Poorly known aspects of external dimorphism, maturation, early development and the annual reproductive cycle of Euastacus spinifer have been investigated in populations south of Sydney (Georges River, Hacking River, Loddon River). Setal development surrounding gonopores is a reliable field indicator of maturity in females and the degree of inflation of genital papillae is a useful maturity indicator in males. Females commence maturing at 65 mm carapace length (CL), but many don't mature until 70-75 mm CL; a majority spawn once each year after reaching maturity. Two groups of reproductively functional males were identified in Loddon River populations; normal males became functionally mature at 45-55 mm (CL), but small 'precocious' individuals were mature at 12-20 mm CL. The robust spermatophore structure is considered to be related to the protracted period (4-6 weeks) between mating and release of the ellipsoid, yolky eggs (means 3.5, 2.7 mm); fecundity increased with size (268 at 73.1 mm CL to 1299 at 109.4 mm CL). Early embryonic development and the three juvenile stages between hatching and release are similar to those of other parastacids; development of offspring on individual E. spinifer females is synchronised. In the Loddon River mating occurs in late May or early June when water temperatures fall rapidly below 15°C. Most breeding females are carrying spermatophores in early June and eggs by early July; incubation extends for 110-140 days over winter. Juveniles remain with the parent for a further 28-70 days before release in early December (water temperatures 20-24°C). Timing of events in this annual cycle is known to vary in different river systems; however, E. spinifer is clearly a winter brooder. The selection mechanisms, that may have produced the precocious males remain unknown.
|Number of pages||25|
|Journal||Proceedings of the Linnean Society of New South Wales|
|Publication status||Published - 1997|
- Euastacus spinifer