Larval Characters Research Articles

Genetic diversity in the Diplosoma listerianum complex (Ascidiacea: Didemnidae) from the Western Atlantic

(Received 19 January 2021; revised 27 September 2021; accepted 27 September 2021) Diplosoma listerianum has been re-described with more than 40 currently invalid names, but recent data suggests that some of those names may be valid. At least four distinct clades were recently revealed by molecular analysis using mitochondrial DNA (mtDNA). Yet, very few samples were analyzed from the western Atlantic, of which none were from the extensive Brazilian coast. Here, we analyze genetic diversity in D. listerianum in light of morphological data. We sequenced 55 samples from Brazil, Panama, Mexico, and the United States and analyzed them together with published data, to test whether local populations are part of widespread, known, clades or are native species hidden within this complex. Phylogenetic analysis found eight clades, three of which were different from the ones recovered before. Former clade A was split into two larger clades: clade A1 occurs in the western Atlantic, on the Pacific side of Panama and in South Africa; clade A2 occurs worldwide, with representatives found on every continent. Species delimitation analyses (ABGD, bPTP and GMYC) found 16 MOTUs, which suggests that those large clades are very diverse and may comprise more than one species. Diversity was greatest in Panama (6 clades) and Mexico (3 clades). Larval morphological characters were examined and described here. However, for only a few of the sequenced samples could fully grown larvae be obtained and phenotypic variation was large. Thus, larval morphology could not be used to diagnose molecular clades. Diplosoma listerianum remains a species complex, with evidence of ongoing speciation, and high genetic diversity, especially in the tropical western Atlantic. Fast-growing colonies, rapid life cycles, and amenability to cultivation in the laboratory indicate that this species can be a model for studies in speciation.

Oxidative Stress Parameters in Goitrogen-Exposed Crested Newt Larvae (Triturus spp.): Arrested Metamorphosis.

Thiourea is an established disruptor of thyroid hormone synthesis and is frequently used as an inhibitor of metamorphosis. The changes caused by thiourea can affect processes associated with the oxidative status of individuals (metabolic rate, the HPI axis, antioxidant system). We investigated the parameters of oxidative stress in crested newt (Triturus spp.) larvae during normal development in late larval stage 62 and newly metamorphosed individuals, and during thiourea-stimulated metamorphosis arrest in individuals exposed to low (0.05%) and high (0.1%) concentrations of thiourea. Both groups of crested newts exposed to thiourea retained their larval characteristics until the end of the experiment. The low activities of antioxidant enzymes and the high lipid peroxidation level pointed to increased oxidative stress in larvae at the beginning of stage 62 as compared to fully metamorphosed individuals. The activities of catalase (CAT) and glutathione-S-transferase (GST) and the concentration of sulfhydryl (SH) groups were significantly lower in larvae reared in aqueous solutions containing thiourea than in newly metamorphosed individuals. The high thiourea concentration (0.1%) affected the antioxidative parameters to the extent that oxidative damage could not be avoided, contrary to a lower concentration. Our results provide a first insight into the physiological adaptations of crested newts during normal development and simulated metamorphosis arrest.

Larval morphology of Ilybiosoma Crotch, 1873 (Coleoptera: Dytiscidae: Agabinae): description of five Nearctic species with phylogenetic considerations

The larvae of five Nearctic species of Ilybiosoma Crotch, 1873, I. bjorkmanae (Hatch, 1939), I. lugens (LeConte, 1852), I. minnesotensis (Wallis, 1933), I. pandurus (Leech, 1942), and I. regularis (LeConte, 1852) are described for the first time including a detailed chaetotaxy analysis of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi. A provisional parsimony analysis based on 55 informative larval characteristics of 18 species in seven genera of the subfamily Agabinae was conducted using the program TNT. The larvae of the five Ilybiosoma species described were found to be fairly similar morphologically. Compared to the other species of Agabinae studied, larvae of Ilybiosoma stand out from most Agabini by the presence of the strongly emarginated siphon, which are reminiscent of the condition observed in Hydrotrupes Sharp, 1882 and Platynectes Régimbart, 1879.

Morphological comparison between the first-instar larvae of the scorpionflies Panorpa kunmingensis and P. changbaishana (Mecoptera: Panorpidae)

The first-instar larvae of the scorpionflies Panorpa kunmingensis Fu & Hua, 2009 and Panorpa changbaishana Hua in Hou & Hua, 2008 were compared using scanning electron microscopy. The larvae of both species are eruciform and similar in gross morphology, each bearing three pairs of thoracic legs and eight pairs of abdominal prolegs. The head is more flattened and widened in P. changbaishana than in P. kunmingensis. Cephalic setae are mostly setiform in P. kunmingensis, but are apically expanded in some setae of P. changbaishana. Annulated processes are more prominent in P. changbaishana than in P. kunmingensis. The potential value of larval characters in phylogenetic analyses is briefly discussed in the Panorpidae.

