Reproductive senescence and parental effects in an indeterminate grower.

Reproductive senescence is the decrease of reproductive performance with increasing age and can potentially include trans-generational effects as the offspring produced by old parents might have a lower fitness than those produced by young parents. This negative effect may be caused either by the age of the father, mother or the interaction between the ages of both parents. Using the common woodlouse Armadillidium vulgare, an indeterminate grower, as a biological model, we tested for the existence of a deleterious effect of parental age on fitness components. Contrary to previous findings reported from vertebrate studies, old parents produced both a higher number and larger offspring than young parents. However, their offspring had lower fitness components (by surviving less, producing a smaller number of clutches or not reproducing at all) than offspring born to young parents. Our findings strongly support the existence of trans-generational senescence in woodlice and contradict the belief that old individuals in indeterminate growers contribute the most to recruitment and correspond thereby to the key life stage for population dynamics. Our work also provides rare evidence that the trans-generational effect of senescence can be stronger than direct reproductive senescence in indeterminate growers.

Thermal and oxygen conditions during development cause common rough woodlice (Porcellio scaber) to alter the size of their gas-exchange organs.

Terrestrial isopods have evolved pleopodal lungs that provide access to the rich aerial supply of oxygen. However, isopods occupy conditions with wide and unpredictable thermal and oxygen gradients, suggesting that they might have evolved adaptive developmental plasticity in their respiratory organs to help meet metabolic demand over a wide range of oxygen conditions. To explore this plasticity, we conducted an experiment in which we reared common rough woodlice (Porcellio scaber) from eggs to maturation at different temperatures (15 and 22 °C) combined with different oxygen levels (10% and 22% O2). We sampled animals during development (only females) and then examined mature adults (both sexes). We compared woodlice between treatments with respect to the area of their pleopod exopodites (our proxy of lung size) and the shape of Bertalanffy's equations (our proxy of individual growth curves). Generally, males exhibited larger lungs than females relative to body size. Woodlice also grew relatively fast but achieved a decreased asymptotic body mass in response to warm conditions; the oxygen did not affect growth. Under hypoxia, growing females developed larger lungs compared to under normoxia, but only in the late stage of development. Among mature animals, this effect was present only in males. Woodlice reared under warm conditions had relatively small lungs, in both developing females (the effect was increased in relatively large females) and among mature males and females. Our results demonstrated that woodlice exhibit phenotypic plasticity in their lung size. We suggest that this plasticity helps woodlice equilibrate their gas exchange capacity to differences in the oxygen supply and metabolic demand along environmental temperature and oxygen gradients. The complex pattern of plasticity might indicate the effects of a balance between water conservation and oxygen uptake, which would be especially pronounced in mature females that need to generate an aqueous environment inside their brood pouch.

Responses of Aquatic Organisms to Cyanobacteria and Elodea in Microcosms.

The aim of the present study is investigation of the impact of mass development of cyanobacteria and Elodea on population characteristics (abundance, biomass, fecundity) and "health" parameters (the state of embryos, heart rate, and thermal resistance) of aquatic invertebrates in experiments with controlled conditions. In July-August 2018, in four variants of microcosms, the conditions were modeled characteristic of the coastal zone of the Rybinsk Reservoir in the period of mass development of cyanobacteria. Mass species were placed in microcosms of planktonic (with domination (80%) Daphnia longispina) and bottom animals (Unio pictorum, Gmelinoides fasciatus, Asellus aquaticus), as well as Elodea canadensis. In the variants with cyanobacteria, the toxic microcystins LR were revealed (24-53% of the sum of toxins, or from 6.6-66.5 µg/L). The presence of cyanobacteria (Aphanizomenon flos-aquae, Microcystis aeruginosa, and Gloeoitrichia spp.) influenced structural parameters of plankton: the quantity to green algae decreased, small-sized crustaceans increased. Influence of cyanobacteria caused reliable changes in parameters of aquatic animal from those of the control: thermal resitance of mollusks and amphipods decreased, time of restoration of heart rate after loads (salinity test) in mollusks increased; in amphipods, individual fecundity decreased, frequency of abnormalities and of mortality of embryos increased. The presence of Elodea intensified these effects. Thus, mass development of cyanobacteria and Elodea influences ecological-physiological parameters of aquatic animals, decreasing their adaptivity to natural stresses and deteriorating the quality of the progeny.

