This study examined aspects of the biology of Oreochromis niloticus, focusing on sexual dimorphism within the Qua Iboe River Estuary, Nigeria, from April 2021 to March 2022. A total of 1,267 specimens were obtained from artisanal fishers using various mesh sizes of gill nets and cast nets. Sex identification was based on genital papilla morphology, with males possessing a single opening and a distinct genital papilla, while females exhibited two openings. Additional dimorphic features included pointed dorsal and anal fins in males and rounded, more expanded fins in females. The overall population consisted of 689 males (54.38%) and 578 females (45.62%), yielding a male–female ratio of 1:0.83, which significantly deviated from parity (χ² = 87.299, df = 1, P < 0.05). Biometric characteristics showed minimal size dimorphism. Males recorded a mean total length of 12.08 ± 0.157 cm and mean total weight of 37.77 ± 1.10 g, while females measured 12.05 ± 0.11 cm and 35.66 ± 0.903 g, respectively. The condition factor (K) was slightly higher in males (2.14 ± 0.04) than in females (2.04 ± 0.03), indicating good physiological status across the population. Length–frequency distribution revealed that most individuals occurred within the 10–14 cm size class, suggesting strong recruitment, continuous breeding activity, and a stable, thriving stock. The findings provide essential baseline information on sexual dimorphism, population structure, and length–weight characteristics of O. niloticus in the Qua Iboe River Estuary. These insights are valuable for improving local aquaculture practices, enhancing broodstock selection, supporting sustainable fisheries management, and guiding conservation strategies for the species in Nigerian estuarine ecosystems.

Sebastexins: Novel members of the three-finger protein family found in urine of viviparous Sebastes rockfish.

The genus Farlowella has been historically challenging, in part due to the difficulty in defining diagnostic characters for defining and identifying the species. Farlowella colombiensis is one such example, whose diagnostic characters are based on caudal‐fin colour pattern, ventral pattern of body cover and anatomical details of the head, such as the arrangement of odontodes and the presence/absence of dorsomedian ridge. We herein reassess the taxonomic status of this species against congeners of the F. acus species group (F. acus, F. martini, F. mitoupibo, F. venezuelensis and F. vittata). We found no significant differences between F. colombiensis and F. acus in morphometric, meristic and colouration pattern, therefore rendering Farlowella colombiensis a junior synonym of Farlowella acus. We provide remarks on different species of the F. acus group in Colombia, as well as a description of sexual dimorphism in the genital papilla for the first time in the subfamily. We also provide a key to the species of the F. acus species group in Colombia.

Summary An undescribed rhabditid species was isolated from the termite Stylotermes halumicus collected in Taiwan. The nematode was cultured using nematode growth medium seeded with Escherichia coli , and the cultured material was examined morphologically and molecularly. The nematode shares several typological characters with some Poikilolaimus spp.: namely, presence of stomatal flaps, posteriorly shifted amphid, hexagonal basal bulb, antidromously reflexed ovaries, pore-like female vulva, and lack of bursa or bursal flap. However, the species is distinguished from Poikilolaimus by its very short vs moderately-long pharyngeal sleeve, presence vs absence of deirid and post-deirid, filiform vs conical tail of both sexes, nine vs less than eight pairs of male genital papillae, and wide vs narrow lateral field. Phylogenetically, the species is located at a basal or a sister position to the clade represented by Poikilolaimus but is clearly separated from the genus by genetic distance. Therefore, the species is described herein as Protopoikilolaimus formosanus n. gen., n. sp.

Summary Seinura morellae n. sp. is described and illustrated. The new species was isolated from stag beetle larval frass obtained from dead wood of the bayberry tree, Morella rubra , and cultured using Acrobeloides sp. as prey. Seinura morellae n. sp. is characterised by its three-lined lateral field, secretory-excretory pore located at the level of the metacorpus, long post-uterine sac and elongate conical tail with filiform tip in females, male spicule with small expansion at the posterior base of the rostrum, and male tail with seven genital papillae and spike-like projection. Although the new species cannot be distinguished typologically or morphometrically from Seinura italiensis ( i.e. , it is a cryptic species), S. morellae n. sp. is distinguished from its close relatives, Seinura caverna , S. shigaensis and S. persica , and from S. italiensis by its independent phylogenetic status inferred from near-full-length ribosomal RNA small-subunit and D2-D3 expansion segments.

