Morphological adaptations and plasticity of radular teeth of the Sacoglossa (= Ascoglossa) (Mollusca: Opisthobranchia) in relation to their food plants

Jensen, Kathe R.

doi:10.1111/j.1095-8312.1993.tb00883.x

Cited by 82 publications

(69 citation statements)

References 15 publications

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“…E. viridis feeds by piercing and sucking the cytoplasm from algal cells, and differences in the cell wall chemistry of the algal diets or the tooth morphology of the slugs could potentially constrain E. viridis switching to new hosts [23]. Previous studies have found variation in tooth morphology in different populations of E. viridis residing on different algal species [23], [36]. Slugs from Danish populations residing on Chaetomorpha linum possessed narrower and shorter teeth compared to French and English slugs found on C. fragile [23], [36].…”

Section: Discussionmentioning

confidence: 99%

Individual Specialization to Non-Optimal Hosts in a Polyphagous Marine Invertebrate Herbivore

2014

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Factors determining the degree of dietary generalism versus specialism are central in ecology. Species that are generalists at the population level may in fact be composed of specialized individuals. The optimal diet theory assumes that individuals choose diets that maximize fitness, and individual specialization may occur if individuals' ability to locate, recognize, and handle different food types differ. We investigate if individuals of the marine herbivorous slug Elysia viridis, which co-occur at different densities on several green macroalgal species in the field, are specialized to different algal hosts. Individual slugs were collected from three original algal host species (Cladophora sericea, Cladophora rupestris and Codium fragile) in the field, and short-term habitat choice and consumption, as well as long-term growth (proxy for fitness), on four algal diet species (the original algal host species and Chaetomorpha melagonium) were studied in laboratory experiments. Nutritional (protein, nitrogen, and carbon content) and morphological (dry weight, and cell/utricle volume) algal traits were also measured to investigate if they correlated with the growth value of the different algal diets. E. viridis individuals tended to choose and consume algal species that were similar to their original algal host. Long-term growth of E. viridis, however, was mostly independent of original algal host, as all individuals reached a larger size on the non-host C. melagonium. E. viridis growth was positively correlated to algal cell/utricle volume but not to any of the other measured algal traits. Because E. viridis feeds by piercing individual algal cells, the results indicate that slugs may receive more cytoplasm, and thus more energy per unit time, on algal species with large cells/utricles. We conclude that E. viridis individuals are specialized on different hosts, but host choice in natural E. viridis populations is not determined by the energetic value of seaweed diets as predicted by the ODT.

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Section: Discussionmentioning

confidence: 99%

Individual Specialization to Non-Optimal Hosts in a Polyphagous Marine Invertebrate Herbivore

2014

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“…Although this has not been tested for sea hares, it has been shown that diet can influence tooth morphology (size and number) in other ''opisthobranch'' sea slugs. For example, in sacoglossans, smooth teeth can be associated with filamentous food (Bleakney 1990;Jensen 1993). Bleakney (1989) also noted some other morphological differences in the teeth of a species of ''opisthobranchs'' from different geographic regions.…”

Section: Discussionmentioning

confidence: 99%

It’s not what it looks like: molecular data fails to substantiate morphological differences in two sea hares (Mollusca, Heterobranchia, Aplysiidae) from southern Brazil

et al. 2014

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Species of sea hares have been recognized traditionally based on morphological traits, mainly the radula, external coloration, and reproductive anatomy. However, recent studies have shown substantial color variation in some sea slug species. Molecular data have been successfully used to differentiate morphologically similar species of ''opisthobranchs'' and resolve questions on the taxonomic value of color. The objective of this paper is to use molecular data in an attempt to elucidate whether specimens of Aplysia brasiliana with distinct colorations and morphologies are actually the same species. To this end, DNA from 14 specimens of A. brasiliana was extracted, including five specimens identified as a distinct morphotype from typical A. brasiliana. Although the two morphotypes have consistent differences in their external morphology and radula, the molecular data confirmed that there are no significant genetic differences between them. This is another example of the need to reevaluate taxonomic decisions based on morphology in light of molecular evidence.

