A pinboard by
Phillip Dettleff

Postdoc, University of Chile


The Yellowtail kingfish (Seriola lalandi) is a native fish of Chile and one of the key species for the diversification of the Chilean aquaculture. In this sense, the genetic variability across populations is required in order to establish a sustainable breeding program. Paternity assignment is a key issue when implementing breeding programs in this species. The objectives of this work were: (i) identify the population structure of the wild and commercial population of S. lalandi of several countries and (ii) study the reproductive behavior of commercial broodstock through a paternity testing, considering the communal spawning behavior if this species. We used a set of molecular markers to genotype group of wild S. lalandi of different locations join to four sets of commercial broodstock and larvae generated from different spawning during the reproductive season. The parentage analysis allows establishing some important knowledge related to the reproductive behavior of this species, including average relation male/female contributing in a spawning event and difference in the contribution of each sex during the reproductive season. The population structure analysis showed that exist several populations of this species worldwide, with an admixture of two population observed in the Chilean coast. This study provides useful genetic information to be implemented for the long-term development of the Chilean Yellowtail kingfish industry. In this sense, the knowledge generated in my research is being incorporated to the national program of diversification of Chilean aquaculture for Seriola lalandi, with the objective to increase the production of this species and preserve the wild populations of this species.


Growth differentiation factor 9 and bone morphogenetic protein 15 expression in previtellogenic oocytes and during early embryonic development of Yellow-tail Kingfish Seriola lalandi.

Abstract: During fish oocyte maturation, specific molecules are expressed and accumulated within oocyte until fertilization and embryo development. Special attention have been paid in members of the transforming growth factor (TGF-β) superfamily; growth differentiation factor 9 (GDF9/gdf9) and bone morphogenetic protein 15 (BMP15/bmp15), which exert regulatory functions during oocyte maturation and follicle development. However, little attention has been paid to the involvement of these molecules during embryogenesis considering its importance for the formation of a good quality egg and subsequent embryo survival. The purpose of this study was to analyze the expression of gdf9 and bmp15 in previtellogenic oocytes and during early embryonic development in Seriola lalandi, a pelagic fish with increasing prospect for its aquaculture development, which however, show high mortality at embryo and larval stages.Through RT-qPCR it was found that gdf9 expression was higher in previtellogenic oocytes decreasing after ovulation. This expression profile agrees with its participation in early stages of the follicular development. The transcripts for bmp15 also showed the highest levels in previtellogenic oocytes, however this expression was lower than obtained with gdf9. Conversely, in recently spawned oocytes mRNA bmp15 levels were highest than observed to gdf9. This, is consequent with the main role proposed for this growth factor at the final fish oocyte maturation: avoid the ovulation of an immature oocyte. During embryo development, low levels of mRNA were detected to gdf9, with an increase in 48 H post-fertilization embryos. The bmp15 expression did not change throughout development and was higher than gdf9 at 16 cells, blastula and appearance embryos stages.Both (gdf9 and bmp15) expression profiles in previtellogenic oocytes and newly spawned eggs are consistent with the described functions for these growth factors in vertebrate ovarian physiology in early and late stages of the follicular development. So, these genes could be considered as quality biomarkers at these stages. However, further studies of these proteins throughout folliculogenesis, are necessaries to fully understand their functions during the oocyte formation. In addition, the persistent expression of these growth factors during development, allows us to speculate possible roles in embryonic processes, which must also be addressed.

Pub.: 28 Feb '15, Pinned: 04 Jan '18

A comprehensive transcriptome of early development in yellowtail kingfish (Seriola lalandi).