Competitive growth, energy allocation, and host modification in the acanthocephalan Acanthocephalus dirus: field data.

The acanthocephalan Acanthocephalus dirus is a trophically transmitted parasite that modifies both the physiology and behavior of its intermediate host (isopod) prior to transmission to its definitive host (fish). Infected isopods often contain multiple A. dirus individuals and we examined the relationships between host sharing, body size, energy content, and host modification to determine if host sharing was costly and if these costs could influence the modification of host behavior (mating behavior). Using field-based measures of parasite energy content (glycogen, lipid) and parasite body size (volume), we showed that host sharing was costly in terms of energy content but not in terms of body size. Analysis of the predictors of host behavior revealed that energy content, and body size, were not predictors of host behavior. Of the variables examined, parasite intensity was the only predictor of host behavior. Hosts that contained more parasites were less likely to be modified (i.e., less likely to undergo mating suppression). We suggest that intraspecific competition influenced parasite energy content and that the costs associated with competition are likely to shape the strategy of growth and energy allocation adopted by the parasites. These costs did not appear to have a direct effect on the modification of host mating behavior.

Mothocya renardi (Bleeker, 1857) (Crustacea: Isopoda: Cymothoidae) parasitising Strongylura leiura (Bleeker) (Belonidae) off the Malabar coast of India: Redescription, occurrence and life-cycle.

Mothocya renardi (Bleeker, 1857), a protandrically hermaphroditic cymothoid, parasitising the banded needle fish Strongylura leiura (Bleeker) from the Malabar Coast, India is redescribed and morphological data for different life-cycle stages [male, transitional and ovigerous female, larvae (pre-manca and manca) and juvenile] are provided. Mothocya renardi exhibited strict oligoxenous host specificity by infesting only S. leiura and showed high prevalence levels (reaching up to 92%). The life-cycle of M. renardi comprises three major phases (marsupial phase, free living phase and infestive phase). The marsupial phase comprised one zygotic, three embryonic and two larval stages, all of which remained in the marsupium until the final staged manca is released into the surrounding water. After having led a short free- swimming life, the manca infested the branchial cavity of the host fish, S. leiura. Subsequently it was transformed successively into juvenile, male, transitional and finally functional female through biphasic moult which occurs in between each stage. Based on the presence (or absence) of a brood pouch and/or marsupiumites, six successive stages of the female population were also identified. These data will help precise identification of the female M. renardi irrespective of their stage. The present paper also discusses the host-parasite interactions between S. leiura and M. renardi.

Adverse effects of bisphenol A on water louse (Asellus aquaticus).

Experiments were performed to study the effects of short and long-term exposure to bisphenol A (BPA) on a freshwater crustacean isopod Asellus aquaticus (L.). Two life stages of isopods were exposed to a range of BPA concentrations, from aqueous and two dietary sources, in the form of with BPA spiked conditioned alder leaf (Alnus glutinosa) discs, or spiked formulated sediment, to determine the relative importance of each source of exposure on the uptake of this contaminant. Several lethal and sublethal endpoints were evaluated in this study to measure the potential effects of BPA on A. aquaticus, including mortality, growth and feeding rate inhibition, mobility inhibition, de-pigmentation and molting disturbances. They signify a correlation to BPA levels and a difference in BPA uptake efficiency from different uptake sources. Results of acute exposure to BPA show a greater sensitivity of test systems using juvenile specimens with a 96 h LC50 of 8.6 mg L(-1) BPA in water medium and a 96 h LC50 of 13.5 mg L(-1) BPA in sediment. In comparison, adult isopods show a 96 h LC50 of 25.1 mg L(-1) BPA in water medium and a 96 h LC50 of 65.1 mg L(-1) BPA in sediment. Observed endpoints of chronic exposures suggest the alder leave discs to be the most efficient uptake source of BPA, in contrast to uptake from water or heterogeneous sediment. Significant (p<0.05) growth inhibition, with a 21d NOEC of 0.5/2.5 mg L(-1) (for juvenile/adult organisms), and feeding rate inhibition, with a 21d NOEC of 0.5/1.0 mg L(-1) (for juvenile/adult organisms), were proven to be the most sensitive toxicity endpoints. An even more sensitive effect turned out to be molting frequency, which was significantly reduced; a 21d NOEC was 1.0 mg L(-1) of BPA for adult organisms and an even lower 21d NOEC of 0.05 mg L(-1) of BPA for juveniles. The observed endpoints are recorded at very low, non-toxic exposure concentrations, indicating that BPA acts as an endocrine disrupting compound, as well as a toxic substance. We also determined the importance of the direct dietary uptake of the pollutants, significant for juveniles as well as adult animals.

