Larval Segments Research Articles

The tail segments are required by the performance but not the accomplishment of various modes of Drosophila larval locomotion

The tail plays important roles in locomotion control in many animals. But in animals with multiple body segments, the roles of the hind body segments and corresponding innervating neurons in locomotion control are not clear. Here, using the Drosophila larva as the model animal, we investigated the roles of the posterior terminal segments in various modes of locomotion and found that they participate in all of them. In forward crawling, paralysis of the larval tail by blocking the Abdb-Gal4 labeled neurons in the posterior segments of VNC led to a slower locomotion speed but did not prevent the initiation of forward peristalsis. In backward crawling, larvae with the Abdb-Gal4 neurons inhibited were unable to generate effective displacement although waves of backward peristalsis could be initiated and persist. In head swing where the movement of the tail is not obvious, disabling the larval tail by blocking Abdb-Gal4 neurons led to increased bending amplitude upon touching the head. In the case of larval lateral rolling, larval tail paralysis by inhibition of Abdb-Gal4 neurons did not prevent the accomplishment of rolling, but resulted in slower rolling speed. Our work reveals that the contribution of Drosophila larval posterior VNC segments and corresponding body segments in the tail to locomotion is comprehensive but could be compensated at least partially by other body segments. We suggest that the decentralization in locomotion control with respect to animal body parts helps to maintain the robustness of locomotion in multi-segment animals.

Multiplexed Optogenetics with Striped Organic LEDs

AbstractOptogenetic stimulation of living systems enables control of neuronal functions with extraordinary cell‐type specificity. The expression of more than one optogenetic actuator grants the possibility to mediate cellular activity via activation and inhibition upon illumination, with a spatial resolution that is hardly matched by electrical and pharmacological paradigms. In addition, delivering light with adequate spatial resolution is of utmost importance to achieve precise control over targeted cells. To this aim, the design strategy and realization of micro‐structured dual‐color organic light‐emitting diodes (OLEDs) are presented with a high degree of light confinement, reaching optical power densities up to 1 mW mm−2, microsecond response speed, and device heat‐up below 3 °C upon constant drive conditions at high brightness. The devices are applied for localized stimulation of Drosophila melanogaster (D. melanogaster) larvae expressing BiPOLES as a bidirectional light‐sensitive actuator. The results suggest the presence of an anterior‐posterior hierarchy for motoneuron signal procession, which is concluded from behavioral observations upon simultaneous and timely controlled activation and inhibition of neuronal activity in different larval segments. Thus, the devices are highly effective in generating complex light patterns for multi‐color optogenetics and lay the basis for cell‐specific multiplexed optogenetics in freely moving animals.

Spatial transcriptomics reveals a cnidarian segment polarity program in Nematostella vectensis

During early animal evolution, the emergence of axially polarized segments was central to the diversification of complex bilaterian body plans. Nevertheless, precisely how and when segment polarity pathways arose remains obscure. Here, we demonstrate the molecular basis for segment polarization in developing larvae of the sea anemone Nematostella vectensis. Utilizing spatial transcriptomics, we first constructed a 3D gene expression atlas of developing larval segments. Capitalizing on accurate in silico predictions, we identified Lbx and Uncx, conserved homeodomain-containing genes that occupy opposing subsegmental domains under the control of both bone morphogenetic protein (BMP) signaling and the Hox-Gbx cascade. Functionally, Lbx mutagenesis eliminated all molecular evidence of segment polarization at the larval stage and caused an aberrant mirror-symmetric pattern of retractor muscles (RMs) in primary polyps. These results demonstrate the molecular basis for segment polarity in a non-bilaterian animal, suggesting that polarized metameric structures were present in the Cnidaria-Bilateria common ancestor over 600 million years ago.

Nasopharyngeal myiasis due to Cephalopina titillator in Southeastern Iran: a prevalence, histopathological, and molecular assessment.