Embryo and larval biology of the deep-sea octocoral Dentomuricea aff. meteor under different temperature regimes.

Deep-sea octocorals are common habitat-formers in deep-sea ecosystems, however, our knowledge on their early life history stages is extremely limited. The present study focuses on the early life history of the species Dentomuricea aff. meteor, a common deep-sea octocoral in the Azores. The objective was to describe the embryo and larval biology of the target species under two temperature regimes, corresponding to the minimum and maximum temperatures in its natural environment during the spawning season. At temperature of 13 ±0.5 °C, embryos of the species reached the planula stage after 96h and displayed a median survival of 11 days. Planulae displayed swimming only after stimulation, swimming speed was 0.24 ±0.16 mm s−1 and increased slightly but significantly with time. Under a higher temperature (15 °C ±0.5 °C) embryos reached the planula stage 24 h earlier (after 72 h), displayed a median survival of 16 days and had significantly higher swimming speed (0.3 ±0.27 mm s−1). Although the differences in survival were not statistically significant, our results highlight how small changes in temperature can affect embryo and larval characteristics with potential cascading effects in larval dispersal and success. In both temperatures, settlement rates were low and metamorphosis occurred even without settlement. Such information is rarely available for deep-sea corals, although essential to achieve a better understanding of dispersal, connectivity and biogeographical patterns of benthic species.

Egg lipid and thiamine vary between early and late spawning lake sturgeon

Nutritional deficiency associated with reduced thiamine (vitamin B1) and reduced natural reproduction of salmonid species in the Great Lake Region is well established. The negative relationship between egg thiamine and lipid concentration to post-hatch larval growth and survival in teleost species, coupled with the limited research of egg thiamine in Acipenseriform species of conservation concern, including lake sturgeon, indicates that study of thiamine concentrations lake sturgeon eggs is warranted. Eggs were collected from females (N = 12) during the early and late portion of the spawning run in 2007 in a wild population from Black Lake, MI. Concentrations of thiamine, lipid and fatty acid concentration were measured along with female biological information (body size and egg size) and characteristics of larvae at hatch. Significant differences in egg thiamine concentrations were observed between early- and late-spawning females (mean ± SD: 2.36 nmol·g−1 ± 1.09 vs. 0.73 ± 0.25 nmol·g−1, W = 0.05, p < .01). No significant relationships were observed between female body size or egg size and egg lipid or thiamine concentration. Differences in lipid and thiamine concentrations were not predictive of larval body size or yolk sac volume at hatch. Total and phosphorylated thiamine were correlated with n-3 polyunsaturated fatty acids, suggesting that dietary items were likely partially responsible for provisioning of essential compounds. Given the negative effects of low egg thiamine concentration on larval survival in other fish species globally, results indicate that further research in areas of nutrient acquisition and thiamine effects on larval survival, natural recruitment, and hatchery feeding strategies is warranted for lake sturgeon.

The preimaginal stages of Galerita ruficollis Dejean, 1825 and the position of the tribe Galeritini in the classification of ground beetles (Coleoptera, Carabidae).

The complete development cycle of Galerita (Galerita) ruficollis Dejean, 1825 was studied for the first time. In laboratory, at a temperature of 22 °C and long-day conditions, the development from egg to adult lasted 58–60 days. The development of the third instar larva lasted particularly long (on average, 19 days), and the most intense increase in biomass (from 20 to 100 mg) was observed at that phase as well. The extended embryonic development (11–20 days) and the relatively short development time of the third instar larva were found to be characteristic of G. ruficollis. The bifurcated protrusion of the anterior edge of the head was proven to represent an outgrowth of the frontal sclerite (frontale), but not of the nasale, as believed previously. The chaetotaxy of Galerita larvae is described in detail for the first time.Based on larval features, the monophyly of the Galeritini + Dryptini group is confirmed. Based on the morphology of the larvae and pupae, this group can be suggested as occupying a separate position within the Truncatipennia, possibly being related to the assemblage that includes Pterostichini, Harpalini, Licinini, Chlaenini, and Platynini. The monophyly of Zuphiitae (sensu Erwin and Sims 1984; Erwin 1985) and the Zuphiitae clade (sensu Ober and Maddison 2008) is confirmed.

