Towards a ‘Sea‐Level Sensitive’ dynamic model: impact of island ontogeny and glacio‐eustasy on global patterns of marine island biogeography

A synthetic model is presented to enlarge the evolutionary framework of the General Dynamic Model (GDM) and the Glacial Sensitive Model (GSM) of oceanic island biogeography from the terrestrial to the marine realm. The proposed ‘Sea‐Level Sensitive’ dynamic model (SLS) of marine island biogeography integrates historical and ecological biogeography with patterns of glacio‐eustasy, merging concepts from areas as diverse as taxonomy, biogeography, marine biology, volcanology, sedimentology, stratigraphy, palaeontology, geochronology and geomorphology. Fundamental to the SLS model is the dynamic variation of the littoral area of volcanic oceanic islands (defined as the area between the intertidal and the 50‐m isobath) in response to sea‐level oscillations driven by glacial–interglacial cycles. The following questions are considered by means of this revision: (i) what was the impact of (global) glacio‐eustatic sea‐level oscillations, particularly those of the Pleistocene glacial–interglacial episodes, on the littoral marine fauna and flora of volcanic oceanic islands? (ii) What are the main factors that explain the present littoral marine biodiversity on volcanic oceanic islands? (iii) How can differences in historical and ecological biogeography be reconciled, from a marine point of view? These questions are addressed by compiling the bathymetry of 11 Atlantic archipelagos/islands to obtain quantitative data regarding changes in the littoral area based on Pleistocene sea‐level oscillations, from 150 thousand years ago (ka) to the present. Within the framework of a model sensitive to changing sea levels, we discuss the principal factors affecting the geographical range of marine species; the relationships between modes of larval development, dispersal strategies and geographical range; the relationships between times of speciation, modes of larval development, ecological zonation and geographical range; the influence of sea‐surface temperatures and latitude on littoral marine species diversity; the effect of eustatic sea‐level changes and their impact on the littoral marine biota; island marine species–area relationships; and finally, the physical effects of island ontogeny and its associated submarine topography and marine substrate on littoral biota. Based on the SLS dynamic model, we offer a number of predictions for tropical, subtropical and temperate volcanic oceanic islands on how rates of immigration, colonization, in‐situ speciation, local disappearance, and extinction interact and affect the marine biodiversity around islands during glacials and interglacials, thus allowing future testing of the theory.     

The Distribution of Isopoda in the Delaware Bay Region

The distributions of 24 marine and estuarine isopods have been reviewed. Lironeca ovalis, Aegathoa medialis, Olencira praegustator, and Probopyrus pandalicola were the only parasitic species found. Of the 20 free-living isopods, Asellus communis and Chiridotea almyra were the only fresh to brackish water species, and Chiridotea arenicola, C. stenops, Cirolana impressa, C. polita and Edotea montosa were the true marine species. The salinity range of Cyathura burbancki was extended and the range of Chiridotea stenops was extended northward while the ranges of Chiridotea nigrescens and C. arenicola were extended southward. The contribution of isopod distributions to the concept of a shallow water Transatlantic zoogeographic province is discussed.     

Mesograzer identity,not host algae,determines consumer stable isotope ratios

Species-specific foraging habits or feeding preferences influence the overall trophic functioning in consumer assemblages. We set out to assess the in situ trophic diversity in a mesograzer assemblage (isopods, amphipods and gastropods) associated with marine littoral macroalgae. More specifically, we set out to establish whether stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) are dependent on primary consumer identity or expressed in relation to the identity of the algal host, i.e. the habitat of the consumer. Consumer locations in bivariate isotope space revealed significant differences among grazer taxa, but no effect of the algal host. This suggests that grazer-specific foraging is more important in driving the qualitative range of feeding in the consumer assemblage than host diversity per se within a macrohabitat, such as a bay or a lagoon. The stable isotope ratios of the mesoherbivores were in line with expectations based on the known feeding ecology of the grazers. However, the trophic diversity suggested by stable isotope analysis implies that even an established concept such as the mesograzer guild may encompass simplifications in terms of functional group membership.     