The Cephalopina titillator is one of the most important causative agents of nasal myiasis in camels. This study aimed to explore the prevalence, histopathological effects, and molecular identification of C. titillator infestation in camels of Kerman province, South-Eastern Iran, between 2019 and 2021. The larvae were placed in 10% formalin for histopathological evaluation and species identification. Pieces of larval abdominal segments of C. titillator were selected for extraction of DNA. Partial mitochondrial CO1 genes were sequenced for final analysis. Out of the 870 camels examined, 339 (38.9%) were infested with larval stages of C. titillator. There was a significant difference between age and infection rate (P = 0.001), while no association between males and females (P = 0.074) was found. The infection rate was significantly higher in the winter (P < 0.001) than in the other seasons. In this study, different lesions depending on duration, locations, and the depth of larval adhesion notably degeneration changes, necrosis, and ulceration were observed. Also, in chronic cases, granulation tissue reactions were organized. Cephalopina titillator was confirmed by PCR sequencing analysis using mitochondrial CO1 region. A 582bp nucleotide sequence was deposited in GenBank under the MW136151 accession number. Phylogenetic analysis of CO1 produced a single uniform sister clade to MZ209004 and MW167083 records from China and Iraq, respectively. The high prevalence of C. titillator in camels in this region and other areas of Iran declares that the country is in an endemic status and displays the existence of the potential risk for camels.

Parampelomyia, another new gall midge genus (Diptera: Cecidomyiidae) associated with Vitaceae, with description of a new species developing in flower buds of the porcelain berry in Japan

We describe a gall midge Parampelomyia yukawai Elsayed and Tokuda gen. nov. sp. nov. belonging to the subtribe Schizomyiina (Diptera: Cecidomyiidae: Asphondyliini) based on an integrative taxonomic study. This species forms barely-swollen flower bud galls on the porcelain berry Ampelopsis brevipedunculata var. heterophylla (Vitaceae) in Japan. The new genus is distinguishable from all known schizomyiine genera by tarsomere I lacking a ventroapical extension, the bulbous base of the protrusible portion of the ovipositor, the fused and sclerotized female cerci, the bidentate gonostylus, and the larval terminal abdominal segment that bears two corniform, two asetose and six setose papillae. The new genus is compared with and separated from the similar genera Schizomyia and Ampelomyia morphologically and phylogenetically.

A new species of Simulium (Gomphostilbia) (Diptera: Simuliidae) from Northern Thailand, with its genetic relationship in the S. asakoae species-group

A new black fly species, Simulium (Gomphostilbia) kiewlomense, is described from females, males, pupae and mature larvae in Thailand. This new species is placed in the S. asakoae species-group and is characterized by having a combination of the elongate female sensory vesicle, widened male hind basitarsus, which is much wider than the hind femur, small pupal terminal hooks, and light greenish larval abdominal segments 1–3. Taxonomic notes are given to separate this new species from other related species. A DNA analysis using the COI gene shows that this new species has two genoforms with 1.21% difference. This is the 28th species of the S. asakoae species-group in Thailand, strengthening the evidence for high species diversity of this species-group.

Segmentation and limb formation during naupliar development of Tigriopus californicus (Copepoda, Harpacticoida)

Naupliar development in copepods includes the generation of usually five pairs of post-mandibular segments. Since copepod nauplii show no outer body articulation, the only indication of larval segmentation is the expression of limb buds. Yet, in copepods the timing and sequence of limb bud expression in larval development varies to a large degree. In harpacticoid nauplii for instance, the 1st maxillae are formed at an early naupliar stage. By contrast, the four remaining pairs of limb buds frequently appear simultaneously with the last naupliar stage. The complete process of larval segment formation takes place under the body surface and has never been described in detail. To broaden our knowledge of early segmentation in copepods, we here describe the segmentation of the harpacticoid nauplius Tigriopus californicus by analysing the expression of the segment marker Engrailed and uncover the sequential addition of seven post-mandibular segments. The stripe formation and arrangement of labelled cells corresponds largely to those of other crustaceans studied in this respect. Together with a morphological approach using histology, SEM, and 3D-reconstructions based on CLSM we solve the so far controversial identity of the external limb buds in the final naupliar stage. In contrast to previous studies, we can show that all limb pairs from the 1st maxillae to the 3rd thoracopods are formed. Yet, the anlage of the maxilliped (1st thoracopod) remains hidden underneath the cuticle being never externally expressed in the nauplius.

Transcriptome Analysis of Larval Segment Formation and Secondary Loss in the Echiuran Worm Urechis unicinctus.