A detailed morphological characterization is presented for Oriboglyphus maorianus gen. et sp. nov., a newly discovered modern representative of the relict family Schizoglyphidae, found in a nest of the termite Stolotermes ruficeps in New Zealand. This is the second extant schizoglyphid species known from modern material, and its discovery provides rare insight into a transitional stage in the evolution of astigmatid life cycles. The phoretic stage appears to be a tritonymph—rather than the typical deutonymph—based on key morphological traits including three-segmented palps, three pairs of genital papillae, and the presence of a pharynx. These features suggest that early astigmatid mites evolved multiple ontogenetic routes to dispersal, including tritonymphal, deutonymphal, and possibly adult phoresy, before the canalization of life cycles around deutonymphal dispersal. The persistence of putatively ancestral traits in schizoglyphids, along with their apparent ecological conservatism in termite nests, indicates the role of environmental stability in preserving modes of life history that otherwise appear extinct. We also provide a key to describe Schizoglyphidae species and discuss the implications of this discovery for understanding the origins of phoresy-related metamorphosis in Astigmata.

Parasitic infections in freshwater fish, such as Clarias gariepinus, are influenced by various environmental and host-related factors, impacting aquaculture productivity and biodiversity. A parasitological survey of 120 Clarias gariepinus specimens from Kalgwai, Dingare, and Marke were randomly collected between January 2022 and December 2023 to assess parasitic prevalence and distribution. Fish were captured using various nets and transported either fresh on ice or alive to the Biology Laboratory of Binyaminu Usman Polytechnic, Hadejia. Identification was based on morphological characteristics, while sexing was determined through physical examination of the urogenital papilla. Morphometric parameters, including weight and length, were recorded. Ectoparasites were examined using hand lens and gill dissections, while endoparasites were identified through dissection of the gastrointestinal tract. Results revealed a moderate parasitic prevalence, with females exhibiting a higher infection rate (50%) than males. Among parasites identified, Trichodina spp. showed the highest prevalence on skin and gills, while Rhabdochona spp. and Monobothrium spp. dominated intestinal and stomach infections, respectively. Notably, haemoparasitic infection by Trypanosoma spp. was recorded only in females. Parasite prevalence was significantly higher in smaller-sized and lighter-weight fish, indicating size-related susceptibility. Seasonal variation showed greater parasitic infections during the rainy season (51.66%) compared to the dry season (31.66%). The findings suggest that host sex, size, and seasonal factors influence parasite distribution in Clarias gariepinus from the Kalgwai reservoir, with observed parasite diversity lower compared to other studies. This study provides important baseline data for managing fish health and sustaining aquaculture practices in the region.

Summary An Aphelenchoides species was isolated from figs of Ficus septica collected from Okinawa, Japan. The nematode was morphologically and molecularly examined and found to be an undescribed species. Phylogenetic analyses based on near-full-length 18S (small subunit) and D2-D3 expansion segments of 28S (large subunit) ribosomal RNA revealed the species to be conspecific to an unidentified Aphelenchoides sp. isolated from pine cones in Japan and pine trees in China. The nematode is typologically characterised by a lateral field bearing three lines (two bands), a secretory-excretory pore positioned approximately at the level of the nerve ring, a relatively long pharyngeal gland lobe extending approximately 5-6 times the metacorpal length, an inconspicuous (not definitively confirmed) hemizonid, three pairs of male genital papillae (adcloacal papilliform P2, papilliform P3 at mid-tail, P5 gland papillae near the tail tip), and a somewhat stepwise appendage on the tail tip of both sexes, consisting of a thick basal part with numerous small nodule-like projections and a posterior part forming a simple spike. In terms of typical characteristics, this new species exhibits similarities to Aphelenchoides clarolineatus , A. emiliae and A. petersi . It shares the somewhat stepwise female tail appendage with these three species and the three-lined lateral field with A. petersi (lateral lines were not described for the former two species). However, the new species can be differentiated from these related species based on subtle differences in its typical characteristics and morphometric values. Based on prior isolation records, it is hypothesised that this new species inhabits the surface of woody plants and may occasionally enter the internal tissues through natural openings. Herein it is described as Aphelenchoides epiphyticus n. sp., with the species epithet derived from its presumed epiphytic habitat.