Behavioral Adaptations of Terrestrial Isopods

In their response to environmental stimuli, terrestrial isopodsshow various trends that are correlated with their ecology andphysiology. With the transition from sea to the littoral zone (Ligia), orientationto light changes from positive to negative. Yet, since theseisopods are positively hygrokinetic even at very high humidities,their hygroreaction is of greater significance than their photoreaction. In isopods from mesic habitats (Oniscus, Porcellio, Armadillidium)photoreaction becomes of less significance than in littoralspecies, until in some species it reverts to positive (Armadillidium).Sometimes the positive photoreaction occurs only at high temperatures(Porcellio), a pattern of behavior correlated with thermoregulationby evaporative cooling. Similarly, in mesic species the responseto humidity becomes less significant than in littoral species,resuming importance mainly when the isopods become dehydrated(Armadillidium). Finally, in isopods from xeric habitats in semi-arid and desertregions (Armadillo, Venezillo), photoreaction is strongly negativeexcept in Hemilepistus at lower temperatures. All of these isopodsare positively hygrokinetic only at low humidities and are stronglynegatively thermoactive, indicating a drop in activity at hightemperatures. The photonegative response in these isopods isstronger than the hygroreaction.     

Effects of intrinsic and extrinsic factors on the diet of Bathyraja macloviana,a benthophagous skate

The effects of intrinsic (sex, maturity stage and body size) and extrinsic (depth and region) factors on the diet of Bathyraja macloviana, in the south‐west Atlantic Ocean, were evaluated using a multiple‐hypothesis modelling approach. Bathyraja macloviana fed mainly on polychaetes followed by amphipods, isopods and decapods. Effects of intrinsic and extrinsic factors on diet composition of this species were found. The consumption of polychaetes had a humped relationship with total length (L_T), and isopods and decapods increased with increasing L_T. Immature individuals preyed on amphipods more heavily than mature individuals. Furthermore, region and depth had an important effect on the consumption of isopods, decapods and amphipods. Such ontogenetic changes and spatial patterns may provide insights into understanding the regulatory mechanisms of marine communities.     

Taxonomy,natural history and zoogeography of sand beach isopods from the coast of Southern Chile

Seven species of marine isopods were collected on sandy beaches of Southern Chile (from about 37° S until 42° S). From these, Excirolana hirsuticauda Menzies, Excirolana monodi Carvacho, Chaetilia paucidens Menzies, Macrochiridothea setifer Menzies and M. mehuinensis Jaramillo are known only from the Chilean coasts. Another species, Excirolana braziliensis Richardson, is known from other areas of American coasts. One species is identified here as Macrochiridothea aff. lilianae by its resemblance with M. lilianae Moreira from Southern Brazil. All these species are here briefly described and some aspects of their ecology added. Also Zoogeographic characterization of the studied area is discussed in relation to the distributional patterns of isopods living in them.     

Bryozoan colonization of the marine isopod Glyptonotus antarcticus at Signy Island, Antarctica

Sixty specimens of the giant marine isopod Glyptonotus antarcticus Eights, collected from Borge Bay, Signy Island, Antarctica were examined for epizoans. Ten species of cheilostomatid bryozoans were found on the isopods. The purpose of the study was to quantify the prevalence, intensity, abundance, and spatial distribution of the bryozoans on the isopods. The proportion of isopods colonized was 42%. The larger isopods had both significantly more epizoic bryozoan colonies and species. The greatest density of bryozoans was on the fused pleon and telson. There was no significant difference between the dorsal and ventral abundance of bryozoan colonies. The diversity of epizoic bryozoans on the isopods is higher than on other host organisms from more stable environments. This may be because of active selection by settling larvae. The frequency of local substrata being scoured by ice is high around Signy Island, so there may be a selective advantage in colonizing a motile host. Accepted: 20 June 1998     

Parasitism by isopods in sandy beach fish assemblages: role of urbanization and environmental characteristics

Parasitism by isopods is a common phenomenon in marine fishes and may induce negative effects, especially in juvenile stages. The surf-zones of sandy beaches are an important nursery habitat for many fish species, including commercially important ones, and are structured by beach characteristics and human activities, which are suggested to influence the fishes’ susceptibility to parasitism. Here, we analyze the early infestation and prevalence of parasitism in surf zones fishes of 27 beaches in southeastern Brazil with different characteristics. Parasites were recorded in only seven of the beaches. A high infestation was found in a single site, the highly urbanized Itaguá beach, where the prevalence of parasitism on juveniles and early adults of the Atlantic anchoveta Cetengraulis edentulus was high (68.11%). Four species of parasitic isopods were found, all belonging to the Cymothoidae family, but Livoneca desterroensis was the most abundant (78.7%). No effects of parasitism were detected on the size, weight and physiological condition of fishes, but presence of parasites and prevalence of infestation were positively affected by urbanization. Overall, our results indicate that the surf-zones have low parasite infestation, yet, they suggest that anthropic effects such as urbanization may enhance the prevalence of isopod parasitism.

