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We have compiled the toxicity data on stygofauna and other aquatic subterranean organisms in one (eco)toxicological database. A total of 46 studies were found, containing 472 toxic endpoints covering 43 different stressors. These compounds were tested on subterranean organisms from four phyla, 12 orders, 24 genera, and 55 species. The studies included were published between 1976 and December 2023 using fauna collected in 13 different countries. The suitability of the studies was assessed to indicate the completeness of reporting and their suitability for use in hazard and risk assessment. This compilation provides a valuable source of data for future development of toxicity testing protocols for groundwater organisms, and to support decision‐making, ecological risk assessments and the derivation of water quality criteria for the protection of groundwater ecosystems. Environ Toxicol Chem 2024;43:2492–2500. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Identifying feeding strategies at lower bounds of habitat productivity is fundamental to understand the relationship between energy availability and trophic specialization. Low productivity is expected to severely constrain trophic specialization because organisms may no longer be able to fulfil their energy requirements by feeding on a reduced set of resources. However, species living in low-productivity habitats often exhibit particular biological traits such as low metabolic rates and high food-finding abilities, which may release constraints on trophic specialization., In the present study, we used carbon (C) and nitrogen (N) stable isotopes to measure the degree of trophic specialization in two species of isopods ( Proasellus valdensis and Proasellus cavaticus) living in groundwater, one of the most energy-limited environments on earth. Fundamental specialization was obtained from a 13C/15N-labelling experiment in the laboratory: we measured separately the carbon and nitrogen assimilation rates of the two species across the three food sources encountered in their natural cave habitats (fine and coarse particulate organic matter and sedimentary biofilm). Then, for each species, we tested for variation in diet composition among individuals and populations by quantifying the relative contribution of the three food sources to the diet of multiple individuals within 5 cave populations., The labelling experiment showed that both species assimilated about 10 times more carbon and at least 4 times more nitrogen from sedimentary biofilm than from both forms of particulate organic matter. Field samplings showed that sedimentary biofilm made up, on average, 83% of the diet of isopods. Moreover, we found almost no variation in diet among individuals of a cave population as well as among cave populations within species., This study provides the first evidence of a high degree of trophic specialization in a low-productivity cave environment. Both species exhibited a strong fundamental specialization on sedimentary biofilm and most probably fed selectively on this food source in their natural environment. Our findings challenge the prediction that species would adopt generalist feeding strategies at lower bounds of habitat productivity. [ABSTRACT FROM AUTHOR]

We implemented a detailed morphometry and multivariate statistics to establish a general, large-scale racial differentiation in Asellus aquaticus (L.) sensu Racovitza. We ascertained that in surface populations a set of 11 morphometric characters might equivalently be represented by the pleopod respiratory area size alone. The analyses resulted in a distinct distribution pattern, with the large respiratory area populations disposed mainly along the Dinaric karst between southern Slovenia and western Macedonia and surrounded by the medium respiratory area morph, spatially irregularly substituted by the small area morph. This pattern is in contradiction with the distribution pattern of molecularly defined clades (as shown by Verovnik et al. 2005 ). We could find no ecological, hydrographical or paleogeographical explanations for such distribution pattern either. The only hypothetical explanation would be a preservation of the large respiratory area as a plesiomorphic character in the comparatively sheltered karst habitats, while throughout the easier accessible parts of the species range it was replaced by the ‘modern’ smaller area size. While a diminution of the respiratory area functionally means an increased sclerotization – hardening of pleopod IV–V exopodites, endopodites of pleopods III–V remain less sclerotized, probably respiratory and osmoregulatory functional. [ABSTRACT FROM AUTHOR]

