Posterolateral Spines Research Articles

Taxonomic re-evaluation of the Brachionus calyciflorus species complex (Rotifera) in Japanese freshwaters

AbstractRecently, the Brachionus calyciflorus species complex was divided into four nominal species: B. calyciflorus sensu stricto (s.s.) Pallas, 1766; Brachionus dorcas Gosse, 1851, Brachionus elevatus Michaloudi et al., 2018, and Brachionus fernandoi Michaloudi et al., 2018 based on the results of both morphological and molecular investigations. We applied this systematic approach to B. “calyciflorus” collected from lakes and ponds in various parts of Japan to examine spatial and temporal distributions of these species. We found that all four species indeed distributed in Japan. Among the species, B. fernandoi exhibited a somewhat different occurrence pattern and morphology. Generally, B. fernandoi appeared to occur in the winter–spring, while the other three species seemed to occur in the early summer–late autumn. A seasonal succession from B. fernandoi-dominant community to other species-dominant communities was observed in the same lakes/ponds. A statistical analysis showed that B. fernandoi-dominant species composition was also related to low temperatures. It was also found that the body of B. fernandoi was more elongated compared to those of other species. These results suggest that B. fernandoi is a distinct species in terms of morphology and phenology. Among the other three species, we observed a variation in the length of posterolateral spines. However, it was not clear if this variation is a trait that distinguish these species morphologically. In addition, some of these species co-occurred in the same lakes and ponds. The mechanism by which they coexist is a topic for future study.

A new species of Siphlonurus Eaton, 1868 (Ephemeroptera, Siphlonuridae) from Yunnan, China.

Siphlonurusdongxi Li & Tong, sp. nov. from Shangri-La City, Yunnan Province, China, is described based on egg, nymph, and winged stages. The new species is closely related to S.davidi (Navás, 1932), and can be distinguished by the colour of the imago, the forking point of MP, the penis, posterolateral spines of tergum IX of imagoes, and first abdominal terga nymph, as well as the structure of the egg. The new species and S.davidi have the same morphological and structural characteristics, such as the long cubital area with many intercalaries, cross veins between C, Sc, RA, and RSa1 surrounded with distinct pigments, the strong curvature of vein CuP in the forewing, the broad expansion of the hindwing, the membranous penis lobes fused without teeth, supporting the proposition of a new species complex, the Siphlonurusdavidi group. The structures of the penis and the egg of the new species could help understand the origin and evolution of the genus Siphlonurus.

A remarkable finding of Centroptilum Eaton, 1869 (Ephemeroptera: Baetidae) in Georgia, Turkey and Iran: one new species evidenced by morphology and DNA

The genus Centroptilum Eaton, 1869 is widely distributed in the West Palaearctic region, but poorly diversified as it previously only encompassed two valid species, C. luteolum (Müller, 1776) and C. pirinense Ikonomov, 1962. The discovery of a new congener, C. volodymyri Martynov, Godunko and Palatov, sp. nov., is therefore remarkable; the new species is described based on larvae collected in Georgia, Turkey and Iran in 2012–2019. This new species can be distinguished by the structure of the cuticle with flattened, stretched shallow, triangular and semilunar-shaped corrugations; scales and their bases densely scattered on body surface; features of the mouth parts, including the presence of an expanded laterally labrum, in combination with segment III of maxillary palp and superlinguae of hypopharynx rounded apically, without any pointed projections at the tip; numerous small teeth scattered proximally in two rows along inner margin of the pretarsal claw; the shape of denticulation along the posterior margin of the abdominal terga, and the number of prominent posterolateral spines on tergum VII; and the shape of gills II–VII, with a distinctly concave posterior margin. Together with a morphological description, data on the distribution and mitochondrial cytochrome c oxidase subunit I gene (COI) barcode sequences of the species are provided. The species delimitation of C. volodymyri Martynov, Godunko and Palatov, sp. nov. and C. luteolum is tested using COI barcode sequences. The data obtained show that the new species can be distinctly recognised as a separate lineage. The habitat preferences associated with the different parts of the area of C. volodymyri Martynov, Godunko and Palatov, sp. nov. are described and compared. Distribution of C. volodymyri Martynov, Godunko and Palatov, sp. nov. confirms the connections between Caucasian and Asian fauna of Ephemeroptera, as already demonstrated in various families and genera. Short notes on the distribution of mayfly species common to the Caucasus, north-western Iran and Central Asia are presented. http://www.zoobank.org/urn:lsid:zoobank.org:act:1D2B7557-0DEC-4ACD-8CA3-A6B50FCC4A51.

