Prey selection by the dobsonfly larva, Protohermes grandis (Megaloptera: Corydalidae)

SUMMARY 1. Prey selection by the dobsonfly larva, Protohermes grandis (Thunberg), was studied in stony riffles of the Yataro River, central Japan. The density, size distribution and taxonomic composition of available prey were assessed for 2 years. In order to know the encounter rate between prey and this ambush predator, prey mobility was also estimated from patterns of colonization of experimentally detiuded stones.
2. Foregut analyses revealed that maximum size of prey eaten increased with larval size, and large larvae did not take the smallest prey in spite of high availability in all seasons.
3. Charnov's (1976) optimal diet model quantitatively predicted such size-selective feeding under seasonally fluctuating conditions of water temperature and prey availability. Larvae maximized the feeding rate by selecting prey.
4. Maximum width of prey eaten coincided approximately with larval mandible length. Mandible size seemed to play an important role in the selection of prey in the optimal size range.     

Radio tracking and activity monitoring of the dobsonfly larva,Protohermes grandis (Megaloptera: Corydalidae)

Summary A miniature crystal-controlled radio transmitter, 7x17x2 mm³ and 185 mg in water, was attached to the back of prothorax of individual dobsonfly larvae, Protohermes grandis. Positions of these larvae in the stream bed were determined using a loop antenna, and they were tracked for 19 days. Actograms were also taken by recording the frequency variation of transmitting signals which were changed according to the larval posture. Larvae changed their positions in the stream bed in some nights, but never in the daytime. However, in most nights (92.7%), they continued to stay at the same position. Actograms revealed that larvae were quite motionless in most time (90.8% of daytime and 89.7% of night). Thus, larvae use the ambush mode of foraging in the central part of riffles where prey are continuously redistributed and sufficient oxygen is supplied with a water current.     

Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis(Megaloptera: Corydalidae)

SUMMARY 1. Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis ,was studied by measuring the oxygen consumption rate (resting metabolism) bimonthly for 2 years. The respiratory rate of the larva was significantly lower during the summer season when the stream temperature rose to 30°C.
2. Summer depression of respiration was confirmed by measuring the rate of carbon dioxide evolution. The mean value of the respiratory quotient was estimated to be 0.76 ± 0.05 SE. The larva is believed to conserve energy by this reduction in respiratory rate,
3. In other seasons, however, the larva maintained a higher respiratory rate and remained active even in the winter when the stream temperature decreased near to 0°C. In fact, significant growth in weight occurred from mid-October to late March.
4. This acclimation to temperature may enable the efficient allocation of energy during the long larval period (3 years) in streams which have large annual fluctuations in temperature.     

Trophic discrimination factor of nitrogen isotopes within amino acids in the dobsonfly Protohermes grandis (Megaloptera: Corydalidae) larvae in a controlled feeding experiment

The trophic discrimination factor (TDF) of nitrogen isotopes (¹⁵N/¹⁴N) within amino acids, between a stream‐dwelling dobsonfly larva (Protohermes grandis: Megaloptera; Corydalidae) and its diet (chironomid larvae), was determined in controlled feeding experiments. Last‐instar larvae of P. grandis were collected from the Yozawa‐gawa River, central Japan, and reared in the laboratory. After fed to satiation for 1 month, one group of larvae was each fed one living chironomid larva per day for 4 weeks, while a second group was starved for 8 weeks. The larvae were harvested at intervals and the nitrogen isotopic composition of glutamic acid (δ¹⁵N_Glu) and phenylalanine (δ¹⁵N_Phe) were determined to calculate TDF. The mean TDF of satiated and starved larvae were 7.1‰ ± 0.5‰ (n = 3) and 7.3‰ ± 0.5‰ (n = 5), respectively. Thus, the TDF for P. grandis larvae in this study was similar to that reported for other arthropods (approximately 7‰) and was independent of satiation or starvation. A previous study of wild P. grandis larvae, based on the δ¹⁵N_Glu and δ¹⁵N_Phe values, estimated its trophic position (TP) as approximately 2.0 ± 0.1 (n = 5), a low value close to that of algivores, although they are generally characterized as carnivores (usually accepted as TP ≥ 3). The TDF for P. grandis larvae suggests that their low TPs in nature were caused by incorporation of vascular plant‐derived amino acids (with a different δ¹⁵N profile from that of algae) and not by an unusually low TDF or by the effects of the satiation/starvation on amino acid metabolism.     

