Low diversity, high dominance, and high host prevalence of parasitic isopods of the family Cymothoidae in Chilika lagoon, India: a comparative study between a semi-enclosed ecosystem and its adjoining open region.

Patterns in parasite diversity are shaped by their environmental and ecological settings, and to better understand their interactions with hosts and the corresponding biology, it is crucial to understand these context-dependent patterns. To achieve this, we use cymothoid isopods, an important group of fish parasites, to test a long-standing hypothesis about parasite diversity and prevalence pattern: whether semi-enclosed water bodies allow low diversity and high prevalence of parasitic isopods. Specifically, we compare these patterns between Chilika lagoon (Odisha, India), a semi-enclosed water body, and the adjoining Odisha coast (India). Our finding reveals that the semi-enclosed Chilika lagoon has a considerably lower diversity of parasitic isopods than its adjoining open sea along the Odisha coast. Additionally, the parasitic isopod infection levels in Chilika lagoon are noticeably higher, and isopod assemblage is less even than those in coastal waters along the Odisha coast. Our results support the hypothesised association between enclosed water bodies, parasite diversity, and host prevalence and contribute to an enhanced comprehension of the ecology of parasitic isopods in distinct marine environments.

Convergent evolution of ventral adaptations for enrolment in trilobites and extant euarthropods.

The ability to enrol for protection is an effective defensive strategy that has convergently evolved multiple times in disparate animal groups ranging from euarthropods to mammals. Enrolment is a staple habit of trilobites, and their biomineralized dorsal exoskeleton offered a versatile substrate for the evolution of interlocking devices. However, it is unknown whether trilobites also featured ventral adaptations for enrolment. Here, we report ventral exoskeletal adaptations that facilitate enrolment in exceptionally preserved trilobites from the Middle Ordovician Walcott-Rust Quarry in New York State, USA. Walcott-Rust trilobites reveal the intricate three-dimensional organization of the non-biomineralized ventral anatomy preserved as calcite casts, including the spatial relationship between the articulated sternites (i.e. ventral exoskeletal plates) and the wedge-shaped protopodites. Enrolment in trilobites is achieved by ventrally dipping the anterior margin of the sternites during trunk flexure, facilitated by the presence of flexible membranes, and with the close coupling of the wedge-shaped protopodites. Comparisons with the ventral morphology of extant glomerid millipedes and terrestrial isopods reveal similar mechanisms used for enrolment. The wedge-shaped protopodites of trilobites closely resemble the gnathobasic coxa/protopodite of extant horseshoe crabs. We propose that the trilobites' wedge-shaped protopodite simultaneously facilitated tight enrolment and gnathobasic feeding with the trunk appendages.

Dissecting the costs of a facultative symbiosis in an isopod living with ants.

The balance between costs and benefits is expected to drive associations between species. While these balances are well understood for strict associations, we have no insights to which extent they determine facultative associations between species. Here, we quantified the costs of living in a facultative association, by studying the effects of red wood ants on the facultatively associated isopod Porcellio scaber. Porcellio scaber frequently occurred in and near hostile red wood ant nests and might outnumber obligate nest associates. The facultative association involved different costs for the isopod. We found that the density of the isopod decreases near the nest with higher ant traffic. Individuals in and near the nest were smaller than individuals further away from the nest. Smaller individuals were also found at sites with higher ant traffic. A higher proportion of wounded individuals was found closer to the nest and with higher ant traffic. We recorded pregnant females and juveniles in the nest suggesting that the life cycle can be completed inside the nests. Lab experiments showed that females died sooner and invested less in reproduction in presence of red wood ants. Porcellio scaber rarely provoked an aggression response, but large numbers were carried as prey to the nest. These preyed isopods were mainly dried out corpses. Our results showed that the ant association incurred several costs for a facultative associate. Consequently, red wood ant nests and their surrounding territory act as an alternative habitat where demographic costs are offset by a stable resource provisioning and protection.

Size Relationship of the Ectoparasite Tachaea chinensis in the Host Shrimp Palaemon paucidens From Shiga Prefecture, Japan.

