Caudal Filaments Research Articles

Early development of Brachyplatystoma juruense (Boulenger, 1898) (Siluriformes: Pimelodidae)

The early development stages of Brachyplatystoma juruense (Boulenger) are described through morphological, meristic, and morphometric data, providing useful traits to identify its larvae and juveniles. Additionally, the growth pattern throughout the species’ development has been determined from the smallest specimen of 3.93 mm (flexion) to the largest of 25.77 mm (juvenile). Ninety-one specimens classified into two larval stages (flexion and postflexion) and five juveniles were analyzed. The individuals were collected between 2011 and 2019 at sampling stations distributed across the Amazon basin, in the water systems of the Japurá, Solimões, and Amazonas rivers. The larvae and juveniles are characterized by having small, spherical eye, terminal mouth, rounded snout, and a dorsoventrally flattened head with three pairs of barbels (two pairs of mental barbels and one pair of maxillary). The anus does not reach the midbody region, and the adipose fin has a triangular shape. The upper caudal-fin rays extend, forming long caudal filaments. Initial pigmentation is restricted to dendritic and punctiform chromatophores irregularly distributed on the dorsal region of the head, and from postflexion onwards, along the dorsal region of the body. The total number of myomeres varies from 58 to 59 (22 pre-anal and 36 to 37 post-anal). During early development, B. juruense exhibits predominantly isometric growth. Larvae and juveniles of B. juruense can be identified by the number of myomeres, external morphology including pigmentation, head shape, and morphometric proportions. This information is essential for the accurate identification of larvae and juveniles captured in their natural environment.

A new species of the electric fish Microsternarchus Fernández-Yépez 1968 (Gymnotiformes: Hypopomidae) from the lower Amazon basin, Brazil

A new species of Microsternarchus is described from clear water streams in the lower Rio Amazonas basin, Brazil, increasing the known species in the genus to three. The new species is distinguished from congeners by a unique set of characters including an elongated caudal filament (35.1–36.8% of the total length) and distinct irregular suborbital blotches. A dichotomous key to the species of Microsternarchus is provided.

The imaginal morphology of the species Kangella brocha (Kang and Yang, 1995) from southern China (Ephemeroptera: Ephemerellidae)

Kangella brocha (Kang & Yang, 1995), a mayfly species known on nymphs only, has been previously placed in three different genera. Here, their first-found adults and additional nymphs from southern China reveal some new characteristics. Apart from its elongated mouthparts, extended outer incisors, widened prothorax, and shortened caudal filaments in the nymph stage, the adult exhibits a robust thorax, straight forceps, and large penes with dorsal projections. These distinct features, observed in both immature and alate stages, provide compelling evidence that this species deserves an independent genus. Therefore, the genus Kangella Sartori, 2004 is reinstated, and this species is reclassified under it. Functionally, the outstanding outer incisor likely serves purposes such as digging or capturing prey. Our finding not only narrows the distribution gap between two populations of this species but also enriches the diversity of ephemerellids in terms of ecological adaptations.

The ultrastructure of nymphal dermal pores and the genitalia of adult male of Phenacoccus solenopsis (Hemiptera: Pseudococcidae)

The cotton mealybug, Phenacoccus solenopsis, has established itself as an invasive insect pest worldwide. It causes structural and physiological damage to various crops and can cause substantial financial losses in their production. The successful reproduction of this pest under a wide range of conditions is a key to its success. Despite this, the morphology of its genitalia, genital sensilla, and wax-producing dermal pores has received little attention, with little descriptions of their ultrastructure. By investigating those features with SEM, the present study revealed considerable new insights into the identification of the nymphal and adult stages of P. solenopsis. In addition, the description of the ultrastructural genital morphology of the immature stages of P. solenopsis has revealed characteristics that facilitate their discrimination. Trilocular pores were observed on both sides of the body, while the quinquelocular pores were distributed only on the ventral surface in both the first and second nymphal instars. The adult male is characterized by two pairs of waxy caudal filaments surrounded by clusters of 55 to 60 stellate pores, and each pregenital segment bears a pair of stellate pores composed of 4 or 5 peripheral loculi. Sensilla trichodea and numerous microtrichia are present on the pregenital segments. The penile sheath bears three subtypes of sensilla basiconica and also campaniformia, whereas the style bears three subtypes of sensilla campaniformia. The findings of this study could assist in the identification of the adult and nymphal stages of P. solenopsis, and also provide insights into the structures found on the genitalia of the adult male that possibly have an important role in mating events and copulatory behavior. Furthermore, these findings were able to contribute to better understanding the functional morphology of P. solenopsis.