Evolutionary history of the complex polymorphic dobsonfly genus Neoneuromus (Megaloptera: Corydalidae)

The dobsonfly genus Neoneuromus van der Weele is endemic to the Oriental region. Species possess highly variable body and wing colouration and markings, not only among species but also among conspecific individuals of certain species. This stark polymorphism hinders accurate species identification, and obscures an undocumented species diversity as well as our understanding of the evolutionary history of this genus. We used multiple methods of molecular identification combined with morphological evidence to delimitate species, circumscribing a total of 13 species in Neoneuromus . Five new species are herein described: Neoneuromus indistinctus Liu, Hayashi & Yang, sp.n. , Neoneuromus maculatus Liu, Hayashi & Yang, sp.n. , Neoneuromus niger Liu, Hayashi & Yang, sp.n. , Neoneuromus similis Liu, Hayashi & Yang, sp.n. and Neoneuromus vanderweelei Liu, Hayashi & Yang, sp.n. The dated phylogeny with reconstructed ancestral areas indicates an initial divergence of Neoneuromus during the mid‐Eocene. A broad area including northeastern India and northern Indochina could be a centre for early divergence of the genus, while complex dispersal and vicariance events dating from the late Eocene to the Pliocene probably shaped the present diversity and distribution of the genus. Our ancestral character state reconstruction suggests that the pale and dark colour forms among different species, or conspecifics, could evolve rapidly and that changes in colouration could be driven by species‐specific mate recognition.     

Systematics of the dobsonfly subfamily Corydalinae (Megaloptera: Corydalidae)

Abstract. The genera of Corydalinae are redefined, and representative characters are figured for each genus. New character sources, such as mouthparts and internal female genitalia, are investigated, as well as traditional male genitalia and wings. Allohermes is synonymized with Protohermes, Doeringia with Platyneuromus . Intergeneric relationships are hypothesized on the basis of a cladistic analysis. Acanthacorydalis and the New World genera form a monophyletic group, as do Protohermes and Neurhermes , and Neuromus and Neoneuromus. Chloroniella belongs in the Acanthacorydalis - New World lineage, but exact placement is uncertain. A phyletic sequence classification is proposed on the basis of the cladistic analysis.     

Systematics of the Protohermes xanthodes species-group in eastern Asia (Megaloptera: Corydalidae)

A new species‐group of the dobsonfly genus Protohermes is proposed, the Protohermes xanthodes species‐group. Three species from eastern Asia belonging to the new species‐group are redescribed and illustrated. Phylogenetic relationships among the species in this group, as well as the biogeography of these species, are discussed on the basis of a cladistic analysis.     

Revision of the Protohermes changningensis species group from China (Megaloptera: Corydalidae: Corydalinae)

A new species group, the Protohermes changningensis group, of the dobsonfly genus Protohermes is established. Three species belonging to the new species group from China are described and illustrated, including one new species. Phylogenetic relationships among the species in this group and biogeography are discussed on the basis of a cladistic analysis using Hennig 86.     

Intra- and interspecific variation in body size ofProtohermes (Megaloptera: Corydalidae)

The life history of three populations ofProtohermes grandis and two populations ofProtohermes immaculatus (Megaloptera: Corydalidae) was compared. In general, the larvae lived in stream riffles for 2 years and the adults appeared in summer. Adult body size differed between these closely related species and also between the populations ofP. grandis. Dwarfism occurred inP. immaculatus, a species that is endemic to the small, isolated island, Amami Island. The population ofP. grandis on Yaku Island, located between Amami Island and the mainland Kyushu, had an intermediate body size between that ofP. immaculatus and the mainland population ofP. grandis. Despite being an insular population,P. grandis on Tsushima Island had a similar body size to mainlandP. grandis. In these populations with large adults, some larvae lived in the streams for 3 years. The size distribution of benthic animals, which are the prey available toProtohermes larvae, differed between the streams studied. The density of large prey was lowest on Amami Island, intermediate on Yaku Island, and highest on the mainland and Tsushima Island. Different size distributions of available prey may be caused by the differences of benthic fauna; most of Ecdyonuridae and Ephemerellidae (large mayflies) and Perlidae (large stoneflies) were not found on Amami and Yaku Islands. Thus, there is a tendency to dwarfism in the populations ofProtobermes inhabiting streams where the density of large prey is low.     

Systematics and biogeography of the dobsonfly genus Nevromus Rambur (Megaloptera: Corydalidae: Corydalinae) from the Oriental realm

The Asian endemic dobsonfly genus Nevromus Rambur is revised. Six species of Nevromus are described or re‐described, and illustrated. Nevromus aspoeck Liu, Hayashi & Yang sp.n. , Nevromus austroindicus Liu & Viraktamath sp.n. and Nevromus gloriosoi Liu, Hayashi & Yang sp.n. are described from southernmost Yunnan of China and northern Thailand, southern India, and Borneo, respectively. A new combination Nevromus intimus (McLachlan) comb.n. is also identified. An interspecific phylogeny of Nevromus is reconstructed based on the adult morphological data, resulting in identification/recognition of two main clades, i.e. the mainland clade and the insular clade. Combining this phylogeny and the updated geographical distribution, an Indian origin and a historically widespread distribution in southern Eurasia is proposed for Nevromus. The deep divergence between the mainland and insular clades within Nevromus might have happened during the separation of Sundaland from Eurasia. The Tertiary orogenic events after the collision between the Indian subcontinent and Eurasia probably affected the speciation within the mainland clade of Nevromus, whereas the island formation of Borneo, Java and Sumatra shaped the fauna within the insular clade of this genus. The biogeographical pattern of Nevromus revealed in this study appears to have more general significance for understanding the faunal origin and diversification of the habitat‐specific or poorly dispersing insects from the Oriental realm.     