A new species of Thraulus Eaton, 1881 (Ephemeroptera: Leptophlebiidae) from the Western Ghats, South India

Thraulus jacobusi sp. n. is described based on the nymphs collected from the Veerapandi River in the south of the Western Ghats. Thraulus jacobusi sp. n. may be distinguished from other oriental species of Thraulus Eaton, 1881 by the following combination of characters in the nymphs: labial palp ratio, maxillary palp ratio of segments II and III, the colouration of legs, shape and denticulation of claws, shape of tergalius I, and posterolateral spines on the tergum VIII and IX. Nymphal diagnostic keys to Indian species of Thraulus are provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:69019BD1-BE64-4186-8DA9-C67D28DD6135

A new mayfly species of Choroterpes (Choroterpes) Eaton, 1881 (Ephemeroptera: Leptophlebiidae) from southern Western Ghats, India

A new species of Choroterpes (Choroterpes) Eaton, 1881 is described based on nymphs from southern Western Ghats, Karnataka, India. Choroterpes (Choroterpes) kumaradhara sp. nov. can be distinguished from other Oriental species of Choroterpes s.str. by the following combination of characters: (i) median emargination of labrum deeply cleft (U-shaped) with few denticle-like protuberances; (ii) the lateral margin of mandibles with a cluster of thin, long setae medially; (iii) gill I single lamellate, basal half broader and tapered to apex; (iv) median projection of dorsal lamella of gills IIVII plate-like and markedly larger and longer than laterals, ventral lamella small, trifurcated and (v) abdominal segments IIIX with posterolateral spines progressively longer posteriorly. Distribution and habitat ecology of the new species are provided.

Ecological benefits of consistent expression of posterolateral spines in Brachionus calyciflorus

Plasticity of spine morphology is a universal phenomenon in rotifers. Some Brachionus calyciflorus clones consistently develop two posterolateral spines (PS) with similar length (Type A), but others (Type B) not. The underlying mechanisms remain unknown. In the present study, the resting eggs were collected from the same B. calyciflorus strain, their hatchlings (stem rotifers) were categorized into types A and B, and then, clonally cultured for eight generations at different algal densities or temperatures. The results showed that the PS varied in length among different temperatures and food levels, but inherent differences between types A and B were always observed, indicating that differentiation between types A and B might not associate with temperature or food availability. Next, we compared the population growth and PS length between types A and B at the general condition (control), in responses to Asplanchna kairomone, Keratella tropica and Moina macrocopa. The results showed that type B had higher population growth rate than type A, suggesting the higher adaptability of type B in the general condition. In response to Asplanchna kairomone, the PS length of both types A and B was significantly induced, and their PS length was similar, but type B showed higher population growth rate than type A. Coculture with M. macrocopa significantly lengthened the PS of type B but not type A, and types A and B showed similar population growth curves. Coculture with K. tropica did not affect significantly the PS length of types A and B. However, type A showed significantly and greatly higher population density and population growth rate than type B, indicating a much stronger competition ability of type A than type B against K. tropica. Overall, these results indicated that consistent development of PS might facilitate B. calyciflorus to defend against small competitors.

A new species of flat-headed mayfly Afronurus meenmutti (Ephemeroptera: Heptageniidae: Ecdyonurinae) from Kerala, India

A new species of mayfly (Heptageniidae: Ecdyonurinae) Afronurus meenmutti sp. nov. is described based on larvae and imagoes from the state of Kerala, southern India. The main characteristics that distinguish the new species from all other species are in having glossae oblong with two stout spines medially; lingua of hypopharynx deeply cleft; absence of postero-lateral spines on terga and gill I slightly lobate in the nymph. Hind wing with the acute costal process; stout spine dispersed on basal and surface of forceps in the adults.