Immunological characterization of the rainbow trout bursa.

Summary A new Pristionchus species, P. kravanhensis n. sp. (Nematoda: Diplogastridae), from Cambodia is described. It was isolated from a melolonthine beetle in the Cardamom Mountains, has a gonochoristic mode of reproduction, and falls into the triformis group of Pristionchus species using a phylogeny based on orthologous proteins. Pristionchus kravanhensis n. sp. is sister to all other species in its group and most closely related to P. yamagatae and P. magnoliae. The new species is characterised by the arrangement of male genital papillae, ⟨v1, v2, v3d/v4, ad, ph, (v5, v6, v7, pd)⟩, where v2, v3d, co and v4 and v5, v6, v7, pd are close to each other, the distance v1-v2 is generally shorter than v2-v4, and v5-7 and pd overlap. The stomatal morphology is also used to distinguish P. kravanhensis n. sp. from other species in the triformis group. It has anteriorly split cheilostomatal plates, which rarely occur in eurystomatous form, and has only two alternative mouth forms (stenostomatous and one type of eurystomatous forms), while others have three (stenostomatous and two types of eurystomatous forms). Hence, this new species represents an interesting biological entity to study the molecular basis underlying the transition from dimorphism to triformism.

Background: The study investigated the Length-weight relationship (LWR), relative condition factor (Kn) and sexual dimorphism in Pristipomoides filamentosus, a deep-water snapper of economic importance in the tropical Indo-Pacific region. Methods: A total of 891 fish (476 females and 415 males) were collected from the Vizhinjam fish landing centre at the southern tip of Kerala, India and analyzed from October 2022 to March 2023. The cube law and student’s t-test were applied to calculate LWR and used to check if there was any significant deviation from the cubic relationship of both female and male P. filamentosus. Month-wise and Length class-wise, mean Kn was calculated to check the health conditions of both female and male P. filamentosus. Body colouration, fin pigmentation and external characteristics of genital papillae and urogenital regions are used to explore the sexual dimorphic characteristics of P. filamentosus. Result: Growth was negatively allometric and the coefficient of determination (R2) for female, male and pooled sexes were 0.966, 0.976 and 0.970, respectively. The relative condition factor (Kn) was highest for females (1.20±0.02) in November and for males (1.17±0.02) in October. Additionally, fish with fork lengths (FL) between 49.5-54.5 cm exhibited the highest Kn values for females (1.31±0.04), while those with FL ranging from 54.5-59.5 cm showed peak Kn values for males (1.21±0.05). The average Kn value for P. filamentosus was approximately one, indicating that the fish were generally in good condition. Sexual dimorphism is more evident in mature P. filamentosus shows characteristic changes in females and males, including body and fin colouration (dichromatism) and external characteristics of the urogenital region and genital papillae. This study provides baseline information and reference points for effectively managing and conserving P. filamentosus.

Phalloceros mimbi sp. nov. is described from specimens collected in the floodplains of the middle and lower Uruguay River in Uruguay (Río Negro and Salto Departments) and Argentina (Entre Ríos Province). This species belongs to the P. harpagos species complex and is diagnosed by the following unique combination of characters: 1) presence of a symmetric hood-like structure located immediately anterior to the urogenital papilla in females, 2) absence of large papillae at the mandibular symphysis of large adult females, 3) possession of well-developed hooks positioned in distal portion of gonopodial appendices of males and4) lateral spot usually present in both sexes. To date, P. mimbi has not been found coexisting in sympatry with other Phalloceros species. The geographically closest species is P. caudimaculatus, who differs from P. mimbi by the absence of hooks in gonopodial appendix in males. Two of the three known populations of P. mimbi are relatively protected from the main threats to the species. However, conservation initiatives should consider its presence and ensure that it receives the necessary attention; considering that its global distribution occupies less than 200.000 km2 and its occurrence area represents less than 10% of the national territory it must be considered a priority for conservation and an Threatened Species for the species list of Sistema Nacional de Áreas Protegidas (SNAP) of Uruguay.

