Larval Morphotypes Research Articles

Molecular identification and morphological description of Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus larvae, collected in the upper Gulf of California during Summer 2012

Sciaenidae fish larvae were collected from the upper Gulf of California during September 2012 using a conical net (505 μm) through surface tows. These were pre-classified into four larval morphotypes, based on external characteristics (mainly meristic and pigmentation). Partial sequences of cytochrome c oxidase, subunit 1 and 16S rRNA (16S) genes of mitochondrial DNA, were used in molecular genetic identification from each larval morphotype. Genetic results indicated the identification of four larval morphotypes as Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus. Pigmentation patterns of larvae described after molecular genetic identification made it possible to distinguish between M. megalops, M. nasus and C. othonopterus (postflexion). However, pigmentation was not reliable for differentiating between preflexion larvae of C. othonopterus and C. reticulatus. From these results, both morphological and genetic approaches were proposed as complementary tools in taxonomic studies of ichthyoplankton, particularly in early fish larvae identification of congeneric species with similar morphological characteristics.

Integrative Taxonomy of the Micrura alaskensis Coe, 1901 Species Complex (Nemertea: Heteronemertea), with Descriptions of a New Genus Maculaura gen. nov. and Four New Species from the NE Pacific.

Micrura alaskensis Coe, 1901 is a common intertidal heteronemertean known from eastern and northwest Pacific (Alaska to Ensenada, Mexico and Akkeshi, Japan, respectively). It is an emerging model system in developmental biology research. We present evidence from morphology of the adults, gametes, and sequences of cytochrome c oxidase subunit I and 16S rRNA genes that it is not one, but a complex of five, cryptic species. All five of these species co-occur at least in part of their geographic range (e.g. southern Oregon). Preliminary cross-hybridization experiments suggest that at least some of these species are reproductively isolated. The five species share characteristics of adult morphology (e.g. accessory buccal glands) and at least four are known to possess a unique larval morphotype--pilidium maculosum. We propose that these characters define a new genus, Maculaura gen. nov., which contains the following five species: Maculaura alaskensis comb. nov., Maculaura aquilonia sp. nov., Maculaura cerebrosa sp. nov., Maculaura oregonensis sp. nov., and Maculaura magna sp. nov. It is unclear which of the five species Coe originally encountered and described. We chose to retain the name "alaskensis" for the species that current researchers know as "Micrura alaskensis", although, presently, it is only known from Washington and Oregon, and has not been collected from Alaska. Maculaura aquilonia sp. nov. is the only member of the genus we have encountered in Alaska, and we show that it also occurs in the Sea of Okhotsk, Russia.

Datos sobre la presencia de una larva de Cyematidae en el océano Atlántico oriental (Pisces: Saccopharyngiformes)

Larval morphotype species 1 (Smith & Miller, 1996) of Leptocephalus holti Schmidt, 1909 is recorded for the third time from the Eastern Atlantic Ocean, as a result of the capture of a large specimen in epipelagic hauls carried out in waters of El Hierro (Canary Islands), during the third cruise of VULCANO project (CTM2012-36317). Morphometric and descriptive data of the specimen are given and its geographic range in this part of the Atlantic is discussed

Lignocellulolytic enzymes and bacteria associated with the digestive tracts of Stenochironomus (Diptera: Chironomidae) larvae

We analyzed the digestive activity of the enzymes that digest cellulose and hemicellulose and the bacterial community that is capable of hydrolyzing wood compounds in the digestive tracts of Stenochironomus (Diptera: Chironomidae) larvae, which are miners of decomposing submerged tree and bush branches. Based on quantification of reducing sugars, these larvae have a limited capacity for cellulose degradation but a good capacity for xylan hydrolysis. We isolated 31 types of colonies from two larval morphotypes, of which 19 tested positive for the capacity to hydrolyze at least one of the four substrates that were used as the main carbon source in the culture media. Their woody compound degradation capacity was assessed using colorimetric tests. The bacteria were identified by the analysis of the 16S rRNA gene. None of the bacteria were capable of degrading lignin. The genus Pseudomonas had the greatest species richness; Bacillus spp exhibited the greatest capacity for degrading the different substrates, and Sphingobium was found in both morphotypes. Microorganisms participate in the degradation of wood consumed by Stenochironomus larvae. This is the first report of lignocellulolytic bacteria and enzymes in the digestive tracts of mining chironomids.