Plasticity in rotifer morphology induced by conflicting threats from multiple predators

AbstractOne of the major research goals in ecology is to understand predator–prey interactions. However, our understanding of how prey express phenotypic plasticity in response to co‐occurring multiple predators is limited in many systems.Here, we use the rotiferBrachionus calyciflorusas model organism to test how prey responds to co‐occurring predators through a series of related experiments. Firstly, we examined the effects of the density of a fish predatorCarassius auratuson morphological traits inB. calyciflorus. Secondly, we examined the effects of larvalC. auratusandAsplanchna brightwellii(a rotifer predator) on morphological defensive traits (body length, body width, anterior spine length, and posterolateral spine length) ofB. calyciflorus.We show thatB. calyciflorusdevelops smaller body size and shorter spine length when exposed to media conditioned using larval fish, and that high larval fish densities induce more pronounced responses than low densities. We also show thatB. calyciflorusis able to discriminate between the two predators by producing opposing morphological adaptations (i.e., larger body size and longer posterolateral spines againstA. brightwellii,but smaller body size and shorter spine length when exposed to the visual predator [larval fish]). However,B. calyciflorusdevelops intermediate, trade‐off responses in all morphological traits when exposed to conflicting threats from a combination of predators with different size and feeding strategies.These results show how prey are not necessarily passive victims, but rather, use countermeasures against predation – they actively develop responses to counteract their vulnerability to different predators by rapidly adjusting their morphology and life‐history traits to the existing predator regimes.

Description of the larva of Planiplax sanguiniventris (Calvert, 1907) (Odonata: Libellulidae).

The last instar larva of Planiplax sanguiniventris (Calvert, 1907) is described and illustrated in detail based on one specimen collected in the municipality of Tenosique, Tabasco, Mexico. It is compared with the larvae of P. phoenicura Ris, 1912 and a congeneric unidentified species from Colombia. The main structural features are the number of setae on palp and prementum, the size of dorsal protuberance on S3, and the length of posterolateral spines on S89 and caudal appendages.

Divergent responses in morphology and life history to an Asplanchna kairomone between attached and free-swimming Brachionus dorcas (Rotifera)

In the presence of the predatory rotifer Asplanchna, some Brachionus and Keratella species develop inducible morphological, behavioral, and life history defenses that enable prey to survive predation pressure. However, whether clones belonging to the same rotifer species but with different behaviors (attached and free-swimming) exhibit divergent responses in morphology and life history remains largely unknown. In this study, neonates of an attached and a free-swimming clone of B. dorcas were exposed to media conditioned by A. brightwellii neonates at densities of 0 (control), 40, 80, and 160 ind l−1 for 24 h, and their morphological and life-table demographic parameters were measured and calculated. We showed that the Asplanchna kairomone significantly increased the propensity to attach in the attached clone only, with attached individuals effectively protected from Asplanchna predation. In response to increasing Asplanchna kairomone concentration, the attached clone did not show any morphological changes, but it did exhibit a decreased net reproductive rate and intrinsic rate of population increase. The free-swimming clone developed elongated posterolateral spines and a decreased intrinsic rate of population increase, as well as a decrease in the proportion of sexual offspring. Thus, both clones exhibited reproductive costs.

Description of zoeal stages of Albunea paretii Guérin-Méneville, 1853(Decapoda: Albuneidae) collected from the Amazon Continental Shelf (Brazil).

The present work describes and illustrates in detail the six zoeal stages of Albunea paretii collected from plankton samples on the Amazon continental shelf in Brazil. The morphological characters are compared with those of other known albuneid larvae. As in other albuneids, the zoeae of Albunea paretii have a semi-globose carapace, a long rostral spine and a pair of long posterolateral spines on pereon, as well as three aesthetascs on the antennule of zoea I, a strong antennal spinous process and a convex telson with a stout posterolateral spine. The zoeal morphology of Albunea paretii and other species of the genus differs, especially regarding the unique presence of the posterolateral spine only on the 5th pleonite in zoea I-IV and the absence in later zoeal stages. The differing features of the albuneid subfamilies are in the telson, antenna and maxilla format and number of setae.

