Congenital anomalies of the inferior vena cava (IVC) and its tributaries have become more commonly recognized in asymptomatic patients. The embryogenesis of the IVC is a complex process involving the formation of several anastomoses between three paired embryonic veins. The result is numerous variations in the basic venous plan of the abdomen and pelvis. A left IVC typically ends at the left renal vein, which crosses anterior to the aorta to form a normal right-sided prerenal IVC. In double IVC, the left IVC typically ends at the left renal vein, which crosses anterior to the aorta to join the right IVC. In azygos continuation of the IVC, the prerenal IVC passes posterior to the diaphragmatic crura to enter the thorax as the azygos vein. In circumaortic left renal vein, one left renal vein crosses anterior to the aorta and another crosses posterior to the aorta. In retroaortic left renal vein, the left renal vein passes posterior to the aorta. In circumcaval ureter, the proximal ureter courses posterior to the IVC. Other anomalies include absence of the infrarenal IVC or the entire IVC. These anomalies can have significant clinical implications. Awareness of these anomalies is necessary to avoid diagnostic pitfalls.

No abstract

The reproduction of Australian bass from the Sydney Basin was studied between 1977 and 1982. The gonadal cycle was investigated using a four-stage gonad maturity classification, the gonado-somatic index, oocyte measurements, and histological examination of representative gonads. An ichthyoplankton survey was conducted, fecundity was estimated, and sperm viability in different salinities was also measured. Spermatogenesis and vitellogenesis commenced between February and April each year. Bass spawned between late June and early September in 1978 and 1981. Final ovarian maturation, and the catadromous migration of females from freshwater to the brackish spawning zone were dependent on flooding. Ovarian involution ensued if river levels did not rise before September. Reproductive success was high after floods in1978. Bass did not reproduce during the drought in 1979 and 1980, and reproductive success was low in the low river flows of the 1981 winter. The results suggest that bass are cyclical spawners, shedding eggs that are demersal in the spawning salinity. Fecundity is high (mean = 440 000). The location of spawning and recently spent bass, the distribution of larvae in the estuary, and results of the sperm viability experiments indicated that bass spawn in the estuary in salinities between 8 and 14 g kg-1. Most males were sexually mature by age 3 + years, and females by 5 + or 6 + years.

No abstract

Fish provide powerful tools for assessing aquatic environments. Three attributes are especially significant: the sensitivity of fish to most forms of human disturbance, their usefulness at all levels of biological organization and the favourable benefit-to-cost ratio offish assessment programmes. Fish can be used as indicators over wide temporal and spatial ranges. Because they cover all trophic levels of consumer ecology, fish can effectively integrate the whole range of ecological processes in waterways. Fish have been used in many different roles for assessing river health and monitoring responses to remedial management. Three of these applications appear to have particular value for management of Australian rivers: (i) automated systems monitoring fish ventilation can provide sensitive, broad-spectrum and continuous sensing of water quality to protect receiving waters or water-supply intakes; (ii) programmes collecting routine data on commercial or recreational fisheries can be designed and analysed so as to isolate confounding effects due to fishery-specific factors and, hence, used to detect and monitor environmental change on large scales; (iii) the Index of Biotic Integrity (IBI) can be modified to suit Australian conditions and fish communities to meet the important need for a predictive model of aquatic environmental quality. The IBI is a quantitative biological tool with a strong ecological foundation that integrates attributes from several levels of ecosystem organization. Examples of the use of IBI elsewhere suggest its robustness, flexibility and sensitivity can cope effectively with the low diversity of the Australian fish fauna and the dominance of ecological generalists. A provisional structure is suggested for a test of the IBI in four riverine regions of New South Wales.