Granivory (seed feeding) evolved in many animal groups. Field observations hint at the existence of granivory in terrestrial isopods (Crustacea: Isopoda: Oniscidea), for which it was previously unknown. In this paper granivory in terrestrial isopods is addressed for the first time, focusing on (i) seed acceptance in the presence of plant litter and (ii) size as a constraint for acceptance and consumption. In a laboratory choice experiment, Armadillidium vulgare consumed seeds of Capsella bursa-pastoris and Poa annua when plant litter was present. In a no-choice experiment, seeds of seven plant species were offered to four isopod species giving 13 combinations in total [ A. vulgare (seven species of seeds), Oniscus asellus (two), Porcellio scaber (two), and Porcellionides pruinosus (two)]. The tested isopods differed in their acceptance (proportion of individuals consuming seeds) and consumption (both number and amount of seeds eaten) of seed species. Size as a constraint was demonstrated in A. vulgare offered Cirsium arvense seed, since the probability that this large seed was eaten increased with body size of the isopod. In the other 10 seed–isopod pairs, seed consumption increased linearly with isopod body size. Granivory is thus widespread in terrestrial isopods, although the tendency to eat seeds differs between species. [ABSTRACT FROM AUTHOR]

In the present study we present a population model (Metapopulation model for Assessing Spatial and Temporal Effects of Pesticides [MASTEP]) describing the effects on and recovery of the waterlouse Asellus aquaticus after exposure to a fast-acting, nonpersistent insecticide as a result of spray drift in pond, ditch, and stream scenarios. The model used the spatial and temporal distribution of the exposure in different treatment conditions as an input parameter. A dose-response relation derived from a hypothetical mesocosm study was used to link the exposure with the effects. The modeled landscape was represented as a lattice of 1- by 1-m cells. The model included processes of mortality of A. aquaticus, life history, random walk between cells, density dependence of population regulation, and, in the case of the stream scenario, medium-distance drift of A. aquaticus due to flow. All parameter estimates were based on expert judgment and the results of a thorough review of published information on the ecology of A. aquaticus. In the treated part of the water body, the ditch scenario proved to be the worst-case situation, due to the absence of drift of A. aquaticus. Effects in the pond scenario were smaller because the pond was exposed from one side, allowing migration from the other, less contaminated side. The results of the stream scenario showed the importance of including drift for the population recovery in the 100-m stretch of the stream that was treated. It should be noted, however, that the inclusion of drift had a negligible impact on numbers in the stream as a whole (600 m). [ABSTRACT FROM AUTHOR]

We demonstrate for the first time the presence of bacterial endosymbionts in the midgut glands (hepatopancreas) of the freshwater detritivore Asellus aquaticus (Isopoda), whereas the hepatopancreas of another crustacean detritivore, Gammarus pulex (Amphipoda), which coexists with the former species, was devoid of such bacteria. We detected both phenol oxidase and cellulase activity in hepatopancreatic extracts from both detritivores, which suggests that both of these enzymes are produced in the midgut glands of both species. After treatment with antibiotics, both the number of hepatopancreatic bacteria and enzymatic activity were reduced in the isopod hepatopancreas, but antibiotics had no effect on enzyme activity in the amphipod hepatopancreas. Feeding on microbially inactivated leaf litter did not affect enzyme activity in hepatopancreatic extracts from A. asellus, but increased cellulase activity was seen in the hepatopancreas of G. pulex. These results (1) confirm the hypothesized enzymatic adaptation of crustacean freshwater detritivores to their food sources of terrestrial origin, (2) demonstrate that the isopod A. aquaticus, like its terrestrial relatives, contains endosymbiotic bacteria that contribute to digestive processes, and (3) show interspecific differences between these coexisting crustacean detritivores in terms of enzyme origin and their dependence on microbiota. [ABSTRACT FROM AUTHOR]

Abstract The subterranean Isopods belonging to the genus Stenasellus have an interesting disjunct distribution in the peri-Tyrrhenian area with morphologically closely related taxa occurring in Sardinia, Corsica, Tuscany and in the Pyrenees phreatic and interstitial waters. Because the dispersal capacities of these organisms are limited, their distribution has been associated traditionally with the tectonic events leading to the separation of the Sardinia–Corsica microplate from the Pyrenees and its subsequent movement towards the Italian peninsula. We sequenced a fragment of the mtDNA cytochrome oxidase I gene (COI) for multiple populations of the S. racovitzai species-group (Corsica, Sardinia, Tuscany) and S. virei (Pyrenees). We found that multiple phylogenetic analyses always gave the same topology, which is consistent with the genetic relations found using allozyme data, and with the palaeogeography of the area. The molecular data suggest that a combination of vicariance and dispersal events explain most effectively the present distribution pattern of these organisms. We also calculated COI rates and calibrated them against absolute time, taking advantage of the availability of two geologically based time estimates. Rates on all substitutions are similar to those published for other crustaceans for the same COI fragment, including taxonomically and ecologically distant groups. Rates on third codon positions or on transversions are generally lower than those found in other crustaceans. [ABSTRACT FROM AUTHOR]

