Improved Health in Arctic Charr Farming
Some Icelandic Arctic charr (Salvelinus alpinus) farming facilities are increasingly confronted with outbreaks of atypical furunculosis – a disease caused by bacteria – that occurs despite the vaccination of the fish. The farmed fish have undergone selective breeding since 1992 for increased body mass and delayed sexual maturation, but bacterial resistance or disease tolerance have not yet been included in the breeding goals.
The project will test whether variation in load with the bacteria that cause furunculosis (Aeromonas salmonicida) in fish that grew under standard farming conditions can be quantified using a targeted genotyping assay (GT-seq). The GT-seq is targeted at both fish and bacterial sequences to determine a bacterial cell count standardised to fish cell counts. This method may be a non-invasive alternative to the conventional but cruel challenge tests in which fish get advertently infected with an agent that causes a deadly disease and mortality variation is recorded. If GT-seq is reliably allowing for determination of bacterial load variation (preliminary tests show it may, but the sampled fish still have to show variation), we will apply genomic selection for increased bacterial resistance in the brood stock, which are the siblings of the farmed fish, with the goal to reduce furunculosis in the Icelandic aquaculture production.
We now obtained GT-seq results on individual bacterial load. The results indicate that some individuals had a high bacterial load (even though they appeared healthy) whereas most had either low, very low, or no bacterial load. Now, we are re-running the assay with a modified protocol because the resolution of bacterial load at the lower end appeared, unfortunately, too low to reliably estimate among family variation. We are hoping that an increased assay sensitivity may increase the resolution.
This project is funded by the Icelandic government (via Matvælasjóður) and conducted in collaboration with Theodór Kristjánsson from the Icelandic Marine and Freshwater Research Institute, Hafnarfjörður, Iceland, and Einar Svavarsson, the breeding programme manager in Hólar, Iceland, and several Icelandic farming companies.
Sex Difference in Spider Body Size Architecture
Sexual size dimorphism occurs when individuals from one sex are larger than those from the other sex. In many species, including spiders, the female is larger then the male. It is commonly assumed that larger females may produce more or better offspring but that smaller males may be better at other tasks. In spiders, this may be adventuring towards female spider webs. In the African hermit spider (Nephilingis cruentata) males that successfully found a female, will often wait in her web until her final moult and only then can they copulate (if they are not eaten by her). The females are around 80 times heavier than the males. How can such a large size difference emerge and how would it be possible to remain adaptive towards possibly dynamic sex-specific size optima when both sexes share common genes (a so-called intralocus sexual conflict)?
The project exploits size data of many generations of pedigreed laboratory-reared spiders to test whether the architecture of body size differs between the sexes, which would resolve the intra-locus sexual conflict. The results indicate that male adult body size underlies predominantly maternal effects but that female adult body size underlies predominantly direct genetic effects. This suggests a surprising architecture of male body size but also how intra-locus sexual conflict may be resolved in this spider with extreme female-biased sexual size dimorphism.
The pre-print of this work can be found here on bioRxiv.
This Slovenian Research Agency-funded project is led by Simona Kralj-Fišer from the Scientific Research Centre of the Slovenian Academy of Sciences and Arts, Ig, Slovenia, where the spiders are kept and data are recorded, and is conducted in collaboration with Matjaž Kuntner from the National Institute of Biology, Ljubljana, Slovenia.
Feasibility of a Nigerian Selective Breeding Programme for African Catfish
Although the sturdy African catfish (Clarias gariepinus) is commonly farmed in many Asian and African countries, we do not know of any successful breeding programme in this species. In Nigeria, the African catfish is one of the commonest aquaculture species and many small-scale fish farmers would profit from fish with selectively improved suitability for aquaculture. This project investigates the requirements and conditions necessary to start a breeding programme (but will not directly initiate one) to increase the likelihood of success for a potential future breeding programme.
The project was conducted within the UNESCO GRÓ FTP programme by Ibukunoluwa Akintayo from the Nigerian Institute for Oceanography and Marine Research.
The report should soon become available at https://www.grocentre.is/ftp/media-ftp/publication.