Is the temperature-size rule mediated by oxygen in aquatic ectotherms?

Temperature is an important environmental factor that influences key traits like body size, growth rate and maturity. Ectotherms reared under high temperatures usually show faster growth, but reach a smaller final size, a phenomenon known as the temperature-size rule (TSR). Oxygen may become a limiting resource at high temperatures, when demand for oxygen is high, especially in water as oxygen uptake is far more challenging under water than in air. Therefore, in aquatic ectotherms, the TSR might very well be mediated by temperature effects on oxygen availability and oxygen demand. To distinguish between the direct effects of temperature and oxygen mediated effects, growth rate and final size were measured in the aquatic ectotherm Asellus aquaticus (Linnaeus, 1758) reared under different temperature and oxygen conditions in a factorial design. Growth could be best described by a modified Von Bertalanffy growth function. Both temperature and oxygen affected age at maturity and growth. Growth responses to temperature were dependent on oxygen conditions (interactive effect of temperature and oxygen). Only under hypoxic conditions, when oxygen was most limiting, did we find a classic TSR. Moreover, when comparing treatments differing in temperature, but where the balance between oxygen demand and supply was similar, high temperature increased both growth rate and final size. Thus effects of oxygen may resolve the life-history puzzle of the TSR in aquatic ectotherms.

Review of the buccal-attaching fish parasite genus Glossobius Schioedte & Meinert, 1883 (Crustacea: Isopoda: Cymothoidae).

Two species of Glossobius Schioedte & Meinert, 1883 are known from Australia: Glossobius anctus Bruce & Bowman, 1989 and Glossobius impressus (Say, 1818), the latter recorded here for the first time from Australia and southern Africa. Glossobius ogasawarensis Nunomura, 1994 is here placed in synonymy with Glossobius auritus Bovallius, 1885; whereas Glossobius crassa (Dana, 1853) is removed from synonymy with G. auritus and placed into nomen dubium. Glossobius arimae Nunomura, 2001 is transferred to the genus Ceratothoa Dana, 1852. A key to the species of Glossobius is presented.

Testing the heat-invariant and cold-variability tolerance hypotheses across geographic gradients.

Changes in temperature across geographic gradients can occur on a wide temporal range, from fluctuations within hours as a result of day-night to those over many years. These events will drive many organisms towards their physiological limits of thermal tolerance. Recently, many reports support a limited scope for adaptive evolutionary responses to high temperatures, meaning a conserved heat tolerance among ectotherms in general. We address this problem and tested the heat and cold tolerance invariant-variant hypotheses in terrestrial isopods. We studied five different populations of Porcellio laevis and three populations of Porcellio scaber, spanning 30° S latitudinal gradient in Chile. The heat tolerance of woodlice was conserved with little variation along latitude and environmental temperatures, but cold tolerance decreases significantly with environmental temperatures and latitudes. Indeed, a significant and negative correlation was observed between cold tolerance and latitude. Also, significant and positive correlations were observed among cold tolerance and environmental temperatures. Conversely, heat tolerance was not significantly correlated with any of the environmental temperatures tested neither with latitude. This macrophysiological pattern indicated that heat and cold-tolerances of species and populations not always change across geographical gradients meaning that thermal tolerance responses to high temperatures may be evolutionary constrained.

Female Gnathia marleyi (Isopoda: Gnathiidae) feeding on more susceptible fish hosts produce larger but not more offspring.

