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"Gastropoda"
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Physiological advantages of dwarfing in surviving extinctions in high-CO sub(2) oceans
Excessive CO sub(2) in the present-day ocean-atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future, mirroring effects in many past mass extinctions. Fossil records demonstrate that organisms surviving such events were often smaller than those before, a phenomenon called the Lilliput effect. Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO sub(2) seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partially repair shell dissolution. These observations of the long-term chronic effects of increased CO sub(2) levels forewarn of changes we can expect in marine ecosystems as CO sub(2) emissions continue to rise unchecked, and support the hypothesis that ocean acidification contributed to past extinction events. The ability to adapt through dwarfing can confer physiological advantages as the rate of CO sub(2) emissions continues to increase.
Journal Article
Everything you know about bugs (and other tiny creatures) is wrong!
Do you know all there is to know about insects and other tiny creatures? Bees die when they sting you, centipedes have 100 legs, and cockroaches are indestructible, right? Well, this book is here to show you that you're WRONG! But don't worry, there are so many bugs and other creepy-crawlies out there it's impossible to know everything about all of them . . . So, let's uncover the truth! From incredible insect architects to eating spiders in your sleep, discover how everything you think you know about creepy-crawlies is actually untrue in this in-depth, ingenious book which debunks many common myths .
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Herbivory mediates the expansion of an algal habitat under nutrient and CO sub(2) enrichment
Certain environmental conditions facilitate the control of primary producers by herbivores. Environmental change can, therefore, mediate the strength of consumption relative to production such that the abundance of primary producers is altered, potentially driving phase-shifts from one habitat type to another (e.g. the displacement kelp forests by mats of turfs along temperate coasts). Here, we assessed the extent to which herbivores may counter the increased cover of kelpcompetitors (i.e. turfs) anticipated to be caused by enriched nutrients and CO sub(2). Specifically, we experimentally enriched nutrients and CO sub(2) and quantified the change in cover of algal turfs in the presence and absence of gastropod grazers. In the absence of grazers, turf algae responded positively to the combination of enriched nutrients and CO sub(2) such that they occupied >95% of available space. In contrast, where grazers were present, sparse covers of algal turfs were maintained even under CO sub(2) and nutrient enrichment (i.e. turfs occupied <5% of available space). This result indicates that consumption by grazers increased where enrichment of nutrients and CO sub(2) facilitated greater algal cover such that cover continued to be largely restricted. By recognising the environmental conditions which will maintain or disrupt the balance between the processes of production and consumption, we may improve forecasts regarding the probability of habitat stasis or shifts.
Journal Article
Body-size evolution in gastropods across the Plio-Pleistocene extinction in the western Atlantic
The Plio-Pleistocene turnover event in the western Atlantic following the closure of the Central American Seaway involved high rates of extinction for both gastropod and bivalve molluscs. This extinction was associated with declining nutrient conditions and has been presumed to be associated with a decrease in molluscan body size. Previous work which has been concordant with this expectation, however, has either focused on bivalves or not considered the effects of the recovery post extinction. In three phylogenetically diverse clades, we found that body-size evolution in gastropods across the turnover event is likely tied to ecology. One clade increased in size, one decreased, and another exhibited no substantial change. Individual species lineages exhibit a mixture of microevolutionary changes from the Pliocene to today. This study indicates that gastropod body-size evolution may be more complex than in bivalves, with ecology and other functional traits playing a significant role. Macroevolutionary processes, especially whether a clade re-radiated post extinction, were found to be important. Indeed, a low portion of extant diversity consists of survivors from clades that increased in size or have similar size distributions among their species relative to the Pliocene.
Journal Article
Intense Naticid Drilling Predation on Turritelline Gastropods From Below the K-T Boundary at Rajaumnndry, India
Evidence of intense naticid drilling predation occurs on turritelline prey from a turritelline-dominated assemblage (TDA) which lies below the K-T boundary sections in Rajahmundry, India. Previously, it was believed that drilling frequency (DF) on turritelline taxa was low during the Cretaceous. Data from the study area indicates that the Cenozoic level of predation on turritelline taxa already occurred by the Late Cretaceous in the study area. The paleobiogeography of naticid predation is extended from the western world to India, which was located in the southern hemisphere during the Cretaceous. In addition to the high drilling frequency, the Indian fossil record shows that many aspects of naticid behavior; for example, size and site stereotypy, which are characteristic features of Cenozoic predators, were also established by the Late Cretaceous. These data support previous views that the Mesozoic Marine Revolution had minimal influence on morphological change in Late Cretaceous turritelline gastropods and that turritelline gastropods may have developed behavioral and/or physiological antipredatory adaptations. TDAs in general may indicate tremendous fecundity that may act as a buffer against high juvenile mortality due to predation.
