Allometric growth patterns and development in larvae and juveniles of thick-lipped grey mullet Chelon labrosus reared in mesocosm conditions

Allometric growth and ontogeny were studied in thick-lipped grey mullet Chelon labrosus reared in mesocosms from 1 to 71 day post hatching (dph). Multivariate allometric analysis of morphometric growth distinguished three distinct developmental stanzas separated by two morphometric metamorphosis lengths (L-m1=4.46 +/- 0.06mm; L-m2= 28.56 +/- 1.04mm). Body mass growth also showed three distinct episodes separated by two inflections, correlated with morpho-functional changes. First episode concerned pre-flexion larvae and ended around 4.5mm-L-T (14-dph), coinciding with estimated L-m1. It was distinguished by reduced growth, but intense morphogenesis and differentiation processes. Organogenesis and allometric changes indicated that development priorities concerned feeding efficiency, by improving detection ability (sensory system development), ingestion capacity (head growth) and assimilation performance (digestive system differentiation), together with respiration efficiency (gill development). Second episode concerned post-flexion larvae and, ended around 8.6mm-L-T (25-dph). It was distinguished by fast growth of trunk and tail, acquisition of adult axial muscle distribution and completion of gill filament development, improving locomotion and oxygenation performances. It corresponded to transition towards metamorphosing stage as indicated by later isometric growth, musculature maturation and acquisition of juvenile phenotype. Metamorphosis seemed to end at L-m2, suggesting to avoid zootechnic handling before this size

Comparison of growth, digestive system maturation and skeletal development in sea bass larvae reared in an intensive or a mesocosm system

The quality of development in intensive or mesocosm hatchery-reared Dicentrarchus labrax larvae was investigated using physiological indicators assessing ontogeny. Larvae were reared in intensive (120 L tanks) and in mesocosm systems (20 m(3) enclosures) with the same feeding sequence, excluding the wild zooplankton naturally available in mesocosms. Faster growth was recorded since early development [16 day after hatching (DAH)] in the mesocosm. Maturation of the digestive system also occurred earlier as indicated by the higher amylase secretion ratios, the intestinal maturation index (alkaline phosphatase/leucine-alanine peptidase and aminopeptidase-N/leucine-alanine peptidase ratios) and the more developed intestinal epithelium at 23 DAH. Nevertheless, the delay in digestive maturation in the intensive system seemed retrieved within few days. In both the groups, the number of vertebrae ranged between 24 and 26, with the dominant class being 25 vertebrae. However, the distributions differed between treatments for meristic characteristics, ossification stages and incidence of malformation types. Loss of a vertebra was more frequent in the intensive system, while the appearance of an additional vertebra was more frequent in the mesocosm. Ossification at 37 DAH was also more advanced in the mesocosm in addition to a lesser rate and severity of skeletal malformations. It is suggested that the early nutritional contribution of mesocosm wild zooplankton, yet at densities of 0.2-0.7 prey mL(-1), had key effects on larvae development since the early stages

ZZ domain of dystrophin and utrophin: topology and mapping of a β-dystroglycan interaction site

Dystrophin forms part of a vital link between actin cytoskeleton and extracellular matrix via the transmembrane adhesion receptor dystroglycan. Dystrophin and its autosomal homologue utrophin interact with β-dystroglycan via their highly conserved C-terminal cysteine-rich regions, comprising the WW domain (protein–protein interaction domain containing two conserved tryptophan residues), EF hand and ZZ domains. The EF hand region stabilizes the WW domain providing the main interaction site between dystrophin or utrophin and dystroglycan. The ZZ domain, containing a predicted zinc finger motif, stabilizes the WW and EF hand domains and strengthens the overall interaction between dystrophin or utrophin and β-dystroglycan. Using bacterially expressed ZZ domain, we demonstrate a conformational effect of zinc binding to the ZZ domain, and identify two zinc-binding regions within the ZZ domain by SPOTs overlay assays. Epitope mapping of the dystrophin ZZ domain was carried out with new monoclonal antibodies by ELISA, overlay assay and immunohistochemistry. One monoclonal antibody defined a discrete region of the ZZ domain that interacts with β-dystroglycan. The epitope was localized to the conformationally sensitive second zinc-binding site in the ZZ domain. Our results suggest that residues 3326–3332 of dystrophin form a crucial part of the contact region between dystrophin and β-dystroglycan and provide new insight into ZZ domain organization and function