The larval segment formation and secondary loss in echiurans is a special phenomenon, which is considered to be one of the important characteristics in the evolutionary relationship between the Echiura and Annelida. To better understand the molecular mechanism of this phenomenon, we revealed the larval transcriptome profile of the echiuran worm Urechis unicinctus using RNA-Seq technology. Twelve cDNA libraries of U. unicinctus larvae, late-trochophore (LT), early-segmentation larva (ES), segmentation larva (SL), and worm-shaped larva (WL) were constructed. Totally 243,381 unigenes were assembled with an average length of 1125 bp and N50 of 1836 bp, and 149,488 unigenes (61.42%) were annotated. We obtained 70,517 differentially expressed genes (DEGs) by pairwise comparison of the larval transcriptome data at different developmental stages and clustered them into 20 gene expression profiles using STEM software. Based on the typical profiles during the larval segment formation and secondary loss, eight signaling pathways were enriched, and five of which, mTOR, PI3K-AKT, TGF-β, MAPK, and Dorso-ventral axis formation signaling pathway, were proposed for the first time to be involved in the segment formation. Furthermore, we identified 119 unigenes related to the segment formation of annelids, arthropods, and chordates, in which 101 genes were identified in Drosophila and annelids. The function of most segment polarity gene homologs (hedgehog, wingless, engrailed, etc.) was conserved in echiurans, annelids, and arthropods based on their expression profiles, while the gap and pair-rule gene homologs were not. Finally, we verified that strong positive signals of Hedgehog were indeed located on the boundary of larval segments using immunofluorescence. Data in this study provide molecular evidence for the understanding of larval segment development in echiurans and may serve as a blueprint for segmented ancestors in future research.

Ampelomyia, a new genus of Schizomyiina (Diptera: Cecidomyiidae) associated with Vitis (Vitaceae) in the Palaearctic and Nearctic regions, with description of a new species from Japan

AbstractA gall midge that induces conical leaf galls on wild Vitis Linnaeus (Vitaceae) species in Japan was previously identified based on the gall shape as the Nearctic Schizomyia viticola (Osten Sacken) (Diptera: Cecidomyiidae: Cecidomyiinae: Asphondyliini: Schizomyiina). In 2016, leaf galls were newly found on cultivated Vitis coignetiae Pulliat ex Planchon cultivar Suzumi-murasaki and the wild V. coignetiae, Vitis flexuosa Thunberg, and Vitis ficifolia Bunge in northern Japan. Morphological studies of the larvae and adults obtained from the galls revealed that they were an undescribed taxon distinct from the Nearctic species and did not belong to any known genera of Schizomyiina. A new genus, Ampelomyia Elsayed and Tokuda, is erected for Ampelomyia conicocoricis Elsayed and Tokuda new species. The new genus can be distinguished from other genera of Schizomyiina by having ventroapical extension on tarsomere I, the larval abdominal segment VIII with a posterodorsal lobe, and dorsally shifted pair of larval pleural papillae. Molecular phylogenetic analysis supports this taxonomic treatment. In addition, we also place three Vitis-associated Nearctic species in the new genus: Ampelomyia viticola (Osten Sacken) new combination, A. vitiscoryloides (Packard) new combination, and A. vitispomum (Osten Sacken) new combination.

A new genus and a new species of Schizomyiina (Diptera: Cecidomyiidae: Asphondyliini) inducing petiole galls on Macaranga bancana (Miq.) in Borneo, Malaysia.

We describe a gall midge Macarangamyia itiokai Elsayed Tokuda gen. n., sp. n. belonging to the subtribe Schizomyiina (Diptera: Cecidomyiidae: Asphondyliini) inducing petiole galls on Macaranga bancana (Miq.) in Lambir Hills National Park, Borneo, Malaysia. The new genus is distinguishable from all known genera of Schizomyiina by the unique dorsally-placed aedeagus slit, the short, membranous, protrusible ovipositor, with scattered strong setae ventrally and dorsally, and the presence of spiracles on all larval thoracic segments. It is compared and separated from its closely related Oriental genera of Schizomyiina.