Abstract The performance of Oniscus asellus (Isopoda) and its influence on litter mass loss and mineralization was assessed in a microcosm experiment, using beech (Fagus sylvatica) leaf litter that was produced on different soil types, contrasting atmospheric CO2 concentrations, and different nitrogen deposition rates. Litter quality was significantly altered by these treatments, and many of the CO2 and N effects differed between soil types. Litter quality affected subsequent litter mass loss rates, microbial respiration, and leaching of dissolved organic carbon (DOC) and nitrate. These effects were largely independent of the presence of isopods, even though isopods highly accelerated litter mass loss, stimulated microbial respiration by 37%, and increased nitrate leaching by 50%. Isopods did not change their relative rates of litter consumption and growth in response to litter quality. Isopod mortality, however, increased with increasing litter lignin/N ratios, and was significantly different between soil types, which may indicate long-term effects on litter decomposition through altered isopod densities. Having the choice among the litter of three different species [maple (Acer pseudoplatanus), beech (Fagus sylvatica) and oak (Quercus robur)] grown at either ambient or elevated CO2, isopods preferred maple to beech when all the litter was produced under elevated CO2. This suggests that beyond changes in consumption, an altered food selection by isopods in a CO2-enriched atmosphere may affect the temporal and spatial composition of the litter layer in temperate forests. In contrast to previous findings, we conclude that isopods do not always increase their consumption rates, and hence do not differentially affect microbial decomposition in litter of poorer quality. Nevertheless changes in animal densities and/or shifts in their food preferences, could result in altered decomposition and carbon and nutrient turnover rates. [ABSTRACT FROM AUTHOR]

Summary The effect of differences in food composition on growth, body composition and cold tolerance of the isopods Porcellio scaber (Latreille) and Oniscus asellus (L.) has been studied. The effect on reproduction of P. scaber was included. Total lipid and protein content remained the same in O. asellus, given food with a nitrogen content of 2.4, 2.5, 2.8 or 3.1% for 8 weeks. Those fed on 3.1% N gained significantly more weight than those fed on 2.4, 2.5 or 2.8% N. Cold tolerance after a period of low temperature acclimation could not be tested, due to high mortality at the subzero treatment. Haemolymph osmolality increased after the winter acclimation for all food treatments. Juvenile P. scaber, given food of 1.8, 2.5 or 3.1% N, showed no difference in growth over 18 weeks, nor in body composition over 14 weeks. Diet did not influence cold tolerance ability and haemolymph osmolality remained the same with changing cold tolerance of the animals. Gravid females of P. scaber were separated to examine the effect of diet on reproduction. Diet did not influence the number of juveniles, nor their weight. In all food treatments, a significant correlation was found between the weight of the female and the number and weight of her offspring. [ABSTRACT FROM AUTHOR]

Summary 1. In long-term laboratory studies, the influence of different food materials on parameters of population dynamics was compared in the sympatric woodlice, Porcellio scaber and Oniscus asellus, as a measure of interspecific differences in the utilization of food. 2. Freshly fallen leaf litter of different tree species had been acidified and microbially inoculated prior to the experiments. By analysing the influence of pH level, density and activity of litter-colonizing microbiota and several physico-chemical characteristics of the leaf litter, we obtained information on those factors that determine food quality. 3. The studied species responded similarly to different leaf litter species in that both P. scaber and O. asellus performed better on litter with low C:N ratio. Overall, both isopod species reproduced more successfully on litter with higher pH levels, containing half the levels of tannins and other phenolics. 4. Interspecific differences were obvious with respect to the significance of litter-colonizing microbiota, and the dependence of juveniles on particular food parameters. While the performance of adult P. scaber was influenced by both litter-colonizing microbiota and physico-chemical characteristics of the leaf litter, adult O. asellus were influenced by leaf litter characteristics, but not by litter-colonizing microbiota. Juvenile mortality was affected by the tested food parameters in O. asellus, but not in P. scaber. Growth rates of juveniles of both species were influenced by physico-chemical characteristics of the leaf litter. Additionally, leaf litter microbiota had a significant influence on growth rates in juvenile P. scaber, but not in juvenile O. asellus. 5 Reasons for, and consequences of, similarities and differences between the observed sympatric species, and intraspecific differences between ontogenetic stages, are important aspects of soil ecology and may help explain the sympatric coexistence of two species belonging to the... [ABSTRACT FROM AUTHOR]

