Arthropoda

Invertebrates, including Asellidae, are part of the natural ecosystem of the drinking water distribution system (DWDS) and are known to cause a nuisance to consumers. In addition, recently, the potential role of the species Asellus aquaticus (L. 1758) in the regrowth of Aeromonas bacteria was published. Aeromonas is included in the Dutch drinking water guidelines as a process parameter, and the guideline values are regularly exceeded. Although neither A. aquaticus nor Aeromonas is associated with health risks, the Evides drinking water utility shows a strong interest in the possible reasons for these exceedances and possible control measures. In surface waters, Asellidae feed mainly on decaying leaves that are abundantly present. These food sources are not present in the DWDS. Therefore, we determined suitable food sources for A. aquaticus in the DWDS. Laboratory experiments show that A. aquaticus individuals survive on biofilm on pipe wall material and loose deposits (sediments) collected from DWDS. Growth and survival rates on these loose deposits were even higher than on the positive control (decaying leaves). As the basis of these loose deposits is inorganic (iron deposits, sand, and pipe particles), the organic matter (living and decaying bacteria, protozoans, fungi, and invertebrates) must be their substrate. These experiments validate hypotheses that Asellidae can grow and survive on organic matter in deposits in DWDS. Full article

Lyme disease, the leading vector-borne ailment in the U.S., annually affects an estimated 476,000 individuals, predominantly in the Northeast and Upper Midwest. Despite its increasing incidence, the evaluation of risk within U.S. cities, including natural public lands, remains inadequate. This study focuses on blacklegged tick occurrences and Borrelia burgdorferi infection prevalence in 24 Staten Island parks, aiming to assess Lyme disease exposure risk. Monthly acarological risk index (ARI) calculations from 2019 to 2022 revealed elevated values (0.16–0.53) in specific parks, notably Wolfe’s Pond Park, High Rock Park, Clay Pit Pond Park, Clove Lake Park, and Fair View Park. June (0.36) and November (0.21) consistently exhibited heightened ARIs, aligning with peak tick collection months. Despite stable yearly infection rates at 28.97%, tick densities varied significantly between parks and years. Identifying a high transmission risk in specific parks in Staten Island, a highly urbanized part of New York City, emphasizes the continuous necessity for Lyme disease risk management, even within the greenspaces of large cities. Full article

The family Atyidae is composed of species whose existence has been known since the seventeenth century. Widely found in the Caribbean, Atya lanipes is a freshwater scraper/filter feeder shrimp with an amphidromous complex life cycle. Hunte (1975) described the first larval (zoeal) stage of the species. However, no scientific study has described the early larval development of this species after the first stage. This study aimed to document the early larval development of Atya lanipes under laboratory conditions and compare its larval development with other previously described species of the Atyidae family. Larval development was recorded by taking daily photos and videos of larval (zoeal) growth using a stereo microscope. Larvae were also preserved in ethanol for further morphological analysis. The results revealed that the best conditions for Atya lanipes development were 30 ppm water salinity, constant gentle aeration, and 27 °C water temperature. Nine stages were identified for the description of the early larval development of Atya lanipes. Early larval stages differ primarily in interstage larval size, the appearance and development of the telson, appendage appearance, growth of antennae and antennules, and pigmentation. The present contribution represents the first study that describes the larval development of the Caribbean shrimp Atya lanipes. Full article

Limb anomalies are widespread and diversified in arthropods. From trilobites to insects, they range from the loss to the addition or fusion of legs and may appear congenitally or be induced experimentally (e.g., amputation or injury). Basal chelicerates pycnogonids, or sea spiders, also show deformities. Despite being understudied compared to other arthropods, quite a high diversity of limb malformations has been reported in the literature. The present study reports the leg anomalies of two adult females Ammothea hilgendorfi (Böhm, 1879) observed with duplicated leg podomeres. Both individuals were described ethologically and morphologically. Although the current knowledge on pycnogonids is limited, the anomaly is likely due to a problem in the molting process; the specimens were unable to totally remove their old exuviae, which then stacked after the proximal leg segments. The second specimen also showed other leg deformities, hinting at a problem during the molting process itself. The discussion emphasizes that understanding how pycnogonids normally molt would not only help our understanding of how the abnormal patterns appeared but also put pycnogonids into perspective with other arthropods, a phylum in which they have a key taxonomic position. Full article