Monthly sampling of freshwater shrimps infested by the corallanid ectoparasite Tachaea chinensis was conducted at an agricultural canal of the Etsura River system, Shiga Prefecture, Japan, from April 2018 through December 2019. A total of 944 Palaemon paucidens and 279 Neocaridina spp. were collected, and 203 immature T. chinensis were found attached to the carapace of these hosts. Mean prevalence was 23.1% for P. paucidens and 6.4% for Neocaridina spp. Newly hatched T. chinensis ectoparasitizing P. paucidens were detected in August 2018 (minimum body length of parasite 3.2 mm) and appeared continually until June 2019 (maximum body length of 10.3 mm) and were not observed in July. In contrast, T. chinensis on Neocaridina spp. were first detected in August of each year (with minimum body length of 2.0 mm) and were observed until September in 2018 and to November in 2019 (maximum body length of 5.8 mm). Ratios of the body length of T. chinensis to the carapace length of the host shrimp were almost constant (0.8-0.9) with the host species and parasite growth. Although infestation by early-life-stage individuals of T. chinensis was observed on both shrimp species, P. paucidens appeared to be the principal host for individuals larger than 6 mm in body length.

Functional adaptations in the tergite cuticle of the desert isopod Hemilepistus reaumuri (Milne-Edwards, 1840).

To survive in its extreme habitat, the cuticle of the burrowing desert isopod Hemilepistus reaumuri requires properties distinct from isopods living in moist or mesic habitats. In particular, the anterior tergites are exposed to high mechanical loads and temperatures when individuals guard the entrance of their burrow. We have, therefore, investigated the architecture, composition, calcite texture and local mechanical properties of the tergite cuticle, with particular emphasis on large anterior cuticle tubercles and differences between the anterior and posterior tergite. Unexpectedly, structure and thickness of the epicuticle resemble those in mesic isopod species. The anterior tergite has a thicker endocuticle and a higher local stiffness than the posterior tergite. Calcite distribution in the cuticle is unusual, because in addition to the exocuticle the endocuticle distally also contains calcite. The calcite consists of a distal layer of dense and highly co-oriented crystal-units, followed proximally by irregularly distributed and, with respect to each other, misoriented calcite crystallites. The calcite layer at the tip of the tubercle is thicker relative to the tubercle slopes, and its crystallites are more misoriented to each other. A steep decrease of local stiffness and hardness is observed within a distal region of the cuticle, likely caused by a successive increase in the ACC/calcite ratio rather than changes in the degree of mineralisation. Comparison of the results with other isopods reveals a much lower ACC/calcite ratio in H. reaumuri and a correlation between the degree of terrestriality of isopod species and the magnesium content of the cuticle.

Intracellular calcium phosphate deposits contribute to transcellular calcium transport within the hepatopancreas of Porcellio scaber.

Like in most Crustacea, the cuticle of terrestrial isopods is hardened by a calcareous mineral phase. This rigid cuticle is frequently shed during a process called moulting. To reduce calcium loss, Porcellio scaber eats the shed cuticle, the exuviae, and absorb the calcium from it through large tubular diverticula of the intestine, called the mid gut glands or hepatopancreas. After moulting the absorbed calcium should be transported immediately into the hemolymph from which it is used to rapidly mineralize the new cuticle. This suggests that the hepatopancreas epithelium transports calcium from the lumen to the hemolymph. We used TEM, energy-filtered TEM and electron-probe X-ray microanalysis to analyse the distribution of elevated calcium within the hepatopancreas cells of P. scaber. We used animals in the postmoult stage that have eaten their exuviae and, as a control, those that have not ingested the exuviae. To minimize calcium loss within the samples, we used high pressure frozen and freeze substituted samples and propane-1-3-diol as floatation medium for thin-sectioning. The results reveal intracellular dense deposits containing calcium, phosphorus and oxygen at the apical microvillus membrane, within the cytoplasm, attached to vesicles and to the basolateral membrane, as well as extracellular between cells and the basal lamina. Control animals were devoid of these deposits. The results indicate that calcium from the exuviae is absorbed and transported across the epithelium into the hemolymph. We propose that during transport, intracellular calcium is bound to phosphate avoiding toxic effects of high concentrations of ionized calcium.

The effect of exuviae ingestion on lysosomal calcium accumulation and the presence of exosomes in the hepatopancreas of Porcellio scaber.

