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Markers for Atlantic halibut metamorphosis

Flatfish species such as halibut, turbot and sole form a major focus of the diversification of European aquaculture industry. However, production has been severely hampered by biological problems in larval rearing. In the case of flatfish this is frequently associated with failed metamorphosis.The identification of reliable markers which can act as indices of flatfish metamorphosis progression implies that the markers identified should differentiate between normal and abnormal metamorphosis.

Putative candidate markers have been identified and defined as molecular or morphological indicators which changed between the pre-metamorphic larvae (stage 8) and post-metamorphic juveniles (stage 10). Useful markers for metamorphosis should be those which differentiate life-stages and are diagnostic of normal and abnormal metamorphosis. Numerous markers have been identified during ARRDE which change during metamorphosis in Atlantic halibut: Musculo-skeletal system - Markers for metamophosis:- YES (MLC1, 2 and 3, fTnT); Invasive:- YES (larvae have to be killed), Candidate indicators of normal/abnormal metamophosis:- YES (efTnT but further validation required). Skeletal system - Markers for metamophosis:- YES; Invasive:- NO (live animal can be assessed);
Candidate indicators of normal/abnormal metamophosis:- YES (Abnormal stage 8 fish abnormal remodelling of the frontals shows bilaterally equal activity of the osteoclasts. In abnormal stage 9 fish the sinistral eye has not migrated, the frontals are symmetrical and there is equal lateral osteoclastic activity in the frontal processes). Gastrointestinal system - Markers for metamophosis:- YES (pepsinogen and trypsin); Invasive:- YES (larvae have to be killed); Candidate indicators of normal/abnormal metamophosis:- YES (further validation of the use of pepsin and trypsin required, but they are significantly different in normal and abnormal stg, 8, 9 and 10 halibut). Skin - Markers for metamophosis:- YES (epidermal keratin); Invasive: YES (larvae have to be killed); Candidate indicators of normal/abnormal metamophosis: Unlikely to be useful marker of normal/abnormal metamorphosis. Blood - Markers for metamophosis:- YES; Invasive:- YES (larvae have to be killed); Candidate indicators of normal/abnormal metamophosis:- No information is available from abnormal larvae.

It is expected that markers will be aplicable to flatfish in general but requires further testing. Markers which are diagnostic of abnormal metamorphosis of flatfish are difficult to encounter and substantial validation of their potential use is still required.
The generation of a tool to improve, quality, health and predictability of fish larval production have important implications on improving sustainability of aquaculture which is frequently located in rural areas with limited employment opportunities. Aquaculture represents a sustainable and probably the only means of generating high quality fish available to all Europeans with its recognised beneficial impact on health.

Related information

Reported by

Universidade do Algarve
Centro de Ciencias de Mar
8000-810 Faro
Portugal
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