Comparative mitochondrial genomics and phylogenetics among species of the Oriental dobsonfly genus Neoneuromus van der Weele, 1909 (Megaloptera: Corydalidae)

The dobsonfly genus Neoneuromus van der Weele, 1909 represents one of the megalopteran lineages with large body-size, and comprises 13 species all endemic to the Oriental region. In the present study, the mitochondrial genomes (mitogenomes) of 12 species of this genus were determined and analyzed for the first time. The mitogenome of the genus-type, Neoneuromus fenestralis (McLachlan, 1869), as a representative of these congeneric species, is herein described in detail. All of the mitogenomes of Neoneuromus are composed of 37 encoded genes and a control region. The evolutionary rates of the protein coding genes (PCGs) of the 13 species of Neoneuromus as well as different genera of Corydalinae are estimated. All the transfer RNA genes (tRNAs) have the typical clover-leaf secondary structure except trnS1 (AGN). Interspecific relationships within Neoneuromus were reconstructed based on different datasets generated from mitogenomic sequences. Our results indicate that tRNA and ribosomal RNA genes (rRNAs) of Neoneuromus species contribute phylogenetic signal when being concatenated with the PCGs, thus should be kept during phylogenetic analysis. The results sheds light on understanding the evolution of these aquatic and predatory insects.     

First development and characterization of 27 novel microsatellite markers in the dobsonfly Neoneuromus ignobilis (Megaloptera: Corydalidae) at genome-scale level

The dobsonfly species Neoneuromus ignobilis Navás (Megaloptera: Corydalidae) is endemic to but widely distributed from eastern and southeastern Asia, being an important insect indicator for freshwater biomonitoring. At present, there is no report on the development of microsatellites of Megaloptera. Here, we developed 27 novel microsatellite markers of N. ignobilis from 850,920 candidate microsatellites with the stringent screening criteria considering the amplification success rate, the presence or absence of stutter peaks, the peak intensity, the polymorphism of the loci, the heterozygosity, and the number of alleles. The allele number of 27 microsatellite markers ranges from 3 to 12 with an average value of 6.19 per locus. The observed heterozygosity (H_O) and expected heterozygosity (H_E) revealed a range from 0.000 to 0.947 and 0.000 to 0.842, respectively. We constructed three panels (MP panel, most polymorphic; SS panel, most stringent strategy; ALL panel, total 27 microsatellite markers) and compared the analyses on population genetic diversity and structure. The result showed that the MP panel can significantly improve the analyses of individual assignment and genetic diversity. Accordingly, we advocate selecting the most polymorphic microsatellite marker for analyzing population genetics based on microsatellite data. The present work represents the first study on the microsatellite development of Megaloptera.

     

The Protohermes fruhstorferi species group (Megaloptera: Corydalidae: Corydalinae), with description of a new species from Vietnam

A new species group, the Protohermes fruhstorferi group of the dobsonfly genus Protohermes, is recognised. Three species belonging to the new species group are described and illustrated, including one new species from northern Vietnam.     

Sequencing and analysis of the complete mitochondrial genome of the giant dobsonfly Acanthacorydalis orientalis(McLachlan)(Insecta:Megaloptera:Corydalidae)

The complete mitochondrial genome of Acanthacorydalis orientalis(McLachlan)was determined and analyzed(GenBank accession number:KF840564).This paper represents the first mitochondrial(mt) genome of the dobsonfly genus Acanthacorydalis.The mt genome is a typical circular DNA of 15 753 bp composed of 37 genes with an A+T content of 76.7%.It has an ancestral gene arrangement of the insect mt genomes.Eleven of the 13 PCGs start with codon ATT and ATG,while several exceptions such as ATA and TTG respectively for atpS and nad\ are also present.Five protein-coding genes end with a single T,while others have a termination codon of TAA or TAG.Most tRNAs are folded into the typical clover-leaf structure except for the trnS 1 whose dihydrouridine arm was a simple loop.The secondary structure of rrnl consists of five structural domains and 50 helices,while the rrns includes three domains and 34 helices.The control region has a stretches of Ts with a length of 22 bp but lacks obvious tandem repeat region.Both Bayesian inference and maximum likelihood(ML) analyses,based on all 13 protein-coding genes and two rRNA genes of the mt genomes,confirm the monophyly of Corydalinae and suggest that Acanthacorydalis,together with Corydalus,which is an endemic dobsonfly genus from the New World,belong to a monophyletic lineage.     

