Serological evidence of an antibody response in farmed southern bluefin tuna naturally infected with the blood fluke Cardicola forsteri

In this study, adaptive immune response was investigated in farmed southern bluefin tuna, Thunnus maccoyii, infected with a sanguinicolid Cardicola forsteri. A cohort (Cohort₂₀₀₅) of southern bluefin tuna was sampled between March 2005 and August 2006. Samples were taken at the transfer of wild caught tuna to sea cages and then at regular intervals. Parasite intensity, abundance and prevalence data were recorded. An ELISA was developed to detect and quantify an antibody response against the blood fluke in southern bluefin tuna serum. Intensity and prevalence of the blood fluke were shown to peak in May 2005 at 10.9 flukes per infected fish (SE = 1.72) and 97.5% prevalence and then decreased to low prevalence (10%) and intensity (1.0). There were no significant changes in prevalence or intensity in 2006. Antibody titres and seroprevalence increased from 1.37 U μl⁻¹ and 10% at transfer in March 2005 to reach a peak in December 2005 of 25.86 U μl⁻¹ (SE = 6.26 U μl⁻¹) and 66.66%. No significant changes were observed in antibody titres for the same cohort of fish during 2006. Parasitological and serological values from Cohort₂₀₀₅ were compared to a 2006 cohort (Cohort₂₀₀₆) in March 2006 and August 2006 to determine if prior infection in Cohort₂₀₀₅ elicited any protection against infection in 2006. Although significant differences were not observed in intensities between cohorts it was shown that Cohort₂₀₀₅ had significantly lower abundances and prevalences of blood fluke infection than Cohort₂₀₀₆. Although there was no significant difference in mean antibody titres between cohorts in March 2006, the mean antibody titre of Cohort₂₀₀₆ was significantly greater than that of Cohort₂₀₀₅ in August 2006. No significant differences were observed in seroprevalence. This is one of the few studies to demonstrate the development of acquired resistance in fish against a parasite in an aquaculture environment under natural infection conditions.     

Invaders of an invader - Trematodes in Potamopyrgus antipodarum in Poland

The subject of the following study was the natural and experimental invasion of trematode larvae in Potamopyrgus antipodarum from Bory Tucholskie National Park (Poland). Only one out of the 14,908 dissected specimens had oval sporocysts and mature cercariae of fish fluke, which belongs to the Sanguinicolidae family. It is the first recorded case in the European population of P. antipodarum living in inland water. The experimental study showed the possibility of native metacercariae (Echinostoma revolutum, Echinoparyphium aconiatum and Hypoderaeum conoideum) settlement in those immigrant snail species; however, exposure to parasites resulted in an increase in snail mortality. The three out of six used cercariae species were able to transform into metacercariae in P. antipodarum as in the second intermediate host, but the exposure to parasitic larvae of four of the used species resulted in an increase in snails’ mortality. It may suggest that not only metacercariae settlement but also the attack of cercariae (Rubenstrema opisthovitellinum at a temperature of 22 °C) affected the low survival of experimental snails in comparison to control animals. The subject of discussion presented in this paper is also the hypothesis on probable effect of the interaction between P. antipodarum and native snail species (as a source of invasive larvae of parasites) living in the same habitat.     

福建海产鱼类寄生吸虫二新种（吸虫纲;复殖目）

从福建沿海的横纹东方钝肠道里检获鳞肉科和血居科吸虫一新种,即等口双肛吸虫Ｂｉａｎｉｕｍ ｉｓｏｓｔｏｍａ ｓｐ．ｎｏｖ。中华拟德氏吸虫Ｐａｒａｄｅｏｎｔａｃｙｌｉｘ ｓｉｎｅｎｓｉｓ ｓｐ．ｎｏｖ．新种与近似种进行比较,模式标本存放在汕头大学生物系。     

Two new blood flukes (Digenea: Sanguinicolidae) from Epinephelinae (Perciformes: Serranidae) of the Pacific Ocean

Pearsonellum pygmaeus n. sp. is described from Cromileptes altivelis (Serranidae), the Barramundi Cod, from Heron Island (southern Great Barrier Reef) and Lizard Island (northern Great Barrier Reef). This new species differs from Pearsonellum corventum (type and only species) in the combination of smaller overall body size, the relative distance of the brain from the anterior end, the relative lengths of both the oesophagus and the testis, the degree to which the testis extends outside the intercaecal field, the shape of the testis, the shape and size of the ovary and the extent to which the uterus loops around the ovary. There are in addition, 20 base pair differences between the ITS2 rDNA sequence of P. pygmaeus n. sp. and that of P. corventum. Three new host records for P. corventum are reported. Adelomyllos teenae n. g., n. sp. is described from Epinephelus coioides (Serranidae), the Estuary Cod, from Moreton Bay, southeast Queensland. The new genus differs from the 22 other sanguinicolid genera in the combined possession of two testes, a cirrus-sac, separate genital pores, a post-ovarian uterus and an H-shaped intestine. A. teenae n. sp. is the third sanguinicolid described from the Epinephelinae. Sanguinicolids have now been reported from 11 species of Serranidae.     

Littorellicola billhawkinsi n. gen., n. sp. (Digenea: Aporocotylidae) from the myocardial lacunae of Florida pompano, Trachinotus carolinus (Carangidae) in the Gulf of Mexico; with a comment on the interrelationships and functional morphology of intertrabecular aporocotylids

Littorellicola billhawkinsi n. gen., n. sp. infects the myocardial lacunae of the ventricle and atrium of Florida pompano, Trachinotus carolinus in the northern Gulf of Mexico. It differs from other aporocotylid genera by the combination of having a body 10–30× longer than wide, a posterolateral body protuberance, lateral spine rows, an aspinous anterior sucker comprising a slightly muscular rim circumscribing the mouth, asymmetrical posterior ceca 14–20× length of the anterior ceca and lacking diverticula or secondary rami, tens of testes distributing in a cobblestone-like field anterior and posterior to the distal ends of the posterior ceca, an oviducal seminal receptacle comprising the distal portion of the oviduct, and a post-cecal ovary plus by lacking rosethorn-shaped spines, a pharynx, and a Laurer's canal. The new species appears host specific to Florida pompano because no conspecific infection was detected in 134 carangids of 8 species in 4 genera captured nearby the type locality. Psettarium sebastodorum Holmes, 1971 is transferred to the new genus, as Littorellicola sebastodorum (Holmes, 1971) n. comb., because it and the new species differ from species of Psettarium by the combination of having multiple testes plus 8 other features detailed herein. This report brings the number of nominal Gulf of Mexico aporocotylids to 12 species of 8 genera, represents only the second record of an aporocotylid from a carangid there, and supports the notion that elongated, “thread-like” aporocotylids with lateral spine rows are seemingly well-adapted for infecting myocardial lacunae or embedding in the myocardium of their definitive fish hosts.