Evaluation of an improved RNA/DNA quantification method in a common carp (Cyprinus carpio Linnaeus 1758) larval feeding trial with Artemia, two nematodes (Panagrellus redivivus Linnaeus 1758, Panagrolaimus sp. Fuchs 1930) and dry feed. (14th March 2015)

• Record Type: Journal Article
• Authors: Tillner, R.; Assheuer, T.; Rennert, B.; Trubiroha, A.; Clemmesen, C.; Wuertz, S.
• Is Part Of: Journal of applied ichthyology. Volume 31:Number 3(2015:Jun.)
• Page Start: 466
• Page End: 473
• Publication Date: 2015-03-14
• Subjects: Fishes -- Periodicals; Fish culture -- Periodicals; Fisheries -- Periodicals; Ichthyology -- Periodicals; 597
• DOI: 10.1111/jai.12715
• Languages: English
• ISSNs: 0175-8659

Abstract

Summary: The RNA/DNA ratio commonly used as proxy for the nutritional condition of fish larvae is affected by RNA degradation during analysis. For evaluation of two strategies to improve RNA integrity, a three‐week feeding trial was carried out to assess the suitability of two nematode species (fam. Panagrolaimidae ) as feed for newly hatched carp larvae ( Cyprinus carpio ) in comparison to Artemia nauplii ( Artemia sp.) and a commercial dry feed. Aiming for an increased reproducibility of RNA/DNA determination, a high‐salt inactivation (RNA later) as well as a targeted approach with a recombinant RNase inhibitor were compared to the classical protocol using lab chip technology. Improved RNA integrity was observed with high‐salt inactivation when compared with a strategy applying a specific RNase inhibitor or the classic protocol. Carp larvae fed Artemia for 2 weeks and then dry feed for 1 week revealed the best overall growth performance as well as survival [83.0 ± 35.2 mg fresh weight (FW), 20.0 ± 2.4 mm total length (TL), 86.6 ± 11.7% survival]. Larvae fed the nematode species Panagrellus redivivus for 1 week and subsequently dry feed for 2 weeks (37.4 ± 29.1 mg FW, 14.7 ± 2.8 mm TL, 76.0 ± 6.0% survival) performed better than larvae fed with dry feed alone (28.2 ± 29.6 mg FW, 14.3 ± 2.9 mm TL, 54.3 ± 14.2% survival) or those receiving Panagrellus for 2 weeks. Between both nematode species, Panagrellus was a better feed with regard to growth performance and survival. RNA/DNA ratios ranged between 0.65 ± 0.27 (8 days post‐hatch) and 1.96 ± 0.63 (22 days post‐hatch) and were in the same treatment order as the other growth parameters. RNA/DNA ratios were significantly correlated with the growth rate, and decreasing RNA/DNA ratios in larger larvae may reflect decreasing growth rates with size rather than decreased nutritional status. Here, an improved RNA/DNA ratio protocol is presented in a feeding trial that reveals the suitability of nematodes as a first feed for common carp larvae.