Proeryon, a geographically and stratigraphically widespread genus of polychelidan lobsters

Polychelidan lobsters are decapod crustaceans characterized by their four to five pairs of claws. The first description of a polychelidan lobster dates back to 1817, and since then, numerous species have been described with varying level of details. This situation sometimes led to the description of synonymous species, and more generally, led to a lack of overview on the group systematic and evolutionary history. Herein, we review Proeryon¸ one of the most diversified and stratigraphically widespread polychelidan. We argue that Proeryon is closely allied to Tethyseryon and Gabaleryon and propose to assign them to Proeryoninae nov. subfam., which are mainly characterized by their hemicircular ocular incision, postorbital and branchial carinae not joined together, and axial carina on pleonites cut by transverse grooves. Proeryon is in turn characterized by its marked cervical and hepatic incisions, simple posterolateral spines and arched uropodal exopod diaeresis. Thus defined, we assign the following species to Proeryon: P. charbonnieri, P. giganteus, P. hauffi, P. laticaudatus, P. richardsoni, P. stoddarti and two unnamed species from the Hauterivian of Germany and Switzerland, respectively. In addition, we refer to Proeryon, with some reservations, two new species,?Proeryon quiltyi from the Callovian of Antarctica and?Proeryon erinaceus from the Oxfordian of France. Proeryon has highly discontinuous but large stratigraphic (Pliensbachian – Hauterivian: about 60 MA) and palaeogeographic (from United Kingdom to Siberia, and to Antarctica) distribution. Most of these species occurs in relatively deep neritic or deeper palaeoenvironments. It is possible that this deep-sea dwelling is one of the reasons why Proeryon survived so long. Also, we note the presence of abundant oysters living as epibionts on some specimens of Proeryon hartmanni. Their disposition and number suggest that P. hartmanni was an epibenthic animal.

Joint effects of predation risk and food nutrient on sexual and asexual reproductions, and morphological defenses of freshwater rotifer Brachionus calyciflorus

Ecological stoichiometry predicts that the extent to which herbivores are limited by nutrients depends on their metabolic demands. Nonconsumptive effects (NCEs) caused by predators have been demonstrated to trigger not only inducible defenses but also physiological stresses in prey. Stressed prey always exhibit increased metabolism and decreased nutrient deposition (e.g., nitrogen and phosphorus) as physiological stress responses to their predators. Consequently, prey exposed to predation risk should reduce demands for nutrients intake and become adaptive to nutrient limitations. In this study, results obtained from classic Brachionus–Asplanchna model revealed that Brachionus calyciflorus fed with full nutrient algal food showed energetic costs, e.g., reduced investment in asexual (lifetime fecundity) and sexual (mixis ratio) reproductions, in response to predation risk. However, reduction in sexual and asexual reproductions diminished when herbivorous Brachionus were supplied with nitrogen- or phosphorus-limited algal food. Moreover, long posterolateral spines and high posterolateral spine-body length ratio developed in either nitrogen- or phosphorus-deficient conditions containing Asplanchna kairomones, indicating an additive effect of nutrient limitation and predation risk on posterolateral spine development in Brachionus. The findings of this study highlighted predator-facilitated adaptation of prey to nutrient limitations of primary producers, which may have implications in understanding roles of NCEs in regulating trophic interactions.

A redescription of Liangwangshania biloba Chen, 2005, from the Chengjiang biota (Cambrian, China), with a discussion of possible sexual dimorphism in fuxianhuiid arthropods

Material attributed to Liangwangshania biloba, a fuxianhuiid arthropod from the lower Cambrian (Series 2, Stage 3) of southwest China, is redescribed, with many specimens illustrated for the first time. Newly recognized features include, potential optical neuropils, a stout posterolateral carapace spine, serrated tergal pleurae, two rows of mediolateral carinae, an abdomen composed of seven segments, the last possessing a tripartite lateral flap, and a triangular telson. The presence of tergal carinae, a prothorax composed of six segments, and a trunk composed of 43 segments tipped with a flap-like terminal segment, increase similarities with the previously described Shankouia zhenghei, thus prompting a reevaluation of the potential synonymy of these taxa. These previously recognized species also show considerable overlap in body size, and the ratios of selected body features, such as the carapace. This, combined with their co-occurrence over a temporally and geographically limited range, further support their synonymy. L. biloba is considered the senior synonym in accordance with ICZN rulings, with morphological differences, specifically the presence of posterolateral spines on the carapace, serrated tergopleurae, and spines on the terminal abdominal segment, attributed to sexual variation. An evaluation of potential sexual dimorphism in other fuxianhuiids, and a reassessment of terminology applied to this group is also provided.

