Co-consumption and protective coating: two new proposed effects of epiphytes on their macroalgal hosts in mesograzer-epiphyte-host interactions

Abstract

Multiple-choice feeding experiments were performed with the isopod Idotea granulosa and the amphipod Gammarus locusta as consumers. In a first experiment, 2 different types of tissues of the brown seaweed Fucus vesiculosus and its main macroepiphytes, Ulva lactuca and Elachista fucicola, were offered. I. granulosa rejected apices of F. vesiculosus and preferred E. fucicola, while G. locusta clearly preferred F. vesiculosus tissue, especially the meristematic apices. In a second experiment, F. vesiculosus tissue with and without E. fucicola was offered together. For I. granulosa, the consumption of F. vesiculosus was enhanced by the presence of the epiphyte, while for G. locusta there was no difference in consumed F. vesiculosus mass. G. locusta, however, showed behavioural rejection of E. fucicola, and thus, the epiphyte acted as 'protective coating'. We conclude that host (F. vesiculosus) tissue could be 'co-consumed' by mesograzers ( I. granulosa) that were attracted by the presence of epiphytes and that these epiphytes therefore may have a 2-fold negative effect on the host (i.e. competion for light, nutrients etc. and attraction of consumers). 'Co-consumption' and 'protective coating' add 2 more facets to the very variable and case-dependent interrelationships of mesograzer-epiphyte-host systems; their relevance in nature, however, remains to be demonstrated.

Macroalgas varadas sobre la superficie de una playa arenosa del sur de Chile: preferencias alimentarias y de habitat de juveniles y adultos de Orchestoidea tuberculata (Nicolet), (Amphipoda, Talitridae)

“…La marcada diferencia en los patrones de preferencia de juveniles y adultos, demuestra la importancia de considerar la variabilidad intraespecífica de los organismos, en estudios de preferencias alimentarias (Sandlin & Willig 1993, Poore 1994, Pavia et al 1999. Aun cuando existe una variedad de trabajos que muestran que varios anfípodos revelan preferencias por distintos ítemes alimentarios (Karez et al 2000, Pennings et al 2000, Adin & Riera 2003, pocos estudios se han realizado para examinar eventuales diferencias intraespecíficas en la selección de la dieta (Salema 1987, Byrén et al 2006. Similar a los resultados de este trabajo, Pavia et al (1999), mostraron que mientras los adultos del anfípodo Gammarus locusta (Linnaeus, 1758) prefirieron los macroepífitos del alga parda Ascophyllum nodosum (Linnaeus) Le Jolis, los juveniles también se alimentaron de las partes meristemáticas de esa macroalga.…”

Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population

“…Our results clearly demonstrate that allelochemicals can protect both the producers as well as a non-producing conspecific against grazing. The observed facilitation by grazing protection might resemble associational resistance [56,57], described for terrestrial plant communities [58][59][60], as well as among macroalgal species and their epiphytes [61][62][63]. Such associational resistance may also occur in pelagic microalgae populations even at the intraspecific level, within assemblages of sufficiently high population densities.…”

Seasonal variability in the grazing potential of the invasive amphipod Gammarus tigrinus and the native amphipod Gammarus salinus (Amphipoda: Crustacea) in the northern Baltic Sea

“…However, this figure actually reflects a strong negative effect of G. tigrinus on G. salinus within P. littoralis. Following the increasing eutrophication the biomass of ephemeral algae especially P. littoralis have increased tremendously in the last decades and currently P. littoralis prevails in the northern Baltic Sea (Rönnberg et al 1992;Karez et al 2000;Kotta et al 2000;Lauringson and Kotta 2006). In concurrent with filamentous algal blooms the diversity of macroalgal species has significantly declined (Rönn-berg et al 1992;Kotta et al 2006).…”

“…Animals respond more strongly to the amount of available resource than the diversity of plants providing it (Parker et al 2001) suggesting that mesoherbivores have often broad diet and selectivity is rare (Cruz-Rivera and Hay 2001). There is some evidence that mesoherbivores may feed directly on perennial macrophytes (Poore 1994;Viejo 1999;Karez et al 2000). The majority of studies, however, indicate that mesoherbivores live within the bushes of perennial macrophytes and feed on the epiphytes attached to the host plant (Brawley and Adey 1981;D 0 Antonio 1985).…”

“…There exist many studies demonstrating that macrophyte communities affect the structure of associated fauna, especially mesoherbivore communities (Huntly 1991;Lawton 1994;Knowles and Bell 1998;Kotta and Orav 2001;Parker et al 2001). On the other hand, mesoherbivores are known to affect their host plant and in some cases even modify the structure of the whole macroalgal assemblage (Cronin and Hay 1996;Duffy and Hay 2000;Karez et al 2000). The biomasses of aquatic plants and mesoherbivores are positively correlated in many waterbodies as plant provides mesoherbivores habitat and food resources (Orav-Kotta 2004).…”