Sea Slugs—“Rare in Space and Time”—But Not Always

Schubert, Julie; Smith, Stephen

doi:10.3390/d12110423

Cited by 7 publications

(10 citation statements)

References 34 publications

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“…The highest density was 4 slugs per quadrate and in numerous quadrates no slugs were observed. Most sea slug species have been reported to be rare [18]; therefore, the pattern of variation observed in our samples can be seen as a typical pattern of sea slug occurrence. The density of egg masses varied significantly between months (H = 33.25, p = 0.001; Figure 4(b)).…”

Section: Resultssupporting

confidence: 61%

Population Ecology and Habitat use of the Sea Slug Elysia pusilla (Bergh, 1872) (Sacoglossa) in A Tropical Halimeda macroloba Decaisne Meadow

2022

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Relationship between abundance of specialist marine herbivores and their food sources is poorly known because these herbivores are relatively rare in marine systems. The relationship between the cryptic sea slug Elysia pusilla (Bergh, 1872) and its host alga, Halimeda macroloba Decaisne, was evaluated in terms of spatial association and habitat utilization in a tropical algal meadow in southern Thailand that exclusively comprised of H. macroloba. The density of H. macroloba and of E. pusilla egg masses varied temporally throughout the sampling period, but temporal variation was not detected in the density of E. pusilla individuals, which was generally low with a maximum of 4 individuals per 400 cm2. Analysis suggests that the occurrence of the slug and its egg masses might be determined by the availability of the algal host. The slug was more likely to be observed in dense patches of algae that which offered a large total algal surface area. Occurrence of the slug was also higher when the algae were abundant. The numbers of slugs, egg masses and grazing marks were higher on mature thalli, which have larger surface areas than younger thalli. Egg masses and grazing marks were observed more often on segments at terminal positions on thalli. According to previous works, these segments contain low levels of accumulated calcium carbonate and high levels of secondary metabolites, which are sequestered by the slug and used to deter predators. The findings provide an insight into the life history of E. pusilla and variations in a natural population which that were previously little known. HIGHLIGHTS The relationship between the cryptic sea slug Elysia pusilla (Bergh, 1872) and its host alga, Halimeda macroloba Decaisne, was evaluated in terms of spatial association and habitat utilization in a tropical algal meadow in southern Thailand The slug pusilla was more likely to be observed in dense patches of its algal host H. macroloba Occurrence of the slug was also higher when the algae were abundant The numbers of slugs, egg masses and grazing marks were higher on mature thalli Egg masses and grazing marks were observed more often on segments at terminal positions on thalli GRAPHICAL ABSTRACT

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Section: Resultssupporting

confidence: 61%

Population Ecology and Habitat use of the Sea Slug Elysia pusilla (Bergh, 1872) (Sacoglossa) in A Tropical Halimeda macroloba Decaisne Meadow

2022

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“…Furthermore, how and if environmental factors, such as turbidity, temperature and variability in spatial and seasonal processes (e.g. [83][84][85][86]) interact with such selection pressures and thus variability in phenotype, remains unknown as well. Lastly, the defensive properties of secondary metabolites can be highly context and predator specific [35,87,88].…”

Section: Discussionmentioning

confidence: 99%

Chemical defences indicate distinct colour patterns with reduced variability in aposematic nudibranchs

Berg¹,

Endler²,

Drummond³

et al. 2023

Preprint

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Predators learn and memorise the association between conspicuous colour patterns of aposematic prey and their underlying chemical or secondary defences. Consequently, variation in signal design within a species should be selected against, because it can decrease the rate of predator learning and enhance the rates of predator errors. However, quantitative assessments have not been made on whether the strength of chemical defences influences colour pattern variation. We examined this by quantifying colour pattern variation using Quantitative Colour Pattern Analysis (QCPA) in 12 Dorid nudibranch species (Infraorder: Doridoidei) that varied in their unpalatability. We accounted for the physiological limitations of a potential predator visual system (a triggerfish,Rhinecanthus aculeatus), modelling animal appearance along an escalating predation sequence. We found that various colour pattern statistics were less variable in highly unpalatable species, with pattern statistics being up to 72% less variable than those of more palatable species. No correlations indicating the opposite were found across 157 colour pattern statistics. However, the strength and number of correlations depended on viewing distance. Our results suggest that low colour pattern variability could be favourable for aposematic signalling in Dorid nudibranchs. We provide evidence for distance-dependent signalling facilitating context-specific feature selection in multicomponent visual signals.

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“…Finally, it is possible that, for some colour pattern statistics, there could be a strong phylogenetic signal, which we have not been able to pick up in this study as we only sampled 13 out of many co-occurring sea slug species at either sampling site (e.g. Schubert & Smith, 2020). To test this, we would need to increase our sample sizes and more systematic sampling across geographical and seasonal ranges.…”

Section: Discussionmentioning

confidence: 99%

“…Our study considers many of the more commonly found Dorid nudibranchs in the study sites (e.g. (Larkin et al, 2018;Schubert & Smith, 2020;Smith & Davis, 2019)). Species were identified visually using various nudibranch ID guides (Coleman et al, 2015;Debelius & Kuiter, 2007;Gosliner et al, 2018) (Larkin et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Highly defended nudibranchs ‘escape’ to visually distinct background habitats

Berg

Endler

Cheney

2022

Preprint

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The ′escape and radiate′ hypothesis predicts that once species have evolved aposematism, defended species can utilise more visually diverse background habitats as they ′escape′ the need to be well camouflaged. This enables species to explore new ecological niches, resulting in increased diversification rates. To test the ′escape′ component of this hypothesis, we examined whether the background habitats of 13 nudibranch mollusc species were more variable for highly defended species (in terms of unpalatability), compared to undefended (palatable) species. We obtained 157 colour pattern statistics from the Quantitative Colour Pattern Analysis (QCPA) framework to analyse backgrounds viewed through the eyes of a potential predator (triggerfish,Rhinecanthus aculeatus). This was done at viewing distances simulating an escalating predation sequence. Contrary to the hypothesis, we found no significant positive correlations between the diversity of visual backgrounds and the strength of chemical defences, but instead found numerous significant negative correlations. Highly defended species were viewed against backgrounds up to 56.9% less variable than non-defended species. Furthermore, the strongest correlations were found at viewing distances coinciding with likely prey detection and identification. Our results provide empirical evidence against background generalisation in aposematic nudibranch species. Instead, we suggest that less variable visual backgrounds may strengthen aposematic signalling.

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Sea Slugs—“Rare in Space and Time”—But Not Always

Cited by 7 publications

References 34 publications

Population Ecology and Habitat use of the Sea Slug Elysia pusilla (Bergh, 1872) (Sacoglossa) in A Tropical Halimeda macroloba Decaisne Meadow

Population Ecology and Habitat use of the Sea Slug Elysia pusilla (Bergh, 1872) (Sacoglossa) in A Tropical Halimeda macroloba Decaisne Meadow

Chemical defences indicate distinct colour patterns with reduced variability in aposematic nudibranchs

Highly defended nudibranchs ‘escape’ to visually distinct background habitats

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