The reproductive success of female Gnathia marleyi (Crustacea: Isopoda) was examined among individuals from eight species belonging to five families of common Caribbean reef fishes of St. John, US Virgin Islands that differ in susceptibility to G. marleyi infestation. Fish were placed in cages during times of peak gnathiid activity. Gnathiids were recovered from host fishes and reared to adulthood in the laboratory. Ovigerous females were then placed in individual containers until offspring were released. Measures of reproductive success used were the number of hatched zuphea 1 larvae that emerged from the brood pouch, "brood size," and the average total length of newly emerged zuphea larvae, "average z-length." Among the five host fish families tested, females that fed on the two families most susceptible to gnathiid infestation (Haemulidae and Lutjanidae) produced longer larvae than those feeding on the three less susceptible host families. However, there was no significant difference in the number of viable offspring produced. To our knowledge, this is the first study to examine the relationship between the source of the blood meal and any measure of reproductive success in female gnathiid isopods. These findings open the door to future research on potential differences in host blood quality and defense mechanisms that may cause variations in susceptibility to gnathiid among different host fishes.

New species of the deep-sea munnopsid genus Tytthocope (Crustacea, Isopoda, Asellota) from the South Atlantic and the Southern Ocean.

In the benthic samples collected during the deep-sea expeditions ANDEEP from the Weddell Sea and DIVA from the Argentine Basin the isopod family Munnopsidae was the most specious and numerous. Among the collected munnopsids three new species of Tytthocope Wilson & Hessler, 1981 have been discovered. Tytthocope is one of six genera of the subfamily Eurycopinae. It differs from other genera of the Eurycopinae by having a strongly reduced pereonite 7 and inflated pleotelson. Until now the genus consisted of five described species: four of them are known from the northern Atlantic and only one species, T. sulcifrons (Barnard, 1920) was described from the southern Atlantic off the South Africa coast. The five known species of Tytthocope have been recorded from depths less than 1461 m. Descriptions of three new species of Tytthocope collected in the South Atlantic and Southern Ocean at depths between 1530-4608 m, T. divae sp. nov., T. fahrbachi sp. nov. and T. longitelson sp. nov. are presented in the paper. T. sulcifrons is redescribed herein based on the type material.

Description of the Life Cycle Stages of the Parasitic Cymothoid, Cymothoa indica Schioedte and Meinert, 1884, and Its Prevalence in Commercial Fishes from Chilika Lagoon, India.

PURPOSE: To study the morphology of all the life stages and the life cycle of the parasitic isopod Cymothoa indica Schioedte and Meinert, 1884, and its prevalence in different commercial fishes in the Chilika Lagoon, India. METHODS: From April 2021 to December 2022, different life stages of the said parasites were collected from five different fish species from four localities of the Chilika Lagoon. The parasites were carefully removed from the host with a pair of forceps and then identified following standard literature and description. The morphology of all life stages, life cycle, and prevalence of the isopod C. indica were carried out as per the standard protocol. RESULTS: A total of 1252 host fishes were analysed. The total prevalence was 44.5%. The host with the highest prevalence of C. indica was Glossogobius giuris, with 58.79% of the hosts parasitized by at least one parasite individual. Followed by the host Datnoides polota (50.98%), Johnius dussumieri (46.25%), Etroplus suratensis (28.45%) and the least prevalence was in Lates calcarifer (14.70%). The description of the life stages is based on the observation of 523 females, 116 males, 46 Juveniles, and 50 embryonic stages of the said parasites. CONCLUSION: The description of all the life stages and life cycles certainly helps to identify this species with clarity and ease in understanding the species' biology. In future, this study may be helpful in the effective management towards the improvement of aquaculture productivity.

The relative importance of predation risk and water temperature in maintaining Bergmann's rule in a marine ectotherm.