     

A mass mortality of fishes caused by receding water levels in the vegetated littoral zone of the West Kleinemonde Estuary,South Africa

On 15 November 2017 the mouth of the West Kleinemonde Estuary breached following heavy catchment rains and increased river flow. The water level in the estuary following mouth opening decreased by 1.65 m within 24 h, resulting in an almost complete draining of the littoral zone where large beds of the aquatic macrophyte Ruppia cirrhosa and mats of the associated filamentous algae were present. As the water depth within the plant beds decreased, the macrophytes, together with the algal filaments, created an increasingly dense mat, trapping fish that were resident, foraging or passing through the littoral zone. By 16 November 2017 large numbers of fishes belonging to at least 20 species were trapped in pools and depressions within the littoral, as well as within the R. cirrhosa beds and filamentous algal mats in the lower reaches of this system. Other affected taxa included crustaceans, especially isopods, and large numbers of small bivalves attached to macrophyte vegetation. Beneficiaries of the fish kill, in terms of unexpected food availability, included a variety of piscivorous bird species and the Cape clawless otter Aonyx capensis. This is the first documented account of a diverse species fish kill associated with estuary mouth breaching.     

The Trace Fossil Diplopodichnus from the Lower Jurassic Lacustrine Sediments of Central China and the Isopod Armadillidium vulgare (Pillbug) Lebensspuren as its Recent Analogue

The trace fossil Diplopodichnus isp. was identified in lacustrine siliciclastics of the Lower Jurassic Anyao Formation in the Henan Province, central China. This is the youngest occurrence of this ichnogenus. It is similar to some variants of recent surface traces of the isopod Armadillidium vulgare (pillbug) crawling on soft mud in temporal puddles. Therefore, isopods are suggested to be producers of the described Diplopodichnus isp. It seems that isopods should be taken into account as important component of deep lacustrine ecosystems by the Early Jurassic.     

Divergence in host use ability of a marine herbivore from two habitat types

We studied ecological divergence of host use ability in a generalist marine herbivore living in two distinct host plant assemblages. We collected Idotea balthica isopods from three populations dominated by the brown alga Fucus vesiculosus and three dominated by the seagrass Zostera marina. In two reciprocal common garden feeding experiments for adult and laboratory‐born juvenile isopods, we found that isopods from both assemblages performed better with their sympatric dominant host species than did isopods allopatric to this host. This indicates parallel divergence of populations according to the sympatric host plant assemblage. Furthermore, initial body size and body size‐dependent mortality differed between populations from the two assemblages. In nature, this may result in lower fitness of immigrants compared with that of residents and consequently reinforce divergence of the populations. Finally, we discuss how phenotypic plasticity and maternal and random effects may associate with the results.     

Eocene isopods on electric rays: tracking ancient biological interactions from a complex fossil record

Isopod crustaceans have developed a variety of feeding strategies, which impact on their various life habits over time. Apart from morphological adaptations and the typical secondary deformations that some parasitic isopods inflict on their host's exoskeleton, traces of feeding behaviours involving isopods on their victim/food are seldom fossilized. Many of these rare occurrences consist of cases for which the degree of association between the isopods and their potential food source is unclear, or the interaction only very briefly explained (recently analysed cases excepted). There are two limiting problems in identifying the biological nature of fossilized associations: (1) direct associations of organisms preserved as ‘imprint’ (as opposed to inclusions in cherts or amber) are shaped by several taphonomic events difficult to identify (such as the time of death, burial and fossilization of the organism); (2) even in modern nature, differences within syn vivo interactions (like parasitism and micropredation) are poorly understood in marine systems. We report the occurrence of isopods associated with ancient chondrichthyans which also represent rare cases of the preservation of several fossil isopods on larger organisms. These organisms are adult electric rays of the genus ?Titanonarke Carvalho from the late Ypresian (Eocene) of the Monte Postale site, Bolca Lagerstätte, Italy. By examining: (1) the involved lineages of rays and isopods; (2) the taphonomy of the association; (3) its environmental context; and (4) biological/adaptive features; we identify this association as a selective case, either of ancient scavenging or of micropredation on specific electric rays by isopods.     

Amphipods, isopods and surface currents: a case for passive dispersal in the Bay of Fundy, Canada

Six species of isopods and 18 species of amphipods were collectedin the neuston of the Bay of Fundy and adjacent waters. Collectionswere made over a grid of stations covering 2.4x10⁴ km² duringthree spring, three summer and two autumn surveys. No isopodsand only five species of amphipods were found in spring surveys.Isopods and amphipods were diverse and plentiful in the neustonin summer and autumn. Dominant isopods were Idotea baltica andI.metallica, and dominant amphipods were Calliopius laeviusculusand Parathemisto gaudichaudi. Amphipods and isopods reach theneuston of the Bay of Fundy in three ways. Idotea metallica,the only euneustonic species present, was probably advectedinto the Bay of Fundy from southern waters in summer, and didnot appear to overwinter in the Bay. Most species, includingI.baltica, were collected with drifting littoral vegetation,and we suggest that transport by surface currents is an importantfactor in dispersal of some shoreline crustaceans. Midwaterplankton, such as Parathemisto gaudichaudi, reached the neustoneither by advection in upwelling waters or by an extension oftheir normal diel vertical distribution.     

