Cs. Friedman et al., WITHERING SYNDROME OF THE BLACK ABALONE, HALIOTIS-CRACHERODII (LEACH)- WATER TEMPERATURE, FOOD AVAILABILITY, AND PARASITES AS POSSIBLE CAUSES, Journal of shellfish research, 16(2), 1997, pp. 403-411
Withering syndrome (WS) has affected black abalone since the mid-1980s
. We investigated the potential roles of elevated water temperature, f
ood availability, and parasites (renal coccidia and rickettsiales-like
procaryotes or RLPs) in this disease. Results from a temperature-feed
ing experiment suggested that elevated water temperature was not a dir
ect cause of WS, but accelerated mortality. At a particular water temp
erature, both fed and starved abalone had similar survival. Abalone wi
th WS fed on kelp until the animal reached the terminal stages of the
disease, when visible atrophy of the foot muscle was easily observed.
However, fed abalone held at an elevated water temperature, 20 degrees
C, had decreased survival relative to those held at 13 degrees C. The
lack of food in our investigations did not appear to be a direct caus
e of WS. In addition, no consistent statistically significant associat
ions were identified between abalone condition and intensity of coccid
ian infection in both field and laboratory studies. No association was
found between condition of the digestive gland and intensity of the R
LP infection in our laboratory study. However, all abalone with degene
rated digestive glands had visible signs of WS. Time to abalone death
did not correlate with intensity of RLP infection, except in a pool of
the 13 degrees C treatments and possibly the 13 degrees C starved tre
atment. Thus, at lower seawater temperatures, the RLP may affect survi
val. The significance of this observation may have resulted from small
sample sizes. Only 22 abalone were included in the 13 degrees C treat
ment, and 4 of these were in the starved treatment. These data suggest
that further investigation of the role of the RLP in WS is needed.