Chaetotaxic Characters Research Articles

Morphology and feeding biology of larvae of the South African endemic water beetle genus Prosthetops Waterhouse, 1879 (Coleoptera: Hydraenidae)

The larvae of three species of the South African endemic water beetle genus Prosthetops Waterhouse, 1879 are described and illustrated for the first time. The second and third instar larvae of Prosthetops nitens (Péringuey, 1892), as well as third instar larva of P. megacephalus (Boheman, 1851) and P. wolfbergensis Bilton, 2013, are treated here. These three species share a combination of morphological and chaetotaxic characters that can be used for positive identification of larvae of this genus: head capsule with pores FC1 present, second antennomeres with two well-developed distal sensory appendages, maxillary seta Cdo1 very reduced, thoracic subprimary setae Dd’ absent, subprimary setae Dc’ minute and inserted on the boundary between pretergal and tergal areas, urogomphi moderately separated at the base, anal lobe with well-developed dorsal, lateral and ventral plates, and a lack of anal hooks. Some insights on the gut-contents of the larva of P. wolfbergensis are offered and an unusual urogomphal malformation observed in a larva of P. nitens is also described and illustrated. These are the first described larvae of the subfamily Prosthetopinae, and their morphology is compared to that of other known hydraenid larvae.

Larval chaetotaxy and morphometry of Megasternini: Cercyon (Paracercyon) Seidlitz, Cryptopleurum Mulsant and Pelosoma Mulsant (Coleoptera: Hydrophilidae).

The chaetotaxy of the head capsule and head appendages of all the larval instars of Cercyon (Paracercyon) analis and the first and third instars of Cryptopleurum minutum and Pelosoma sp. is described and illustrated for the first time. Morphometric characters derived from the head capsule and mouthparts are also included, together with detailed illustrations of all characters. The morphology and chaetotaxy of these larvae are compared to that of other Megasternini with described larvae. The larval morphology of Megasternini has proven to be very similar, however we provided a group of chaetotaxic characters useful to separate genera. Most of the differences were found in the sensilla of the head capsule, maxilla, and labium, both in size and arrangement, while the chaetotaxy of the antennae and mandibles was strongly conserved.

Larval chaetotaxy and morphology are highly homoplastic yet phylogenetically informative in Hydrobiusini water scavenger beetles (Coleoptera: Hydrophilidae)

Abstract Phylogenetic analyses testing the monophyly of the tribe Hydrobiusini and the relationships among its genera are performed based on a data matrix including characters of larval morphology and morphometrics, larval chaetotaxy and adult morphology, including eight of the nine hydrobiusine genera plus 15 outgroup taxa. The head chaetotaxy of six genera of the tribe Hydrobiusini is described (Ametor, Hybogralius, Hydramara, Limnohydrobius, Limnoxenus and Sperchopsis). Morphometric characters derived from the head capsule and mouthparts are included. All characters are illustrated in detail. The analyses performed on the above datasets and their combinations reveal the monophyly of the Hydrobiusini except for Hybogralius, and reconstruct the internal topology of the tribe, largely corresponding to results of previous molecular analyses. Hybogralius groups with genera having larvae adapted to underwater feeding in all analyses. The position of the genus Tritonus within the Laccobiini is questioned by our analyses, which suggest a closer relationship with the tribes Hydrophilini or Hydrobiusini. Larval characters are revealed as highly homoplastic, with chaetotaxic characters performing slightly worse than usual larval morphology. Nonetheless, they are phylogenetically informative and useful for testing phylogenetic hypotheses resulting from analyses of molecules or adult morphology. A key to larvae of the genera of the Hydrobiusini is presented.

Biogeographical and ecological insights from Australasian faunas: the megadiverse collembolan genus, Entomobrya (Entomobryidae).