43 Years after H.G. Moser’s Seminal “Morphological and Functional Aspects of Marine Fish Larvae”: The Commonalities of Leptocephali and Larvae of Other Marine Teleosts

H.G. Moser was not particularly well known regarding the Elopomorpha, but he began his seminal 1981 fish larvae morphology review by describing the mysteries of European eels and their leptocephali, and he eventually described some California Current leptocephali. Descriptions of all types of leptocephali and then microscope photographs have revealed complex pigmentation patterns and diverse body shapes that parallel the features of the other teleost fish larvae that his review showed so clearly, some of which appear to mimic gelatinous zooplankton (GZ). Most recently, underwater photographs and video of leptocephali indicate that predator avoidance through transparency, shape-change-mediated mimicry, or morphological features have evolved in response to natural selection from predation in ways generally similar to other fish larvae. Several families of leptocephali perform remarkable curling into round or flattened shapes or use expandable chromatophores when threatened, which appears to mimic GZ for predation reduction. Like a number of other teleost fish larvae, some leptocephali have body extensions or telescopic eyes, and at least one has a long caudal filament with pigmented swellings that is similar to the remarkable GZ mimicry appendages of some fish larvae. The morphology and use of mimicry of leptocephali in comparison to other fish larvae is reviewed as a tribute to H.G. Moser’s remarkable career.

Morphological and molecular characterization of Chloromyxum dasyatidis n. sp. (Myxosporea: Chloromyxidae) in the common stingray Dasyatis pastinaca (Linnaeus) from Tunisian waters (Central Mediterranean Sea).

A new species of Chloromyxum Mingazzini, 1890, C. dasyatidis n. sp., is described from the gallbladder of the elasmobranch fish Dasyatis pastinaca (Linnaeus) from the Mediterranean coast off Tunisia. Mature myxospores were subspherical measuring 13.0 ± 0.3 (12.5-13.9) µm in length, 11.3 ± 0.5 (10.2-12.2) µm in width, and 11.8 ± 0.5 (11.4-12.7) µm in thickness. Four pyriform polar capsules 4.4 ± 0.3 (4.0-4.9) µm long and 3.5 ± 0.3 (3.0-3.8) µm wide. Valves were ornamented by 5 to 7 elevated surface ridges and displayed short caudal filaments. Chloromyxum dasyatidis n. sp. had an overall prevalence of infection of 38.5%, with significant seasonal variation, being more prevalent during summer (60.0%) and autumn (70.8%). Phylogenetically, this species grouped within the Chloromyxum sensu stricto lineage, forming a small clade together with the genetically more similar species C. acuminatum and C. myolibati, both from stingray hosts.

Record of an encapsulated embryo of Bathyraja brachyurops captured by bottom trawl off Uruguay, South-West Atlantic ocean

In this note the occurrence of an encapsulated embryo of Bathyraja brachyurops is reported. The embryo was in advanced stage of development. The capsule was collected after a bottom trawl operation, in the Argentinean-Uruguayan Common Fishing Zone, Southwest Atlantic, in September of 2000. After collection, the egg capsule was fixed in formalin 10% and preserved in ethanol 70%. The egg capsule was dark brown and measured 79.0 mm in length and 46.0 cm in width and was opened at its posterior. The embryo was a 100.0 mm total length female with a mass was 5.5 g. The specimen was in advanced development but the yolk sac was still conspicuous. According to the size of the yolk sac and the presence of caudal filament it could be concluded that there were several weeks to go before hatching.