A new species of Ephoron Williamson, 1802 (Ephemeroptera: Polymitarcyidae) from Thailand.

The genus Ephoron Williamson, 1802 is widely distributed around the world. In Thailand, only Ephoron indicus Pictet, 1843 was reported in 1961. In this study, a new Ephoron mayfly is described as Ephoron ookaewae sp. nov. In this new species description, the morphological characteristics of larvae and eggs in addition to adults are also shown in detail. Number of tubercles on mandibular tusks, and a median frontal process in larvae, distinguish Ephoron ookaewae sp. nov. from other Ephoron species. Their polar cap shape and a concave indentation in their eggs are also unusual. In addition, the mitochondrial DNA COI sequence data of the newly described Ephoron ookaewae sp. nov. is registered in GenBank. Registration of sequence data for the DNA barcode region of Ephoron mayflies inhabiting the Oriental region remains limited, however it will be useful for future research.

Alypiodes flavilinguis Grote, 1883 as a Valid Species (Noctuidae, Agaristinae)

Alypiodes Grote currently includes four recognized species of day-flying agaristine noctuids from Mexico and the American Southwest. Here we add a fifth, elevating the name Alypiodes flavilinguisGrote 1883rev. status from synonymy. DNA barcodes, larval characters, and adult markings that reliably differentiate Alypiodes flavilinguis from Alypiodes bimaculata and other species in the genus are enumerated. Adults, including their male and female genitalia, and the larvae are illustrated for both species.

A Revised Description of the Larva of Leptocerina pauliani (Ross 1957 (Trichoptera: Leptoceridae), an Endemic Species of La Réunion Island.

Leptocerina is an endemic Afrotropical genus of Trichoptera, with 19 species documented but only five partially described at the larval stage. The first description of Leptocerina pauliani (Ross 1957) larva by Marlier Marlier (1982) included very few illustrations, making comparisons with other species challenging. I present a revised description of the L. pauliani larval stage, using specimens collected from the River Marsouins in La Réunion Island. I apply a focus stacking approach for emphasizing coloration patterns and providing a detailed description of larval characters. Criteria for distinguishing L. pauliani from the other species of Leptocerina already described or partially described for the larval stage are discussed.

Larval features illuminating adult taxonomy? Case study in the European cardinal beetle species of the genus Pyrochroa (Coleoptera: Pyrochroidae: Pyrochroinae).

Larvae of the two European species of the genus Pyrochroa (P. coccinea and P. serraticornis) are redescribed, for the first time based on Italian samples, and new relevant and distinctive characters have emerged from P. serraticornis. Particularly, the presence of a single urogomphal pit between urogomphi (representing a new condition for the entire family), and new characters of mandibles, open new questions about the current taxonomic status of the European species.

Reproduction and early life stages of the poecilosclerid sponge Crella incrustans

AbstractDespite their important ecological roles in marine ecosystems, reproduction and early life stages of the majority of marine sponges remain undescribed. Here we characterize the mode of reproduction and the early life stages of an abundant sponge in temperate Pacific waters, Crella incrustans. Through histology, we characterized the production of gametes and the sequential steps of larval ontogeny. Using in vivo observations, we described larval release, settlement, and metamorphosis. Specimens of C. incrustans presented spermatocytes, oocytes, and several developmental stages in the sponge mesohyl during the Australasian summer (from January to March 2020), demonstrating this sponge to be a simultaneous hermaphrodite with internal fertilization, asynchronous development, and brooded embryos. As in other viviparous demosponges, mature embryos were released during the Australasian summer as free‐swimming non‐tufted parenchymella larvae. Under laboratory conditions, 94.3% of larvae settled within 2 days and metamorphosed into functional settlers within a week. Gametogenesis, embryonic development, larval characteristics, settlement, and metamorphosis of C. incrustans are consistent with the reproductive features common to the majority of poecilosclerid sponges. Overall, our study provides important information on the early life stages of this temperate model species for future ecophysiological experiments.

Description of the mature larva of four species of the Australasian endemic genus Sternopriscus Sharp, 1882 (Coleoptera: Dytiscidae) with phylogenetic considerations

The instar III larvae of the Australian endemic species Sternopriscus alpinus Hendrich and Watts, 2004, S. clavatus Sharp, 1882, S. hansardii (Clark, 1862) and S. multimaculatus (Clark, 1862) are described and illustrated for the first time. We explore implications for understanding the evolution of larval morphological traits amongst selected Sternopriscina genera. A parsimony analysis based on 84 larval characteristics of 11 species in six genera was conducted using the program TNT. Larvae of Sternopriscus Sharp, 1882 are characterised by the last abdominal segment not extending into siphon and by very elongate urogomphi. Sternopriscus is subdivided into two groups based either on absence or reduction in number of natatory setae along the dorsal margin of femora, tibiae and tarsi. Sternopriscus is postulated to be sister to a clade comprised of Chostonectes Sharp, 1882, Megaporus Brinck, 1943 and Antiporus Sharp, 1882.