Bergmann's rule-an increase in body size with latitude-correlates with latitudinal declines in ambient temperature and predation risk, but relatively few studies simultaneously explore the relative importance of these factors. Along temperate Atlantic shorelines, the isopod Idotea balthica from high latitudes are 53% longer on average than isopods from low latitudes. When reared at 6°-24°C, juveniles increased growth and development rates with temperature. Because the increase in growth rate with temperature outstripped increases in development rate, female size at maturity increased with temperature. This thermal sensitivity of growth cannot account for the latitudinal pattern in body size. Within temperature treatments, females from low latitudes reached sexual maturity at younger ages and at a smaller size than did females from higher latitudes. This shift in life-history strategy is predicted by latitudinal declines in predation pressure, which we tested using field-tethering experiments. Overall, isopods at low latitudes had a 44% greater mortality risk from daytime predators relative to isopods at higher latitudes. We conclude that a latitudinal gradient in predation risk, not temperature, is principally responsible for Bergmann's rule in I. balthica. Increases in body size during future warming of oceans may be constrained by local patterns of predation risk.

An experimental field test of susceptibility to ectoparasitic gnathiid isopods among Caribbean reef fishes.

Susceptibility to infestation by a gnathiid isopod (Gnathia marleyi: Crustacea: Isopoda) was examined among 16 species from 9 families and 3 orders of common Caribbean reef fishes off St. John, United States Virgin Islands. Fish were placed in cages during times of peak gnathiid activity. Individuals from most (n=14) species were compared against a single species (French Grunt, Haemulon flavolineatum) that served as a standard and effectively controlled for the effects of habitat and variation in gnathiid abundance on exposure to and the likelihood and intensity of host infestation by gnathiids. All species were susceptible to infestation by gnathiids, with individual hosts harbouring up to 368 gnathiids. However, there was significant variation in levels of infestation among the 14 comparison species. Controlling for body size, nocturnal species from the families Haemulidae and Lutjanidae had the highest gnathiid infestation. Our finding that haemulids and lutjanids are particularly susceptible has important implications for the role of gnathiids in Caribbean reef food webs, given the role members of these families play in trophic connectivity between reefs and associated habitats. To our knowledge this is the first manipulative field study to examine variation among potential hosts in susceptibility to an ectoparasite in any terrestrial or aquatic system and is the greatest number of teleost hosts documented for any gnathiid species.

Fissarcturus walteri sp. nov. from the Ross Sea of the Southern Ocean (Isopoda, Antarcturidae).

During the Victoria-Land Transect project two specimens of a new species, Fissarcturus walteri sp. nov., were found in the Ross Sea along the Victoria Land Coast, Antarctica, during the 19th Italica expedition in February 2004. This is the second species of Fissarcturus from the Ross Sea after F. rossi Brandt, 2007. F. walteri sp. nov. is most similar to Fissarcturus granulosus (Nordenstam, 1933) from South Georgia but can be distinguished by the blunt short, anteriorly directed supraocular spines and elevations and some other characters as described herewith.

The genus Cymodoce Leach, 1814 (Crustacea: Isopoda: Sphaeromatidae) in the Persian Gulf with description of a new species.

Cymodoce truncata (Leach, 1814), the type species of the genus, C. zanzibarensis (Stebbing, 1910) and C. richardsoniae (Nobili, 1906) are redescribed based on type specimens or topotypic material, and a neotype is designated for Cymodoce richardsoniae. A revised generic diagnosis and description is provided for the genus Cymodoce. Cymodoce delvarii sp. nov. is described from the subtidal zone of the Iranian coasts of the Persian Gulf.

Review of the marine isopod crustacean genus Hansenium Serov and Wilson, 1995 (Asellota: Stenetriidae) from tropical Australia and Papua New Guinea, with description of a new genus.

The genus Hansenium is revised and a new diagnosis presented. A neotype is designated for the type species Hansenium hanseni (Müller, 1991), and the genus is restricted to the type species and Hansenium remocarpus Kensley and Schotte, 2002. Machatrium gen. nov. and the following species are described: Machatrium falcensis sp. nov. (type species), Machatrium thungku sp. nov. from Lizard Island, Great Barrier Reef; Machatrium wongat sp. nov. from Madang, Papua New Guinea, Machatrium tropex (Bolstad and Kensley, 1999), comb. nov. also from Madang, Papua New Guinea; a further five species are transferred from Hansenium to Machatrium gen. nov. The remaining species of Hansenium are retained as incertae sedis in their existing combination (11 species), reallocated to other genera (1 species) or regarded as species inquirenda (3 species). The principal differentiating characters of Hansenium, Machatrium gen. nov. and Stene triumn Haswell, 1881, are the pseudorostrum being short and trapezoid or long and anteriorly narrowed, morphology of the male pereopod 1, notably the shape of the propodus inferior margin, presence or absence of a process on the inferodistal margin of the merus and carpus; and the apex of the appendix masculina being acute or blunt, with or without a concavity and with or without terminal setae.

