Ventromental Plates Research Articles

Chironomidae Morphological Types and Functional Feeding Groups as a Habitat Complexity Vestige

Chironomid (Diptera: Chironomidae) larvae play an important role in a wide range of aquatic ecosystems. The study focuses on Chironomidae trophic guilds and morphological types as indicator traits in reconstructions of habitat changes in shallow water bodies. Mentum and ventromental plates are important mouthparts whose shape depends on food type and feeding behavior. Chironomidae larvae strongly vary in the mode of life and feeding habits, representing almost every feeding group. Here we classified the mentum types into 16 groups and tested if they indicated similar past habitat changes as the Chironomidae functional feeding groups (FFGs), and tribes/subfamilies. Paleoecological data of biotic and abiotic proxies were derived from short sequences from a Late Glacial oxbow and a nearby medieval moat located in Central Poland. The study revealed that the habitat substratum structure, vegetation and physicochemical conditions are associated both with the feeding types and morphological traits. This provides a valuable tool for future reconstructions of habitat changes.

Application of deep learning in aquatic bioassessment: Towards automated identification of non-biting midges

Morphological species identification is often a difficult, expensive, and time-consuming process which hinders the ability for reliable biomonitoring of aquatic ecosystems. An alternative approach is to automate the whole process, accelerating the identification process. Here, we demonstrate an automatic machine-based identification approach for non-biting midges (Diptera: Chironomidae) using Convolutional Neural Networks (CNNs) as a means of increasing taxonomic resolution of biomonitoring data at a minimal cost. Chironomidae were used to build the automatic identifier, as a family of insects that are abundant and ecologically important, yet difficult and time-consuming to accurately identify. The approach was tested with 10 morphologically very similar species from the same genus or subfamilies, comprising 1846 specimens from the South Morava river basin, Serbia. Three CNN models were built utilizing either species, genus, or subfamily data. After training the artificial neural network, images that the network had not seen during the training phase achieved an accuracy of 99.5% for species-level identification, while at the genus and subfamily level all images were correctly assigned (100% accuracy). Gradient-weighted Class Activation Mapping (Grad-CAM) visualized the mentum, ventromental plates, mandibles, submentum, and postoccipital margin to be morphologically important features for CNN classification. Thus, the CNN approach was a highly accurate solution for chironomid identification of aquatic macroinvertebrates opening a new avenue for implementation of artificial intelligence and deep learning methodology in the biomonitoring world. This approach also provides a means to overcome the gap in bioassessment for developing countries where widespread use techniques for routine monitoring are currently limited.

Phylogeny of marine Ainuyusurika tuberculata (Tokunaga) (Diptera: Chironomidae: Chironominae), with description of the immature stages.

The marine Chironomidae Ainuyusurika Sasa et Shirasaka, 1988, previously known from the adults only, is associated with its immature stages for the first time based on reared specimens from Oriental China. The larva resembles those of Sergentia Kieffer and Endochironomus Kieffer in the ventromental plate with an anteromedial projection and the 5-segmented antenna with opposite Lauterborn organs. The pupal thoracic horn has 12 branches at maximum and netted tergite spinulation which appears to be similar to those of Polypedilum Kieffer, Endotribelos Grodhaus, Phaenopsectra Kieffer and Sergentia. The phylogenetic relationship was furtherly explored through molecular analysis based on concatenation of five gene makers (18S, 28S, CAD1, CAD4 and COI-3P) using both mixed-model Bayesian and maximum likelihood inference methods. The result shows Ainuyusurika is nested with an assemblage of Endochironomus, Phaenopsectra and Endotribelos. We concluded that Ainuyusurika is a good independent genus showing affinity with Endochironomus-Phaenopsectra related genera.

Morphological characterization of Chironomidae (Diptera) larvae in Anzali Wetland, Southwest Caspian Sea: First record of Chironomus plumosus

Chironomids (Diptera) include the most abundant group of macroinvertebrates. They are usually collected from aquatic environments for quality evaluation. Tolerant aquatic organisms such as Chironomids are more abundant in polluted sites. This note makes the Chironomids as an excellent bioindicators. This group is not characterized in Anzali Wetland as well. So that, the aim of this study was to recover and characterize chironomidlarvae in this wetland. Hence, Chironomidlarvae were collected on the seasonal basis from 13 stations in the wetland. The main characteristics for their identification were eye spot, mentum, ventromental plate, antenna, and ventral tubules. The mitochondrial cytochrome oxidase I (COI) gene was applied to simplify the identification of Chironomus species by polymerase chain reaction (PCR) and sequencing method. The nucleotide sequence alignments were used for construction of the phylogenetic trees based on maximum likelihood method. Six genera were identified in three subfamilies, including: Chironominae (1 genus), Orthocladinae (1 genus), and Tanypodinae (4 genera). Based on ventral tubules, the dominant population of Chironomus larvae found in this study, lie in thummi and plumosus types. Five genera were reported for the first time from Anzali Wetland. The dominant genus was Chironomus. These groups of larvae were ultimately identified as Chironomus plumosus reporting for the first time from the wetland. It was also found that the Chironomids diversity is higher than those described in few studies before, however, further studies are still needed.