Molecular and morphological comparison of larvae and juveniles of five species of callionymids, with ontogenetic evidence on the monophyly of Repomucenus (Callionymidae)

Dragonet fishes (Callionymidae) are benthic inhabitants of shallow waters, even in tidal pools, down to depths below 900 m in all subtropical, tropical and temperate oceans. The family comprises 200 species in 20 genera worldwide, of which 18 species in 6 genera occur in Korea. Classification within the family Callionymidae has been controversial because of the differing proposals of Fricke and Nakabo (Fishes of Japan with pictorial keys to the species, 1983). For example, Fricke suggested genus Repomucenus and Bathycallionymus, whose genera contains most callionymid species in Korean waters, as junior synonym of genus Callionymus while Nakabo (Fishes of Japan with pictorial keys to the species, 1983) suggested as valid. In such cases, when classifications of adults have taxonomic contention, examination of larval characters may prove informative. Therefore, in this study, the authors conducted comprehensive molecular and morphological analyses on larvae and juveniles of five species in the genus Repomucenus and discussed their taxonomic status within the family Callionymidae. Larval and juvenile callionymids show high morphological similarities during their ontogenetic development. Nonetheless, the following morphological differences were observed in melanophore distribution and preopercular spine development: (a) stellate or punctate melanophores in Bathycallionymus kaianus vs. branched melanophores in genus Repomucenus, (b) melanophores on the abdominal cavity gradually disappearing in B. kaianus vs. gradually becoming prominent in Repomucenus and (c) preopercular spine development giving rise to one perpendicular spine in B. kaianus vs. two or three spines in Repomucenus. Molecular analysis based on 16S ribosomal RNA showed similar results to the morphological analysis. Genera Bathycallionymus and Repomucenus showed significant genetic distance (d=0.113-0.120); moreover, genus Callionymus, which was suggested as a senior synonym of genus Bathycallionymus and Repomucenus by Fricke (Journal of Natural History, 2014, 48, 2419-2448), also showed considerable difference (d=0.226-0.246). In the present study, the monophyly of genus Repomucenus seemed well supported by the results of morphological and molecular analyses of larval stage Callionymidae.

Phylogenomic and morphological relationships among the botryllid ascidians (Subphylum Tunicata, Class Ascidiacea, Family Styelidae)

Ascidians (Phylum Chordata, Class Ascidiacea) are a large group of invertebrates which occupy a central role in the ecology of marine benthic communities. Many ascidian species have become successfully introduced around the world via anthropogenic vectors. The botryllid ascidians (Order Stolidobranchia, Family Styelidae) are a group of 53 colonial species, several of which are widespread throughout temperate or tropical and subtropical waters. However, the systematics and biology of this group of ascidians is not well-understood. To provide a systematic framework for this group, we have constructed a well-resolved phylogenomic tree using 200 novel loci and 55 specimens. A Principal Components Analysis of all species described in the literature using 31 taxonomic characteristics revealed that some species occupy a unique morphological space and can be easily identified using characteristics of adult colonies. For other species, additional information such as larval or life history characteristics may be required for taxonomic discrimination. Molecular barcodes are critical for guiding the delineation of morphologically similar species in this group.

A New, Morphologically Cryptic Species of Fanged Frog, Genus Limnonectes (Amphibia: Anura: Dicroglossidae), from Mindoro Island, Central Philippines

We describe a new species of fanged frog (genus Limnonectes) from Mindoro and Semirara Islands, of the Mindoro Pleistocene Aggregate Island Complex, of the central Philippines. Although morphologically indistinguishable from its closest relative, Limnonectes acanthi, of the Palawan faunal region, the two species can be readily diagnosed on the basis of spectral (dominant frequency) and temporal (pulse number and structure) properties of their advertisement calls, and their allopatric insular geographic ranges on permanently separate geological platforms which have not been connected by dry land in the recent geological past—all of which we interpret as congruent and independent lines of evidence supporting our recognition of two independently evolving evolutionary lineages (species). Ribosomal RNA mitochondrial gene sequences were used to provide genetic identification of specimens and estimate phylogenetic relationships; genetic divergences between Palawan and Mindoro faunal regions exceed those estimated among other, uncontroversial, phenotypically distinct Philippine species with equivalent levels of allopatry and biogeographic isolation. The recognition of the new species further emphasizes the degree to which even well-studied Philippine landmasses still harbor unrecognized biodiversity, and suggests that other widespread Philippine fanged frogs should be scrutinized for non-traditional diagnostic character differences (mate-recognition signal divergence, ecological differences, larval characteristics, life-history trait variation), especially when their geographic ranges span the archipelago's permanent, deep-water trenches, which define its well-characterized Pleistocene Aggregate Island Complexes.