A review of the genus Corynoneura Winnertz (Diptera: Chironomidae) from the Neotropical region

Currently the genus Corynoneura Winnertz comprises 10 species already cited or described for the Neotropical region. Inthe present paper 15 new species are described for the Neotropics: 12 new species are described from Brazil, five of themare described as male, female, pupa and larva, Corynoneura canchim sp. n., C. diogo sp. n., C. espraiado sp. n., C.humbertoi sp. n., C. salviniatilis sp. n.; three as male, pupa and larva, C. franciscoi sp. n.; C. longiantenna sp. n. and C.renata sp. n.; the species C. sisbiota sp. n. as male, female and pupa; C. bodoquena sp. n. as male and pupa and C. boraceiasp. n. and C. vidiapodeme sp. n. as males. Corynoneura trondi sp. n. is described from Chile (male, pupa), C. guanacastesp. n. from Costa Rica (male) and C. zempoala sp. n. from Mexico (male). The knowledge of the distribution ofCorynoneura fortispicula, C. sertaodaquina, C. septadentata and C. unicapsulata all species described by Wiedenbrugand Trivinho-Strixino (2011) as well as Corynoneura ferelobata Sublette et Sasa is extended. A larval morphotype is also included. Keys for males, females, pupae and larvae to known species of the Neotropical Corynoneura are given.

Description and genetic characterisation of Hysterothylacium (Nematoda: Raphidascarididae) larvae parasitic in Australian marine fishes

Nematodes belonging to the genus Hysterothylacium (family Raphidascarididae) infect various species of marine fish in both the larval and adult stages. Humans can be accidentally infected upon eating infected seafood. In spite of their importance, relatively little is known of their occurrence and systematics in Australia. An examination of various species of marine teleosts in Australian waters revealed a high prevalence of Hysterothylacium larval types. In the present study, seven previously undescribed Hysterothylacium larval morphotypes (V to VII and IX to XII) were discovered. In total we found 10 different morphotypes and we genetically characterised nine morphotypes identified. A morphological dichotomous identification key has been established to differentiate these morphotypes. Since some larvae of Hysterothylacium from marine fishes cannot be differentiated morphologically from other nematode larvae, such as Paraheterotyphlum, Heterotyphlum, Iheringascaris and Lapetascaris, the first and second internal transcribed spacers (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA) of these larvae were characterised to confirm their taxonomic status. This genetic characterisation implied that some distinct morphotypes belong to different developmental stages of the same species. In addition, it revealed that some morphotypes can comprise distinct genotypes. No match was found between ITS-1 and ITS-2 sequences obtained from larvae in the present study and those from adults available in the GenBank, highlighting the lack of knowledge on occurrence of adult nematodes infecting Australian fish.

Infection levels and diversity of anisakid nematodes in blackspot seabream, Pagellus bogaraveo, from Portuguese waters

The blackspot seabream, Pagellus bogaraveo, is a sparid fish of great economic importance in the northeast Atlantic. The main aim of this work was to assess the infection levels and diversity of anisakid nematodes parasitizing P. bogaraveo from Portuguese waters. The anisakid larvae were identified by polymerase chain reaction-restriction fragment length polymorphism analysis and ten different patterns were observed, four of which were not previously reported in the literature. Moreover, several species were detected for the first time in this host: Anisakis simplex × Anisakis pegreffii hybrids, Anisakis ziphidarum, Anisakis typica, Anisakis physeteris, as well as three undescribed anisakids Anisakis sp. PB-2009, Anisakis sp. PB-2010, and Contracaecum sp. PB-2010. The ITS1-5.8S-ITS2 region was sequenced and analyzed phylogenetically, revealing that our anisakids were distributed by the two distinct clades reported previously, corresponding to the two recognized larval morphotypes. Moreover, a group of organisms, including our specimens from Madeira and the previously reported Anisakis sp. HC-2005, cluster together and seem to belong to clade I. A certain degree of intraspecific diversity was also detected. Samples from mainland waters had the highest infection levels and were dominated by A. pegreffii. Madeira had the highest diversity overall, dominated by Anisakis sp. PB-2010. Fish from the Azores had the lowest infection levels, and the species with the highest relative abundance was A. physeteris. The anisakid nematode communities were relatively similar in mainland waters but very distinct in both the Azores and Madeira islands, suggesting the existence of at least three different stocks of P. bogaraveo in the northeast Atlantic.