Originally the genus Entomobrya (Collembola: Entomobryidae) comprised 25 species names in Australia including 7 subspecies of which 13 were exotic (50%) and the rest native. All native species had been either described by H. Schött or H. Womersley and had not been examined since 1942. Specific characters they used were few, mainly colour pattern and gross morphological features such as unguis, unguis teeth and mucronal form. Chaetotaxic characters have now been developed. We now here recognise 47 species of Australian Entomobrya and Hymalanura based on a large collection made over 50 years. Six species (12%) are now recognised as introduced, 37 are new and three unresolved because of lack of specimens in good condition. Detailed descriptions and figures are supplied. Several new species are short-range endemics of conservation significance, others are specialised as to habitat, but most are widespread. Entomobrya is now the most species rich genus of Australian Collembola. A phylogenetic tree based on morphological and biological characters revealed clusters of exotic and montane habitat specialists, indicating that the genus is paraphyletic and so confirms other authors' work based on molecular characters. A key is supplied to Australian genera of Entomobryomorpha. A new genus record, Himalanura, is recognised extending its range to the Southern Hemisphere and 5,000 km further southeast.

Comparative analysis of diagnostic and phylogenetic chaetotaxic characters of Berosus Leach and their implications on the relationships of the tribe Berosini (Coleoptera: Hydrophilidae)

Larvae of water scavenger beetles are found in all types of aquatic and semi-aquatic environments and play an important role in the structure of these communities. Despite their diversity, morphological characters that allow the identification of larvae at species level are usually inconspicuous. In this paper we analyze the head capsule and mouthparts chaetotaxy of hydrophilid larvae belonging to the tribe Berosini, with the purpose of identifying variations on the external sensory organs that may be used for species delimitations. We focus on two species of Berosus Leach (Berosus festivus Berg, 1885 and Berosus patruelis Berg, 1885) and compare larval structures within Berosus and among other genera of Berosini. We include morphometric characters together with detailed illustrations of all characters, SEM images of selected structures and micrographs of a sensory organ present on the inner margin of the first antennomere which is a novelty within larval Coleoptera. Our analysis shows that the number, shape, relative position and organization of sensilla, especially those of labroclypeus and mouthparts, provide diagnostic characters for the separation of Berosus species. Also, we found a new set of characters derived from chaetotaxy that supports current phylogenetic relationships within the tribe Berosini. Most of these chaetic characters are associated with structures that have undergone strong modifications as adaptation to a benthic lifestyle in the clade Berosus + Hemiosus.

Two new genera and five new species of Tullbergiidae (Collembola) from the southern Appalachian Mountains of North America, with redescription of Tullbergia clavata Mills.

Two new genera and five new species of Tullbergiidae (Collembola) are described from the North American Appalachian zone in eastern Tennessee and western North Carolina. Ameritulla n. gen. is established for species with 15 setae on the middle tibiotarsus, blunt papilla A on the labial palpus, two long rows of vesicles in the postantennal organ (PAO), two dorsal sensilla on the third antennal segment and crescentic pseudocelli. Ameritulla clavata (Mills, 1934) n. comb. (=Tullbergia clavata Mills, 1934) is designated as type species and redescribed from type specimens, and A. obscura n. sp. is described. On Mixturatulla ozwini n. gen., n. sp. papillae A and B of the labial palpus are thick and blunt, the second row of the PAO is laterally broken into numerous spherical vesicles, and the dorsum of Abd. VI has two rows of large, coalesced tubercles. Psammophorura miniclavata n. sp. lacks pseudocelli on the third abdominal segment, which are present in previously described species. Stenaphorura shaconage n. sp. is the first species of its genus reliably recorded from North America. It differs from its Palaearctic relatives in having 2+2 pseudocelli on most body segments. Tullbergia nearctica n. sp. resembles T. arctica (Wahlgren, 1900) but differs in several chaetotaxic characters. Sensilliform setae traditionally considered as ordinary pointed setae are recognized and charted. A new setal nomenclature is proposed for the ventral setae of the sixth abdominal segment.

A remarkable new genus and a new species of chewing louse (Phthiraptera, Ischnocera, Philopteridae) from Brazil.