Phylogenetic review of the Chinese species of Acanthacorydalis (Megaloptera, Corydalidae)

The dobsonfly genus Acanthacorydalis Weele is a small genus which only occurs in Asia and comprises eight species. Seven species are restricted to the Oriental realm, while A. orientalis (McLachlan) extends into the Palaearctic realm. There are five species in China, four of which are endemic. In the present paper, the Chinese species are redescribed, illustrated, keyed, and subjected to phylogenetic and biogeographical analyses for the first time. Geographic distributions are updated. The cladistic analysis for the Chinese species was constructed by using Hennig86, based on 17 adult morphological characters. The phylogenetic relationships obtained are ( A. orientalis + A. yunnanensis + A. unimaculata + ( A. fruhstorferi + A. sinensis )). Six areas of endemism are identified based on Acanthacorydalis distributions: north, south-west, central and south China, north-eastern India and northern Vietnam.     

A new species of Corydalus Latreille from Venezuela (Megaloptera, Corydalidae)

A new species of dobsonfly, Corydalus wanningeri, from Venezuela, is described and illustrated. It superficially resembles Corydalus neblinensis Contreras-Ramos, with a uniform reddish coloration of body and wings. Yet, because of male genitalic structure it might be closely related to Corydalus crossi Contreras-Ramos. Specimens were collected from a rain forest transitional zone between the Orinoco lowlands and the Gran Sabana plateau, in Bolívar state. This is the 15(th) species of Corydalus to be recorded from Venezuela, rendering this the country with the highest number of documented Corydalus species. A key to the sexually dimorphic, long-mandibled Venezuelan species of the genus is provided.     

Six New Species of Dobsonflies from Venezuela (Megaloptera: Corydalidae: Corydalinae)

Six new species of dobsonflies (Megaloptera: Corydalidae: Corydalinae) from Venezuela are described and illustrated, two in the Neotropical genus Chloronia and four within the New World genus Corydalus. Chloronia contains 15 previously described species. The new species Chloronia gaianii and C. marthae, each from the southern tepui and Andean regions, appear to be most closely related to C. hieroglyphica (Rambur) and C. mirifica Navás, respectively. Corydalus contains 30 previously described species. The new species Corydalus clavijoi, of Andean affinity, appears most closely related to C. tesselatus Stitz; C. crossi, from Auyán-tepuí, might be closely related to C. nubilus Erichson; and both C. hayashii and C. mayri, from westernmost Guayana Shield area and Aracamuni tepuis, respectively, clearly belong in the distinct and monophyletic C. arpi Navás species group. Keys for identification of the Venezuelan species of both genera are provided.     

A revision of the genus Neoneuromus in China (Megaloptera: Corydalidae)

Lake Illawarra, is a typical shallow intertidal coastal barrier lagoon in New South Wales, Australia. This paper reports the first examination of photosynthetic characteristics of benthic microalgae and seagrass in this lake by measuring the oxygen exchange procedure (flux) using sediment-core incubations in the laboratory. Photosynthesis vs irradiance relationships (P–I curves) were generated from measurements made at nine irradiances for microphytobenthos (MPB) at five different water depths (sites) during September 2002. Maximum benthic gross primary production (GP_max) for MPB in this lake tended to decrease with the increasing water depth from Site 5 (about 0.2 m deep) to Site 1 (about 3.0 m deep), and was correlated with decreasing surface sediment Chl-a concentrations.     

Notes on the genus Neochauliodes Weele (Megaloptera: Corydalidae) from Henan, China

The species of the genus Neochauliodes from Henan are reviewed. Three species are described as new to science: Neochauliodes digitiformis sp. nov., Neochauliodes parasparsus sp. nov. and Neochauliodes sparsus sp. nov. A key to the species from Henan is presented.     

Complete mitochondrial genome of Neochauliodes parasparsus (Megaloptera: Corydalidae) with phylogenetic consideration

We sequenced the complete mitochondrial genome (mitogenome) of Neochauliodes parasparsus. The 15,995-bp mitogenome contained the standard set of 13 protein-coding genes, 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs), and a putative control region, with a gene arrangement that was identical to that reported for most other megalopteran species. We also predicted the secondary structure of all the RNA genes and analysed the preferred codon usage of the protein-coding genes. The putative 1265-bp control region contained two tandem repeated regions and several microsatellite-like elements. The phylogenetic analysis of available neuropteridan mitogenomes, based on the 13 protein-coding genes, appeared to support the current view of the neuropteridan phylogeny, and among the Neochauliodes spp., N. parasparsus was the most closely related to N. punctatolosus.