Additions and corrections to taxonomy of Apobaetis fiuzai Salles & Lugo-Ortiz, 2002 and Apobaetis kallawaya Nieto, 2006 (Ephemeroptera, Baetidae)

Recently, it has been hypothesized that the wide distribution of A. fiuzai Salles & Lugo-Ortiz is due to a wide diagnosis and conflicting keys. The same arguments can be applied to A. kallawaya Nieto. In order to test this hypothesis, we revised the type material of A. fiuzai, literature of A. kallawaya, and part of the recorded specimens in Brazil. As a result, three new species from previous records are recognized: Apobaetis pasternakae sp. nov., former A. fiuzai in Amazonas, Roraima and Maranhão states; Apobaetis jaquelinae sp. nov., former A. fiuzai in Rondônia State; Apobaetis luanae sp. nov., former A. kallawaya in Rondônia State. The new data showed that A. fiuzai does not occur in the Amazon Biome and A. kallawaya does not occur in Brazil. Records of A. fiuzai that could not be reviewed in this study are treated as putative and should be evaluated in the light of the new evidence. We also studied the intraspecific variation in A. fiuzai and A. pasternakae sp. nov. The pigment pattern of the nymphs was not considered a robust characteristic for the species differentiation due to the wide variation in and between populations, and interspecific similarity of many features. On the other hand, classical morphological characters such as mouthparts, legs, spines of terga, paraproct and caudal filaments have minimal variation, stable and reliable for specific identification.

First record of hygropetric species in the genus Paegniodes Eaton, 1881 (Ephemeroptera: Heptageniidae) with description of a new species from China

Paegniodes oligopilus sp. nov., a first hygropetric species in the genus Paegniodes Eaton, 1881 found from madicolous habitat, is described based on larvae from Southwest China. The new species is characterized by the posterior margin of 1st segment bearing a row of 13-15 stout setae; mesonotum and abdominal tergites II-IX having a reddish brown median stripe; swimming setae of cerci and median caudal filament are vestigial. The morphological affinities and feeding habits with other known species are discussed.

The Real Characters of Heptagenia ngi Hsu (1936) from China Representing a New Genus (Ephemeroptera: Heptageniidae)

A very common and early named mayfly species from China, Heptagenia ngi Hsu, 1936, has no exact descriptions of its imago nor nymph, so its generic status is not clear. Based on detailed re-descriptions and pictures of all its stages from fresh materials, it is transferred into a new genus Maculogenia Zhou, gen. nov. Its nymph has conspicuous pale-dark colored body, slightly concave posterior margin of head, scattered simple setae on ventral maxillae, spines and very fine hair-like setae on caudal filaments. Similarly, its imago also has remarkable dark stripes and dots on the pale body, small median titillators and short first segment of foretarsi, apically expanded penes without any spines. It is similar to the genera Electrogena, Thamnodontus, and Parafronurus but they can be differentiated easily by above selected key structures.

A Review of the Genus Serratella Edmunds, 1959 in China with Description of a New Species (Ephemeroptera: Ephemerellidae).