A new genus of chewing louse as Bobdalgleishia, and its type species Bobdalgleishia stephanophallus sp. n. (Phthiraptera) belonging to the Brueelia-complex (Ischnocera: Philopteridae) are described. Adults of the new species are fully described, illustrated and compared morphologically with the type species of Motmotnirmus Mey & Barker, 2014, which is its closest relative. The type host of Bobdalgleishia stephanophallus is a subspecies of the great jacamar Jacamerops aureus ridgwayi Todd, 1943, an endemic Amazonian bird distributed in northern Brazil, and the type locality is the State of Pará. Bobdalgleishia is a remarkable genus with unique morphological and chaetotaxic characters which readily separate it from other members of the Brueelia-complex, in particular by having the first two marginal temporal and ocular setae very long.

Redescription of late-instar larva of Scydmoraphes sparshalli (Denny)Coleoptera: Staphylinidae, Scydmaeninae).

The larva of Scydmoraphes sparshalli is redescribed. This is the first complete description of an immature Scydmoraphes with special focus on the chaetotaxic characters. The larva is unique among Cyrtoscydmini in having three pairs of stemmata, a very long sensory appendage of the antennomere II, mandibles with mesal row of microserrations interrupted by smooth portion of mandibular margin; maxillary mala with asetose apex and a row of very long, modified setae on mesal margin, and extremely elongate maxillary palpomere III and labium. A comparative study of previous descriptions resulted in recognizing a misidentification of a Scydmoraphes larva (the "Typ 2-Larve" of Schmid) as a putative Neuraphes (Pararaphes). The serial homology of chaetotaxic structures in the larva of Scydmoraphes sparshalli is discussed, and comparative notes on the larvae of Scydmoraphes, Neuraphes and Stenichnus are given, with an identification key.

Larval Morphology ofYolaGozis, 1886 (Coleoptera: Dytiscidae: Bidessini) and Comparison with other Genera of the Tribe Bidessini

The second and third instars of Yola wraniki Wewalka, 2004 are described and illustrated for the first time, with detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi. The mature larva of Yola Gozis, 1886 can be distinguished from those of the other known Bidessini genera by the following combination of morphometric and chaetotaxic characters: ratio length of metathoracic leg/head width greater than 2.85; ratio length of urogomphus/head width greater than 2.70; absence of a ventroapical spinula on third antennomere; secondary temporal spine-like setae on parietale; natatory setae on tibia; secondary posteroventral setae on tarsus and secondary setae on urogomphus; presence of pore PAk and secondary dorsal setae on protarsus; and mandibular pore MNa located in a clearly distal position with respect to pore MNb. A key for the identification of the third instars of the genera of Bidessini known in detail is provided.

Skadisotoma, a new genus of Isotomidae (Collembola) from Australia.

A new species and genus, Skadisotoma inpericulosa, is described from south-eastern Australia. It possesses some characters that are found in Tomoceridae, such as a long cylindrical dens that is medially bent and a mucro with at least six teeth of different sizes and three setae but in other characters it resembles an isotomid. In this it shows similarities to the Boreal genus Mucronia Fjellberg, but differs from it in the possession of spines on the dens and in some chaetotaxic characters.

Ptenidium pusillum (Gyllenhal, 1808) from egg to pupa (Coleoptera: Ptiliidae).

Eggs, larvae and pupae of Ptenidium pusillum obtained by rearing adults are described. Larval chaetotaxy is treated in detail. Two larval instars are identified, differing in minor chaetotaxic characters, pigmentation and measurements. The lack of urogomphi, confirmed in Ptenidium, is discussed in the context of current systematics of Ptiliidae. Serial chaetotaxic homology and between-instar homology are discussed. Observations related to biology of P. pusillum and associations with phoretic mites and nematodes are given.

A new species of Seira (Collembola: Entomobryidae: Seirini) from Northern Brazil, with the addition of new chaetotaxic characters

Seira caerucinerea sp. nov. , a new species of springtail from the Cerrado domain, state of Tocantins, Brazil, is described and illustrated. The new species is mainly characterized by bluish-gray coloration and dorsal chaetotaxy presenting macrochaeta S7 on head, three macrochaetae (a6, m6 and p6) on margin of metathorax and 4+4 macrochaetae (a1, m2, m3 and m4i) on abdomen I. Characteristics of maxillary and labial papillae, chaetotaxy of subcoxae, collophore, ventral region of head, ventral and lateral region of abdomen IV and V, which are usually omitted in species descriptions within the genus, are also provided. This is the first species of Seira described from the Cerrado domain, as well as the first record of the genus from the state of Tocantins.