Geographical divergence in host use ability of a marine herbivore in alga–grazer interaction

When the selective environment differs geographically, local herbivore populations may diverge in their host use ability and adapt locally to exploit the sympatric host population. We tested whether populations of the marine generalist herbivore Idotea baltica have diverged in host us ability and whether they locally adapted to exploit the sympatric population of their main host species, the bladderwrack Fucus vesiculosus. We fed isopods from three local populations reciprocally with the sympatric and two allopatric populations of the host. The bladderwrack populations varied in their quality as food for isopods suggesting variation in the selective environment. The ability to exploit the main host showed considerable divergence among the isopod populations. There was no significant interaction between host and isopod origin, indicating that the patterns observed in the reciprocal feeding experiment could be explained by differences in overall suitability of the hosts and differences in overall performance of the isopod populations. Isopod population that was sympatric to a bladderwrack population with low phlorotannin content showed high performance on the algae from the sympatric but low performance on the algae from the two allopatric populations. Performance of isopods, especially in this population, decreased quickly with the increasing phlorotannin content of food algae. We therefore hypothesize that the isopods adapted to a low phlorotannin content were unable to utilize high-phlorotannin algae efficiently. Isopod populations sympatric to the high-phlorotannin bladderwrack populations may be generally better adapted to deal with phlorotannins, being thereby able to utilize a range of bladderwrack populations.     

<Emphasis Type="Italic">Prorocentrum vietnamensis</Emphasis> sp. nov. (Prorocentraceae Dinophyta): A new armored dinoflagellate from Vietnam coastal waters

TheProrocentrum species, which are primarily marine, are distributed worldwide and occur in ocean, neritic, and littoral environments.Prorocentrum is either a planktonic or benthic genus, with some species possibly being both. Until now, about 35 species had been reported including two that are fresh-water. Some species contain toxic substances. As one of many currently active studies, we collectedP. vietnamensis sp. nov. from Hon Mé, Gulf of Tongkin, Vietnam. Based on its cell shape, smooth valve surface, arrangement of valves and marginal pores, plus characteristics of the central pyrenoid, we propose thatP. vietnamensis is a new species. Its attributes include straight cell sides that are parallel to each other, as well as anterior and posterior areas with rounded ends that form a short, rod-shaped cell that is unique to this species.     

The role of invertebrates in seedling establishment in a heterocarpic plant,Atriplex sagittata

Seed heteromorphism is a marked character of many Chenopodioideae (Amaranthaceae). Seed morphs differ in dormancy, germination and seedling biology, but differences in their predation have not yet been studied. Atriplex sagittata produces small black dormant and large brown non‐dormant seeds. In this study, the timing of seed release and seedling establishment were ascertained, and their consumption by invertebrates (carabids, isopods and slugs) was studied. Seeds dispersed in the autumn passed the winter on the ground surface, protected from invertebrate predation by low temperatures. In the following vegetative season, ungerminated black seeds exposed to predation on ground surface were preferred by a large carabid species, Pseudoophonus rufipes. Some black and all brown seeds escaped predation by germinating in early spring. The seedlings were little endangered by carabids and isopods but were preferred by an invasive slug, Arion vulgaris, the feeding of which can exterminate seedlings at places in which slugs are abundant. Invertebrate predation is important factor of seed and seedling mortality of A. sagittata and seed heteromorphism modifies its intensity and timing.     

New species of Halacaridae (Acari) from New Zealand

Abstract

Seven new taxa of marine mites (Halacaridae) are described from the marine littoral zone of northern and southern New Zealand: Agauopsis novaezelandiae, A. luxtoni, Halacarellus lubricus, Copidognathus lubricus, Simognathus glaber, S. glareus, and Rhombognathus novaezelandicus. A list of halacarid species known from New Zealand waters is added.     

