Isopod Species Research Articles

Shape matters: investigating the utility of geometric morphometric techniques in the deep-sea isopod family Macrostylidae (Isopoda: Asellota)

Accurate taxonomic classification of deep-sea taxa is often impeded by the presence of highly morphologically similar but genetically distinct species. This issue is particularly pronounced in the isopods of the deep-sea family Macrostylidae, which exhibit remarkably low morphological variation despite significant genetic diversity. In this study, we present the first application of geometric morphometric techniques to 41 specimens across five species of deep-sea macrostylid isopods collected from Icelandic waters. Our results suggest that geometric morphometric techniques can effectively discriminate between macrostylid species. These techniques, hence, promise to be an important addition to the toolset of macrostylid taxonomists.

Resurrection of the parasitic isopod genus Cryptione Hansen, 1897 (Epicaridea: Bopyridae) and description of a new species of parasitic isopod (Epicaridea: Bopyridae) from the deep-sea shrimp Notostomus gibbosus (Caridea: Acanthephyridae) with an analysis of its phylogenetic position based on molecular data

A new species of pseudionine parasite is described from the deep-sea shrimp Notostomus gibbosus A. Milne-Edwards, 1881, collected in the Gulf of Mexico, the first record of a bopyrid parasitizing any member of the family Acanthephyridae Spence Bate, 1888. Morphological and molecular data are provided to support the inclusion of the new species and 12 other branchial ectoparasites of caridean shrimps in the genus Cryptione Hansen, 1897 that is resurrected herein. Cryptione is sister to the genus Pseudione sensu stricto, ectoparasites of axiid and callianassid shrimps as well as nephropid lobsters. The new species Cryptione grandis can be distinguished from its closest congeners including C. parviramus (Adkison, 1988) from the Gulf of Mexico by several female and male characters. The epicaridium larvae of C. grandis were examined with scanning electron microscopy (SEM), only the second description of this stage for any species in the genus. A table listing all species in Cryptione and taxonomic notes on some species are provided.

Finding a balance: Reproductive trade-offs in parasitic isopods of the family Cymothoidae.

In this study conducted along the coast of Odisha, India, reproductive trade-offs in isopods of the family Cymothoidae were investigated, focusing on the relationship between the number vs. volume of eggs and the percentage of brood to body volume. Ovigerous females from species with substantial sample sizes (n > 30) were analyzed to understand their survival strategies. The findings highlight distinct strategies among different parasite types within Cymothoidae. Buccal parasites such as Cymothoa frontalis and Cymothoa indica, along with branchial parasites like Joryma sawayah and Agarna malayi, generally produced a higher number of smaller eggs, except for A. malayi, which produced fewer but larger eggs. In contrast, the external body surface-attaching parasite, Nerocila orbignyi, was observed to produce fewer eggs of larger size. Across all parasite types (intraspecific), there was a statistically significant negative correlation between egg number and egg volume (p < 0.05). Buccal parasites were observed to have the highest percentage of marsupium volume relative to body volume, indicating a strategy to maximize egg storage. Conversely, external body surface-attaching parasites had the lowest percentage, possibly reflecting adaptation to a different reproductive environment. Additional observations revealed anatomical adaptations in all the studied isopod species which include the shift of the alimentary canal to the dorsal side to accommodate the development of the marsupial sac for egg incubation. In summary, these findings illustrate how parasitic isopods of the family Cymothoidae manage trade-offs between reproductive potential and success, crucial for their species' continuity and survival strategies in coastal ecosystems.

Molecular approach challenges the monophyly of the genus Benthana Budde-Lund, 1908 (Oniscidea, Philosciidae)

ABSTRACT Although new data and methodologies are gaining prominence in the field of taxonomy, the vast majority of terrestrial isopod species are still described solely based on morphology. The genus Benthana was recently revised and currently comprises 30 species found in South America. However, the broad geographic distribution of some species, coupled with the presence of few diagnostic characters, raises doubts about the validity of the described species. This study aimed to test the applicability of DNA Barcoding to assess the congruence between morphological and molecular identification of Benthana species. We analyzed 72 individuals belonging to 13 species from the scientific collection of the UFRGS Crustacean Laboratory. We obtained 24 sequences from ten Benthana species. The molecular phylogenies demonstrated that Benthana forms a paraphyletic group. Even at the species level, paraphyletic taxa were observed. Species delimitation methods revealed the presence of eight molecular entities within Benthana. Regarding genetic distances, we observed low intra-specific distances and significantly high inter-specific distances. Our results show that molecular analysis does not support the current taxonomy of Benthana. Therefore, a reassessment of the genus systematics based on integrative taxonomy is warranted.