Study on the genus Morulina (Collembola: Neanuridae) with description of a new species from Northwest China.

A new species of Morulina from China is described and illustrated. It is close to M. orientis Tanaka from Japan and M. himalayana Cassagnau from Nepal. There are 12 tubercles on the head of all three species, but they can be separated by a number of chaetotaxic characters. A key for identification of all the species in the genus is given.

The dorsal chaetotaxy of Trogolaphysa (Collembola, Paronellidae), with descriptions of two new species from caves in Belize

Species diagnosis in Trogolaphysa has been based, until now, almost exclusively on number of eyes and shape of claws and mucro. Chaetotaxy, a character system important to diagnose species in other genera of scaled Entomobryoidea, has been described only for a few Trogolaphysa species. Here the complete dorsal chaetotaxy of six species of Trogolaphysa is described using the AMS and Szeptycki’s systems for head and body, respectively. A morphology-based parsimony analysis was performed to evaluate whether chaetotaxic characters overcome the influence of putatively cave adaptive convergent characters to resolve species level relationships, and to evaluate the evolution of the dorsal macrochaetae of the head. Phylogenetic analysis using only putative cave-adaptive characters support clades of unrelated taxa, but the addition of chaetotaxy overcomes the influence of convergent characters. A phylogeny based on all characters supports a trend towards reduced head macrochaetae number. Head macrochaetae are lost beginning with A3 and followed, in order, by S5, S3 and M3. In addition, a checklist of New World Trogolaphysa is provided and two new species, Trogolaphysa giordanoae sp. n. and Trogolaphysa jacobyi sp. n., are described on the basis of material collected in six caves in southern Belize.

Phylogenetic relationships of Leuronectes Sharp (Coleoptera: Dytiscidae: Agabinae) based on larval morphology and chaetotaxy

AbstractThe phylogenetic relationships of the diving beetle (Dytiscidae) genus Leuronectes Sharp are revised based on a cladistic analysis of seven Agabinae genera and 54 morphological and chaetotaxic characters from larvae. For this purpose, larvae of L. curtulus Régimbart are described and illustrated in detail for the first time, with particular emphasis on morphometry and chaetotaxy. The results show that Leuronectes is well placed within Agabinae based on the absence of natatory setae on tibia and tarsus in instars II and III, the urogomphus composed of two urogomphomeres, and the absence of secondary setae on urogomphus. Leuronectes is resolved as part of a basal polytomy along with Platynectes Régimbart and a clade formed by the remaining agabine genera. Leuronectes shares with Platynectes the setae UR2, UR3 and UR4 not inserted contiguously, with Platambus Thomson the anterolateral lobes of frontoclypeus not projected beyond anterior margin, with Hydrotrupes Sharp the seta AB9 inserted dorsolaterally, and with Ilybius Erichson the seta LA10 inserted submedially. Leuronectes is unique within Agabinae in having the apical lateroventral process of the third antennomere not protruding and additional ventroapical pores on third antennomere, and is unique within the dytiscid genera studied in having the seta LA12 inserted submedially and one additional spine-like seta inserted on the lateral margin of abdominal segment VIII.

Primary chaetotaxy of the larval head capsule and head appendages of the Hydrophilidae (Coleoptera) based on larva of Hydrobius fuscipes (Linnaeus, 1758)

The primary chaetotaxy of the larval head capsule and head appendages of the family Hydrophilidae (Insecta: Coleoptera) is described and illustrated using the larva of Hydrobius fuscipes (Linnaeus, 1758) as a model, and compared with fifteen hydrophilid taxa representing all main taxonomic groups within the family; brief comparative notes with representatives of the families Helophoridae, Spercheidae, Hydrochidae and Histeridae are also provided. Primary chaetotaxic nomenclature is developed for the Hydrophilidae, allowing the use of chaetotaxic characters for phylogenetic studies as well as diagnostic purposes. The study of representatives of the families Helophoridae, Hydrochidae and Spercheidae suggests that this nomenclature can also be effectively applied to other hydrophiloid families. Chaetotaxic nomenclature systems used in larvae of other groups of Coleoptera are briefly reviewed.

