Effect of Salinity on Hatching in Neobenedenia melleni, a Monogenean Ectoparasite of Seawater‐Cultured Tilapia

Abstract

Laboratory experiments were conducted to determine the effect of salinity on embryonic development and hatching in Neobenedenia melleni, a monogenean ectoparasite of seawater‐cultured (37 ppt) Florida red tilapia (Oreochromis urolepis hornorum × O. mossambicus). Eggs, collected from adult monogeneans at 37 ppt, were exposed to different salinities (0, 6, 12, 18, 24, 30 and 37 ppt) for 48, 72 or 96 h. Varying degrees of post‐treatment development and hatching occurred when natural seawater conditions were restored. Hatching success generally declined with decreasing salinity and increasing duration of exposure. Under all durations of exposure, hatching success remained relatively high (≥ 69.6%) at salinities of 24 ppt and above, but declined markedly (≤ 32.5%) at lower salinities. Hatching did not occur in eggs exposed to fresh water (0 ppt) for 72 and 96 h. The most effective treatments in preventing hatching, other than prolonged exposure to fresh water, were 96 h exposures to low‐salinity brackish water. Percent hatch after 96 h exposure to 6, 12 and 18 ppt was 5.5, 11.9 and 5.8%, respectively.

A revision ofNeobenedeniaYamaguti, 1963 (Monogenea: Capsalidae) including a redescription ofN. melleni(MacCallum, 1927) Yamaguti, 1963

“…Eyes (MacCallum, 1927;Jahn and Kuhn, 1932;Nigrelli and Breder, 1934;Nigrelli, 1937Brooks and Mayes 1975;Colorni, 1994;Mueller et al, 1994;present study); skin/head/body (Jahn and Kuhn, 1932;Nigrelli and Breder, 1934;Nigrelli, 1937Hargis, 1955, Bravo-Hollis andDeloya, 1973;Brooks and Mayes, 1975;Robinson et al, 1989;Gallet de St. Aurin et al, 1990;Gaida and Frost, 1991;Goldberg et al, 1991;Mueller et al, 1992Mueller et al, , 1994Cowell et al, 1993;Ellis and Watanabe, 1993;Colorni, 1994;Watanabe et al, in press; present study); gills (Jahn and Kuhn, 1932;Bravo-Hollis, 1958;Gaida and Frost, 1991;Dyer et aL, 1992; present study), nasal cavities (Jahn and Kuhn, 1932).…”

“…Atlantic Ocean [Caribbean Sea: Bimini, British West Indies ; Jamaica (Robinson et al, 1989); French West Indies (Gallet de St. Aurin et al, 1990); Puerto Rico ; Bahamas (Gallet de St Aurin et al, 1990;Mueller et al, 1992Mueller et al, , 1994Cowell et al, 1993;Ellis and Watanabe, 1993; in press)]; Red Sea (Colorni, 1994).…”

“…Whittington and M. A. Horton Published records. MacCallum (1927); Jahn and Kuhn (1932); Nigrelli and Breder (1934); Nigrelli (1935Nigrelli ( , 1937; Hargis (1955); Bravo-Hollis (1958); Bravo-Hollis and Deloya (1973); Brooks and Mayes (1975); LamotheArgumedo (1963) in Lawler (1981); Kaneko et al (1988); Robinson et al (1989); Gallet de St. Aurin et al (1990); Gaida and Frost (1991); Goldberg et al (1991) ;Dyer et al (1992) ;Mueller et al (1992Mueller et al ( , 1994; Cowell et al (1993); Ellis and Watanabe (1993); Colorni (1994); Watanabe et al (in press); present study.…”

First published record of the pathogenic mono-genean parasite Neobenedenia melleni (Capsalidae) from Australia

“…N. melleni is recognised as a lethal pathogen of captive marine teleosts, whether held in aquaria (e.g., MacCallum 1927, Jahn & Kuhn 1932, Thoney & Hargis 1991 or in sea cages for aquaculture (e.g., Kaneko et al 1988, Mueller et al 1992. Furthermore, unlike most monogenean parasites, N. melleni is notorious for its lack of host-specificity.…”

Comparative susceptibility of two different genetic types of tilapia to Neobenedenia sp. (Monogenea)

“…when exposed to unfiltered seawater from the Gulf of Mexico and died within 2 to 3 wk -although mortality rates were noticeably higher for PU than for MT. Previously, Neobenedenia melleni (MacCallum 1927) Yamaguti, 1963, has been shown to infect tilapia reared in sea cages in Hawaii (Kaneko et al 1988), Martinique (Gallet de St. Aurin et al 1990), the Bahamas (Mueller et al 1992, Cowell et al 1993, Ellis & Watanabe 1993, and Jamaica (Robinson et al 1992(Robinson et al , 2008. There are no reports of Neobenedenia spp.…”