Fluctuating asymmetry has sometimes been employed to indicate disruption of developmental homeostasis. Such disruption is thought to be a result of increased developmental stress. In this study we examine the relationship between fluctuating asymmetry and inbreeding level in two differing breeding systems: the marine harpacticoid copepod Tisbe holothuriae, a typically outbreeding diploid, and the common honeybee Apis melli/era, which is haplo-diploid. Inbreeding has previously been shown to constitute a developmental stress in populations of T. holothuriae, but the same is yet to be conclusively shown in A. melli/era.T. holothuriae showed an increase in the level of fluctuating asymmetry with increased levels of inbreeding. No difference in the level of asymmetry was observed for A. melli/era when outbred lines were compared with inbred lines. It is concluded that fluctuating asymmetry provides a useful technique for the measurement of developmental stress caused by inbreeding.
Chemical data are presented for several lakes and two impoundments on the
Kosciusko and Monaro plateaux in south-eastern New South Wales, and for two rivers
(Paroo and Darling), several freshwater lakes, and deposits from some dry salt lakes in
western New South Wales. The concentrations of the major cations and anions, nitrate
plus nitrite, and orthophosphate were investigated. For lake deposits, only major ions
were investigated. The Kosciusko lakes were extremely fresh (salinity <3 p.p.m.)
and chemically dominated by sodium and either bicarbonate, chloride or sulphate
ions ; the Monaro peneplain lakes had a considerable salinity range (69-21,244 p.p.m.),
and, with increasing salinity, sodium and chloride quickly assumed dominance. The
Paroo and Darling Rivers had salinities <400 p.p.m, and the western freshwater lakes
<850 p.p.m.; in both rivers and lakes, sodium and bicarbonate were the dominant
ions. Deposits from dry salt lakes were mainly sodium chloride.
Effects of food quality and quantity on certain fitness traits of G. pectrnatus were examined to develop methods of culture. Five generations were successfully reared on excess Isochrysis galbana, despite intense inbreeding. The effect of food quantity was tested using outcrossed offspring fed I. Galbana at four concentrations. Generation time (from hatching to egg) decreased from 43.2 days at 1 × 104 cells ml-1 (lowest concentration) to 19.6 days at 5 × 105 cells ml-1 (highest concentration). An increase occurred in female body length (0.88 to 1.01 mm) and egg number (21.2 to 51.3) with increasing food concentration, and the total number of adults produced per brood was significantly lower at 1 × 104 cells ml-1. Results on a Dunaliella tertiolecta diet were similar to those for I. Galbana at the one food concentration tested (1 × 105-2 × 105 cells ml-1); however, unlike I. galbana, D. tertiolecta did not sustain viable egg production and was therefore nutritionally inadequate for multiple generation culture. Larval mortality was high on diets of Tetraselmis chuii and Phaeodactylum tricornutum. Body lengths and egg numbers of cultured females fed I. Galbana were greater than those of the 'wild' parental females, thus indicating the suitability of the culture conditions.
Replicate laboratory populations of T. holothuriae initiated by founder females standardized in terms of reproductive status, age and environmental background were exposed to three levels of cadmium for 24 days and compared with untreated controls. At a cadmium concentration of 159 �g l-1 populations failed to increase and became virtually extinct, probably because of larval impairment. At concentrations of 2.3 and 40 �g l-1 population growth occurred but total population size (males plus females plus copepodids) and both male and female numbers were significantly reduced relative to controls. Knowledge of the response of harpacticoids to low levels of toxic metals therefore appears to be significant in developing an understanding of the effects of metals on marine ecosystems.
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