Larval Characters Research Articles

Redescription of the subgenus Securiops Jacobus, McCafferty & Gattolliat 2006 (Ephemeroptera, Baetidae, Procloeon Bengtsson 1915).

The taxon Securiops Jacobus, McCafferty& Gattolliat 2006 is treated here as a subgenus of the genus Procloeon Bengtsson 1915; it shares all characters of Procloeon s.l. and besides them, has peculiar autapomorphies in mouthparts structure. Diagnoses of Cloeon/fg1 (or the tribe Cloeonini sensu Kluge 2016), Procloeon/g1 (or the genus Procloeon sensu Kluge 2016) and Securiops are given. Larvae of the South African species Procloeon (Securiops) falcatum (Crass 1947) comb. n. are described for the first time. Based on reared specimens from Zambia, larvae of Procloeon (Securiops) macafertiorum Lugo-Ortiz (in Lugo-Ortiz & McCafferty) 1996 are redescribed; subimagines, imagines and eggs of this species are described for the first time. New larval characters of Procloeon (Securiops) mutadens (Jacobus et al. 2006) comb. n. are reported based on a larva from Gambia. Based on reared specimens from Thailand, larvae of Procloeon (Securiops) primasia (Kaltenbach et al. 2023) comb. n. are redescribed; subimagines, imagines and well-developed eggs of this species are described for the first time. Genitalia of Cheleocloeon excisum (Barnard 1932) are figured for the first time.

Description of immature stages of Cephitinea colonella (Erschoff, 1874) (Lepidoptera: Tineidae: Myrmecozelinae)

Cephitinea colonella (Erschoff, 1874) (Lepidoptera: Tineidae: Myrmecozelinae) is known as a pest of stored products. However, detailed information on its life history is poor. In the present investigation, larvae of this species feeding on the rice bran were found in a rice mill. In order to make possible the correct identification of the immature stages of C.colonella, their morphology is described and illustrated. In addition, the larval character of the genus is morphologically discussed comparing from allied species.

Larval features of the Italian endemic Pyrochroa serraticornis kiesenwetteri Fairmaire, 1849 (Coleoptera: Pyrochroidae: Pyrochroinae) solve taxonomic uncertainties.

Recent findings rearranged the taxonomy of the European species of the genus Pyrochroa Geoffroy (Coleoptera: Pyrochroidae), and to date three species are recognized: P. bifoveata Molfini et al., 2022 and P. coccinea (Linnaeus, 1761) with cryptic adults and distinctive larvae, and the polytypic P. serraticornis (Scopoli, 1763), including the subspecies kiesenwetteri Fairmaire, 1849. Incongruences between molecular and morphological analyses questioned the recognition of P. s. serraticornis and P. s. kiesenwetteri as taxa of the same species. In the present paper, observations of larval characters of P. s. kiesenwetteri confirm this taxon as a subspecies of P. serraticornis. Moreover, new characters of P. s. serraticornis larvae are offered by analysing specimens from a new European locality.

Revision of the enigmatic South African Cryptolaryngini (Coleoptera, Curculionidae), with description of a new genus and twenty-two new species

