Observations on the seasonal occurrence of two species of transversotrematid digenea parasitising the sparid fish Acanthopagrus australis in Moreton Bay, eastern Australia.
Ectoparasitic Prototransversotrema steeri Angel infected Acanthopagrus australis (Günther) in western (W. Bay) and southern (S. Bay) Moreton Bay with greatest abundance in winter (June-August), and none in summer (December-February). This confirms previous observations on seasonality of P. steeri from a small estuary in New South Wales. Transversotrema licinum Manter, which is a new host and geographical record, infects A. australis in W. Bay but not S. Bay, with large abundances in summer and winter, lowest abundance in spring. Increased size of P. steeri in winter in S. Bay could be explained by increased size of fish sampled since fish length and size of each parasite species were correlated positively. Transversotrema licinum increased in size from summer to winter irrespective of fish size. Number of eggs in utero and parasite size were correlated for both species; worms in mid-size range had most eggs, and P. steeri had more eggs (average = 19.2, 0-80) than T. licinum (3.3, 0-21); eggs were similar in length. Number of eggs per parasite, adjusted for parasite size, was greatest in autumn (P. steeri) or summer (T. licinum), i.e. early in infection period. Spawning migration to eastern Moreton Bay did not influence number of eggs per parasite.
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Department of Parasitology, University of Queensland, Australia. taylorja@usq.edu.au
D000818:Animals; D001315:Australia; D005399:Fishes / Q000469:parasitology*; D010270:Parasite Egg Count; D012621:Seasons; D014200:Trematoda / Q000254:growth & development / Q000302:isolation & purification*