Unique larval morphology of Prionochaeta opaca (Say, 1825) (Coleoptera: Leiodidae: Cholevinae: Cholevini), the only Nearctic representative of Cholevina

The first detailed description of the late-instar larva of Prionochaeta opaca (Say, 1825) is provided, with chaetotaxy, illustrations and photos. The single Nearctic representative of Cholevina and the only known larval stage of Prionochaeta Horn, 1880 is discussed and compared to other known larvae of Cholevini with special reference to its autapomorphic characters: pectinate tergal setae and four-segmented antenna. New data confirmed a mosaic distribution of larval characters within the subtribes Cholevina and Catopina and only one character supporting division into subtribes (mandibular prostheca), after excluding Cholevinus Reitter, 1901. The placement of Prionochaeta in the clade of Cholevina, based on larval morphological characters, is doubtful because of many characters unique to this larva, but the unusual prostheca (apically wide with minute spines) places them in this subtribe.

Morphological features of larvae of Drusus osogovicus Kumanski, 1980 (Insecta, Trichoptera) from the Republic of North Macedonia, DNA barcoding of the species and notes on its ecology and distribution

The Balkan endemic caddisfly species Drusus osogovicus Kumanski, 1980 that was previously known only from Bulgaria was recently reported from the Republic of North Macedonia as well. However, all data on the presence of the species included only adult specimens as the larval stage remained unknown. In the following study we present the first description of the larval stage of Drusus osogovicus based on morphological characters. In order to prove the conspecificity between the larvae and the adults, DNA barcoding of the specimens was also conducted. Furthermore, lists of the crucial diagnostic characters present only in D. osogovicus larvae as well as information on the distribution and ecological preferences of the species are also provided.

Regulatory Mechanisms Underlying the Differentiation of Neotenic Reproductives in Termites: Partial Release From Arrested Development

Eusocial insects exhibit reproductive division of labor, in which only a part of colony members differentiates into reproductives. In termite colonies, the division of labors is performed among multiple types of individuals (i.e., castes), such as reproductives, workers, and soldiers to organize their society. Caste differentiation occurs according to extrinsic factors, such as social interactions, leading to developmental modifications during postembryonic development, and consequently, the caste ratio in a colony is appropriately coordinated. In particular, when the current reproductives die or become senescent, some immature individuals molt into supplementary reproductives, also known as “neotenics,” that take over the reproductive task in their natal colony. Neotenics exhibit variety of larval features, such as winglessness, and thus, immature individuals are suggested to differentiate by a partial release from arrested development, particularly in the reproductive organs. These neotenic features, which have long been assumed to develop via heterochronic regulation, provide us opportunities to understand the developmental mechanisms and evolutionary origin of the novel caste. This article overviews the accumulated data on the physiological and developmental mechanisms that regulate the neotenic differentiation in termites. Furthermore, the evolutionary trajectories leading to neotenic differentiation are discussed, namely the acquisition of a regulatory mechanism that enable the partial release from a developmentally arrested state.

Review of East Palaearctic Elliptera (Diptera, Limoniidae) immatures with description of a new species

The genus Elliptera Schiner, 1863 is represented by ten species worldwide, but immatures of only the European species E. omissa Schiner has been described so far. Molecular methods were used to associate larvae and adults for two East Asian species from South Korea. Elliptera jacoti Alexander and E. zipanguensis zipanguensis Alexander are common species in aquatic, hygropetric habitats in mountainous parts of the Korean peninsula. Elliptera mongolica Podeniene, Podenas &amp;#38; Gelhaus sp. nov. from Mongolia and China (Inner Mongolia) is described based on mitochondrial DNA COI gene barcode sequences and morphological characters of larvae. Larvae of all three species and pupae of E. jacoti are described and illustrated. Morphological characters of the larvae useful for discrimination of species are given. An identification key for East Asian larvae of the genus Elliptera is compiled.