Microplastic ingestion affects hydrogen production and microbiomes in the gut of the terrestrial isopod Porcellio scaber

Microplastic (MP) is an environmental burden and enters food webs via ingestion by macrofauna, including isopods (Porcellio scaber) in terrestrial ecosystems. Isopods represent ubiquitously abundant, ecologically important detritivores. However, MP-polymer specific effects on the host and its gut microbiota are unknown. We tested the hypothesis that biodegradable (polylactic acid [PLA]) and non-biodegradable (polyethylene terephthalate [PET]; polystyrene [PS]) MPs have contrasting effects on P. scaber mediated by changes of the gut microbiota. The isopod fitness after an 8-week MP-exposure was generally unaffected, although the isopods showed avoidance behaviour to PS-food. MP-polymer specific effects on gut microbes were detected, including a stimulation of microbial activity by PLA compared with MP-free controls. PLA stimulated hydrogen emission from isopod guts, while PET and PS were inhibitory. We roughly estimated 10⁷ kg year⁻¹ hydrogen emitted from the isopods globally and identified their guts as anoxic, significant mobile sources of reductant for soil microbes despite the absence of classical obligate anaerobes, likely due to Enterobacteriaceae-related fermentation activities that were stimulated by lactate generated during PLA-degradation. The findings suggest negative effects of PET and PS on gut fermentation, modulation of important isopod hydrogen emissions by MP pollution and the potential of MP to affect terrestrial food webs.     

Feeding habits of the Magellan skate: effects of sex, maturity stage, and body size on diet

The aim of this study was to evaluate the effects of sex, maturity stage, and body size on the diet of the Magellan skate, Bathyraja magellanica, in the Southwest Atlantic off Argentina, by examining stomach contents using a multiple hypothesis modeling approach. Relationships between the number of prey and sex, maturity stage, and total length (TL) were assessed by built generalized linear models (GLM). Furthermore, we tested whether there was a threshold size at which B. magellanica started or quit consuming a given prey. The overall diet of B. magellanica was mainly consisted of teleosts, followed by amphipods, isopods, and decapods. Ontogenetic diet shifts were independent of sex and maturity stage. However, discrete shifts in diet with TL were found, with individuals larger than 554 and 623 mm TL ceasing to consume amphipods and isopods, respectively. The consumption of teleosts progressively increased with increasing predator size. Likewise, ontogenetic shifts in foraging behavior were also observed with smaller individuals showing specialization on amphipods with larger specimens consuming teleosts. These results confirm that ontogenetic shifts in diet of B. magellanica are more a function of predator size rather than any other life-history traits. We propose that these food shifts are probably related to morphological limitations and abilities associated with feeding habits of skate, so when specimens of B. magellanica reach an optimum body size, they may have access to higher quality trophic resources. Our results suggest that evaluating the importance of life-history stages on the feeding habits of a species is essential for understanding how that species exploits food resources, which, in turn, is an important factor in developing a suitable plan of marine ecosystem conservation.     

Escaping malnutrition by shifting habitats: A driver of three-spined stickleback invasion in Lake Constance

Fatty acids, and especially long-chain polyunsaturated fatty acids, are biologically important components in the metabolism of vertebrates, including fish. Essential fatty acids (EFA) are those that in a given animal cannot be synthesized or modified from precursors and must therefore be acquired via the diet. Because EFAs are often unevenly distributed in nature, this requirement may drive species to make behavioral or ecological adaptations to avoid malnutrition. This is especially true for fish like the three-spined stickleback (Gasterosteus aculeatus L.) of Upper Lake Constance (ULC), whose recent marine ancestors evolved with access to EFA-rich prey, but which found themselves in an EFA-deficient habitat. An unexpected and unprecedented ecological shift in the ULC stickleback population from the littoral to pelagic zones in 2012 might be linked to EFA availability, triggering ecological release and enabling them to build a hyperabundant population while displacing the former keystone species, the pelagic whitefish Coregonus wartmanni. To test this hypothesis, sticklebacks from the littoral and pelagic zones of ULC were sampled seasonally in two consecutive years, and their stomach contents and fatty acid profiles were analysed. Pelagic sticklebacks were found to possess significantly higher values of an important EFA, docosahexaenoic acid (DHA), especially during autumn. Evaluation of the DHA supply suggests that sticklebacks feeding in the littoral zone during autumn could not meet their DHA requirement, whereas DHA availability in the pelagic zone was surplus to demand. During autumn, pelagic sticklebacks consumed large amounts of DHA-rich prey, that is, copepods, whereas littoral sticklebacks relied mainly mostly on cladocerans, which provide much lower quantities of DHA. Access to pelagic zooplankton in 2012 was possibly facilitated by low densities of previously dominant zooplanktivorous whitefish. The present study offers a convincing physiological explanation for the observed expansion of invasive sticklebacks from the littoral to the pelagic zones of Lake Constance, contributing to a phase shift with severe consequences for fisheries.