Larva of Glyptotendipes (Glyptotendipes) glaucus (Meigen 1818) (Chironomidae, Diptera)-morphology by Scanning Electron Microscope (SEM), karyotype, and biology in laboratory conditions.

Larvae belonging to the family Chironomidae are difficult to identify. The aim of the present study was to describe the larval morphology of G. (G.) glaucus with the aid of a Scanning Electron Microscope (SEM), the karyotype and biology based on materials obtained from laboratory culture. Describing the morphology of larvae, special attention was paid to rarely or never described structures like the maxilla (lacinia and maxillary palp), the long plate situated below the ventromental plate, and plate X situated between lacinia and mentum. The use of SEM allowed also to obtain better images of labrum and ventromental plate. Morphological features of this species have been supplemented by karyotype and biology of larvae in laboratory conditions. Under controlled experimental conditions we found non-synchronous development of G. (G.) glaucus larvae hatched from one egg mass reflected in different lengths of larvae and emerged imagoes.

The Photographic Checklist of the Freshwater Chironomids of the Niger Delta, Nigeria

A photographic checklist of the Chirominids under the subfamily Chironominanea from the Niger Delta of Nigeria was compiled using records of specimens collected over a period of thirty years from many field trips. The photographic keys were described to show the cephalothorax with mentum, mandibles, premandibles and ventromental plates. A total of twelve illustrations, consisting of nine genera and twelve species, were documented. These were Chironomus imicola , Chironomus transvaalensis , Endochironomus sp. , Parachironomus biannulatus, Parachironominae sp. , Limnochironomus sp. , Pseudochironomus prasinatus, Tanytarsus curticornis and Tanytarsus thienemanni, Paratanytarsus sp. , Microtendipes sp ., Pentapedilum sp. Six of these species namely Microtendipes sp. , Parachironomus biannulatus , Pentapedilum sp. , Pseudochironomus prasinatus , Tanytarsus curticornis and Tanytarsus thienemanni occur in both lotic and lentic waters. Those that occurred only in lentic waters were Chironomus imicola , and Parachironominae sp. , while Endochironomus sp., Limnochironomus sp. and Paratanytarsus sp. occurred only in lotic water.

Guia Para la Identificación de Tanytarsini Subfosiles (Diptera: Chironomidae: Chironominae) de la Patagonia

Abstract. A GUIDELINE FOR THE IDENTIFICATION OF SUBFOSSIL TANYTARSINI (DIPTERA: CHIRONOMIDAE: CHIRONOMINAE) FROM PATAGONIA. This paper presents a key for the identification of nine subfossil morphotypes of the Tribe Tanytarsini (Subfamily Chironominae), described for Argentinean and Chilean Patagonia, from 39° to 54°S. The key is structured based on the head capsules, which is the only material preserved in the sedimentary record. Tribe Tanytarsini is of particular importance as it includes species with high environmental importance, especially climatic. The material collected in Argentinean and Chilean Patagonia allowed the classification of nine morphotypes, distinguished mainly by four easily observables characteristics; (1) the spur shape of the antennal pedestal, (2) presence and shape of post-occipital plate, (3) number of premandible teeth, and (4) mentum and ventromental plates. The main goal of this contribution is to bring together the very sparse and limited knowledge on Tanytarsini from southe...

Determination of larval instars in Chironomus sancticaroli (Diptera: Chironomidae) using novel head capsule structures

Determining the age composition of a population is important when conducting ecological, taxonomic and environmental assessments. Morphometric measurements of the head capsule, especially the length and width, are widely used in the identification of insect instars, but alternative ways for determining the age of insects can expand the options for the analysis of field and laboratory populations. This study evaluated the morphometry of the antennae, mandibles, mentum and ventromental plates to discriminate among the four larval instars of Chironomus sancticaroli Strixino & Strixino, 1981. The larvae were reared in the laboratory under constant temperature (25°C) and photoperiod of 12/12 hours for 19 days, with a supply of food. Fifteen larvae were removed randomly every day, cleared in KOH, and slide-mounted, and had the antennae, mandibles, mentum and ventromental plates measured. The dimensions of the four structures studied allowed us to statistically distinguish each of the four larval instars. The data fit an exponential equation according to the Brooks-Dyar rule, which allows an estimate of the larval instar of specimens collected in the field, even when development takes place under different conditions. The duration of each instar was also obtained from our data, and showed an overlap of instars during development.