The weevil genus Cryptolarynx Van Schalkwyk, 1966 is endemic to the Northern and Western Cape provinces of South Africa. The two previously known species of the genus, C. vitis (Marshall, 1957) and C. estriatus (Marshall, 1957), have an aberrant globular body and head shape, which has made it difficult to place the genus into the classification systems of the Curculionoidea. This paper presents the description of 21 new species of Cryptolarynx from South Africa (C. subglaber Haran sp. nov., C. squamulatus Haran sp. nov., C. muellerae Haran sp. nov., C. hirtulus Haran sp. nov., C. robustus Haran sp. nov., C. namaquanus Haran sp. nov., C. carinatus Haran sp. nov., C. variabilis Haran sp. nov., C. pyrophilus Haran sp. nov., C. pilipes Haran sp. nov., C. armatus Haran sp. nov., C. falciformis Haran sp. nov., C. oberprieleri Haran sp. nov., C. spinicornis Haran sp. nov., C. cederbergensis Haran sp. nov., C. homaroides Haran sp. nov., C. marshalli Haran sp. nov., C. endroedyi Haran sp. nov., C. oberlanderi Haran sp. nov., C. san Haran sp. nov., and C. luteipennis Haran sp. nov.) and of one new genus and species, Hadrocryptolarynx major Haran gen. et sp. nov., also from South Africa. A redescription of the genus Cryptolarynx is provided to incorporate the characters of the new species. The plant genus Oxalis (Oxalidaceae) is recorded as larval host for several species of Cryptolarynx and for Hadrocryptolarynx Haran gen. nov., as their larvae develop in the subterranean bulbs of members of the genus, and the egg, larva and pupa of C. variabilis are described. The characters of the Cryptolarynx larva confirm that Cryptolaryngini are an early-diverging group of Curculionidae, with a placement among taxa currently classified in the subfamily Brachycerinae sensu lato, and although their exact taxonomic position remains unresolved, some larval characters, and also pupal ones, suggest a close relationship between Cryptolaryngini and Stenopelmus Schoenherr. Potential use of species of Cryptolarynx in the biological control of weedy South African species of Oxalis is discussed.

Morphological redescription of Simulium takahasii (Rubtsov), the first species of the subgenus Wilhelmia Enderlein (Diptera: Simuliidae) recognized in East Asia.

Simulium takahasii (Rubtsov), which was originally described from Japan, and recorded from Korea and China, is the first among the 19 species of the subgenus Wilhelmia Enderlein recorded from East Asia. It is striking in mating, blood-feeding and ovipositing in captivity and in experimentally transmitting Dirofilaria immitis (Leidy) and Brugia pahangi (Buckley & Edeson), and it is a severe biter of cattle and horses, rarely of humans. Nevertheless, updated information about its morphological characteristics was lacking, making comparisons with related species described from China difficult, since species of the subgenus Wilhelmia are almost indistinguishable from one another, in particular, in their female terminalia, male genitalia and most of larval features. In this study, as many morphological characteristics as possible of S. takahasii based on specimens from Japan are redescribed. New information about many features of this species including the length of the female sensory vesicle against the third palpal segment, number of male upper-eye (large) facets, arrangement of the eight pupal gill filaments, presence or absence of tiny dark setae on the dorsum of the larval abdomen and the number of rows and hooklets of the larval posterior circlet will be useful in evaluating the species status of several Wilhelmia species in China including the species regarded as S. takahasii.

Morphology of the early larval stages of Lysmata ankeri Rhyne & Lin, 2006 and Lysmata bahia Rhyne & Lin, 2006 (Caridea: Lysmatidae) and a review of the larval morphology of the early Lysmata stages.

The early larval stages of the shrimps Lysmata ankeri and L. bahia were described, illustrated, and compared among other Lysmata species, providing important information on post-embryonic development and insights into its evolutionary history. Ovigerous specimens of L. ankeri and L. bahia were sampled from southeastern and northeastern Brazilian coast, respectively. For L. ankeri and L. bahia, five and three larval stages were obtained, respectively. Unique features were observed for L. ankeri and L. bahia larvae, and some characteristics may differ only for L. ankeri and L. bahia, which were not observed in the other species analyzed, such as: presence of a pair of simple setae on the third pleonal somite in zoea I and number of setae on the uropod exopod greater than 11. Moreover, several other features are similar between species from the diferent clades of the Lysmata-Exhippolysmata complex, making it possible to identify the early stages of Lysmata larvae. However, future studies will be essential to confirm or not the existence of some phylogenetic patterns and their relevance and other larval characters for better understanding the evolutionary history of this group.