Ocypode Weber, 1795 (Brachyura: Ocypodidae) is popularly known as ghost crab, and encompasses 21 valid species, including Ocypode quadrata (Fabricius, 1787). This species has wide distribution along the Atlantic coast of America, from the USA (Massachusetts) to Brazil (Rio Grande do Sul), Central America, and Antilles. Such distribution, along with some biological characteristics of its life cycle and the presence of geographic barriers, could lead to genetic structuring. Herein, we evaluate the hypothesis of the presence of geographic barriers using COI and 16S partial gene fragments. The Maximum Likelihood tree suggests the monophyly of O. quadrata, while the values of intraspecific genetic distance along with the star-shaped haplotype network suggested a lack of genetic structure in Brazilian, Panama, and French Guiana populations, probably caused by larval dispersion. USA and Mexico populations may be a new lineage, but we cannot say it with few sequences and with no morphological characters. Full article

While originally intending to explore the venom gland microbiome of the desert hairy scorpion Hadrurus arizonensis Ewing, 1928, nanopore sequencing serendipitously recovered complete mitochondrial genomes for this iconic arachnid. Phylogenetic analysis of these high-quality genomes places Hadrurus as sister to Uroctonus, in agreement with some phylogenomic hypotheses. Additionally, we reveal significant genetic variation among individuals from the same population, highlighting the potential of mitogenomics for population genetics and phylogeography. This study showcases the effectiveness and affordability of nanopore sequencing for research with non-model organisms, opening new avenues for investigating arachnid biodiversity, evolution, and biogeography. Full article

Three new species of the genus Caridina are described from the northernmost part of Australia. Caridina darwin n. sp. resembles Caridina temasek Choy and Ng, 1991 but differs in the armature of the rostrum, the development of epipods on the pereiopods and the absence of an appendix interna on the male first pleopods. Caridina magnovis n. sp. resembles Caridina serratirostris de Man, 1892 but differs in the armature of the ventral margin of the rostrum, a shorter stylocerite, a stouter carpus of the first pereiopod, the number and size of spiniform setae on the third and fifth pereiopods, the shape of the preanal carina and the size of the embryos (referred to as “eggs” in most previous publications). Caridina wilsoni n. sp. resembles Caridina gracilirostris de Man, 1892 but differs in the size of the embryos and in some length to width ratios of the segments of the pereiopods. Detailed morphological descriptions of all three new species are given. A molecular phylogeny (mt DNA 16S) supports the morphospecies hypothesis and illustrates the phylogenetic relationship with morphologically similar species from outside Australia. Full article

Horseshoe crabs represent the most ancestral chelicerate lineage characterized by marine ecology and the possession of lateral compound eyes. While considered living fossils, recent studies reported an unusual number of Pax6 genes in the Atlantic horseshoe crab Limulus polyphemus. Pax genes encode ancient metazoan transcription factors, which comprise seven subfamilies. Among these, the members of the Pax6 subfamily confer critical functions in the development of the head, the visual system, and further body plan components. Arthropods are generally characterized by two Pax6 subfamily homologs that were discovered in Drosophila and named eyeless (ey) and twin of eyeless (toy). However, whole genome sequence searches uncovered three homologs of ey and two homologs of toy in L. polyphemus. These numbers are explained by the occurrence of likely three whole genome duplications in the lineage to the last common ancestor of L. polyphemus and the three additional members of the extant horseshoe crab species cluster. Here, we report that all five L. polyphemus Pax6 paralogs are conserved in the approximately 135-million-year-old horseshoe crab species cluster and that they evolve under strong purifying selection. Largely homogenous protein sequence diversification rates of ey and toy paralogs suggest subfunctionalization as the likeliest preservation trajectory. However, our studies further revealed evidence that the horseshoe crab ey1 and ey2 paralogs share a derived splice isoform that encodes a unique five amino acid-long insertion in helix 3 of the homeodomain. This suggests that the exceptional expansion of the horseshoe crab Pax6 gene family repertoire was also associated with regulatory diversification and possibly innovation. Full article

Herein, we redescribe Neostenotarsus guianensis (Caporiacco, 1954) nearly seven decades after its original description. In the original description of Neostenotarsus scissistylus Tesmoingt & Schmidt, 2002, we found characters incongruent with N. guianensis, namely, the purported presence of serration on the prolateral keels of the palpal bulb; a narrower apical third of the embolus; the absence of a patch of bristles on the retrolateral face of the palpal tibia and of a baso-retrolateral protuberance on metatarsus I; and a shorter and more apically situated megaspine on the retrolateral branch of the tibial apophyses. The characters from its original description are discussed. N. scissistylus stat. rev. has been revalidated until such time as the type material, or topotypic material, can be examined by future workers. Full article