Larval pattern morphotypes in the Western Palaearctic Hyles euphorbiae complex (Lepidoptera: Sphingidae: Macroglossinae)

AbstractExternal morphological variation in larval pattern elements in the Hyles euphorbiae complex is documented and described from independent samples of numerous populations across Europe and North Africa. Variability in the distribution of black cuticle and other colours was found to be much higher within populations than previously believed and it proved difficult to characterize any species, subspecies and even local population unequivocally using this feature alone. A representative sample of larvae from the Canary Islands, Madeira, North Africa, Iberia, Italy, Germany, Eastern Europe, Malta, Greece and Yemen, is illustrated, supplemented by observations from photographs of larvae from the Middle East and Western Asia. Taxonomy-independent definitions of larval morphotypes demonstrate significant overlap between species. We discuss the results in the context of Western Palaearctic biogeography, postulating several areas of hybridisation between the more northern Hyles euphorbiae and more southern H. tithymali that have led to the mosaic distribution patterns observed, and consider the potential of these moths for tracking the future eff ects of climate change in the Mediterranean Basin.

Identification of stomatopod larvae (Crustacea: Stomatopoda) from Hong Kong waters using DNA barcodes

The Stomatopoda (Crustacea: Malacostraca) from the South China Sea region are of commercial importance and although limited studies have been conducted on the adults, no research has ever been attempted on the larval stages because of the lack of identification keys or taxonomic descriptions. In the first study of its kind in the region, DNA barcoding was used successfully to identify unknown stomatopod larvae from plankton samples. Sequences of two mitochondrial genes, namely the cytochrome c oxidase subunit-I (COI) and the large ribosomal subunit (16S) rRNA, were applied as the barcodes to match DNA sequences from unknown larval morphotypes against those of known, locally occurring adult species. Intraspecific variations for the COI and 16S rRNA genes were found to be <2.4% and <2.1% respectively in terms of Kimura 2-Parameter (K2P) divergence of the adults, whereas variations between genera ranged from 13% to 24% and 3% to 11% respectively. These results imply that both genes are suitable for use in species identification of stomatopods; thus 14 of the 16 larval morphotypes (87.5%) obtained in Hong Kong waters can be identified to seven species through DNA barcoding. The findings of this study would also facilitate future research on the larval ecology and phylogenetic relationship of these crustaceans.

Ecological correlates of trophic polyphenism in spadefoot tadpoles inhabiting playas

Polyphenism in larval amphibians has been related to several factors, including wetland hydroperiod, food availability, competition, and predation. Spadefoot toads (genus Spea Cope, 1866) often exhibit a trophic polyphenism by developing distinct carnivore and omnivore larval morphotypes. Using a multimodel selection approach, we investigated the influence of land use (cropland vs. grassland type) and differences in annual precipitation on morphotype expression in Plains spadefoot ( Spea bombifrons (Cope, 1863)) and New Mexico spadefoot ( Spea multiplicata (Cope, 1863)) toads in playas. We also examined the relative importance of tadpole density, tadpole age, water-loss stress, wetland size, density of larval mole salamanders (genus Ambystoma Tschudi, 1838; a predator on Spea tadpoles), and food resources on morph occurrence. The carnivore morphotype developed almost exclusively in S. bombifrons and rarely in S. multiplicata regardless of land use. Habitat availability measured by water-loss rate, as well as predation risk and tadpole age, were the most important factors influencing carnivore proportions. Ambystoma density was positively associated, whereas water-depth loss and tadpole age were negatively associated with the proportion of carnivores. The greatest proportion of carnivores was observed in grassland playas, which had the highest density of Ambystoma predators, longest hydroperiods, and experienced water-depth gain. Fairy shrimp density was not correlated with the proportion of carnivores. Upland land use through cultivation-associated erosion is altering wetland trophic structure, which further influences morphotype expression in Spea tadpoles and playa amphibian community structure.