Bruggmannia chapadensis sp. nov. (Diptera: Cecidomyiidae), a new midge inducing galls on Guapira pernambucensis (Nyctaginaceae) from the Parque Nacional da Chapada dos Guimarães, Mato Grosso State, Brazil

Bruggmannia &amp;gt;chapadensis sp. nov. is described and illustrated based on characters of the larva, pupa and adults of both sexes, from specimens collected in Cerrado areas of Parque Nacional da Chapada dos Guimarães, state of Mato Grosso, Brazil. The new species is characterized by tarsal claws bent at distal 1/3; well-developed empodia, not reaching the bend in claws; cerci rounded; hipoproct shorter than cerci; aedeagus with globose apex; gonostylus semicircular; ovipositor protrusible about 1.4 times longer than sternite 7; pupal antennal bases enlarged, conical, upper facial horns semicircular; prothoracic spiracle short, abdominal segments 2–8 with one row of dorsal spines; larval terminal segment elongate, with four setose terminal papillae. This new species was collected from lenticular leaf galls of Guapirapernambucensis (Casar.) Lundell (Nyctaginaceae). This is the first record of Bruggmannia galls on this plant species. In Brazil, 13 species of Bruggmannia were previously known, none recorded from Mato Grosso.

Importance of the Chaetotaxy in Larval Identification of &lt;I&gt;Galleria mellonella&lt;/I&gt; (Linnaeus) (Lepidoptera: Pyralidae) along with some Notes on its Life History

Earlier studies on identification of Galleria mellonella emphasized mainly on characterization of wing venation and maculation, larval or pupal morphology and other taxonomic characters such as male and female genitalia. The larval identification and diagnostic characters of pest species can best be strengthen through diagnosis of the setal arrangement and position of punctures present of different larval body segments. The cephalic region and all the bodily segments such as thoracic, abdominal etc of the last instar larva of Greater waxmoth, Galleria mellonella (Linnaeus) belonging to family (Pyralidae) have been examined along with some biological aspects.

Early mesodermal expression of Hox genes in the polychaete Alitta virens (Annelida, Lophotrochozoa).

Hox genes are the key regulators of axial regionalization of bilaterian animals. However, their main function is fulfilled differently in the development of animals from different evolutionary branches. Early patterning of the developing embryos by Hox gene expression in the representatives of protostomes (arthropods, mollusks) starts in the ectodermal cells. On the contrary, the instructive role of the mesoderm in the axial patterning was demonstrated for vertebrates. This makes it difficult to understand if during the axial regionalization of ancestral bilaterians Hox genes first expressed in the developing mesoderm or the ectoderm. To resolve this question, it is necessary to expand the number of models for investigation of the early axial patterning. Here, we show that three Hox genes of the polychaete Alitta virens (formerly Nereis virens, Annelida, Lophotrochozoa)-Hox2, Hox4, and Lox5-are expressed in the mesodermal anlagen of the three future larval chaetigerous segments in spatially colinear manner before the initiation of Hox expression in the larval ectoderm. This is the first evidence of sequential Hox gene expression in the mesoderm of protostomes to date.

New morphological information on Simulium wygodzinskyorum Coscarón & Py-Daniel, 1989 (Diptera: Simuliidae).

Simulium wygodzinskyorum Coscarón & Py-Daniel was originally described based on a small number of specimens collected in Junín Province, Peru. We sampled in the same province as the type locality of this species, collecting last-instar larvae and pupae. Since the original larval description of this species was based on a single immature individual, our objective is to provide a last-instar larval description and also to provide additional morphological information on the pupa and male genitalia of this species. Some morphological characteristics not reported before for this species, such as, dorsal tubercles on larval abdominal segments, are described. Abdominal chaetotaxy of pupae is revised and the male ventral plate is fully illustrated, also it is discussed the importance of standardizing the position in which the ventral plate is illustrated. This species was collected in a stream with 2-8 m in width, exposed to sunlight with rocks of different sizes, in low density.

New species of mayflies (Ephemeroptera) from Cape Verde.

