Combined effects of pentachlorophenol and salinity stress on phagocytic and chemotactic function in two species of abalone

The effect of pentachlorophenol (PCP) combined with salinity stress on spec ific aspects of cellular immunity was examined in two species of abalone. C hemotactic and phagocytic ability (percent phagocytosis, %P; and phagocytic index, PI), as well as gross morphological characteristics, of hemocytes w ithdrawn from red (Haliotis rufescens) and black abalone (H. cracherodii) a fter in vivo exposure to 25, 35, or 45 parts per thousand seawater salinity plus 1.2 mg/l PCP were determined. Abalone exposures of 3.5 and 6.5 h, res pectively, were based on species-specific metabolic endpoints (MEPs) derive d from previous NMR data. Hemocyte chemotaxis was found to be augmented by low salinity in red but not black abalone, while high salinity seemed to re duce chemotactic ability in both species. PCP did not potentiate the effect s demonstrated by salinity variations alone in red abalone, although chemot axis was further compromised in black abalone exposed to high salinity stre ss combined with PCP. Although chemotactic ability was similar among both s pecies, both %P and PI was greater among black abalone. Low salinity may of fset the effects of PCP in red but not black abalone. Whereas red abalone d emonstrated a reduction in phagocytic ability upon exposure to high salinit y alone, black abalone appeared more resilient to high salinity stress alon e. Furthermore, while the effect of high salinity plus PCP is subadditive a mong red abalone, high salinity seems to potentiate the effect of PCP on bl ack abalone, Finally, hemocytes exposed to acute salinity variations plus P CP showed varying morphological characteristics when compared to controls. Over 30% of hemocytes of high salinity plus PCP exposed abalone remained ro unded and generally unattached to glass slides with only a few pseudopod ex tensions. Hemocyte preparations incubated in rhodamine-conjugated phalloidi n were observed with fluorescence microscopy and reveal an altered actin fi lament pattern. Overall, black abalone demonstrate greater phagocytic abili ty than red abalone both in the presence and absence of PCP. Furthermore, i ncreases in salinity are accompanied with reduced phagocytic ability with r ed abalone demonstrating particular sensitivity to salinity variations. Whi le PCP inhibits ATP synthesis, salinity variations may impose an additional stress on intertidal animals exposed to transient or seasonal environmenta l changes. (C) 2000 Elsevier Science B.V. All rights reserved.