Fungi of Penaeidae Boas 1880 and Pandalidae Dana 1852

'Black-gill disease' is caused by deuteromycete fungi belonging to the genus Fusarium (principally F. solani). The disease affects P. japonicus, P. duoraraum, P. setiferus, P. aztecus, P. vannamei, P. stylirostris and P. californiensis (Brock and Lightner, 1990) and can cause significant mortality. Under intense culture, over 90% cumulative mortalities of P. japonicus and P. californiensis may occur over 4-5 months (Lightner et al., 1979). Infections are initiated via epicuticle abrasion and first appear as raised lesions on the gills, eyes, appendages or other integument surfaces (Alderman, 1981). Gill squashes show masses of septate hyphae, with boat-shaped macroconidia (Lightner and Fontaine, 1975). Histologically, early stages of infection elicit intense haemocyte infiltration and melanization of the invasive hyphae. As the disease progresses, haemocyte concentrations decrease, the mycelia spread and secondary infections may occur (Solangi and Lightner, 1976; Lightner, 1988d). Treatment and control of F. solani are difficult since it is a ubiquitous soil- or water-borne saprobiont.

Nauplii, zoea and mysis stages of penaeid shrimps are also infected by Lagenidium callinectes (Couch, 1942), L. scyllae (Bian et al., 1979), Sirolpidium zoophthorum (Vishniac, 1955) and Haliphthorus spp. (Hatai et al.,

1980). According to Brock and Lightner (1990), L. scyJJae and L. caJJinectes are not clearly distinct and require more comparative investigation. Lagenidium caJJinectes is distinguished from Sirolpidium by the absence of terminal sporangia on L. caJJinectes discharge tubes. Sirolpidium also has a highly variable hyphal width (7-40 mm) compared with that of L. caJJinectes (5-14 mm) (Vishniac, 1955). Several culture characteristics can also be used to distinguish Lagenidium, AtkinsieJJa, SiroJpidium and HaJiphthorus (Hatai, 1989). Lagenidium forms vesicles within which zoospores form, whereas the other three genera use parts of the thallus for zoospore development. Lagenidium zoospores are larger (8-10 mm) than those of the other genera (5-7 mm). Differentiation between SiroJpidium spp., H. miJfordensis and other HaJiphthorus spp. (as well as AtkinsieJJa from crabs, described below) requires experience (Hatai, 1989; Brock and Lightner, 1990).

Nauplii and protozoeal stages of penaeids are infected predominantly by L. caJJinectes, while later stages appear to be more susceptible to SiroJpidium sp. (Lightner, 1983). Infected larvae show hyphal proliferation throughout the body, resulting in 100% mortality (Lightner, 1981); however, the significance of these fungi to wild shrimp populations is unknown.

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