Calcium bodies of Titanethes albus (Crustacea: Isopoda): molt-related structural dynamics and calcified matrix-associated bacteria.

Crustaceans form a variety of calcium deposits in which they store calcium necessary for the mineralization of their exoskeletons. Calcium bodies, organs containing large amounts of calcium, have been reported in some terrestrial isopod crustaceans, but have not yet been extensively studied. We analyzed the architecture of these organs during the molt cycle in the isopod Titanethes albus. Two pairs of calcium bodies are positioned ventrolaterally in posterior pereonites of T. albus. Individual organs are epithelial sacs that contain material arranged in concentric layers delimited by thin laminae. As demonstrated by electron microscopy and fluorescence in situ hybridization, abundant bacteria are present within the calcium bodies. Regardless of the molt cycle stage, crystalline concretions are present in the central areas of the calcium bodies. Energy dispersive X-ray spectrometry of the concretions demonstrated that they are composed predominantly of calcium and phosphorus and selected area electron diffraction indicated the presence of hydroxyapatite. In molting animals, a glassy layer of mineralized matrix is formed between the envelope and the outermost lamina of the calcium body. This layer consists of an amorphous calcium mineral which contains less phosphorus than the central concretions and is resorbed after molt. Since changes in the mineralized matrix are synchronized with the molt cycle, the calcium bodies likely function as a storage compartment that complements sternal deposits as a source of calcium for the mineralization of the exoskeleton. Bacteria associated with the mineralized matrix of calcium bodies are evidently involved in calcium dynamics.

Warming alters community size structure and ecosystem functioning.

Global warming can affect all levels of biological complexity, though we currently understand least about its potential impact on communities and ecosystems. At the ecosystem level, warming has the capacity to alter the structure of communities and the rates of key ecosystem processes they mediate. Here we assessed the effects of a 4°C rise in temperature on the size structure and taxonomic composition of benthic communities in aquatic mesocosms, and the rates of detrital decomposition they mediated. Warming had no effect on biodiversity, but altered community size structure in two ways. In spring, warmer systems exhibited steeper size spectra driven by declines in total community biomass and the proportion of large organisms. By contrast, in autumn, warmer systems had shallower size spectra driven by elevated total community biomass and a greater proportion of large organisms. Community-level shifts were mirrored by changes in decomposition rates. Temperature-corrected microbial and macrofaunal decomposition rates reflected the shifts in community structure and were strongly correlated with biomass across mesocosms. Our study demonstrates that the 4°C rise in temperature expected by the end of the century has the potential to alter the structure and functioning of aquatic ecosystems profoundly, as well as the intimate linkages between these levels of ecological organization.

Magnesium-aspartate-based crystallization switch inspired from shell molt of crustacean.

Many animals such as crustacean periodically undergo cyclic molt of the exoskeleton. During this process, amorphous calcium mineral phases are biologically stabilized by magnesium and are reserved for the subsequent rapid formation of new shell tissue. However, it is a mystery how living organisms can regulate the transition of the precursor phases precisely. We reveal that the shell mineralization from the magnesium stabilized precursors is associated with the presence of Asp-rich proteins. It is suggested that a cooperative effect of magnesium and Asp-rich compound can result into a crystallization switch in biomineralization. Our in vitro experiments confirm that magnesium increases the lifetime of amorphous calcium carbonate and calcium phosphate in solution so that the crystallization can be temporarily switched off. Although Asp monomer alone inhibits the crystallization of pure amorphous calcium minerals, it actually reduces the stability of the magnesium-stabilized precursors to switch on the transformation from the amorphous to crystallized phases. These modification effects on crystallization kinetics can be understood by an Asp-enhanced magnesium desolvation model. The interesting magnesium-Asp-based switch is a biologically inspired lesson from nature, which can be developed into an advanced strategy to control material fabrications.