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“…We selected one such seaweed, H. incrassata, to study, because it is (i) colonized by the sacoglossan sea slug Elysia (16); (ii) well described in terms of its chemical defenses (14); (iii) the dominant seaweed within seagrass habitats throughout both the Florida Keys reef tract (11) and the wider Caribbean (12); and (iv) critical to the ecology of (13) and carbonate cycling within (12) Caribbean seagrass ecosystems. We studied Elysia because it (i) is thought to be a specialist, presumably associating with and feeding on Halimeda species (16,17,19,21,25); (ii) has been studied previously with regard to its sequestration of seaweed chloroplasts (34) and chemical defenses (19); and (iii) is the most abundant and widespread sacoglossan in the Florida Keys, which harbors the highest densities of sacoglossans in the Caribbean (35). Organisms were collected in the immediate vicinity of Pickles Reef and Rodriguez Key.…”

Section: Methodsmentioning

confidence: 99%

“…However, the sea slug Elysia tuca (hereafter Elysia) tolerates these defenses and selectively associates with and feeds on chemically rich species of green seaweed including H. incrassata (16). Elysia pierces the calcified thallus of its prey with a modified radula (17) and then feeds suctorially (18). It performs pharyngeal regurgitation while feeding to reduce the viscosity and facilitate withdrawal of cytoplasm (18).…”

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confidence: 99%

Marine and terrestrial herbivores display convergent chemical ecology despite 400 million years of independent evolution

Rasher

Stout

Engel

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Chemical cues regulate key ecological interactions in marine and terrestrial ecosystems. They are particularly important in terrestrial plant-herbivore interactions, where they mediate both herbivore foraging and plant defense. Although well described for terrestrial interactions, the identity and ecological importance of herbivore foraging cues in marine ecosystems remain unknown. Here we show that the specialist gastropod Elysia tuca hunts its seaweed prey, Halimeda incrassata, by tracking 4-hydroxybenzoic acid to find vegetative prey and the defensive metabolite halimedatetraacetate to find reproductive prey. Foraging cues were predicted to be polar compounds but instead were nonpolar secondary metabolites similar to those used by specialist terrestrial insects. Tracking halimedatetraacetate enables Elysia to increase in abundance by 12-to 18-fold on reproductive Halimeda, despite reproduction in Halimeda being rare and lasting for only ∼36 h. Elysia swarm to reproductive Halimeda where they consume the alga's gametes, which are resource rich but are chemically defended from most consumers. Elysia sequester functional chloroplasts and halimedatetraacetate from Halimeda to become photosynthetic and chemically defended. Feeding by Elysia suppresses the growth of vegetative Halimeda by ∼50%. Halimeda responds by dropping branches occupied by Elysia, apparently to prevent fungal infection associated with Elysia feeding. Elysia is remarkably similar to some terrestrial insects, not only in its hunting strategy, but also its feeding method, defense tactics, and effects on prey behavior and performance. Such striking parallels indicate that specialist herbivores in marine and terrestrial systems can evolve convergent ecological strategies despite 400 million years of independent evolution in vastly different habitats.C hemical cues and signals govern the processes that shape species demography, community structure, and ecosystem function in both terrestrial and marine ecosystems. However, the chemicals regulating these processes are better known for terrestrial systems, especially with regard to plant-herbivore interactions (1, 2). Terrestrial insect herbivores, most of which are trophic specialists (3), commonly locate prey by tracking plant volatiles (4). In response, plants induce chemical defenses both to reduce herbivory and to limit the spread of pathogens introduced by herbivore feeding (5); some also release volatile compounds that attract predators of their herbivores (6, 7). These volatile compounds involved in insect foraging and plant defense are well described; generally, they are nonpolar secondary compounds (or blends of compounds) that are plantspecific. In contrast, few herbivores in marine ecosystems are trophic specialists (8), and whether they use chemical cues to locate their prey remains poorly understood (9, 10). The identities of such foraging cues are unknown but are predicted to be polar compounds that diffuse readily through water (9, 10).Halimeda incrassata is the dominant seaweed within ...

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Morphological adaptations and plasticity of radular teeth of the Sacoglossa (= Ascoglossa) (Mollusca: Opisthobranchia) in relation to their food plants

Cited by 82 publications

References 15 publications

Individual Specialization to Non-Optimal Hosts in a Polyphagous Marine Invertebrate Herbivore

Individual Specialization to Non-Optimal Hosts in a Polyphagous Marine Invertebrate Herbivore

It’s not what it looks like: molecular data fails to substantiate morphological differences in two sea hares (Mollusca, Heterobranchia, Aplysiidae) from southern Brazil

Marine and terrestrial herbivores display convergent chemical ecology despite 400 million years of independent evolution

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