Coral-dwelling gall crabs (Cryptochiridae) are common inhabitants of scleractinian corals. Several species have been described as new in recent years, including Lithoscaptus doughnut, which was described from Hong Kong based on a single female retrieved from the coral Plesiastrea peroni. Here we extend the distribution range of L. doughnut with nine additional localities throughout the Indo-West Pacific, from the Red Sea to the Coral Triangle and Japan. We describe a male specimen of L. doughnut for the first time, based on a specimen from Malaysia, and provide photographs of life and preserved material. Haplotype networks based on COI mtDNA (n = 12) and 16 rRNA sequences (n = 12) were created. We retrieved eleven COI haplotypes and six 16S haplotypes, however no clear geographic distribution pattern was discerned. Intraspecific variation in L. doughnut was 1.4% for COI and 0.2% for 16S. Lastly, the first colour photos and records of associated parasites of this species are provided. Full article

An invasive orb-weaving spider from east Asia is now spreading through the southeastern United States; Trichonephila clavata (the “jorō spider”) makes large, imposing webs seemingly everywhere, including in urban landscapes, and even next to busy roads. However, areas near roads come with frequent disturbances, including auditory and vibrational, which for many animals, leads to physiological or behavioral changes. Here we tested if varying levels of road traffic affect the prey–capture behavior of jorō spiders in northeast Georgia. We visited roadsides that ranged in traffic density and exposed nearby jorō spiders to a simulated prey (a tuning fork at 128 hz frequency, touched to the web), and recorded whether or not the spider attacked it. Out of 357 total trials across 20 different roads, jorō spiders attacked the simulated prey 59% of the time, but at the local scale, there was high variability in this rate; at some roadsides, over 80% of the spiders attacked, while at others, less than 30% did. When all roads were considered collectively, there was a small but significant (negative) correlation between daily road traffic and spider attack rates. Put another way, spiders near moderate- to heavy-traffic roads were slightly less likely to attack than those near low-traffic roads (51% vs. 65%). Jorō spiders appear to be able to live near roads, but this does come with a cost in terms of prey capture. However, spiders near busier roads did not weigh less than those in other sites, suggesting they may be able to compensate for the disturbance. These findings add to the accumulating evidence around this species that points to its ability to exist in human-dominated landscapes, which will likely aid its spread in the introduced range. Full article

A study was conducted to evaluate zooplankton species composition, abundance, and diversity in both natural and artificial lakes with varying trophic levels and to determine the relationship between zooplankton community structure and lake environmental conditions. This study hypothesized that correlations exist between zooplankton community structures and environmental parameters associated with eutrophication in natural and artificial lakes. Sampling was conducted across 16 distinct freshwater lentic ecosystems in Malaysia, including natural lakes/swamps, reservoirs, constructed lakes/ponds, and old mining lakes, spanning a range of trophic levels from mesotrophic to hypereutrophic conditions. Physicochemical parameters were measured in situ, while water and zooplankton samples were collected for nutrient analyses, as well as for zooplankton identification and enumeration. Throughout this study, a total of 58 zooplankton species, consisting of 36 species of rotifers, 12 species of cladocerans, and 10 species of copepods, were recorded. The highest zooplankton density (365.7 ± 13.7 ind L⁻¹) was recorded in constructed lakes/ponds while the lowest density was recorded in natural shallow lakes/swamps (200.5 ± 25.5 ind L⁻¹). On the other hand, significantly higher (p < 0.05) mean species diversity was observed in natural lakes/swamps (H’ = 2.2 ± 0.0); whereas, the lowest diversity was in old mining lakes (H’ = 1.5 ± 0.1). The canonical correspondence analysis (CCA) scores indicated that Polyarthra vulgaris and Chydorus ventricosus were the discriminating species in natural shallow lakes/swamps associated with high water transparency. Meanwhile, the small-sized cladocerans (Ceriodaphnia cornuta) and rotifers (Keratella spp., Brachionus spp., and Trichocerca spp.) were the most discriminating species in lakes with high turbidity, nutrients, and chlorophyll a concentrations, which are the main features of reservoirs and constructed lakes/ponds. Low density and diversity in old mining lakes were due to a low species number and the dominance of two species, Lophocharis curvata (38.8%) and Ptygura libera (39.7%). Overall, the high dominance of a specific zooplankton species resulted in lower biodiversity in artificial ecosystems compared to natural ecosystems. This study elucidated that zooplankton community structure in lakes was significantly influenced by the environmental conditions related to the lake trophic status. Full article

In the American Museum of Natural History, New York, there is an old specimen labelled as “Holodromia harrisonwilliamsi Boone, MS name” that was collected from Cocos Island in 1925. This name has never been published. An examination of the specimen shows that it is a juvenile specimen of Homolodromia robertsi Garth, 1973, a species described from Peru, which has since been reported from Chile and off the coast of Ecuador. This paper reports on the specimen Homolodromia robertsi Garth found in Costa Rica for the first time, a discovery that extends the known range of this species northwards. Full article

