Challenge of New Zealand Greenshell™ mussel Perna canaliculus larvae using two Vibrio pathogens: a hatchery study

Abstract

Bacterial diseases remain a large problem in aquaculture hatcheries. The successful design and implementation of protective measures in the hatchery depends on an understanding of the dynamics of the infection process. Developing an in situ experimental protocol for pathogen challenge is therefore of paramount importance. Here, we demonstrated the minimum effective pathogenic dose (MEPD) of Vibrio splendidus (10 5 CFU ml -1) and a Vibrio coralliilyticus/neptunius-like isolate, Vibrio sp. DO1 (10 6 CFU ml -1), for New Zealand Greenshell™ mussel (GSM, Perna canaliculus) larvae during hatchery production. In a flow-through water hatchery system, larvae given 1 to 2 h of static water exposure to these pathogen doses showed respective average cumulative mortalities of 58 and 69% on the fourth day following pathogen exposure. After the 1 to 2 h static exposure, larvae were returned to flow-through water. Larvae exposed to a dosage one order of magnitude greater than the MEPD had higher mortalities of 73 and 96% for V. splendidus and Vibrio sp. DO1 respectively. These 4 levels of mortality were significantly greater than those of the non-exposed control larvae which respectively averaged 23 and 35% in experiments involving V. splendidus and Vibrio sp. DO1. Experiments were repeated 4 times to confirm reproducibility. After pathogen exposure, pathogens were detected in the larvae and tank water of treatments with dosages of ≥10 5 CFU ml -1 (V. splendidus) and 10 6 CFU ml -1 (Vibrio sp. DO1), but not in treatments with lower pathogen dosages. The challenge protocols are reproducible and provide an opportunity to assess measures for the protection of GSM larvae against infection in the hatchery environment. KEY WORDS: Vibriosis · Challenge protocol · Greenshell™ mussel · Larviculture Resale or republication not permitted without written consent of the publisherDis Aquat Org 86: [15][16][17][18][19][20] 2009 vided and a milieu of ambient microflora is present. In order to understand the dynamics and facilitate effective management of microbial infections occurring at a hatchery facility, it is necessary to have an understanding of the conditions that initiate infection.Many studies have previously demonstrated experimental infections of aquatic animals: shrimp (Roque et al. 1998, Soto-Rodríguez et al. 2006, fish (Bergh et al. 1997, Itano et al. 2006) and molluscs (Sainz et al. 1998, Estes et al. 2004, Gay et al. 2004. Currently, there is a lack of literature on infection models under hatchery conditions, although Planas et al. (2005) developed an infection model under hatchery conditions where static water rather than flow-through systems prevailed. Likewise, there are few reports on infection models in flow-through water systems. Arkush et al. (2005) described an infection model in white seabass incorporating flow-through water and intraperitoneal injection of the pathogen; however, this method of administration is not possible with GSM larvae. Additionally, both Nordmo et al. (1997) and Itano et al. (2006) u...

Vibrios in hatchery cultures of the razor clam, Solen marginatus (Pulteney)

“…; Kesarcodi‐Watson et al . ). In only 6 days, these strains became dominant in larvae and sea water, and this status was maintained until the collapse of batch B .…”

“…; Kesarcodi‐Watson et al . ). These studies reported the disease in a wide range of bivalve species, including oysters ( Ostrea , Crassostrea ), clams ( Mercenaria , Venerupis , Panope ), scallops ( Pecten , Argopecten ) and mussels ( Perna ).…”

New Vibrio species associated to molluscan microbiota: a review

“…The work of Prado and co-workers constituted the first description of V. neptunius as a molluscan pathogen. Later studies with New Zealand Greenshell mussel ( Perna canaliculus ) larvae confirmed the pathogenic potential for other molluscan species (Kesarcodi-Watson et al, 2009a,b). …”

Bacterial diseases in marine bivalves

“…Initially described in association with diseased corals (Vezzulli et al, 2010), V. coralliilyticus was isolated from mortality episodes of Greenshell mussels (Kesarcodi-Watson et al, 2009a) and oysters (Hada et al, 1984), and was shown to be virulent to larval stages of those species (Kesarcodi-Watson et al, 2009b;Genard et al, 2013).…”

“…These include irregular movements, detachment of cilia, aggregation of bacteria around the velum and deterioration of soft tissues (Kesarcodi-Watson et al, 2009a) (Figure 3,Table 1). V. coralliilyticus exposure resulted in reduced feeding activity of oyster larvae, fatty acid remodeling of polar lipids, activation of defenses (antioxidant and immune defenses)(Genard et al, 2013) and larval bivalve mortality(Kesarcodi-Watson et al, 2009a;Kesarcodi-Watson et al, 2009b;Genard et al, 2013;Mersni Achour et al, 2015).…”