Both species have small sessile compound eyes. The dioptric apparatus of J. albifrons consists of a biconvex lens and a pyriform crystalline cone, the latter formed by two principal and two accessory cone cells. A. aquaticus has a reduced lens and a round cone formed by two to four principal cone cells with two to no accessory cone cells. Distal pigment cells and pigmented retinular cells lie between the ommatidia in J. albifrons. A. aquaticus has only the pigmented retinular cells. Both species have a fused, continuous (unbanded) rhabdom formed by eight retinular cells (R1–8), one of which (R8) is situated distally. The retinular cells R1–7 form, in J. albifrons, a cylinder-shaped middle portion with three microvillar directions (60° apart) and a proximal star-shaped portion. The entire rhabdom of A. aquaticus is star-shaped. Distal pigment-ceil processes and basal cells form the fenestrated membrane in J. albifrons and ‘eye-cup cells’ in A. aquaticus. [ABSTRACT FROM AUTHOR]

Discusses a study which collected specimens of the woodlice Oniscus asellus and Porcellio scaber from a contaminated deciduous woodland three kilometers downwind of a primary zinc, lead and cadmium smelting works, and from a similar but uncontaminated site. Maintenance of the samples in factorial combination on leaves of field maple collected from the litter layer at the two sites; Differences in the extent to which the two species accumulated or lost zinc, cadmium, and lead during the experiment; Concentrations of iron.

1. Approximately 700 individuals of Oniscus asellus L. of all sizes were subjected to oxygen consumption tests between March 1963 and March 1964. 2. In the relationship live weight to length a change occurs at approximately 20 mg and 7.5 mm, which also coincides with a change in the respiratory rate to live weight relationship. The high oxygen uptake at live weights less than 20 mg is clearly associated with growth. 3. At weights greater than 20 mg the respiratory rate per unit weight is fairly constant; except during May. June, and July when seasonal aberrance, associated with reproductive activities, occurred. 4. A linear relationship exists between the live weight of an individual and the number of embryos and/or young per brood. Weight increase above 100 mg is mainly accounted for by an increase in the number of young per brood. 6. Seasonal differences in respiratory rates occur in both sexes. The highest respiratory rates per unit weight occur between March and August and are more than twice as high as those obtained for the winter months. 7. Two methods of calculating a 'best estimate' of oxygen consumption per unit weight per unit time are given. The two estimates are close: 4.992 and 5.328 mm³ O2/mg/day. [ABSTRACT FROM AUTHOR]

(1) Comparative studies of the ash-ratio and gravimetric methods of determining assimilation efficiency in Asellus aquaticus showed that the differential use of minerals by this species rendered the ash-ratio method unreliable. Results obtained by the gravimetric method were therefore employed in the analysis of further experiments. (2) The assimilation efficiencies estimated for A. aquaticus ranged between 26 and 44%, and varied according to population density and reproductive condition. (3) Individual winter males had a significantly lower assimilation efficiency (26%) than grouped animals (35%), but the assimilation efficiency of summer males (33%) did not differ significantly from that of winter males at the same density. It is concluded that density affects assimilation efficiency in A. aquaticus, (4) The assimilation efficiency of summer males (33 %) is significantly different from that of summer females (non-ovigerous, 41 %; ovigerous, 44%). A mean assimilation efficiency of 40% is proposed for the summer period whereas an overall annual mean of 30% is suggested. (5) Despite the various assimilation efficiencies reported within any one season consumption rate per unit weight is fairly constant (winter, 0.04–0.05 cal/24 h; summer, 0.36–0.38 cal/24 h) and it is suggested that the different assimilation rates are a mechanism whereby the additional energy and material requirements of females for breeding can be met without increasing food intake. [ABSTRACT FROM AUTHOR]