Tissue effect on RNA:DNA ratios of marine fish larvae

Abstract

SUMMARY:In some routine studies of larval condition based on RNA:DNA ratios, heads and/or guts are removed for further age and feeding analysis. Also, during capture larvae are often found with their eyes missing. In this work we analysed tissues effects (muscle, head, eye, gut and the whole larvae) on RNA:DNA ratios from different species (Sardina pilchardus, Engraulis encrasicolus, Atherina presbyter and Paralichthys orbignyanus) in different developmental stages and from different locations. For all species and development phases, it was shown that RNA:DNA ratios in the head were significantly lower than in muscle or gut. The comparison of RNA:DNA ratios of head with or without eyes did not show significant differences. In a comparison of results from muscle from two tail sections, RNA:DNA ratios were higher for the anterior section in Sardina pilchardus and Engraulis encrasicolus larvae. Caution is needed when RNA:DNA ratios are compared with other studies employing different dissection protocols. For the species studied we propose conversion factors to be applied to RNA:DNA ratio data when different body sections are analysed. We discuss the most appropriate tissues for assessing nutritional condition in fish larvae, based on trends in concentrations of nucleic acids and ratios during starvation experiments.Keywords: RNA:DNA, tissues, starvation, condition, Sardina pilchardus, Engraulis encrasicolus, Atherina presbyter, Paralichthys orbignyanus. RESUMEN: Efecto del tipo de tejido sobre los cocientes ARN:ADN en larvas de peces marinos. -En estudios de condición nutricional larvaria basados en la relación ARN:ADN, las cabezas y/o tubos digestivos suelen diseccionarse para posteriores estudios de edad o alimentación. Además, durante la captura algunas larvas pierden los ojos. En este trabajo analizamos el efecto de diferentes tejidos (músculo, cabeza, ojos y tubo digestivo) sobre la relación ARN:ADN en Sardina pilchardus, Engraulis encrasicolus, Atherina presbyter y Paralichthys orbignyanus, en diferentes estadios de desarrollo y en diversas regiones. En todas las especies la relación ARN:ADN en la cabeza fue significativamente menor que para el músculo o el tubo digestivo. La comparación de la relación ARN:ADN de la cabeza con o sin ojos no mostró diferencias significativas. Al comparar dos secciones de músculo de la cola en Sardina pilchardus y Engraulis encrasicolus se observó mayor ARN:ADN en la parte anterior que en la posterior. Es necesaria precaución cuando se comparan ARN:ADN entre estudios que emplean diferentes protocolos de disección. Proponemos factores de conversión para ser aplicados a las relaciones ARN:ADN cuando se analizan diferentes secciones del cuerpo. Se discute cuales son los tejidos más apropiados para determinar la condición nutricional de larvas de peces, basados en las concentraciones de ácidos nucleicos y sus cocientes obtenidos en experimentos de inanición.

Ontogenetic changes in DNA and RNA content of laboratory-reared Prochilodus lineatus larvae: use of RNA/DNA ratios as indicators of nutritional condition

“…A remarkable result of the present study is that the RDR values recorded were generally lower than those reported in the literature for marine fish larvae, which typically range between 1.0 and 3.0 (Ferron and Leggett 1994). Even fed larvae had median RDR values ,1.0 in the first part of the experiment, although the DNA and RNA content was similar to that of other species of larvae at similar developmental stages (Gwak et al 2003;Tanaka et al 2008;Olivar et al 2009). The reduced RDR value in P. lineatus larvae is consistent with the conclusions of Houde and Zastrow (1993) in that, on average, larger eggs in freshwater species confer certain resistance to starvation to their larvae, which probably could also be linked to a lower metabolism compared with marine fish larvae.…”

“…Standard length (SL) was measured to the nearest 0.01 mm using a Carl Zeiss stereoscope equipped with Axio Vision software (Carl Zeiss, Oberkochen, Germany). The head was dissected according to Olivar et al (2009). Muscular trunks were placed individually in Eppendorf tubes and freeze dried over a period of 24 h. Larvae were weighed (dry weight, DW) using a Sartorius microbalance (Sartorius AG, Goettingen, Germany) to the nearest microgram and stored at À808C until analyses were performed.…”

Swimming Abilities of Temperate Pelagic Fish Larvae Prove that They May Control Their Dispersion in Coastal Areas

“…Nucleic acid-derived indices (RNA, DNA, sRD) showed a tendency to decrease with larval development (size and age), and consequently with swimming performance (U crit and endurance). This is a common phenomenon [19,33,47] since growth depends on the increase in cell size (hypertrophy), which reduces the concentration of nucleic acids in the amount of tissue [64]. Therefore, we used the RNA residual-based index and protein content to circumvent the effect of growth [49].…”

RNA:DNA ratios as a proxy of egg production rates of Acartia

“…The RNA:DNA ratio analysis is based on the fact that DNA content per somatic cell is assumed to be constant in mature adults, therefore this index translates the protein synthetic capacity, once that RNA is needed for the protein synthesis reflecting the growth condition (Bulow, 1987). This technique measures the total amount of nucleic acids of the entire organism or it can be applied to specific tissues of the organism (Olivar et al, 2009). Nucleic acid M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 derived indices of growth and condition have been used in recent decades in several marine organisms such as fish, bivalves, cephalopods and crustaceans (e.g.…”