A new species of Metaphrixus Nierstrasz &amp; Brender à Brandis, 1931 (Isopoda: Bopyridae: Hemiarthrinae) associated with an Hippolytidae shrimp from Costa Rica

A new species of parasitic isopod of the genus Metaphrixus Nierstrasz &amp; Brender à Brandis, 1931 is described from one Hippolyte obliquimanus Dana, 1852 shrimp, collected in Costa Rica. It is the fifth species of the genus worldwide and the first record of the subfamily Hemiarthrinae from Costa Rica. A comparative table, an identification key and a distribution map for all species of the genus are also provided.

Divergent patterns of locomotor activity in cave isopods (Oniscidea: Styloniscidae) in Neotropics

ABSTRACT In cave environments, stable conditions devoid of light-dark cycles and temperature fluctuations sustain circadian clock mechanisms across various species. However, species adapted to these conditions may exhibit disruption of circadian rhythm in locomotor activity. This study examines potential rhythm loss due to convergent evolution in five semi-aquatic troglobitic isopod species (Crustacea: Styloniscidae), focusing on its impact on locomotor activity. The hypothesis posits that these species display aperiodic locomotor activity patterns. Isopods were subjected to three treatments: constant red light (DD), constant light (LL), and light-dark cycles (LD 12:12), totaling 1656 h. Circadian rhythm analysis employed the Sokolove and Bushell periodogram chi-square test, Hurst coefficient calculation, intermediate stability (IS), and activity differences for each species. Predominantly, all species exhibited an infradian rhythm under DD and LL. There was synchronization of the locomotor rhythm in LD, likely as a result of masking. Three species displayed diurnal activity, while two exhibited nocturnal activity. The Hurst coefficient indicated rhythmic persistence, with LD showing higher variability. LD conditions demonstrated higher IS values, suggesting synchronized rhythms across species. Significant individual variations were observed within species across the three conditions. Contrary to the hypothesis, all species exhibited synchronization under light-dark conditions. Analyzing circadian activity provides insights into organism adaptation to non-cyclical environments, emphasizing the importance of exploring underlying mechanisms.

Comparisons of developmental processes of air-breathing organs among terrestrial isopods (Crustacea, Oniscidea): implications for their evolutionary origins

BackgroundThe acquisition of air-breathing organs is one of the key innovations for terrestrialization in animals. Terrestrial isopods, a crustacean lineage, can be interesting models to study the evolution of respiratory organs, as they exhibit varieties of air-breathing structures according to their habitats. However, the evolutionary processes and origins of these structures are unclear, due to the lack of information about their developmental processes. To understand the developmental mechanisms, we compared the developmental processes forming different respiratory structures in three isopod species, i.e., ‘uncovered lungs’ in Nagurus okinawaensis (Trachelipodidae), ‘dorsal respiratory fields’ in Alloniscus balssi (Alloniscidae), and pleopods without respiratory structures in Armadilloniscus cf. ellipticus (Detonidae).ResultsIn N. okinawaensis with uncovered lungs, epithelium and cuticle around the proximal hemolymph sinus developed into respiratory structures at post-manca juvenile stages. On the other hand, in Al. balssi with dorsal respiratory fields, the region for the future respiratory structure was already present at manca 1 stage, immediately after hatching, where the lateral protrusion of ventral epithelium occurred, forming the respiratory structure. Furthermore, on pleopods in Ar. cf. ellipticus, only thickened dorsal cuticle and the proximal hemolymph sinus developed during postembryonic development without special morphogenesis.ConclusionsThis study shows that the respiratory structures in terrestrial isopods develop primarily by postembryonic epithelial modifications, but the epithelial positions developing into respiratory structures differ between uncovered lungs and dorsal respiratory fields. This suggests that these two types of respiratory structures do not result from simple differences in the degree of development. Future analysis of molecular developmental mechanisms will help determine whether these are the result of heterotopic changes or have different evolutionary origins. Overall, this study provides fundamental information for evolutionary developmental studies of isopod respiratory organs.