Coastal wetlands, vital for ecological diversity, have been significantly altered by anthropogenic activities, particularly in the Caribbean. These changes have created a complex mosaic of habitats and physicochemical conditions, further stressed by climate variability and sea-level rise. This study, conducted in Las Cucharillas Natural Reserve, a tropical urban coastal wetland in Puerto Rico, aimed to determine the effects of spatiotemporal variations in phreatic levels and salinity on soil mesofauna assemblages, crucial bio-indicators of environmental change. In 2020 and 2021, soil samples were collected from five diverse habitat types during different hydroperiods. Each sample was taken under four randomly selected plant types and processed using lighted Tullgren–Berlese extractors. Phreatic level and salinity were also measured. A total of 43 families were quantified, underscoring distinct habitat differences, similarities, and overall ecosystem diversity. Moderate correlations between phreatic levels, salinity, and mesofauna richness and abundance were determined. Peak richness and abundance were quantified at shallow (−0.03 to −0.07 m) and slightly moderate (−0.12 to −0.17 m) phreatic levels where oligohaline salinity (>0.5 to 5.0 ppt) prevails. The study highlights the adaptability of mesofauna to environmental shifts and their potential as biosensors for effective coastal wetland management amid climatic and anthropogenic pressures. Full article

Salmoneus sultanus sp. nov. is described based on several specimens collected on the exposed shores of Masirah Island and Dhofar, Oman, a region characterised by seasonal upwellings cooling water temperature to less than 23 °C. The new species is compared with the morphologically most similar congeners present in the north-western Indian Ocean, e.g., S. latirostris (Coutière, 1897), S. cristatus (Coutière, 1897), S. serratidigitus (Coutière, 1897), and S. chadwickae Ďuriš and Horká, 2016; the latter species is recorded for the first time from Oman. The conspicuous colour pattern of S. sultanus sp. nov. appears to be diagnostic, differing greatly from that of S. latirostris, S. cristatus, S. serratidigitus, and S. chadwickae. Full article

The former subfamily Prostygninae was recently elevated to family rank, and its phylogenetic relationships were investigated based on molecular data. In this study, we provide a revised morphological diagnosis for the family, focusing on characters from the exomorphology and male genital morphology. Morphological data supporting their inclusion in the MECO clade are provided. Additionally, a key to the genera is presented, and Prostygnus stellatussp. nov., a new Ecuadorian species, is described. The geographic distribution of prostygnid species is mapped. An overview of the inclusion and exclusion of genera formerly within Prostygninae, but currently in Gonyleptoidea incertae sedis, is presented, and the following new familial assignments are proposed: Binamballeus Roewer, 1952 and Puna metatarsalis (Kury, 1994) comb. nov. (transferred to Cranaidae), Sclerostygnellus Roewer, 1943 (transferred to Manaosbiidae) and Globitarsus Roewer, 1913, Lisarea Roewer, 1943, Meridanatus Roewer, 1943, Micropachylus Roewer, 1913, Prostygnidius Roewer, 1915, and Troya Roewer, 1914 (all transferred to Nomoclastidae). Three subjective synonyms of Troya are proposed: Peladoius Roewer, 1914 syn. nov., Prostygnellus Roewer, 1914 syn. nov., and Minyssus Roewer, 1943 syn. nov., combining their species with Troya and, finally, Prostygnellus riveti Roewer, 1914 is considered as a junior secondary homonym of Troya riveti Roewer, 1914 syn. nov. Full article

A new species of the rare shrimp genus Bresilia is described and illustrated from shallow-water lava tubes in Cabo Verde. Characteristics differentiating the new species from its three known Atlantic congeners are listed and discussed. Scanning electron images (SEM) are provided of the peculiar chela ornamentation of the first pereiopod in the genus. Full article

Why do the eyes remain comparatively large, whereas the cornea is reduced in most troglobiont mysids? Are there any important organ size-dependent functions served by non-visual eye rudiments? This issue was approached by measuring eye structures in five troglobiont species of Mysida and two Stygiomysida compared with 14 troglophiles and 49 trogloxene Mysida species. The Organ of Bellonci (OB) was found in all Mysida and, as first records, also in Stygiomysida. The length of OBs increased with individual body length (BL) and eye length (EL) in four examined species: from postnauplioid larvae to adult stage in a troglophile and a trogloxene mysid species examined; and from juveniles to adults in a troglobiont mysid and a troglobiont stygiomysid. At the interspecific level, EL was, on average, 26% shorter at a given BL, while the OB was 40% longer at a given BL and 54% longer at a given EL, respectively, in adult troglobionts compared with trogloxene mysids. The OB is clearly proliferating, while the cornea is reduced in troglobionts. This points to sensory functions (possibly together with other functions). The sensory pore organ was found in all 15 Mysida species whose eyes were mounted on slides, and the first record of this organ was also found in Stygiomysida. Full article