Species in the genus Serratella Edmunds, 1959 from China have never been compared and photographed systematically. Six valid Chinese Serratella species are recognized and revised in this paper. Among them, the imagos of S. brevicauda Jacobus et al., 2009 are unknown; the nymph of this species has a stout, strong body, with remarkably short caudal filaments and maxillary palpi. In contrast, only the imago stage of Serratella fusongensis (Su and You, 1988) (=Serratella longipennis Zhou et al., 1997, syn. nov.) is known; it has relatively long penes with small dorsal projections. The nymphs of S. setigera Bajkova, 1967 have small abdominal tergal spines but distinct, stout, blunt bristles on the spines, and the apexes of the male penes are round and shallowly divided. The fourth species, S. acutiformis sp. nov., which was collected from Western China, has sharp penial apexes (imagos) and large abdominal spines (nymphs). Unlike the former four species, S. ignita (Poda, 1761) and S. zapekinae Bajkova, 1967 has sub-quadrate penes without prominent dorsal projections. The nymph of S. ignita has lateral hair-like setae on the caudal filaments, while the nymph of S. zapekinae lacks such setae but has pairs of tubercles on the head and pronotum. Some characters used in the generic delineation of the genera Ephemerella Walsh, 1862 and Serratella, such as nymphal maxillary palpi and hair-like setae on caudal filaments as well as features of the imaginal penes and forelegs, are varied in Chinese species. However, all species in this paper have bifurcate ventral lamellae of gill VI. Our work highlights a need for further comparative systematic study of the genera Serratella, Ephemerella, and another related genus Torleya Lestage, 1917.

Primer registro del pez kuya kuya Acanthicus hystrix Agassiz 1829 en la Baja Amazonía Central del Ecuador

This paper reports the first record of the fish kuya kuya Acanthycus hystrix Agassiz, 1829, in the Pinduc river of the province of Pastaza, at 230 m of elevation, in the lower central Amazon of Ecuador, based on photographic records of three specimens (two juveniles and one adult) caught in subsistence fishing activities. The main diagnostic characters of the species are the absence of an adipose fin and the presence of long caudal filaments in juveniles. We suggest to include this record in the fish species list from the Ecuadorian Amazon.

First mayfly larva of Leptophlebiidae (Insecta: Ephemeroptera) in mid-Cretaceous Kachin amber, northern Myanmar

A new genus and species of mayfly, Kachinophlebia zhouchangfai gen. et sp. nov. (Ephemeroptera: Leptophlebiidae), is described and illustrated based on a larva in the mid-Cretaceous amber from Kachin, northern Myanmar. The new taxa are established primarily based on the morphological characters of the mouthparts, legs, abdominal gills, and caudal filaments. The new amber mayfly is the first report of Leptophlebiidae from mid-Cretaceous Kachin amber.

A new species of Sparsorythus Sroka amp; Sold, 2008 (Ephemeroptera: Tricorythidae) from Tamil Nadu, India.

Sparsorythus srokai sp. nov. is described from the Veerapandi River, Theni district, Tamil Nadu, India based on nymphs of both sexes. The nymphs of Sparsorythus srokai sp. nov. can be distinguished by the following combination of characters: i) presence of lateral setae in each segment of caudal filaments, ii) dorsal surface of labrum entirely covered with scattered ribbon-like bristles, iii) posterior margin of mesonotum reaching abdominal segment III in both sexes, and iv) left prostheca with several pointed teeth apically. The new species is compared with other Indian species: S. gracilis Sroka Sold, 2008, S. sivaramakrishnani Sivaruban, Srinivasan, Barathy, Rosi Isack, 2021 and S. nanjangudensis Muthukatturaja Balasubramanian, 2021. The distributional map and key to the genus Sparsorythus in Southern India are also given.

First description of Chloromyxum squali Gleeson and Adlard, 2012 (Myxozoa) in the Mediterranean Sea in a new host Squalus blainville (Chondrichthyes: Squalidae): morphological, ultrastructural and phylogenetic data.