Journal Article
Multilevel fine-scale diversity challenges the ‘cryptic species’ concept
‘Cryptic’ species are an emerging biological problem that is broadly discussed in the present study. Recently, a cryptic species definition was suggested for those species which manifest low morphological, but considerable genetic, disparity. As a case study we present unique material from a charismatic group of nudibranch molluscs of the genus
Trinchesia
from European waters to reveal three new species and demonstrate that they show a dual nature: on one hand, they can be considered a ‘cryptic’ species complex due to their overall similarity, but on the other hand, stable morphological differences as well as molecular differences are demonstrated for every species in that complex. Thus, this species complex can equally be named ‘cryptic’, ‘pseudocryptic’ or ‘non-cryptic’. We also present evidence for an extremely rapid speciation rate in this species complex and link the species problem with epigenetics. Available metazoan-wide data, which are broadly discussed in the present study, show the unsuitability of a ‘cryptic’ species concept because the degree of crypticity represents a continuum when a finer multilevel morphological and molecular scale is applied to uncover more narrowly defined species making the ‘cryptic’ addition to ‘species’ redundant. Morphological and molecular methods should be applied in concordance to form a fine-scale multilevel taxonomic framework, and not necessarily implying only an
a posteriori
transformation of exclusively molecular-based ‘cryptic’ species into morphologically-defined ‘pseudocryptic’ ones. Implications of the present study have importance for many fields, including conservation biology and fine-scale biodiversity assessments.
Journal Article
The Central Paratethys Sea—rise and demise of a Miocene European marine biodiversity hotspot
The Miocene Climate Optimum (MCO, ~ 17–14 Ma) was a time of extraordinary marine biodiversity in the Circum-Mediterranean Region. This boom is best recorded in the deposits of the vanished Central Paratethys Sea, which covered large parts of central to southeastern Europe. This sea harbored an extraordinary tropical to subtropical biotic diversity. Here, we present a georeferenced dataset of 859 gastropod species and discuss geodynamics and climate as the main drivers to explain the changes in diversity. The tectonic reorganization around the Early/Middle Miocene boundary resulted in the formation of an archipelago-like landscape and favorable conditions of the MCO allowed the establishment of coral reefs. Both factors increased habitat heterogeneity, which boosted species richness. The subsequent cooling during the Middle Miocene Climate Transition (~ 14–13 Ma) caused a drastic decline in biodiversity of about 67%. Among the most severely hit groups were corallivorous gastropods, reflecting the loss of coral reefs. Deep-water faunas experienced a loss by 57% of the species due to changing patterns in circulation. The low sea level led to a biogeographic fragmentation reflected in higher turnover rates. The largest turnover occurred with the onset of the Sarmatian when bottom water dysoxia eradicated the deep-water fauna whilst surface waters-dwelling planktotrophic species underwent a crisis.
Journal Article
Species Selection Favors Dispersive Life Histories in Sea Slugs, but Higher Per-Offspring Investment Drives Shifts to Short-Lived Larvae
For 40 years, paleontological studies of marine gastropods have suggested that species selection favors lineages with short-lived (lecithotrophic) larvae, which are less dispersive than long-lived (planktotrophic) larvae. Although lecithotrophs appeared to speciate more often and accumulate over time in some groups, lecithotrophy also increased extinction rates, and tests for state-dependent diversification were never performed. Molecular phylogenies of diverse groups instead suggested lecithotrophs accumulate without diversifying due to frequent, unidirectional character change. Although lecithotrophy has repeatedly originated in most phyla, no adult trait has been correlated with shifts in larval type. Thus, both the evolutionary origins of lecithotrophy and its consequences for patterns of species richness remain poorly understood. Here, we test hypothesized links between development mode and evolutionary rates using likelihood-based methods and a phylogeny of 202 species of gastropod molluscs in Sacoglossa, a clade of herbivorous sea slugs. Evolutionary quantitative genetics modeling and stochastic character mapping supported 27 origins of lecithotrophy. Tests for correlated evolution revealed lecithotrophy evolved more often in lineages investing in extra-embryonic yolk, the first adult trait associated with shifts in development mode across a group. However, contrary to predictions from paleontological studies, species selection actually favored planktotrophy; most extant lecithotrophs originated through recent character change, and did not subsequently diversify. Increased offspring provisioning in planktotrophs thus favored shifts to short-lived larvae, which led to short-lived lineages over macroevolutionary time scales. These findings challenge long-standing assumptions about the effects of alternative life histories in the sea. Species selection can explain the long-term persistence of planktotrophy, the ancestral state in most clades, despite frequent transitions to lecithotrophy.
Journal Article
SlugAtlas, a histological and 3D online resource of the land slugs Deroceras laeve and Ambigolimax valentianus
Due to their distinctive anatomical characteristics, land slugs are appealing research subjects from a variety of angles, including stem cell biology, regeneration, embryonic development, allometry, and neurophysiology. Here we present SlugAtlas, an anatomical and histological online resource of the land slugs Deroceras laeve and Ambigolimax valentianus . The atlas is composed of series of histological sections on the horizontal, sagittal, and transversal planes for both species with 3D viewing tools of their major organs. The atlas was used in this work for a comparative analysis of the major organs and tissues of these two species. We provide a comprehensive histological description of them and an explanation of novel findings of unique features of their anatomy. For D . laeve , we additionally studied its ability for degrowth and regrowth, a feature that characterizes animals with high regeneration potential and obtained initial results on the study of the regeneration of its tail. SlugAtlas is a resource that is also built to accommodate future growth and, along with the experimental techniques that we have developed, will provide the foundation for research projects in a variety of biological domains.
Journal Article