The hepatopancreas of isopods has major functions in food digestion and storage of carbohydrates and lipids. Also, it stores essential and accumulates xenobiotic metals in lysosomal granules within the two major cell types, the S- and B-cells of the tissue. A µCT study on moulting Porcellio scaber has shown mineral within the hepatopancreas lumen, when the animal has ingested their shed cuticle after moulting, suggesting recycling of mineral from the exuviae. This study aims to reveal if the lysosomal metal containing granules store calcium originating from the ingested exuviae. Therefore, we investigated the effect of cuticle ingestion on the elemental composition of the hepatopancreas granules of P. scaber, using electron probe X-ray microanalysis. For the preservation of diffusible elements, samples were high pressure frozen and freeze substituted in acetone and we used Propane-1,3-diol as a floatation medium for sections. We analyzed S- and B-cells of animals in the postmoult and intermoult stage that have ingested their exuviae and, as a negative control, cells from postmoult animals that have not ingested their exuviae. STEM and TEM were used for the investigation of the ultrastructure. Unexpectedly, the cryo-fixed samples contain numerous extracellular vesicles (exosomes) and many multivesicular bodies containing pro-exosomes. We show a significant increase of calcium, copper, zinc and sulphur within the metal granules upon exuviae ingestion, and, after 9 days, a reduction of calcium and zinc. The results indicate transitory storage of calcium from the exuviae within the metal granules and its subsequent utilization in cuticle mineralization.

Are terrestrial isopods able to use stridulation and vibrational communication as forms of intra and interspecific signaling and defense strategies as insects do? A preliminary study in Armadillo officinalis.

The capability of producing sounds and vibrations is well known in insects and is thought to be a form of intra- and interspecific communication. Sounds and vibrations are used and modulated for several aims such as interacting with conspecifics, getting information from the environment, and defending against predators. This phenomenon is less known but also present in other arthropods, including a few roller-type terrestrial isopods. In this study, we used a Y-shape test apparatus to investigate the behavior of adult individuals of Armadillo officinalis Duméril, 1816 (Crustacea: Isopoda: Oniscidea) when exposed to two particular vibrational stimuli, namely species-specific stridulations and non-specific substrate-borne vibrations. Our results showed that adults of A. officinalis significantly react to the presence of both types of vibrational stimuli, by moving away from the vibrational source as if they experienced these vibrations as a sign of danger or disturbance. A. officinalis can produce stridulations only when it rolls into a ball during the so-called conglobation, a possible defense mechanism against predators. Stridulation might thus be a secondary form of defense used during conglobation to deter a predator following contact with it and might be experienced as an alert by conspecifics nearby. The high sensitivity to non-specific substrate-borne vibrations might provide A. officinalis with the possibility to anticipate dangers and adverse conditions, giving it a better chance of survival.

IGFBP-rP1, a strongly conserved member of the androgenic hormone signalling pathway in Isopoda.

The first protein which has been described to interact with the malacostracan Androgenic Gland Hormone (AGH) is a binding protein called IGFBP-rP1. It has been identified and studied in several species of decapods, in which its interaction with the masculinizing hormone and its expression patterns have been established in several ways. However, this protein remains uncharacterised to date in the other malacostracan orders, like Amphipoda and Isopoda, although they were historically the first ones in which the androgenic gland and the corresponding hormone were respectively described. In this article, we identified the IGFBP-rP1 of isopods and established its implication in the pathway of the AGH with a silencing approach in the model species Armadillidium vulgare. We also showed that this gene is expressed in all the tissues of males and females, with a similar pattern in animals infected with Wolbachia, a feminizing endosymbiont of several isopod species. The expression pattern did not differ during the development of uninfected and infected animals either. We finally studied the evolution of the IGFBP-rP1 in 68 isopod species, looking for conserved motifs and evidence of natural selection. Altogether, our results showed that this gene is constitutively expressed and strongly conserved in isopods, in which it likely constitutes a key element of the insulin/IGF signalling pathway. However, we also illustrated that IGFBP-rP1 is not sufficient on its own to explain the different developmental paths taken by the males and the females or feminized genetic males.

Parasitic effects of the bopyrid Megacepon goetici (Crustacea: Isopoda) on the varunid crab Gaetice depressus.

The effects of infestation by the bopyrid isopod Megacepon goetici on the varunid crab Gaetice depressus were investigated. This crab is one of the most common crabs in Japanese intertidal shores where it plays a key role in structuring the benthic community. Samples were collected in Wakayama Prefecture, Japan. From a total of 1694 crabs, 61 (3.6%) were parasitized by bopyrid isopods. No ovigerous females were parasitized, which may be evidence of parasitic castration of female host crabs, as has been described in other parasitized brachyuran crabs. Total weight was reduced in both males and females, and infested crabs also exhibited subtle lateral and dorsal carapace swelling due to the presence of parasites under the carapace. We therefore conclude that the morphology and the reproductive capacity of G. depressus were significantly affected by the bopyrid isopod.