Chloromyxum squali Gleeson and Adlard, 2012 originally described from Squalus acanthias Linnaeus, 1758 is reported for the first time from the gallbladder of Squalus blainville (Risso, 1827) caught from the eastern coast of Tunisia. In the present study, this chloromyxid was described based on morphological and ultrastructural features combined with molecular analysis of 18S rDNA. Young plasmodia were found attached to the gallbladder, while mature plasmodia and myxospores were observed floating free in the bile. Mature plasmodia were polysporic, subspherical in shape, measured 97.8 ± 0.5µm long and 63.4 ± 0.4µm wide. Mature myxospores were ovoid with a pointed anterior end, measuring 10.2 ± 0.5µm long and 8.3 ± 0.5µm wide. Two asymmetrical shell valves adhered together along an S-shaped suture line. Each valve has 5-7 elevated surface ridges parallel to suture line. A bundle of long caudal filaments extended from the basal end of shell valves. Four pyriform polar capsules equal in size, measuring 3.1 ± 0.4µm long and 2.5 ± 0.3µm wide, were situated at the same level in the anterior pole of the myxospore, each with a polar filament coiled in 7-8 turns. Pairwise comparisons among the SSU rDNA sequences revealed significant similarity between Chloromyxum squali infecting S. acanthias with the sequence obtained in this study. Phylogenetic analysis revealed that C. squali clustered in the clade of Chloromyxum species infecting the gallbladder of marine Chondrichthyes. Chloromyxum squali showed a seasonal variation of prevalence with significantly higher prevalence noted in summer and in autumn and absence of infection in winter.

Life history, systematics and flight ability of the Early Permian stem-mayflies in the genus Misthodotes Sellards, 1909 (Insecta, Ephemerida, Permoplectoptera)

BackgroundThe stem-group of Ephemeroptera is phylogenetically important for understanding key steps in evolutionary history of early pterygote insects. However, these taxa have been mostly studied from the taxonomy point of view focused on the pattern of wing venation and often using only classical optical microscopy devices. In-depth studies on detailed morphology of the different body structures are scarcely performed, although the results are critical for elucidation of life history traits and their evolutionary pattern among the basal pterygotes.ResultsNew information is presented on the morphology of two species of Misthodotes, which are stem-mayflies from the Early Permian. Based on new results obtained from a re-examination of the type specimens and supplementary material, we infer the life history traits of both the adult and larval stages of these Palaeozoic insects and reconsider previous interpretations. For the first time, we report the structure of the thoracic pleura and the articulation at the base of the wing in a stem-group of Ephemeroptera and compare them with those of extant mayflies. We also provide additional support for the systematic placement of investigated taxa and an amended diagnosis of the genus Misthodotes.ConclusionsAdult Misthodotes sharovi and Misthodotes zalesskyi had chewing mouthparts, which enabled them to scavenge or feed on plants. The wing apparatus was adapted for slow powered flapping flight and gliding, using long caudal filaments for steering. The wing base does not have rows of articulary sclerites as previously hypothesized for some Palaeozoic taxa but inflexible axilla similar to that found in modern mayflies. The structure of the thoracic pleura is also similar to that in the crown group of Ephemeroptera, while differences in the course of sutures may be explained by an evolutionary trend towards more powerful dorsoventral flying musculature and forewing-based flight (anteromotorism) in modern taxa. There is no evidence for swarming behaviour and mating in the air as occurs in modern mayflies as they had none of the associated morphological adaptations. Putative larvae of Misthodotes can not be unambiguously associated with the adults. They also exhibit some morphological specializations of Protereismatidae like 9 pairs of abdominal tracheal gills supporting their benthic lifestyle with legs adapted to burrowing.

A new species of dartfish of the genus Ptereleotris (Teleostei: Gobiidae) from the East Coast of India.

Ptereleotris cyanops n. sp. is described from five specimens collected in trawl landings at Chennai, Tamil Nadu, East Coast of India. The new species is unusual among congeners in possessing a wide interdorsal space, its width 2.5-3.2% in SL. The new species resembles P. microlepis in general morphology and coloration, but is readily distinguished from it in lacking a black bar at base of pectoral fin, in having a slightly truncate caudal fin with the 5th and 13th branched rays prolonged as filaments (vs. emarginated caudal fin with absence of any caudal filaments), and in having the second dorsal and anal fin not elevated anteriorly (vs. elevated). Ptereleotris cyanops differs from caudal filaments bearing congeners viz., P. arabica and P. hanae, by the absence of chin barbel (vs. present in both); in having a longer pelvic fin (17.7-18.8 vs. 13.1-15.5% SL in P. arabica), and more anal rays (27 vs. 22-25 in P. hanae).