Paedonothridae Norton, Ermilov & Bayartogtokh fam. nov. is proposed as a new family of the oribatid mite hyporder Nothrina. It is monotypic, based on Paedonothrus reductus Norton, Ermilov & Bayartogtokh gen. et sp. nov., which was sampled from floating vegetation in a shallow lagoon in Kavaratti Atoll of the tropical Lakshadweep Islands, Arabian Sea, India. As such, it is the first known aquatic oribatid mite that is truly marine. It is easily distinguished by knife-like claws, wide separation of genital and anal valves, and reduction of genital papillae to a single small pair. The latter two are juvenile traits in other nothrines and, considering the many losses of body and leg setae, P. reductus appears to be the most paedomorphic known member of Nothrina. We argue for the inclusion of Paedonothridae in the superfamily Malaconothroidea and present a table of traits differentiating it from Malaconothridae and Trhypochthoniidae. While specimens are few, all are adult females, so P. reductus probably is thelytokous, like all other known members of the superfamily.

Summary An undescribed Cryptaphelenchus species was isolated from a bark beetle, Cryphalus fulvus, collected from the inner bark of a dead Japanese red pine, Pinus densiflora, in Kyoto, Japan. The nematode is described as a new species, Cryptaphelenchus fulvus n. sp., characterised by the presence of seven genital papillae in the male arranged as 1 + 2 + 2 + 2; a bursal flap-like cuticular extension surrounding the male tail, and intraspecific variation in the female tail, which ranges from broad to conical in overall shape, with the tip pointed, digitate, or rounded. Additionally, females with a broad tail possess a small papilla-like projection on the dorsal side of the tail near the tip, a unique feature of this species. Phylogenetically, the new species is closely related to Cryptaphelenchus orientalis, C. varicaudatus, and C. paravaricaudatus, but can be differentiated from these species based on molecular phylogenetics, several typological characters and morphometric values.

Summary A new species of the genus Panagrolaimus, P. hamomucronatus sp. n., is described from oak bark with lichens in the southern Iberian Peninsula. This species is characterised by having body 1.15-1.18 mm long in females and 0.91-1.16 mm long in males, habitus slightly sigmoid after fixation in females and ‘J’-shaped in males, cuticle with transverse striations, lateral fields with three longitudinal incisures, a lip region with six conoid lips ending in a setiform process, amphids rounded to oval, stoma with cheilostom bearing scarcely refringent rhabdia, a gymnostom as long as wide with very refringent rhabdia and stegostom short with well-sclerotised rhabdia, pharynx with pharyngeal corpus subcylindrical (1.6-1.9 times isthmus length) with metacorpus not swollen, nerve ring surrounding the anterior part of the isthmus, excretory pore at isthmus level, deirids at level of the isthmus, female reproductive system monodelphic-prodelphic with ovary without flexures and post-vulval uterine sac 0.6-0.7 times the corresponding body diam. long, rectum 1.3-1.5 times anal body width long, female tail conoid with fishhook-like mucron and phasmids at 73-76% of its length, male reproductive system monorchid with testis ventrally flexioned anteriorly, eight pairs of genital papillae (three precloacal and five postcloacal) with phasmids located posterior to the papilla GP6, spicules with manubrium ventrally bent and lamina with reduced dorsal hump and well-developed ventral velum, and gubernaculum slightly deltoid. Its phylogenetic position is studied based on 18S rDNA. An updated list of species is provided together with a new illustrated key to species identification.

