Strain-related physiological and behavioral effects of Skeletonema marinoi on three common planktonic copepods

Abstract

Three strains of the chain-forming diatom Skeletonema marinoi, differing in their production of polyunsaturated aldehydes (PUA) and nutritional food components, were used in experiments on feeding, egg production, hatching success, pellet production, and behavior of three common planktonic copepods: Acartia tonsa, Pseudocalanus elongatus, and Temora longicornis. The three different diatom strains (9B, 1G, and 7J) induced widely different effects on Acartia tonsa physiology, and the 9B strain induced different effects for the three copepods. In contrast, different strains induced no or small alterations in the distribution, swimming behavior, and turning frequency of the copepods. 22:6(n-3) fatty acid (DHA) and sterol content of the diet typically showed a positive effect on either egg production (A. tonsa) or hatching success (P. elongatus), while other measured compounds (PUA, other long-chain polyunsaturated fatty acids) of the algae had no obvious effects. Our results demonstrate that differences between strains of a given diatom species can generate effects on copepod physiology, which are as large as those induced by different algae species or groups. This emphasizes the need to identify the specific characteristics of local diatoms together with the interacting effects of different mineral, biochemical, and toxic compounds and their potential implications on different copepod species.

Different Nutritional Histories Affect the Susceptibility of Algae to Grazing

“…This fits with the presence, in B. plicatilis, of chemoreceptive pores located in the anterior integument beneath the cingulum (Snell 1998). Contrarily to what was thought in the past (e.g., Boyd 1976), there is nowadays a general consensus on the ability of copepods to use chemical information for food selection, which is based on a good number of publications involving both calanoid and cyclopoid copepods (Poulet and Marsot 1978, Donaghay and Small 1979, Fernandez 1979, DeMott 1986, Ask et al 2006, Amin et al 2011, Rossoll et al 2012, Schoo et al 2013, Isari et al 2016.…”

Diatom‐produced allelochemicals trigger trophic cascades in the planktonic food web

“…For example, the ingestion rates of A. tonsa on slow‐growing cells of Thalassiosira weissflogii were enhanced by the addition of cell‐free aliquots of algal exudate from the fast growing cells (Cowles et al ). This copepod was able to locate patches of S. marinoi and T. weissflogii (Amin et al ; Tiselius et al ), possibly relying on chemical cues released by these diatoms. In the presence of PUA, ciliates were consumed two‐three times the rates in control and up to ten times faster than dinoflagellates.…”

Centropages typicus(Crustacea, Copepoda) reacts to volatile compounds produced by planktonic algae

“…The adaptive value of this behaviour and its ecological implications remain unexplained but it is known that Centropages typicus actively ingests this diatom, especially when it is abundant in the water column (Amin et al . ).…”

“…At the highest concentration used in the present study this alga became attractive (consistent with the conclusions reported by Barofsky et al 2010) possibly because of the effect of other odoriferous compounds that become 'interesting' at higher concentrations (Taylor et al 2009). The adaptive value of this behaviour and its ecological implications remain unexplained but it is known that Centropages typicus actively ingests this diatom, especially when it is abundant in the water column (Amin et al 2011).…”