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NO53 - 4

Inheritance of the Resistant Trait in Goldfish against Herpesviral Hematopoietic Necrosis

Mikio Tanaka1*, Keitaro Dairiki1, Mayuri Nakajima2, Goshi Kato2, Takashi Sakamoto2 and Motohiko Sano2

1Saitama Fisheries Research Institute, Saitama 347-0011, Japan
2Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan

(Received April 27, 2018)

ABSTRACT--It was reported that progeny from the parents of goldfish Carassius auratus which had survived in herpesviral hematopoietic necrosis (HVHN) increased resistance against the disease, and consequently a resistant strain of Azumanishiki variety has been established in Saitama Fisheries Research Institute. In this study, we started breeding between the resistant Azumanishiki variety and a susceptible Kurodemekin variety and investigated the heredity of the resistant trait in the offspring in order to establish a new resistant strain of Kurodemekin. F1 bred between resistant Azumanishiki and Kurodemekin showed resistance in the challenge test with the causative virus (cyprinid herpesvirus 2), but F1 had no pop-eyed character. Crosses between F1 survivors in virus challenge produced F2, and about 25% of F2 showed pop eyes. We finally obtained the resistant pop-eyed Kurodemekin of F3 crossed between pop-eyed F2 survivors in virus challenge. Backcrosses between F1 survivors and Kurodemekin were also tested for the resistance in virus challenge. The mortality rates of F1, F2, F3 and the backcrosses in virus challenge suggested that the resistant trait against HVHN in the goldfish linage exhibited a Mendelian dominant inheritance pattern.

Key words: inheritance, disease resistance, herpesviral hematopoietic necrosis, cyprinid herpesvirus 2, Carassius auratus, breeding, goldfish

Distinction of the Skin Flukes Benedenia seriolae and Neobenedenia girellae Infecting Seriola spp. by PCR-RFLP Assay

Keigo Kobayshi1, Germaine Lau Gek Khin1, Sho Shirakashi2, Yusuke Mukai3, Yukitaka Sugihara4, Soetsu Yanagi5, Ikuo Hirono1 and Hidehiro Kondo1*

1Laboratory of Genome Science, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan
2Aquaculture Research Institute, Kindai University, Wakayama 649-2211, Japan
3Nagasaki Prefectural Institute of Fisheries, Nagasaki 851-2213, Japan
4Tsushima District Fisheries Extension Advisory Center, Nagasaki Prefectural Institute of Fisheries, Nagasaki 817-0324, Japan
5Kagoshima Prefectural Fisheries Technology and Development Center, Kagoshima 891-0315, Japan

(Received February 19, 2018)

ABSTRACT--We developed a PCR-RFLP method to distinguish Benedenia seriolae and Neobenedenia girellae, both infecting amberjacks Seriola spp. more precisely than a morphological method. PCR products of 28S rRNA and COX1 were digested by Cla I and EcoR I, respectively. For all individuals of B. seriolae, the digestions split each of the PCR products into two fragments. On the other hand, although the products of most of the N. girellae samples were digested by neither the enzymes, only PCR products of 28S rRNA gene of three of the individuals were split into three fragments, suggesting they were the hybrid between the two species.

Key words: capsalid, monogenea, PCR-RFLP, Seriola spp., skin fluke

In Vitro Biofilm Formation of Flavobacterium psychrophilum

Anna Papadopoulou* and Tom Wiklund

Laboratory of Aquatic Pathobiology, Environmental and Marine Biology, Åbo Akademi University, FI-20520, Turku, Finland

(Received April 27, 2018)

ABSTRACT--The fish pathogen Flavobacterium psychrophilum has been shown to occur in two colony phenotypes, rough and smooth. The aim of this study was to examine the effect of environmental and nutritional factors on the biofilm formation of both phenotypes under in vitro static conditions. The present study revealed that smooth cells displayed higher abilities of biofilm formation compared to rough cells in nutrient-rich media (TYES broth and fish feed) under static conditions, while biofilms formed by cells of both phenotypes were mainly Ca2+ dependent than Mg2+. Neither of the colony phenotypes was able to form biofilms in the low-nutrient medium (lake water) within 5 days.

Key words: biofilms, fish feed, Flavobacterium psychrophilum, phenotypes

The Digenean Clinostomum complanatum Found from Great Cormorant Phalacrocorax carbo in Japan

Takashi Iwaki1*, Tsukasa Waki1, Jumpei Arakawa2 and Kazuo Ogawa1

1Meguro Parasitological Museum, Tokyo 153-0064, Japan
2Yatomi Station, Aichi Fisheries Research Institute, Aichi 498-0017, Japan

(Received July 10, 2018)

ABSTRACT--Great cormorants Phalacrocorax carbo were found dead in a goldfish farm in Aichi Prefecture. They were infected with trematodes in the oral cavity. Based on morphological observation and genetic analysis, the trematodes were identified as Clinostomum complanatum. This is the first case reporting C. complanatum infection of great cormorants in Japan. Heavy metacercarial infection of goldfish was found in the same fish farm. The metacercariae were shown to be the same species as the adult worms from the bird by molecular analysis. These results suggest that great cormorant is involved in the life cycle of this trematode in farmed goldfish.

Key words: Clinostomum complanatum, Phalacrocorax carbo, Digenea, goldfish, life cycle