Morphological, Molecular Identification and Genetic Diversity Assessment of Three Terrestrial Isopods from the High-Altitude Region

Terrestrial specimens were collected from Ashshafa, a south-western highland area in Saudi Arabia. Three species, i.e., Porcellio laevis, Porcellionides pruinosus (Porcellionidae), and Armadillidium vulgare (Armadillidiidae), were identified in this study based on their morphological characteristics. Partial mitochondrial cytochrome C oxidase subunit I (COI) gene sequences were used for DNA barcoding and biodiversity assessments. A phylogenetic tree of 22 haplotypes from 35 specimens of the three isopod species was drawn from the most similar sequences obtained from BLAST with the associated accession numbers. The tree included two clades. The first clade included samples of P. laevis and P. pruinosus, whereas the second clade included samples of A. vulgare. Each identified species formed a distinct subclade within the main clade, along with similar sequences obtained from the NCBI database. The heat map of genetic distance among haplotypes shows the haplotype diversity (Hd) ranged from 0.590 to 0.933 (mean = 0.767) and total nucleotide diversity (πT) ranged from 0.001 to 0.089 (mean=0.049), with a similar trend observed for nucleotide diversity per site (θw) ranged from 0.001 to 0.80 (mean = 0.049). In contrast, synonymous nucleotide diversity (πs), mean=0.009, was low compared to nonsynonymous nucleotide diversity (πs), mean=0.060, across all species. In conclusion, the morphological identification of terrestrial isopods was confirmed using COI gene sequencing of mitochondrial DNA. These results will be helpful in developing a deeper isopod identification method.

De novo transcriptomes of cave and surface isopod crustaceans: insights from 11 species across three suborders

Isopods are a diverse group of crustaceans, that inhabit various environments, including terrestrial, freshwater, and marine, both on the surface and in the underground. The biological mechanisms underlying their wide range of adaptations to diverse ecological niches remain elusive. In order to unravel the molecular basis of their adaptability, we generated a comprehensive RNAseq dataset comprising 11 isopod species belonging to the three different suborders: freshwater Asellota, marine, brackish and freshwater Sphaeromatidea, and terrestrial Oniscidea, with representatives from families Asellidae, Sphaeromatidae, and Trichoniscidae, respectively. Representatives of each family were collected from both cave and surface environments, representing at least three independent cave colonization events. Three biological replicates were sequenced from each species to ensure data robustness. The 11 high-quality RNAseq datasets will serve as a valuable resource for understanding cave-specific adaptations, comparative and functional genomics, ecological annotation as well as aid in conservation efforts of these non-model organisms. Importantly, transcriptomes of eight featured species have been made publicly accessible for the first time.

Establishment of a new subfamily for the parasitic isopod genus Pleurocryptella (Isopoda: Bopyridae), including recognition of epicaridium larval yolk sacs and description of a new genus and species of hyperparasite

Abstract External yolk sacs in free-living larvae of marine invertebrates are extremely rare, with all reported cases exhibiting yolk that is taken up through connection with the anterior alimentary canal. Herein, we confirm a novel yolk sac connected to the posterior end of the alimentary canal in the first larval stage of species in the bopyrid isopod genus PleurocryptellaBonnier, 1900, all known as ectoparasites in the branchial chambers of squat lobsters. Pleurocryptella poseidon Williams &amp; Boyko sp. nov. infesting the munidopsid Galacantha bellis Henderson, 1885 in the Arabian Sea, is described on the basis of adults and larvae. In common with conspecifics, the new species exhibits a suite of putative “primitive” characters including the presence of oostegites on the sixth and seventh pereomeres of females and maxillipeds and articulated uropods in males. Pleurocryptella poseidon Williams &amp; Boyko sp. nov. differs from other species of Pleurocryptella by characters of body shape, antennae, oostegite 1, pleon, and uropods of females and midventral tubercles, pleomeres, and pleopods of males. The epicaridium larvae have a large posterior, external yolk sac and segmented maxillipeds, a unique set of characters within Epicaridea. In addition to larval and adult characters, molecular data (COI) indicate that the genus is distinct from other members of Bopyridae, so we erect the new subfamily Pleurocryptellinae for it. Pleurocryptella poseidon Williams &amp; Boyko sp. nov. bears a new genus and species of hyperparasitic isopod that is herein described based on its cryptoniscus stage. A review of epicaridium larval morphology and a key to the species of Pleurocryptella are provided.