Morphology and chaetotaxy of the larval stages of Andogyrus seriatopunctatus Régimbart (Coleoptera: Adephaga: Gyrinidae)

The larval stages of Andogyrus seriatopunctatus Régimbart are described and illustrated, including morphometric and chaetotaxic characters. A larval ground pattern for the chaetotaxic characters is presented; it is based on first instar larvae of A. seriatopunctatus. Unidentified larvae of Dineutus MacLeay and a third instar larva of Gyrinus argentinus Steinheil were also inspected. For chaetotaxic homologization comparisons with other adephagan families were performed, mainly with Carabidae and Dytiscidae. The ground pattern is considered provisional due to the lack of previous studies in this family. Larvae of A. seriatopunctatus are briefly compared to those of A. buqueti (Aubé). Notes on the biology of A. seriatopunctatus are also included.

Comparative morphology of larval Camiarinae (Coleoptera: Leiodidae)Part I. Genus Paragyrtodes Szymczakowski 1966

The first, second and third larval instars of the Australian genus Paragyrtodes Szymczakowski, 1966 are described. Among three described species, larvae of two, P. candens Szymczakowski, 1966 and P. modestus Szymczakowski, 1966, are redescribed in detail, illustrated, photographed and measured. The chaetotaxy and porotaxy are given and their system is discussed. Morphological and chaetotaxic characters distinguishing mature larvae of two species of Paragyrtodes are provided; differences among mature larvae of the genera Agyrtodes Portevin, 1907 and Paragyrtodes are summarized. Pretergal glands, their glandular function, and tergal pores are documented in the family Leiodidae for the the first time. The problem of the identity of the larval glands in the family Leiodidae and superfamily Staphylinoidea is discussed. Data on presence, number and arrangement of the tergal and pretergal glands for all known larvae of Leiodidae and some representatives of Staphylinidae and Hydraenidae are gathered.

Four New Species of Xenylla (Collembola: Hypogastruridae) from Korea

ABSTRACT Four new species of the collembolan genus Xenylla, X. convexopyga, X. longistriata, X. dotata and X. marina from Korea are described. X. convexopyga is characterized by an absence of the dorsal seta m3 on Th. II‐III. While the other three new species share similarities in dorsal chaetotaxic characters. However, they are dissimilar in the following respects: ventral chaetotaxy, body colour, presence or absence of inner teeth on unguis, the length proportion of abdominal segments and thoracic segments, arrangement of anal papillae and the general shape of apical bulb of fourth antennal segment. As a result of this study, a total of 25 species in 6 genera of Hypogastruridae have been recorded from the Korean Peninsula.

Analysis of a species/instars/characters table: a theoretical survey on the use of chaetotaxy in ontophylogenetic studies

Phylogenetic studies on several groups of arthropods, such as Acari (mites) or Collembola (springtails), make wide use of chaetotaxy. Chaetotaxic characters, besides being morphological features (setal shape), often have a binary nature, that is presence vs. absence. A seta can be variable in a population, and one may attribute a presence probability to this seta. In fact, the presence probability should be defined for each instar. One might think that a variable seta corresponds to a polymorphism (e.g., two or more alleles in a population); in fact, setal variability should be regarded as the result of a propensity intrinsic to individuals, i.e., a potentiality being expressed at random among specimens. The phenomenon known as lateral inhibition explains how an early random fluctuation is at the root of the cell fate. Probabilistic organs are likely to originate from a similar phenomenon. A tridimensional species/instars/characters table (SIC table), containing setal presence probabilities, can be built up. Two kinds of analyses may be applied to such a table. In these analyses, the problem of homeotypic setae is emphasized. Related issues are the accuracy of using setal probabilities and the problem of reducing redundancy of information. A first process leads to a bidimensional table with characters in columns, and the species divided into their instars in rows. By using multidimensional statistics we can access ontogenetic trajectories, and in this way, ontogenetic comparisons can be achieved. The aim of the second process is to produce a species/characters table which can be used in a cladistic analysis.