The validity of the Stocky Sculpin Icelus crassus Andriashev, described from the Sea of Okhotsk, was confirmed following examination of the type series; the species having been previously considered a synonym of I. ochotensis Schmidt. Although both species belong to the "I. bicornis" (sensu Nelson 1984) species group, having suborbital spines and additional rows of scales on the body absent (excluding dorsal-row and lateral-line scales), and fine marginal serrations on the dorsal-row scales rather than sharp single spines, I. crassus differs from the type series of I. ochotensis in the absence of parietal spines (vs. present), supraorbital cirri present as expanding, distally branched laminae (vs. simple barbels), dorsal scale row incomplete anteriorly (vs. complete, reaching head); and lateral-line scales serrated below each sensory canal pore (vs. embedded in skin below each pore, usually with no more than 1-2 spinules). Meristic characters of I. crassus, similar to other species of the "I. bicornis" group, include 38-41 vertebrae, IX 18-20 dorsal-fin rays, 15 or 16 anal-fin rays, 17-19 pectoral-fin rays, 41-43 lateral-line scales, 25-31 dorsal-line scales, and 10-17 axillary scales. The urogenital papilla is cylindrical (not spatulate), with a short, claw-like terminal appendage. The holotype is found in ZIN collection, No. 21900, adult male TL 106 mm. Icelus crassus has been recorded in the Sea of Okhotsk and Sea of Japan (Strait of Tartary) 97-327 m depth; near bottom, water temperatures range from -0.7°C to 2.15°C.

Abstract A new species of Phalloceros is described from the upper rio Paraná, the upper rio Paraíba do Sul, and headwaters of coastal rivers in southeastern Brazil. This species is distinguished from congeners by characters of both male and female genitalia, dorsal fin-ray counts, dorsal-profile shape, and pigmentation and position of the vertically elongated dark spot on the flanks. The species has been misidentified in the literature as P. harpagos. Our DNA sequence analysis of specimens from the type-locality has clarified that P. harpagos is restricted to drainages on the right bank of the middle Paraíba do Sul and to coastal drainages in the metropolitan region of Rio de Janeiro. The new species differs from P. harpagos by a flattened, hood-like projection of skin located between the anus and the urogenital papilla in most females, and by a rounded lamellar flap on the distal margin of both gonopodial appendices in small mature males (< 21.2 mm SL). Mitochondrial CO1 gene analysis revealed a 6% genetic divergence between the new species and P. harpagos, providing strong support for the distinctiveness of this new species.

In this study, morphological and molecular features were used to identify a new Steinernema sp. from Kerala, India. Morphological and molecular features provide evidence for placing the new species into the longicaudum clade. The new species is characterized by the following morphological features: infective juveniles with a body length of 1067 μm (914-1268 μm); a distance from the anterior end to excretory pore of 82 μm (73-92 μm); a distance from anterior end to nerve ring of 105 μm (91-118 μm). The distinguishing feature of the infective juveniles of S. keralense n. sp. is the presence of seven ridges in the mid-body region, while all other species classified within the logicaudum clade to date are characterized by eight ridges. The first-generation males are characterised by 25 genital papillae, very short spicules, with a length of 68 μm (60-72 μm), and the SW% ratio is 136 (114-169). The new species is further characterized by sequences of the internal transcribed spacer and partial 28S regions of the ribosomal DNA. Phylogenetic analyses show that S. keralense n. sp. is closely related to species within the longicaudum clade.

The paper presents the analysis of morphological and genetic variations of two species, Metaphire bahli (Gates, 1945) and Metaphire peguana (Rosa, 1900), from Vietnam. As a result, M. bahli has two morphological forms based on the shape of the male region and state of genital markings while M. peguana has two subspecies, M. peguana peguana, and M. peguana laisonensis. M. peguana peguana had genital markings disc-shaped in 17/18/19 and a diverticulum attached to the base of the ampulla duct while M. peguana laisonensis had genital papillae slit-like shaped in xvii and xix, and diverticulum end at the middle of ampulla duct.

The main threats to the extinction of snakes are the loss and degradation of their natural habitat, mainly due to deforestation, urban expansion and fires. One of the ways of preserving snakes can be through the collection, analysis and cryopreservation of semen, and for collection, several techniques have been described, from compression and abdominal massage for ejaculation to the use of 1% lidocaine anesthetic solution for relaxation and direct access to the genital papilla. Therefore, the objective of the work was to revive the technique used in 1980, which consisted of abdominal massage and semen collection with the aid of a syringe. For the study, 5 snakes of the species Crotallus durissus terrificus (rattlesnake) were used, from APASS, in the city of Assis, state of São Paulo. The results obtained were an average seminal volume of 300 uL, with sperm motility of 68%, progressive motility: 3, sperm pathologies: 1, sperm concentration: 1.4 x 109 sptz/mL. Therefore, it is concluded that the non-invasive harvesting method using abdominal massage is still effective.