Confirmation of the species status of the blackfly Simulium galeratum in Britain using molecular taxonomy

Since 1920 Simulium reptans (Linnaeus) (Diptera: Simuliidae) has been reported as exhibiting two different larval morphotypes, a typical S. reptans and an atypical S. reptans var. galeratum, which differ in the markings of the larval head capsule. Inconsistent variation in adults and no apparent variation in the pupae have led taxonomists to conclude that these types in Britain are a single species. We investigated populations in Britain where either the typical form or var. galeratum is found, and one population where the two exist sympatrically. A phylogenetic study based upon a region of the mitochondrial cytochrome c oxidase 1 gene (DNA barcoding) produced a tree that delineated the morphotypes into two distinct monophyletic clades. The average Kimura-2-parameter distances within each clade (i.e. within each morphotype) were very low (0.67% and 0.78%), with the distances between morphotypes being 9-10-fold greater (mean 7.06%). This is concordant with differences within and between species in other taxa; based upon the strict correlation between the molecular variation and the morphotypes, we propose the re-instatement of S. galeratum to species status.

Identity of larval Meristogenys from a single stream in Sabah, Malaysia (Amphibia: Ranidae)

A morphological and molecular survey was conducted to examine the association between larvae and adults of Bornean torrent frog Meristogenys from a stream in Mahua, Crocker Range, Sabah, Malaysia. We identified five discrete morphotypes of larvae, which also showed considerable genetic differentiation. Each larval morphotype was associated through DNA sequence comparisons with adult specimens that had been identified morphologically. One morphotype, identified as M. orphnocnemis, was less similar to the larva of this species than to an unidentified larva, both reported previously. Adults of two other larvae were identified as M. amoropalamus and M. kinabaluensis, but the larval morphotypes differed from previous descriptions of these larvae. Adults associated with another morphotype resembled M. whiteheadi, but had longer tibia. This larval morphotype was dissimilar to previous descriptions of the M. whiteheadi larva, but was similar to another unidentified larva previously reported. No adult specimens were associated with the fifth larval morphotype, which matched the larva reported as M. amoropalamus. From these results, we suspect that either some previous studies include misidentifications or several undescribed, cryptic taxa morphologically resemble known adult species, but differ as larvae.© 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 151, 173-189. © 2007 The Linnean Society of London.

First record of anomuran and brachyuran larvae (Crustacea: Decapoda) from Antarctic waters

Two decapod crustacean larval morphotypes belonging to the Anomura and Brachyura were found for the first time in Antarctic waters. Nine specimens were obtained from qualitative plankton hauls in Maxwell Bay (Bransfield Strait) (62°14'33S; 58°43'81W) off King George Island, Antarctic Peninsula. The anomuran morphotype belonged to the Hippidae, and apparently to the genus Emerita, whereas the brachyuran representative was assigned to the genus Pinnotheres (Pinnotheridae). At present, species determination is not possible due to lack of knowledge of larval morphology in both families. Adult forms of these reptant decapods are not known from Antarctic waters; the occurrence of the present larval forms is considered as a possible intrusion of Subantarctic water masses into the Antarctic environment. This hypothesis is supported by the additional presence of the copepod genus Acartia in the same sample material, which is exclusively known from Subantarctic waters.

Molecular Species Identification of Newly Hatched Hawaiian Amphidromous Gobioid Larvae.

: This report describes a method for the determination of species identity of newly hatched larvae of five sympatric Hawaiian amphidromous gobioids (Lentipes concolor, Sicyopterus stimpsoni, Awaous guamensis, Stenogobius hawaiiensis, and Eleotris sandwichensis). Polymerase chain reaction (PCR) was used to amplify a homologous section of the cytochrome b (Cyt b) region of the mitochondrial genome (mtDNA) from adults of all five species. The resulting PCR-amplified DNA was subjected to restriction fragment length polymorphism (RFLP) analysis producing species-specific restriction patterns. PCR products from the five species were sequenced to substantiate correct amplification, restriction site locations, and fragment sizes. The sequence data were also used to construct a phylogenetic tree. Individual, newly hatched, wild-caught larvae of amphidromous gobioids of unknown species affinity were sorted into six morphotypes based on physical characteristics. These typed larvae and those from two species that spawned in captivity were subjected to the same molecular analysis as the adults. The RFLP results from adults and larvae were compared, allowing larval morphotypes to be assigned to the appropriate species. These comparisons permitted construction of an identification key to the newly hatched larvae of these species based solely on physical characteristics for use in future field studies.Key Words: fish larvae, species identification, Hawaii, gobioidea, PCR, RFLP.http://link.springer-ny.com/link/service/journals/10126/bibs/1n2p167.html

