Seasonal changes in ectoparasite infection of juvenile yellowfin bream, acanthopagrus australis (Giinther) (pisces: Sparidae), from a small estuary in northern new south wales

Seven monogenean, 1 digenean and 9 copepod species of ectoparasite were found on 179 juvenile Acanthopagrus australis collected bimonthly over two 12-month periods from a small estuary at Red Rock in northern New South Wales. The monogenean Allomurraytrema span and the copepod Alella macrotrachelus showed a consistent cycle of spring-summer high and late summer-autumn low in prevalence and intensity of infection, whereas the digenean Prototransversotrema steeri was present only in winter. The monogenean Haliotrema spariensis was highly prevalent year-round, but other monogeneans were inconsistent in seasonal prevalence and intensity. The copepods Paraergasilus acanthopagri and Dermoergasilus acanthopagri showed inconsistent annual cycles, but their fluctuations in prevalence and intensity were nearly identical. The other species of ectoparasite had no consistent cycles or were rarely found. Temperature does not appear to directly regulate the abundance of ectoparasites on juvenile Acanthopagrus australis in Red Rock estuary

Comparative histopathology of Longicollum (Acanthocephala: Pomphorhynchidae) infection in the alimentary tract and spleen of Acanthopagrus australis (Pisces: Sparidae)

The pomphorhynchid acanthocephalan Longicollum alemniscus infected the rectum of 16 and the intestine of five of 628 Acanthopagrus australis from Moreton Bay, Queensland. The neck and proboscis penetrated the entire gut wall and were surrounded by a layer of compact, rounded fibroblasts inside a layer of elongated fibroblasts and scattered connective tissue fibres. These layers extended across the entire gut wall and into the capsule that enclosed the proboscis outside of the gut. A similar parasite occurred extraintestinally in three fish; the proboscis of one penetrated into the spleen. The spleen was shrunken, with the proboscis and anterior part of the neck enclosed in a capsule of proliferated connective tissue and cellular elements similar to that in the response to infection of the gut wall

Changes in monogenean and copepod infestation on captive Acanthopagrus australis (Sparidae)

Infection levels by 17 species of ectoparasite on 491 yellowfin bream collected throughout 1990 from Moreton Bay, S.E. Queensland were compared to infections on 82 bream collected during the same period from a captive population in a large pond at Sea World, Gold Coast, Queensland. There was a significant increase in prevalence and/or intensity of monogeneans Lamellodiscus acanthopagri and Polylabroides multispinosus, but a decrease in the monogenean Anoplodiscus australis and the copepods Ergasilus australiensis, Lernanthropus atrox, Bomolochus stocki and Alella macrotrachelus on captive fish. Twenty‐eight bream collected from the pond during autumn were placed in an experimental 1 m cage within the pond for 4–6 weeks. Compared to the baseline data for the pond, the caged fish showed increased prevalences of the monogeneans Lamellodiscus acanthopagri, L. squamosus, L. major and Haliotrema spariensis, and increased intensities of L. squamosus, Allomurraytrema robustum and P. multispinosus. The copepod Caligus epidemicus dropped off in preservative, but its abundance (average number per fish) was significantly higher on caged fish than on pond or wild fish. Increased infection levels by L. acanthopagri and A. robustum were due in part to autoinfection. The large skin area promoted large populations of C. epidemicus. Copyrigh

Histopathological and ecological aspects of Henneguya and Myxobolus (Myxosporea) infections in Acanthopagrus australis (Gunther) (Pisces: Sparidae) from Moreton Bay, Australia

Abstract. Sporulated plasmodia of Henneguya sp. infected the gill filaments, interhemibranch septum, gut and other microhabitats of Acanthopagrus australis in Moreton Bay, southern Queensland, whereas Myxobolus sp. infected only the gut. There was usually no inflammatory response, but some plasmodia in the gill filaments were associated with a granulomatous, predominantly lymphoid, response that was not determined by either parasite maturity, or sex and size of fish or season. There was a microhabitat shift in branchial Henneguya infection from predominantly gill filament in juvenile bream to gill septum in older fish. The highest prevalences of Henneguya were in the southern part of Moreton Bay, but trends in seasonal infection and prevalences in relation to size and sex of fish were similar in the western and southern parts of the bay. This suggested a widespread distribution of the putative annelid alternate host in Moreton Bay, with highest densities in the southern part. Myxobolus infection was most prevalent in young male fish at the winter spawning grounds on eastern surf bars. Copyrigh

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

Histopathology caused by Caligus epidemicus Hewitt (Copepoda: Caligidae) on captive Acanthopagrus australis (Gunther) (Pisces: Sparidae)

Abstract. Highest densities of copepodids (≤5.3 cm ), chalimus (≤8.5 cm ) and redundant filaments (≤6.7 cm) of Caligus epidemicus were found on the anterodorsal and anteroventral flanks, head and pectoral fins of Acanthopagrus australis (Günther). Copepodids eroded the epidermis and usually attached their frontal filament to the basement membrane on the inter‐ray region of fins, as well as the fin rays or scales. Chalimus stages were associated with a healed epidermis and little tissue response. The most extensive tissue response was associated with the redundant frontal filament, and was characterized by infiltrating macrophages, multinucleated giant cells, and epidermal and fibroblast proliferation. No significant pathology could be attributed to either pre‐adult or adult copepods. Copyrigh