Diversity in form and function: Vertical distribution of soil fauna mediates multidimensional trait variation.

It has been widely recognized that species show extensive variation in form and function. Based on species' attributes, they can be positioned along major axes of variation, which are often defined by life-history traits, such as number of offspring, age at maturity or generation time. Less emphasis has been given in this respect to tolerance traits, especially to resistance to abiotic stress conditions, which often determine community (dis)assembly and distribution. Soil fauna species distribution is governed to a large extent by environmental conditions that filter communities according to functional traits, such as abiotic stress tolerance, morphology and body size. Trait-based approaches have been successfully used to predict soil biota responses to abiotic stress. It remains unclear, though, how these traits relate to life-history traits that determine individual performance, that is, reproduction and survival. Here, we analyse patterns in multidimensional trait distribution of dominant groups of soil fauna, that is, Isopoda, Gastropoda and Collembola, known to be important to the functioning of ecosystems. We compiled trait information from existing literature, trait databases and supplementary measurements. We looked for common patterns in major axes of trait variation and tested if vertical distribution of species in the soil explained trait variation based on three components of trait diversity (trait richness, evenness and divergence). Our results showed that two to three axes of variation structured the trait space of life-history and tolerance traits in each of the taxonomic groups and that vertical distribution in soil explained the main axis of trait variation. We also found evidence of environmental filtering on soil fauna along the vertical soil distribution, with lower trait richness and trait divergence in soil-dwelling than in surface-living species. Our study was partially limited by the lack of detailed trait measurements for the selected taxonomic groups. In this regard, there is an urgent need for standardized trait databases across invertebrate groups to improve trait-based diversity analysis and fill gaps in the mechanistic understanding behind trait distribution, trait filtering and the link with species fitness and performance.

168 million years old "marine lice" and the evolution of parasitism within isopods.

BACKGROUND: Isopods (woodlice, slaters and their relatives) are common crustaceans and abundant in numerous habitats. They employ a variety of lifestyles including free-living scavengers and predators but also obligate parasites. This modern-day variability of lifestyles is not reflected in isopod fossils so far, mostly as the life habits of many fossil isopods are still unclear. A rather common group of fossil isopods is Urda (190-100 million years). Although some of the specimens of different species of Urda are considered well preserved, crucial characters for the interpretation of their lifestyle (and also of their phylogenetic position), have so far not been accessible. RESULTS: Using up-to-date imaging methods, we here present morphological details of the mouthparts and the thoracopods of 168 million years old specimens of Urda rostrata. Mouthparts are of a sucking-piercing-type morphology, similar to the mouthparts of representatives of ectoparasitic isopods in groups such as Aegidae or Cymothoidae. The thoracopods bear strong, curved dactyli most likely for attaching to a host. Therefore, mouthpart and thoracopod morphology indicate a parasitic lifestyle of Urda rostrata. Based on morphological details, Urda seems deeply nested within the parasitic isopods of the group Cymothoida. CONCLUSIONS: Similarities to Aegidae and Cymothoidae are interpreted as ancestral characters; Urda is more closely related to Gnathiidae, which is therefore also interpreted as an ingroup of Cymothoida. With this position Urda provides crucial information for our understanding of the evolution of parasitism within isopods. Finally, the specimens reported herein represent the oldest parasitic isopods known to date.

Functionalization of biomineral reinforcement in crustacean cuticle: Calcite orientation in the partes incisivae of the mandibles of Porcellio scaber and the supralittoral species Tylos europaeus (Oniscidea, Isopoda).

In arthropods the cuticle forms an exoskeleton with its physical and chemical properties adapted to functions of distinct skeletal elements. The cuticle of the partes incisivae (PI) in mandibles of terrestrial isopods is a composite of chitin-protein fibrils/fibres and minerals. It consists of an unmineralized tip, a middle region with organic fibrils reinforced mainly with amorphous calcium phosphate and a base region mineralized with amorphous calcium carbonate and calcite. In this study we extend our work on the structure and material properties of the incisive cuticle employing electron backscatter diffraction (EBSD), and investigate calcite orientation patterns in the PI of two terrestrial isopod species from different habitats. We trace small-scale differences in texture sharpness and calcite microstructure, and compare calcite organization and orientation patterns in the PI with those in the tergites of the same isopod species. We observe that in the PI calcite orientation, the degree of crystal alignment, and mode of crystalline domain assemblage is highly varied within short length scales. This contrasts to calcite organization in the tergite cuticle, where calcite has only one specific texture pattern. Such a large range in the variation of calcite organization has not been observed in other carbonate biological hard tissues, such as shells and teeth, where one specific texture and microstructure prevails. Thus, the investigated isopod species are able to control crystallization of the amorphous carbonate precursor in a differential way, most probably related to the function of the individual skeletal element and the animals' behavior.