Autologous chondrocyte grafting promotes bone formation in the posterolateral spine.

Background contextPseudarthrosis following spinal fusion remains problematic despite modern surgical and grafting techniques. In surgical spinal fusion, new bone forms via intramembranous and endochondral ossification, with endochondral ossification occurring in the hypoxic zones of the fusion bed. During bone development and fracture healing, the key cellular mediator of endochondral ossification is the hypertrophic chondrocyte given its ability to function in hypoxia and induce neovascularization and ossification. We therefore hypothesize that hypertrophic chondrocytes may be an effective bone graft alternative.PurposeSpinal fusion procedures have increased substantially; yet 5% to 35% of all spinal fusions may result in pseudoarthrosis. Pseudoarthrosis may occur because of implant failure, infection, or biological failure, among other reasons. Advances in surgical techniques and bone grafting have improved fusion; however pseudarthrosis rates remain unacceptably high. Thus, the goal of this study is to investigate hypertrophic chondrocytes as a potential biological graft alternative.MethodsUsing a validated murine fracture model, hypertrophic chondrocytes were harvested from fracture calluses and transplanted into the posterolateral spines of identical mice. New bone formation was assessed by X‐ray, microcomputed tomography (μCT), and in vivo fluorescent imaging. Results were compared against a standard iliac crest bone graft and a sham surgery control group. Funding for this work was provided by the Department of Orthopaedics and Rehabilitation, the OREF (Grant #16‐150), and The Caitlin Lovejoy Fund.ResultsRadiography, μCT, and in vivo fluorescent imaging demonstrated that hypertrophic chondrocytes promoted bone formation at rates equivalent to iliac crest autograft. Additionally, μCT analysis demonstrated similar fusion rates in a subset of mice from the iliac crest and hypertrophic chondrocyte groups.ConclusionsThis proof‐of‐concept study indicates that hypertrophic chondrocytes can promote bone formation comparable to iliac crest bone graft. These findings provide the foundation for future studies to investigate the potential therapeutic use of hypertrophic chondrocytes in spinal fusion.

Tricorythodes macuira (Ephemeroptera: Leptohyphidae), new species from Colombia.

Tricorythodes macuira sp n. is described and illustrated based on nymphs of both sexes and eggs from Colombia. This species can be recognized by the following combination of characters: maxillary palp 2-segmented and small, pronotum with rounded anterolateral projection, pronotum and mesonotum with thick and long setae on margins, femora I and II with transverse row of long setae at dorsum, tarsal claws with marginal row of 5-8 denticles and subdistal double row of 4-2 + 1-2 submarginal denticles, subtriangular operculate gills shaded black on a basal stripe, ventralmost lamellae of gills III-V with dorsal extension very well developed, abdominal segments VII-IX with small posterolateral spines. Eggs with one polar cap, polygonal chorionic plates with elevated margins and long adhesive filaments near the uncapped pole.

Maternal Effects Via Resting eggs in Predator Defense of the Rotifer Brachionus calyciflorus.

Maternal effects play important evolutionary and ecological roles. Amictic female mothers of monogonont rotifer Brachionus calyciflorus can transmit predatory information of Asplanchna brightwellii in their environment to their offspring by changing the offspring's defensive morphology to increase their fitness. However, it remains unclear whether such maternal effects also exist during sexual reproduction of a mictic mother. This study explored the maternal effect in mictic mothers using the B. calyciflorus and A. brightwellii as a prey-predator model. We collected resting eggs from two groups of mictic mothers that previously experienced environments with (P environment) or without (NP environment) Asplanchna kairomones. Stem females from the resting eggs of each maternal group were also hatched and reared in P and NP environments. The population growth rate of offspring who experienced the same environment as their mictic mothers was significantly higher than those that experienced a different environment. When exposed to a gradient of predator kairomone levels, the posterolateral spine of the offspring elongated with increasing kairomone concentration. Offspring from the P mictic mother showed significantly shorter posterolateral spines than those from the NP mictic mother at each predator kairomone level. Offspring originating from NP mictic mothers clearly elongated their posterolateral spines at low concentrations of predator kairomones, while those from P mothers elongated their posterolateral spines only at the highest levels of predator kairomone. Our findings highlight the existence of anticipatory maternal effects during the sexual process via resting eggs of B. calyciflorus in response to predator kairomone.