A new species of Janiralata Menzies, 1951 (Isopoda: Asellota, Janiridae) from Korea

A new isopod species, Janiralata kwangsooi sp. nov., from Dokdo Island located in the East Sea off the Korean Peninsula is described here. This species is distinguished from its congeners by the number of antennular articles, setation of mouthparts and pereopods, length and width ratio of appendages, and shape of male pleopods I and II. To aid species identification, a taxonomic key to species of Janiralata Menzies, 1951 in the Japanese and Korean waters is provided. A partial sequence of mitochondrial cytochrome-c-oxidase (COI) of this new species is also provided for DNA barcoding and compared with those of congeners publicly available in GenBank.

The carcinologicaloeuvreof Charles Spence Bate (1819–1889): Checklist of species and genera, dates of publication, and a list of publications (Crustacea: Amphipoda, Cirripedia, Cumacea, Decapoda, Tanaidacea)

AbstractCharles Spence Bate (1818–1889) was one of the more influential mid to late 19th century crustacean taxonomists, with broad interests spanning several taxonomic groups, such as Amphipoda and Decapoda. Despite several contemporary obituaries, no full publication list for him has ever been assembled. In the present contribution, we provide a complete listing of publications and all species- and genus-level crustacean taxa described by Spence Bate, and indicate their current status. Corrections to publication dates are listed, and several decisions are made to stabilise crustacean nomenclature. In a scientific career spanning almost 50 years (1850–1889), Spence Bate described a total of 402 species and 70 genera in Decapoda, 181 species and 46 genera in Amphipoda, as well as eight genera and eight species of Cumacea, four genera and 16 species of Isopoda, three of Tanaidacea and one of Cirripedia. Of these, 36.2% of species and 45.7% of genera are still considered as the accepted names for their taxa today.

First Record of Flesh-burrowing, Fish Parasitic Isopod Genus Ichthyoxenos Herklots, 1870 (Isopoda: Cymothoidae) from India with Morphological Description of a New Species

A new species of parasitic Isopod of the genus Ichthyoxenos Herklots, 1870, is described here based on six specimens collected from the oxbow lake at Purbashtali, of East Burdwan District of West Bengal, India. This cymothoid genus is recorded for the first time from India. The new species, Ichthyoxenos aneeshi sp. nov., can be easily separated from its congeners by its distinguishing morphological characters i.e., rounded body structure; semicircular head; eyes rectangular; pereonite 1 lateral margin straight; mandible broad, molar process covered in pectinate scales, maxilla 1 with 3 setae, maxilla 2 with three segments, maxilliped comprises 4 articles; antennules shorter than antenna, comprises 7 articles, reaches only middle of the eye; antenna hardly reaches up to the distal margin of pereonite 1; antennae comprises 9 articles, terminal article without setae; pereonite 3-7 posterior margin concave; pereonite 4 widest, pereonite 7 shortest; pleotelson 0.8 times as long as maximum width, free edge straight to gently convex, median part slightly concave, longitudinal dorso-median ridge prominent; uropodal endopod and exopods without serration, subequal. Detailed morphological description along with a comparison with nearest congeners is provided in this paper; short ecological observations are also incorporated here. This is the 24th species of the genus Ichthyoxenos, Herklots, 1870.