A correction to: biological and oceanographic insights from larval labrid (Pisces: Labridae) identification using mtDNA sequences

Previously published mtDNA cytochrome b sequences for Xyrichtys novacula (Linnaeus) and two morphologically distinct types of Xyrichtys larvae (Pisces: Labridae) included human cytochrome b sequence, presumably due to sample contamination and/or poor preservation of sample DNA. Those sequences had been used to identify the two types of Xyrichtys larvae as X. novacula, but owing to the contamination, the identifications are invalid. Fresh specimens were collected: X.␣martinicensis (Cuvier and Valenciennes), X. novacula, X. splendens (Castelnau), and Xyrichtys sp. larvae of each of the two morphotypes (dorsal-forward eye and ventral-forward eye). The cytochrome b fragment was amplified from each specimen using the polymerase chain reaction. Comparison of the sequences with human cytochrome b sequence confirmed that the new sequences were not contaminated. The interspecific differences in Xyrichtys sequences were less than previously reported, but still greater than observed in many fish genera. Distance and parsimony analyses indicated that X. novacula and X. martinicensis were more closely related to each other than to X. splendens. This conclusion differs from our previous conclusion that X. martinicensis and X. splendens were more closely related to each other than to X. novacula. Distance and parsimony analyses also demonstrated that both larval morphotypes were X. novacula and, thus, our previous conclusions regarding larval ecology and oceanographic transport remain unchanged.

Hystricurid trilobite larvae from the Garden City Formation (Lower Ordovician) of Idaho and their phylogenetic implications

Hystricurids are considered to constitute the earliest (early Ibexian or Tremadocian) family of Proetida, based on comparisons of hystricurid larvae with younger proetide and Cambrian ptychopariide larvae. The hystricurid larvae share a fusiform glabella falling short of the anterior margin with other proetide larvae, which were derived from Cambrian ptychopariide larvae with a forward-expanding glabella. Two discrete morphotypes of hystricurid larvae are recognized. The first type is characterized by the development of a pattern of regularly distributed tubercles on the shield and the presence of a preglabellar field. The second is characterized by the presence of glabellar furrows (discontinuous or transglabellar), an indented posterior margin, and a lack of tuberculation. Each of these hystricurid lineages represented by a distinct larval morphotype is considered ancestral (or sistergroup) to a different group of younger proetides. The second larval morphotype is considered a phylogenetic intermediate between the first type and ptychopariide larvae. Several larval features of these primitive proetides are considered to have originated by early onset of post-larval features of the ptychopariides (peramorphic pattern).Newly described hystricurid species areHystricurusn. sp. A,Hystricurus? sp. A,Hystricurus? sp. B, ‘Paraplethopeltis’ n. sp. A, ‘Paraplethopeltis’ sp. B, andHyperbolochiluscf.marginauctum.

Kin recognition and cannibalism in spadefoot toad tadpoles

Abstract. Tadpoles of spadefoot toads, Scaphiopus bombifrons, are polymorphic in nature: juveniles that feed on detritus develop into herbivorous omnivores, while those that feed on fairy shrimp sometimes become carnivores that are cannibalistic. The kin recognition abilities of both larval morphotypes were studied. In laboratory tests, omnivores preferentially associated with siblings, while carnivores from the same clutch preferentially associated with non-siblings. In follow-up studies, carnivorous tadpoles were observed to nip at conspecifics, and then either eat them, if they were non-siblings, or release them unharmed, if they were siblings. Carnivores became less selective when hungry, demonstrating that their level of kin discrimination was context-dependent. Three evolutionary hypotheses for avoidance of siblings by the carnivore morph were considered; of these, the most likely is that such behaviour resulted from kin selection.