To date, no mayflies have been described from Cape Verde, an archipelago of volcanic islands in the Atlantic Ocean. Based on the material collected on two islands, Santo Antão and Santiago, two species of the genus Cloeon Leach, 1815 (Ephemeroptera: Baetidae) are described based on larvae and imagines. Cloeon morna sp. n., collected in Santo Antão, and C. sidadi sp. n., collected in Santiago, have 3-segmented maxillary palps and tapered labial palps of larvae. The new species can be distinguished from each other and from other West-African species of the genus mainly according to details of the lateral spines on larval abdominal segments and characteristic colourations of vitta and terga in female imagines and colours of male turbinate eyes. Affinities to the West African species of the genus are discussed.

Ectopic expression of the male BmDSX affects formation of the chitin plate in female Bombyx mori

Mating structures are involved in successful copulation, intromission, and/or insemination. These structures enable tight coupling between external genitalia of two sexes. During Bombyx mori copulation, the double harpagones in the external genitalia of males clasp the female chitin plate, which is derived from the larval eighth abdominal segment; abnormal development of the female chitin plate affects copulation. We report that ERK phosphorylation (p-ERK) and expression of Abdominal-B (Abd-B) in the posterior abdomen of the female adult is lower than in the male. Ectopic expression of the male-specific spliced form of B. mori doublesex (Bmdsx(M)) in females, however, up-regulates Abd-B and spitz (spi) expression, increasing EGFR signaling activity, and thus forming an abnormal chitin plate and reduced female copulation. These findings indicate that Bmdsx affects the development of the eighth abdominal segment by regulating the activity of EGFR signaling and the expression of Abd-B, resulting in an extra eighth abdominal segment (A8) in males versus the loss of this segment in adult females.

Mesoteloblast‐Like Mesodermal Stem Cells in the Polychaete Annelid Platynereis dumerilii (Nereididae)

Spiral cleavage is observed in animals that belong to the lophotrochozoa, a large group of marine invertebrates. As characteristic for spiral cleavage, the bulk of mesoderm forms from one cell, the "4d blastomere." This process has not yet been followed in cellular detail in annelids except in the leech, where "mesoteloblasts," a pair of mesodermal stem cells, generate two bands of mesoderm precursor cells in an iterative fashion. It is so far unknown whether such stem cell-like lineage is a general property of 4d-derived mesoderm in spiralian larvae. To address this, we have analyzed the cell lineage of the 4d blastomere in the polychaete annelid Platynereis dumerilii, an emerging model for lophotrochozoan and spiralian embryology (Fischer et al., 2010), by 4D microscopy, a semi-automated cell tracking technique based on differential interference contrast serial imaging (Schnabel et al. '97). Our data reveal that the two daughter cells of the 4d cell undergo seven consecutive rounds of unequal cell divisions. They bud off smaller cells in ventral-vegetal orientation and thus show mesoteloblast- and stem cell-like behavior. Based on these findings, we suggest that mesoteloblast-like mesodermal stem cells that form continuous mesodermal bands are part of the Errantia + Sedentaria ground pattern. In the course of annelid evolution, the number consecutive divisions of these cells would have been low initially with <10 division cycles, giving rise to larval segments only, and then increased up to 35 as observed in clitellates.

The metatrochophore of a deep-sea hydrothermal vent vestimentiferan (Polychaeta: Siboglinidae).

Vestimentiferans (Siboglinidae, Polychaeta) live as juveniles and adults in an obligate mutualistic association with thiotrophic bacteria. Since their development is aposymbiotic, metatrochophores of vestimentiferans from the East Pacific Rise colonizing deep-sea hydrothermal vents are infected with the specific symbiont, develop the trophosome, and reduce their digestive system. To gain insight into the anatomy and ultrastructure and to compare this stage with metatrochophores from other siboglinids, we serial sectioned and reconstructed three specimens using light and transmission electron microscopy. The metatrochophore was composed of a prostomium, a small peristomium, two chaetigers (or two chaetigers and one additional segment without chaetae), and a minute pygidium. A digestive system and an intraepidermal nervous system were developed. Larval organs such as the prototroch, the neurotroch, and an apical organ were present, along with juvenile/adult organs such as tentacles, uncini, pyriform glands, and the anlage of the nephridial organ. We propose that in vestimentiferans, the vestimentum is the head arising from the prostomium, peristomium, and the anterior part of the first chaetiger. In frenulates, in contrast, the head is composed on the one hand of the cephalic lobe arising from the prostomium and on the other of the forepart developing from the peristomium and the anterior part of the first chaetiger. In frenulates the muscular septum between the forepart and trunk develops later than the first two chaetigers. Since this septum has no counterpart in vestimentiferans, the forepart-trunk border of frenulates is not considered homologous with the vestimentum-trunk border in vestimentiferans. The obturacular region in vestimentiferans does not appear to be a body region but rather the head appendages arising from the first chaetiger. In contrast, the tentacles in frenulates are prostomial head appendages. In both taxa, the trunk is the posterior part of the first chaetiger, and the opisthosoma is the following chaetigers and the pygidium. Comparisons with other polychaetes suggest that two larval segments are autapomorphic for the monophyletic Siboglinidae.