New records of Probopyrus pandalicola and Probopyrinella latreuticola (Epicaridea: Bopyridae) from the southern Mexican Caribbean

The ecology, distribution, and taxonomy of bopyrid isopod species are often omitted from studies not systematically addressed to crustaceans. From a wider study of zooplankton in coastal and reef waters of the Mexican Caribbean Sea, two bopyrid species were collected, Probopyrinella latreuticola, attached to the branchial chamber of Latreutes fucorum and Probopyrus pandalicola parasitizing the branchial chamber of Palaemon northropi. For both parasite-host associations, these records represent a new locality and the southernmost record in the Mexican Caribbean. A map and a list of the bopyrid species belonging to Bopyridae recorded in the Mexican Caribbean are provided.

Review of marine alien isopods in Türkiye with two new records: of Paracerceis sculpta and Paranthura japonica

This study focuses on the alien isopod species recorded in the Turkish seas. To date, two alien species (Paradella dianae, Sphaeroma walkeri) have been reported in the country, accounting for almost 2.4% of the total number of isopod species occurring in the Turkish seas. The faunistic analysis of benthic samples collected from Dardanelles (Çanakkale) Straits and Izmir Bay revealed two new alien isopod species (Paranthura japonica and Paracerceis sculpta), on the Turkish coasts. Additionally, this is the first record of P. japonica in the Black Sea ecosystem. This study analyses and discusses the morphological, ecological and distributional characteristics of the species.

A new species of Caecidotea (Crustacea: Isopoda: Asellidae) from a well in the western slope of Mexico, with occurrence records of C. alvarezi.

Caecidotea isabelae sp. nov., a new freshwater asellid isopod species from Jalisco, Mexico is described. During fieldwork in 2021, we discovered eight new populations of freshwater isopods belonging to the genus Caecidotea. One population corresponded to a new species, Caecidotea isabelae sp. nov., while the other seven populations were identified as Caecidotea alvarezi. These populations are reported from freshwater bodies on the western Trans-Mexican Volcanic Belt, expanding the distributional range of C. alvarezi through the state of Jalisco. The new species can be distinguished of their congeners mainly by the protopod of pleopod I triangular with 3 retinacula, exopod of pleopod III with 6 presutural setae, pleopod IV with 3 spines in the proximal external margin. The present study increases the number of known epigean asellid species in Mexico to 12, and the number of currently described Caecidotea species in North America to 102 with three subspecies.

Iron-isopods: new records and new species of terrestrial isopods (Isopoda, Oniscidea) from Brazilian Amazon iron ore caves

Abstract. Two new species of terrestrial isopods are described from iron ore caves in Brazil, within the Amazon biome, Circoniscus mendesi López-Orozco, Campos-Filho &amp;#38; Bichuette sp. nov. and C. xikrin López-Orozco, Campos-Filho &amp;#38; Carpio-Díaz sp. nov. (Scleropactidae). In addition, the knowledge of the distribution of Ctenorillo ferrarai Campos-Filho, Araujo &amp;#38; Taiti, 2014 (Armadillidae) is extended to Parauapebas, and Benthanoides tarzan Cardoso &amp;#38; Ferreira, 2023 to south area of the Campos Ferruginosos National Park, both in the State of Pará. Moreover, a distribution map and photographs of the species are given.

Terrestrial Isopods Generate Microplastics from Low-Density Polyethylene Without Effects on Survival.

With concern growing regarding the impact of microplastics (MPs) on terrestrial ecosystems, it is important to assess the role invertebrates may play in the fate of MPs within these ecosystems. Commonly, MPs enter these environments through improperly discarded waste or the application of treated biosolids and/or wastewater on agricultural soils. The present study investigated whether three species of terrestrial isopod (Porcellio scaber, Porcellio laevis, and Porcellionides pruinosus) ingest plastic debris and generate MPs during exposures varying from 24 h to 14 days and whether this may have an adverse effect on their health. Test vessels were designed to expose isopods to plastic fragments in the form of polyethylene plastic foam. Isopods were exposed to plastic that was either (1) pristine, or (2) weathered in a soil and water solution prior to incorporation in test vessels. When exposed to weathered polyethylene, all three species generated MPs (minimum-maximum size values for all durations inclusive: P. laevis = 114-1673 µm, P. scaber = 99-1635 µm, P. pruinosus = 85-1113 µm) through the consumption of macroplastic fragments with no observed impact on their health. In the shorter-duration exposures, the number of MPs generated by the isopod species in the present study was highly variable between experimental vessels (minimum-maximum generated MPs for 14-day exposure: P. laevis = 25-420, P. scaber = 50-583, P. pruinosus = 48-311). However, as the exposure durations increased, there was a clear trend of increasing MP generation, indicating that the isopods continued to consume the plastic fragments as long as the surface was weathered. A significant difference in the size of generated MPs was observed as well, with smaller isopod species generating smaller MP fragments on average. The results of the present study confirm that certain species of isopod can contribute to the generation of MPs, which constitutes an additional pathway of MP exposure to soil ecosystems. Environ Toxicol Chem 2024;43:784-792. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Bilocus phylogenetic diversity and biogeographic distribution of isopods infesting Egyptian fishes