Phylogeography of Semiterrestrial Isopod, Tylos granuliferus, on East Asian Coasts.

We conducted phylogenetic analyses using mitochondrial COI gene sequences of Tylos granuliferus, a semiterrestrial coastal isopod in East Asia, to clarify possible phylogeographic patterns and to assess relationships between present and past marine environments and genetic population structures. Our results strongly suggest the presence of four clades of T. granuliferus, one of which consists of three subclades. The distribution pattern of clades and subclades seems to have been affected by ocean current activities. Our results also suggest that historical changes in oceanic environments and the subsequence bifurcation of current streamlines affected the first and second divergences of T. granuliferus during the late Miocene and near the beginning of the Pliocene, respectively.

Function-related adaptations of ultrastructure, mineral phase distribution and mechanical properties in the incisive cuticle of mandibles of Porcellio scaber Latreille, 1804.

In terrestrial isopods the mandibles consist of a corpus carrying strong muscle tissue, and a pars incisiva (PI) that cuts dry leaves into smaller ingestible pieces. We studied the cuticle of the PI of Porcellio scaber in order to understand region-dependent differences in its ultrastructure, composition, and the resulting mechanical properties, employing several microscopic and analytical techniques as well as nanoindentation experiments. The cuticle of the incisive tip is not mineralized and consists of an unusually thick epicuticle containing thin fibrils, two subjacent cuticular layers, and a central core containing fibrils of different orientation, either longitudinal or circumferential. A thick epicuticle of the middle region just behind the tip projects long epicuticular extensions into the subjacent endocuticle, likely to prevent delamination. A distinct exocuticular layer is lacking in the middle region. Most chitin-protein fibrils within the endocuticle are oriented in parallel pointing towards the tip. Surprisingly, the middle region is mineralized by amorphous calcium phosphate (ACP) only. Near the base, ACP is successively replaced by amorphous calcium carbonate and calcite is restricted to a distal layer in the base. At the transition between middle and base, the epicuticle forms a hybrid material containing fibrils of the exocuticle. Nanoindentation experiments reveal an increase of the stiffness and hardness from the tip towards the base and significantly higher values on transversal in comparison to longitudinal planes. The results suggest that ultrastructure and composition are adapted for conveying high forces from a rather thin cutting edge to the stable base of the PI.

New occurrence of Cirolana capricornica (Isopoda: Cirolanidae) from Epinepheluschlorostigma in Suez Governorate, Egypt.

Background and Aim: The isopods of the Crustacea are noteworthy. All marine, fresh, and brackish waterways at all depths are home to aquatic organisms. This order also includes species that live on land. This study aimed to report a new occurrence of the isopod Cirolana capricornica on the operculum, mouth, and body cavities of Epinephilus chlorostigma in the Suez Governorate, Egypt. Materials and Methods: With the help of fishermen, 50 live E. chlorostigma (Linnaeus, 1758) were randomly gathered along the Red Sea coast of the Suez Governorate during November and December 2019 for the current investigation. Isopods were isolated from the fish samples and captured using light and electron microscopy for morphological identification. Results: Some fish were emaciated, and minute white isopods were attached externally to the skin near the gills and mouth cavity, and internally to the mouth cavity. No correlation was observed between body cavity attachment and gross lesions. The prevalence of infestation was 16%. Conclusion: C. capricornica was identified using optical and electron microscopy to analyze the isopod specimens' morphology. This scavenging isopod species is newly discovered in Egypt.

DNA barcoding of the supergiant isopods from Bathynomuskensleyi Lowry & Dempsey, 2006 (Cirolanidae) and a molecular biology comparison of B.jamesi Kou, Chen & Li, 2017.