Missouri State Record forPolypedilum(Pentapedilum)TritumWalker (Diptera: Chironomidae) Based on Larval Identifications from Wadeable Streams

INTRODUCTION Polypedilum (Pentapedilum) tritum (Walker) has a widespread Holarctic dis tribution (Stone et al., 1965; Oliver et al., 1990; Caldwell et al., 1997; Oyewo and Saether, 2008). However, Epler (2001) noted the name P. tritum may represent more than one species in the southeastern USA. We identified larvae of P. tritum in samples collected from 27 of 224 wadeable streams sampled in Missouri during the years 2008-2010. Streams where specimens of P. tritum were collected were sampled during 28 March and 16 to 18 September, 2008, 31 March and 1 April, 2009, and 23 March to 6 April, 2010 in the Osage Plains, Ozark Highlands, and Central Dissected Till Plains ecological sections of Missouri (Cleland et al., 1997; Nigh and Schroeder 2002) (Fig. 1). Our records of P. tritum represent the first for this species in Missouri, although larvae of this species may have been misidentified as members of the Polypedilum illinoense group in earlier collections. The undeveloped posterior lobe in the ventromental plates, antennae with vestigial Lauterborn organs and long segments 3 and 4, and the sunken first lateral teeth of the mentum should be a unique set of characters to distinguish larvae of P. tritum from larvae of other described species (for full description see Oyewo and Saether, 2008). However, there are 52 recognized species in the subgenus Pentapedilum, but only 11 of those have larval descriptions (Oyewo and Saether, 2008). Although undescribed larvae of some Polypedilum species may, possibly, have characteristics in common with some diagnostic characteristics of larval P. tritum, we are confident in our identifications of lar val P. tritum based upon the description for larvae of this species provided by Oyewo and Saether (2008). Volume 122, Number 2, March and April 2011 165

Setting the reference for the use of Chironomus sancticaroli (Diptera: Chironomidae) as bioindicator: Ontogenetic pattern of larval head structures

Species of Chironomidae are widely used as bioindicators of water quality, since their larvae undergo morphological deformities when in contact with sediment contaminated with chemicals. In this work we endeavored to study the morphology of head structures (antennae, mandible, mentum, pecten epipharyngis, ventromental plate and premandible) throughout the development of the four larval instars of Chironomus sancticaroli Strixino & Strixino, 1981, which can be used in environmental impact analyses. Our results show that it is possible to differentiate among larval instars by doing a quantitative analysis on the number of striae on the ventromental plates. The six structures analyzed changed during larval ontogeny. These changes are part of the ontogeny of the immature stages not exposed to xenobiotics. We believe that the morphological pattern defined in this work can be used for comparisons with ontogenetic changes observed in field studies conducted in polluted environments.

The use of cotton blue stain to improve the efficiency of picking and identifying chironomid head capsules

Cotton blue was added to sediment samples at least 2 h before chironomid head capsules were picked under a binocular microscope and mounted on slides for identification. The use of stain greatly increased the visibility of chironomid head capsules during picking and enhanced the contrast of various parts of the head capsules (pores, ventromental plates, striations on ventromental plates), which could aid identification. In the seven samples studied, there was no significant difference between the percentages of taxa found in stained and unstained samples. The number of taxa were also similar in stained and unstained samples. This method allowed samples to be picked faster.

Karyotype and morphology of Chironomus wulkeri (Diptera, Chironomidae) from Lake Baikal region

The karyotype and morphology of the Palaearctic chironomid, Chironomus wulkeri Filinkova et Belyanina 1993, inhabiting the Baikal coast were studied. The banding patterns of chromosomal arms B, C, and D are presented for the first time. The karyotype and chromosome polymorphism of Ch. wulkeri from the Baikal population have no significant difference from those in northern Sweden and the Polar Ural populations. One heterozygous inversion in arm A was found in 38% of larvae. A comparative morphological analysis of 46 quantitative characters of larvae from Baikal region and the Polar Urals showed that they did not differ from each other. However, there are some differences in the width of the ventromental plates and height of the mentum.

Description ofNaonellan. gen. (Diptera: Chironomidae: Orthocladiinae)

Abstract Naonella n. gen. is described forthe first time from the North Island, New Zealand. Diagnoses of males, pupae, and larvae are presented. Naonella can be distinguished by the combination of bare eyes, straight Cu1, well‐developed pulvilli, and the absence of acrostichals and anal point in the adult male; the absence of a thoracic horn, and the presence of caudal spines and weak anterior shagreen on tergites II—VII in the pupa; and by a bifid SI, bifid premandible, and the presence of ventromental plates with beard in the larva. Naonella is characterised by monotypy and designated by the type species: Naonella forsythi.