Phylogenetic diversity studies of parasitic isopods in Egyptian fisheries are very limited, based on a few records of the single mitochondrial gene, COI. Consequently, there has been no mapping study to monitor the phylogenetic diversity and biogeographic distribution of parasitic isopods among a wide range of Egyptian fisheries, leading to gaps in our understanding of the origin and expansion of these parasites. Hence, this study focused on validating the taxonomy and phylogenetic distribution of parasitic isopods using two marker genes, nuclear 18S rDNA and mitochondrial COI. Isopods were collected from seven fish species, Liza ramada, Solea aegyptiaca, Tilapia zillii, Pomadasys sp., Dicentrarchus sp., Atherinomorus lacunosus, and Nemipterus japonicus at four distant Egyptian lakes, Lake Qarun, Bitter Lakes, Lake Burullus, and Lake Manzala; and two marine localities, Red Sea and Suez Gulf, respectively. Sequence analysis revealed 10 and 19 haplotypes of 18S rDNA and COI, respectively. Lake Qarun showed the highest haplotype intra-diversity and is considered a pool of haplotypes with ancestors from other distant lakes. The Red Sea and Suez Gulf haplotypes showed genetic divergence from those recovered from lakes, implicating endemic isopod species. Some haplotypes had mutations in COI-deduced catalytic amino acids. The lake haplotypes belonged to Livoneca redmanii, suggesting a biogeographic expansion of this species among distant Egyptian fisheries. A new genus belonging to the family Cymothoidae was recorded in the Red Sea fish A. lacunosus. Elthusa vulgaris-like haplotypes were recorded in the Suez Gulf fish N. japonicus. Hence, this study clarified the expansion of isopod phylogenetic diversity among varieties of fish species from distant localities.

Morphological and molecular assessment of Livoneca redmanii Leach, 1818, and Anilocra alloceraea Koelbel, 1878 (Isopoda: Cymothoidae) from Egyptian waters

Abstract Background Two cymothoid isopod species, Livoneca redmanii Leach, 1818 and Anilocra alloceraea Koelbel, 1878, have been discovered throughout the research period. These species have been morphologically compared to other closely related species. Their species sequences have been determined using mitochondrial cytochrome c oxidase subunit I (COI) gene fragments and compared to previously identified Livoneca and Anilocra species. The present study aims to provide a detailed morphological description along with parasitological indices of the L. redmanii species in the Mediterranean, which has previously been described in Egypt by several researchers using various misidentifications. Results According to the study findings, Livoneca redmanii was accidentally introduced into Qarun Lake with fish fry from the Mediterranean Sea. The morphological and parasitological descriptions of Anilocra alloceraea and L. redmanii are discussed. Additionally, A. alloceraea species is considered the first to be documented on the Egyptian marine coast. Conclusions Livoneca redmanii species can rapidly adapt to favorable conditions and be found among the most prevalent species in Egyptian marine environments. Our study supports the description of L. redmanii males, as well as some additional morphological features of both cymothoid species females. The discovery of these species in Egyptian waters has extended their geographic distribution. Additionally, this study marks a significant advancement in our knowledge of the dynamics of some parasitic isopod distribution among their preferred species as well as a critical step toward identifying the species that indeed inhabit Egyptian waters.