Morphological and molecular-genetic characterization of Chloromyxum trilineatum n. sp. (Myxosporea: Bivalvulida) in the gall bladder of pale chub (Zacco platypus) in Japan.

The genus Chloromyxum (Myxozoa: Myxosporea: Bivalvulida) is defined as having ridged or smooth bivalvular myxospores containing four polar capsules, with/without caudal filaments. Currently containing more than 140 nominal species, this genus is reasonably speciose with myxospores of unique but heterogeneous morphology. Recent phylogenetic studies have demonstrated its polyphyletic nature. During our myxosporean survey of freshwater fish, a new coelozoic myxosporean species, Chloromyxum trilineatum n. sp., was detected in the gall bladder of the pale chub, Zacco platypus (Cypriniformes: Cyprinidae), which originated from central Japan. Spores were subspherical, measuring 8.5-9.1 (8.8) μm in length, 7.6-8.2 (8.0) μm in width, and 6.8-7.8 (7.4) μm in thickness (n = 20). The valvular surface was smooth and three or four distinct ridges ran parallel to the suture line. Four almost equal polar capsules, 2.9-3.8 (3.3) μm in length and 1.6-2.4 (2.0) μm in width, assembled at the apical part of the spores. The partial nucleotide sequence of the 18S ribosomal RNA gene, 2014bp in length, was closest to that of morphologically distinct Chloromyxum ellipticum, infecting the gall bladder of grass carp (Ctenopharyngodon idella) in China with 96.99% (1673/1725) identity and three insertion/deletion (indel) sites, followed by Chloromyxum legeri, infecting the gall bladder of common carp (Cyprinus carpio) in the Czech Republic with 89.97% (1803/2004) identity and 14 indel sites. Other myxosporean species, including Chloromyxum spp. from the gall bladder or urinary system of freshwater and marine fish, were phylogenetically distant from the present species.

Adaptive morphology of the host-seeking first-instar larva of Stylops advarians Pierce (Strepsiptera, Stylopidae), a parasite of Andrena milwaukeensis Graenicher (Hymenoptera, Andrenidae)

The morphology of the prognathous, host-seeking first-instar larvae of Stylops advarians was examined to advance our understanding of their adaptations to reach immature bee hosts, a process requiring temporal phoresy on an adult bee. Sensory structures on the larval head, including eye spots and two pairs of olfactory pits, evidently assist recognition of an adult bee and eventual detection of a permanent host within a nest cell. First-instar larvae utilize various features of their appendages to travel securely on their phoretic host. Flexible adhesive tarsi of the pro- and mesothoracic legs allow them to embark and be retained on a flying bee. The tips of the pair of caudal filaments appear modified for a similar purpose. Spinulae of two lengths, and arranged in distinct patterns, cover the posterior edges of the thoracic and abdominal segments both dorsally and ventrally. These projections can cause lodging of larvae in the plumose hairs of the phoretic host, and may lock into the exine of pollen collected by the foraging bee. Discovery of a first-instar larva partially packed into a pollen load and in the crop of Andrena milwaukeensis demonstrates that Stylops is adapted to travel with a phoretic host both externally and internally.

Redescription of Parafronurus youi and generic affinities (Ephemeroptera, Heptageniidae, Ecdyonurinae).

The detailed morphology and phylogenetic positon of Parafronurus youi Zhou Braasch, 2003 have not been discussed especially so far. In this study, we re-describe and illustrate all stages in more detail. Compared to other genera in the subfamily Ecdyonurinae, the nymph of P. youi is characterized by rounded supracoxal spurs, rounded rectangular head capsule, dense setae on dorsal side of labrum, simple proximal and distal dentisetae, primarily swimming setae of caudal filaments. Upon the latter two characters, this genus seems closer to Asian Rhithrogeniella Ulmer, 1939.