DNA was extracted from tissue samples from specimens of newly-collected Bathynomuskensleyi from Queensland and subsequently the COI and 16S rRNA sequences were successfully cloned. The holotype of B.kensleyi was also sampled for COI only. Comparison of the sequences showed that, for the COI sequences, B.jamesi and B.kensleyi have more than 59 different DNA positions amongst 596 known reading sequences. The Kimura two parameter (K2P) distance analysis confirmed that B.jamesi and B.kensleyi are two species. Indian records of Bathynomus are reviewed and three of the four identified species from India are shown to be misidentifications. Bathynomusdecemspinosus, B.doederlini and B.kensleyi are found to not occur in India and the only accepted record is that of Bathynomuskeablei Lowry & Dempsey, 2006. We conclude that, based on molecular analysis and morphological comparisons, the correct species identity of Indian species other than Bathynomuskeablei remains unknown.

Cryptic diversity and phylogeographic patterns of Deto echinata (Isopoda: Detonidae) in southern Africa.

Recent phylogeographic studies of poorly-dispersing coastal invertebrates in highly biodiverse regions have led to the discovery of high levels of cryptic diversity and complex phylogeographic patterns that suggest isolation, geological, and ecological processes have shaped their biodiversity. Studies of southern African coastal invertebrates have uncovered cryptic diversity for various taxa and phylogeographic patterns that, although sharing some similarities across taxa, do differ. These findings underscore the need for additional studies to better understand the biodiversity levels, distributional patterns, and processes responsible for producing coastal biodiversity in that region. The coastal isopod Deto echinata is of particular interest, as its complex taxonomic history, poor dispersal capabilities, and broad geographic distribution suggest the potential for cryptic diversity. We use mitochondrial and nuclear sequences to characterize D. echinata individuals from localities ranging from northern Namibia to Glentana, about 2,500 km along the coastline on the south coast of South Africa. These are used to assess whether D. echinata harbors cryptic genetic diversity and whether phylogeographic distributional patterns correlate with those previously documented for other coastal isopods in the region. Analysis of mitochondrial and nuclear sequences revealed two deeply-divergent lineages that exhibit a distributional break in the Cape Peninsula region. These findings suggest D. echinata is a cryptic species complex in need of taxonomic revision and highlight the need for further taxonomic and phylogeographic studies of similarly poorly-dispersing coastal invertebrates in southern Africa.

Progress in the discovery of isopods (Crustacea: Peracarida)-is the description rate slowing down?

Taxonomic species are the best standardised metric of biodiversity. Therefore, there is broad scientific and public interest in how many species have already been named and how many more may exist. Crustaceans comprise about 6% of all named animal species and isopods about 15% of all crustaceans. Here, we review progress in the naming of isopods in relation to the number of people describing new species and estimate how many more species may yet be named by 2050 and 2100, respectively. In over two and a half centuries of discovery, 10,687 isopod species in 1,557 genera and 141 families have been described by 755 first authors. The number of authors has increased over time, especially since the 1950s, indicating increasing effort in the description of new species. Despite that the average number of species described per first author has declined since the 1910s, and the description rate has slowed down over the recent decades. Authors' publication lifetimes did not change considerably over time, and there was a distinct shift towards multi-authored publications in recent decades. Estimates from a non-homogeneous renewal process model predict that an additional 660 isopod species will be described by 2100, assuming that the rate of description continues at its current pace.

Investigation of the potential effects of firefighting water additives on soil invertebrates and terrestrial plants.

The intensity and frequency of forest fires is increasing across the globe due to climate change. Additives are often added to make water more effective at extinguishing fire and preventing re-ignition. This study investigated the toxicity of nine different firefighting water additives to four species of soil invertebrates (Folsomia candida, Porcellio laevis, Porcellio scaber, and Trichorhina tomentosa) and two plant species (Agropyron cristatum and Raphanus sativus). Considerable variation in toxicity was observed among the firefighting products. The toxicity of individual products also varied considerably amongst the tested species. A hazard assessment was conducted by comparing the concentration of firefighting water additive that caused a 50% effect (LC50 or EC50) or a concentration that caused no effect (NOEC) to the concentration recommended by the manufacturer. At a rate of application representative of a forest firefighting scenario, most firefighting water additives tested in this study posed a hazard to F. candida and the three isopod species. The majority of products did not pose a risk to the two plant species included in this study. Consideration of the toxicity of firefighting water additives to terrestrial biota should be considered along with the efficacy of the product to fight fires when deciding which products to use.