effects that were consistently and negatively affected by pentachlorophenol were: post-exposure survival and hatch success, growth, teratology, cranial malformations, swimming performance and heart rates. The parameter time-to-hatch was not consistently altered in either direction, i.e. time-to-hatch after exposure to pentachlorophenol was just as likely to be either shorter than that observed for the controls or longer.
For the remainder of the study, the adults of two species, inanga and common bully were studied for their sublethal responses to pentachlorophenol. The sublethal responses that were studied included: haematological parameters (lactate, glucose, total red blood cell count, total white blood cell count, differential white blood cell count), liver detoxification enzymes (including ethoxyresorufin-O-deethylase and uridine 5’ - phosphoglucuronyl transferase) and the induction of 70 kiloDalton heat shock (stress) protein. These parameters were measured at 25, 50 and 75% of the LD50 values for inanga and common bully, which were 0.30 and 0.23 mM, respectively.
Adult inanga and common bully showed surprisingly few physiological changes in response to sublethal doses of pentachlorophenol. Pentachlorophenol-exposed inanga were characterised by a significant decrease in both blood glucose contents and in uridine 5’-diphosphoglucuronic acid transferase activities. Common bully showed no significant changes in any of the experimental parameters examined, although the increase in the level of 70 kiloDalton heat shock protein was comparable to that of the positive heat-shocked controls.
Very little of this type of research with these species had been undertaken previously, and an important aspect of this study was to investigate the feasibility and efficacy of native fish species for toxicology research. The two main technical difficulties encountered were: one, obtaining fertilised eggs for studying the early life stages of the native fish, and two, obtaining sufficient sample for biochemical and haematological analyses of the adult fish. Despite these shortcomings native fish species have been shown to be a valuable new addition for both early and adult life stage toxicity testing and in measuring both acute and sublethal responses to pentachlorophenol.||