Effects of food concentration on the life table demography and morphology of three Keratella quadrata morphotypes

Keratella quadrata with two (2PS), one (1PS) and none posteolateral (0PS) spines were cultured under four food levels (0.75 × 106, 1.5 × 106, 3.0 × 106 and 6.0 × 106 cells·mL−1 of Scenedesmus obliquus) to test the differences in the life table demography and the morphological characteristics among these three morphotypes. The results showed that each K. quadrata morphotype could produce 2PS, 1PS and 0PS offsprings. The frequencies of 0PS were extremely low (<5%) and could be considered as a small probability event, suggesting that the 0PS morphotype might be an abnormal status. The following life table demographic tests suggested that 0PS morphotype had a relatively lower intrinsic rate of population growth at high food concentrations and a relatively lower average lifespan, in comparison to 2PS rotifers. These results further supported that the 0PS K. quadrata might be an abnormal development. Along with the elevating food concentration, 1PS morphotype reproduced more 2PS offsprings, suggesting that high energy input might be helpful to grow more posterolateral spines. However, in response to the increasing food concentration, 0PS rotifers produced more 1PS offsprings. The underlying mechanisms required further investigations. The posterolateral spine length of offsprings of 0PS K. quadrata was significantly longer than those of 2PS and 1PS rotifer parents at the four food concentrations, which probably help the offsprings of 0PS rotifer parents to survive in natural environments, since long and more posterolateral spines offer rotifers high ability to compete with other rotifers and cladocerans for food or to resist predators.

Spatial heterogeneity in induced defense of Brachionus calyciflorus within a single lake caused by a bed of floating-leaved macrophyte Trapa species

While induced defense of aquatic organisms against predators has been considerably studied by both laboratory and field research, our understanding is still limited about, for example, whether induced defense is variable between microhabitats within the same lake and how multiple predators influence induced defense in the natural environment. Here, we examined whether a rotifer species, Brachionus calyciflorus showed a different development degree of induced defenses against its predator Asplanchna and cyclopoid copepods between the microhabitats of a macrophyte bed consisting of Trapa species and open water. B. calyciflorus was more abundant and had larger posterolateral spines as a defensive trait in open water than in the Trapa bed. Asplanchna was more abundant in open water than in the Trapa bed, whereas cyclopoids were more abundant in the Trapa bed. Both of the predators significantly affected the development of the defense trait. The effect of Asplanchna on the defense trait was positive, whereas the effect of cyclopoids was negative. Thus, a spatial difference in the development degree of induced defense between the microhabitats occurred as the dense Trapa bed influenced the abundance of the two predators. The results also suggest that the induced defense of B. calyciflorus was effective in reducing the predation pressure from Asplanchna while B. calyciflorus was not able to avoid predation by cyclopoids in the Trapa bed.

Interactive effects of algal level and predator density (Asplanchna sieboldi) on the life-history strategy and morphology of Brachionus calyciflorus.

Predation plays an important role in mediating the coexistence and the community structure of rotifera. In response to predation stresses, prey rotifers develop morphological defenses and change their life-history strategy for the reallocation of energy investment. Yet, how these changes respond to different total energy ingestion remains largely unknown. In the present study, we investigated the life-table demographic, population growth and morphological parameters of Brachionus calyciflorus in response to various densities of Asplanchna sieboldi at two food levels (1.0 × 106 and 2.0 × 106 cells per ml of Scenedesmus obliquus). To resist predators, B. calyciflorus developed long postero-lateral spines. The life-table demographic results showed that predation only significantly shortened the generation time of B. calyciflorus at the algal level of 2.0 × 106 cells per ml, but not affect other demographic parameters. The population growth tests revealed that predator density, algal level and their interactions all significantly influenced the population growth rate of prey rotifers. At 1.0 × 106 cells per ml of S. obliquus, treatments with two, four, and eight A. sieboldi individuals per 50ml significantly reduced the population growth rate of B. calyciflorus. In contrast, the population growth rate was not affected in response to two A. sieboldi individuals per 50ml at 2.0 × 106 cells per ml of S. obliquus. These results suggested that algal level probably affected the inhibitory effects of predation on the population growth of prey rotifers, and the underlying mechanisms should be further investigated.