Abstract: Seriola lalandi is an ecologically and economically important species that is globally distributed in temperate and subtropical marine waters. The aim of this study was to identify large numbers of genic single nucleotide polymorphisms (SNPs) and differential gene expression (DGE) related to the early development of normal and deformed S. lalandi larvae using high-throughput RNA-seq data. A de novo assembly of reads generated 40 066 genes ranging from 300 bases to 64 799 bases with an N90 of 788 bases. Homology search and protein signature recognition assigned gene ontology (GO) terms to a total of 15 744 (39.34%) genes. A search against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) retrieved 6808 KEGG orthology (KO) identifiers for 10 520 genes (26.25%), and mapping of KO identifiers generated 337 KEGG pathways. Comparisons of annotated genes revealed that 1262 genes were downregulated and 1047 genes were upregulated in the deformed larvae group compared to the normal group of larvae. Additionally, we identified 6989 high-quality SNPs from the assembled transcriptome. These putative SNPs contain 4415 transitions and 2574 transversions, which will be useful for further ecological studies of S. lalandi. This is the first study to use a global transcriptomic approach in S. lalandi, and the resources generated can be used further for investigation of gene expression of marine teleosts to investigate larval developmental biology. The results of the GO enrichment analysis highlight the crucial role of the extracellular matrix in normal skeleton development, which could be important for future studies of skeletal deformities in S. lalandi and other marine species.

Pub.: 01 Aug '15, Pinned: 04 Jan '18

Assessment of cathepsin mRNA expression and enzymatic activity during early embryonic development in the yellowtail kingfish Seriola lalandi.

Abstract: In pelagic species such as Seriola lalandi, survival of both the eggs and embryos depends on yolk processing during oocyte maturation and embryo development. The main enzymes involved in these processes are the cathepsins, which are essential for the hydration process, acquiring buoyancy and nutrition of the embryo before hatching. This study aimed to investigate the mRNA expression profiles of cathepsins B, D and L (catb, catd and catl) and the activity of these enzymes during early development in S. lalandi. We included previtellogenic oocytes (PO). All three enzymes were highly expressed in PO, but the expression was reduced throughout development. Between PO and recently spawned eggs (E1) the transcript to catb and catd decreased, unlike catl. Cathepsin B activity, showed stable levels between PO until blastula stage (E4). High activities levels of cathepsins D and L were observed in E1 in comparison with later developmental stages. Cathepsin L activity remained constant until E1, consistent with observations in other pelagic spawners, where its participation in a second protolithic cleavage of the yolk proteins, has been proposed for this enzyme. Their profiles of both mRNA expression and enzymatic activity indicate the importance of these enzymes during early development and suggest different roles in egg yolk processing for the hydration process and nutrition in early embryos in this species.

Pub.: 07 Mar '17, Pinned: 04 Jan '18

Making sense of nonsense: Using regression analysis to deal with highly variable data collected from a yellowtail kingfish (Seriola lalandi) digestibility experiment

Abstract: Publication date: 2 February 2018 Source:Aquaculture, Volume 485 Author(s): Mark Booth, Igor Pirozzi When conducting digestibility experiments with fish many researchers encounter problems that result in erroneous digestibility coefficients. Erroneous digestibility coefficients result from variability in the raw data which is amplified by the formulae used to calculate them. Variation can stem from natural differences in the digestibility of the same diet between individuals or groups of fish. It can also creep insidiously into studies due to poor preparation and mixing of ingredients or problems with the collection of faecal material or the veracity of analytical results. Therefore, it is fairly common to expect variability in data collected from digestibility trials with fish. But what can be done about it' In this paper, we present an experiment with yellowtail kingfish (Seriola lalandi) that was done to determine whether the digestibility of extruded wheat (EW) was affected by its inclusion rate (10, 20, 30 or 40% diet−1). The experiment, based on the indicator–ratio method, was conducted without incident, but the raw data on the nutrient and marker concentration of faecal samples was variable. We dealt with this problem by using linear regression to estimate more reliable analytical values for faecal samples. These values were used to recalculate logical digestibility coefficients for EW. Using this approach, we show that dry matter (≈57%–40%), carbohydrate (≈48%–27%) and gross energy (57–42%) digestibility of EW decline as its inclusion rate rises, whereas the digestibility of protein (≈84%) and the digestibility of fat (≈94%), remain reasonably constant. We validated the regression approach applied to yellowtail kingfish by examining published data from a similar digestibility experiment on Australian snapper Pagrus auratus. A regression approach was useful in reducing the variability in our raw data because the design of our experiment approximated a dose-response relationship. Designing digestibility experiments using a dose-response approach may prove useful in overcoming the inherent variability often encountered in these types of experiments.

Pub.: 15 Nov '17, Pinned: 04 Jan '18