New chromosome arm combination of genusGlyptotendipesKieff. (Diptera, Chironomidae)

SUMMARYGlyptotendipes material was collected form the littoral zone in seven reservoirs distributed in three Spanish watersheds (Tajo, Guadiana and Guadalquivir). By the external larval and pupal morphological analysis the material studied could be referred to either as G. glaucus or as G. gripekoveni. But its cytotaxonomical analysis shows that this is a new species, with 2n = 6 and with a new chromosome arm combination: AB, CD, GEF. The main characters used to differentiate the species Glyptotendipes sp. were chromosome number, amount of heterochromatin at the centromeres, simple homozygous inversions between sections of chromosomes, length of larval antennal blade and morphology of front border of ventromental plates.

The saline nuisance chironomidCarteronica longilobus(Diptera: Chironomidae): a systematic reappraisal

Abstract.CarteronicaKieffer andNilodorumKieffersensu auctt.are synonymized withKiefferulusGoetghebuer on the basis of cladistic analysis. An expanded diagnosis for all stages ofKiefferulusand a checklist of included species is given.K.longilobuscomb.n. fromCarteronica, a saline tolerant nuisance pest, is redescribed in all its life history stages. The following additional new combinations are proposed:K.brevibucca(Kieffer),K.brevipalpis(Kieffer),K.rugosum(Freeman),K.tainanus(Kieffer),K.umbraticola(Yamamoto). Many new characters from larval ventromental plates are illustrated and their use in phylo‐genetic analysis is discussed.

Congruence between larval ventromental plate ultrastructure and immature morphology in Yama Sublette & Martin and some Oceanian species of Chironomus Meigen (Diptera: Chironomidae)

The morphology of the larval ventromental plates of Y. tahitiensis Sublette & Martin and four Oceanian species of Chironomus Meigen, C. hawaiiensis Grimshaw, C. javanus Kieffer, C. magnivalva Kieffer and C. samoensis Edwards, has been studied by scanning electron micrography. Data on ventromental plate ultrastructure are used in phenetic and cladistic analyses of the relationships of Y. tahitiensis and the Oceanian Chironomus to other species in Chironomus and additional genera. The results of these analyses support the current generic status of Y. tahitiensis but indicate that Yama is less closely related to Chironomus than previously supposed, a finding that is supported by a reexamination of 'traditional' morphological features.

The case, mouthparts, silk and silk formation ofRheotanytarsus muscicolaKieffer (Chironomidae: Tanytarsini)

The larva, the larval case and the silk of Rheotanytarsus musdcola Kieffer was examined with scanning electron microscopy. The structures of mouthparts and the larval case are described in relation to feeding habits and silk production. Three methods of silk formation seem to be used. One is used in the capture net, and is produced by the act of grooves on the anterior edge of the ventromental plates. The other, which has a finer texture and is used in case construction, seems to be produced by the action of the ventromental and maxillary lamellae. The third silk type is formed as the silk secretion is ejected through the mouth cavity, producing a thicker silk strand, which is used in the framework of the capture net.

The Comparative Morphology of the Larval Ventromental Plates of Australasian Species of Kiefferulus Goetghebuer and Nilodorum Kieffer (Diptera, Chironomidae)

The morphology of larval ventromental plates of Australasian species of Kiefferulus Goetghebuer and Nilodorum Kieffer have been studied by light and scanning electron microscopy. The ventromental plates of all species studied were similar in their general pattern of micro-architecture, which incorporated a lamella-like system of striae and two marginal rows of spines on the inner surface. Information is presented on variation among species in plate features including size, shape, striae, and inner and outer rows of spines. Taxonomic implications of these data are discussed.

Identification of larvae of European species of Chironomus Meigen (Diptera: Chironomidae) by morphological characters

Abstract Variation in the morphology of larvae of twenty‐six cytologically identified species of Chironomus Meigen from Europe is described. Characters studied include tubules on posterior abdominal segments, head pigmentation, mental size and teeth, mandibular and epipharyngeal teeth and antennae. A key to the species, based on these characters and ventromental plate features, is presented.

Comparative morphology of the larval ventromental plates of European species of Chironomus Meigen (Diptera: Chironomidae)

Abstract. The ventromental plates of larvae of twenty‐six cytologi‐cally identified species of Chironomus Meigen from Europe are described. Variation in plate features, including size, striae, inner and outer hook series, and ventral surface ornamentation, is reported. A principal components analysis based on plate characters is undertaken, and the taxonomic composition of the resulting groupings is discussed.