The segmental pattern of otx, gbx, and Hox genes in the annelid Platynereis dumerilii

SUMMARY Annelids and arthropods, despite their distinct classification as Lophotrochozoa and Ecdysozoa, present a morphologically similar, segmented body plan. To elucidate the evolution of segmentation and, ultimately, to align segments across remote phyla, we undertook a refined expression analysis to precisely register the expression of conserved regionalization genes with morphological boundaries and segmental units in the marine annelid Platynereis dumerilii. We find that Pdu-otx defines a brain region anterior to the first discernable segmental entity that is delineated by a stripe of engrailed-expressing cells. The first segment is a "cryptic" segment that lacks chaetae and parapodia. This and the subsequent three chaetigerous larval segments harbor the anterior expression boundary of gbx, hox1, hox4, and lox5 genes, respectively. This molecular segmental topography matches the segmental pattern of otx, gbx, and Hox gene expression in arthropods. Our data thus support the view that an ancestral ground pattern of segmental identities existed in the trunk of the last common protostome ancestor that was lost or modified in protostomes lacking overt segmentation.

Fluctuating Asymmetry of Chironomus spp. (Diptera: Chironomidae) Larvae in Association with Water Quality and Metal Pollution in Permatang Rawa River in the Juru River Basin, Penang, Malaysia

The levels of fluctuating asymmetry [random differences between symmetric organismal traits, fluctuating asymmetry (FA)] in the fourth instar of Chironomus spp. larvae inhabiting an agrochemical polluted river [Permatang Rawa River (PRR)] in the Juru River Basin, northeastern peninsular Malaysia, were measured. The PRR receives waters primarily from adjacent rice fields which are exposed to fertilizer and pesticide residues. Samples of larvae, water, and sediments were collected monthly from November 2007 to June 2008. In situ measurements of water pH and dissolved oxygen were made at three sampling locations along the river. Monthly water and benthic sediment collections were also conducted for the following laboratory water analyses: biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and ammonium-N content. Non-residual metals in the sediment samples were also analyzed. The water quality index (WQI) of the PRR was also calculated. This study attempted to relate FA levels based on selected traits of Chironomus spp. larval head capsule (mentum width and first and second antennal segment length) to water quality and sediment heavy metal contamination in the PRR. All monthly measurements of FA levels including transcriptors (FA10a, FA4a, ME3, and ME1) and indices [FA, absolute asymmetry (AbsFA), and composite fluctuating asymmetry (CFA)] were calculated. The ordination model of redundancy analysis showed that the dissolved oxygen and water quality in the river expressed as WQI were negatively correlated with all FA indices (FA, AbsFA, and CFA) of the larval mentum width and length of antennal segments I and II. The water pH, BOD, and COD and sediment Cu positively influenced the FA incidence in the larval mentum. The FA indices of the antennal segment I were positively correlated with the increase in the levels of water pH, ammonium-N, BOD, and COD. The FA indices, especially CFA, were sensitive to the water pH and ammonium-N and sediment contaminated by Mn, Cu, and Zn. The FA levels calculated as FA indices of the larval antennal segment II length were positively correlated with water TSS and sediment Mn, Cu, Zn, and Ni. This study revealed that the river water quality and heavy metal contamination affect developmental stability in Chironomus spp. larvae. The FA indices of different structures in the Chironomus spp. larval head capsule could be used as bioindicators for water and sediment pollution.