A Juvenile of Rhinopias cf. argoliba (Scorpaenidae) from the Tropical Western Pacific

A juvenile of Rhinopias cf. argoliba 28 mm SL collected in the western part of the Pacific Ocean eastward of the Philippines is described. It is characterized by an incomplete metamorphosis with some larval characters retained such as the developed spination and relatively straight dorsal contour of the head, absence of the scales and the branched fin rays (except in pelvic fins), and a long penultimate dorsal-fin spine. Comparison of this juvenile with juveniles of R. aphanes 11–22 mm SL reveals the diagnostic importance of the pigmentation of the pectoral fin which disappears in the adult fishes. A possible synonymy of the genera Rhinopias and Pogonoscorpius was repeatedly supposed by the former authors. The poorly-known Pogonoscorpius sechellensis retains the features characteristic for the species of Rhinopias from the earliest ontogenetic stages only, and probably represents a neotenic species of the latter genus.

Morphology of the larvae of Sandracottus femoralis Heller, 1934, and S. mixtus (Blanchard, 1843) and phylogenetic comparison with other known Aciliini (Coleoptera: Dytiscidae, Dytiscinae)

We describe the larvae of the diving-beetle genus Sandracottus Sharp, 1882 based on S. femoralis Heller, 1934 and S. mixtus (Blanchard, 1843). We include detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, terminal abdominal segment and urogomphi in order to discover useful characters for distinguishing Sandracottus larvae from those of other known Aciliini (Coleoptera: Dytiscidae, Dytiscinae). A provisional parsimony analysis based on larval characteristics of seven Aciliini species in four genera (Acilius Leach, 1817, Graphoderus Dejean, 1833, Sandracottus, Thermonectus Dejean, 1833) was conducted using the program TNT. A clade grouping Eretini and Aciliini stands out as the most strongly supported in this analysis. The tribe Aciliini finds itself monophyletic with also very good support. Our analysis, however, failed to depict any clear phylogenetic relationships within the Aciliini although each of the four genera studied emerged from our study as morphologically distinct.

Direct development or endotrophic tadpole? Morphological aspects of the early ontogeny of the plump toad Osornophryne occidentalis (Anura: Bufonidae).

Andean Toads of the genus Osornophryne are suspected to have direct development on the basis of clutch and egg features. In this work, we describe the morphology of Osornophryne occidentalis embryos from a nest collected in the field. Several traits are similar to those reported in brachycephaloid Eleutherodactylus coqui and other direct-developing lineages. These include the pattern of formation of the body wall and the absence of oral and buccopharyngeal structures. Other features indicate the retention of ancestral larval characters. The development of forelimbs occurs in part within the operculum as in species with biphasic ontogeny; this has been reported in other direct-developing species, and is similar to what is described in African viviparous bufonids. This salient feature, along with the long, low-finned tail and the long and folded intestine early differentiated, gives these embryos a rather tadpole-like appearance. Our data confirm that development in O. occidentalis occurs within terrestrial eggs until advanced stages, and this would satisfy current definitions of direct development. At the same time, morphological differences regarding other species with comparable breeding reinforce interpretations about the wide anatomical and ontogenetic variations associated with endotrophic nutrition.

Exceptional features of the embryonic ontogeny of a direct‐developing Robber frog

AbstractIn frogs, the loss of the free‐living tadpole stage implies deep transformations in morphology and development, and the result is a combination of traits exclusive to direct development with the reduction or absence of typically larval features. Two traits stand out in terraranans, a mostly Neotropical clade with ca. 1200 species known or suspected to have direct development: (1) the development of forelimbs, which unlike in tadpoles and in several unrelated direct‐developing lineages, in this clade is described to occur completely exposed during ontogeny, and (2) the reduction of gills and their physiological replacement by highly vascularized tails for gas exchange. In this contribution, we report unusual aspects of the embryonic ontogeny in the Confused Robber frog Oreobates berdemenos, which complicate the interpretation of morphological diversity in Terrarana and in direct‐developing frogs in general. First, forelimbs develop initially entirely concealed by a larval operculum. Second, tail fins develop dorsal and ventral to the tail muscular core but their arrangement changes to lateral during ontogeny. Third, the expansion of the tail fins appears to be a plastic character whose variation likely responds to individual conditions of humidity and/or oxygenation of each egg within the clutch. Finally, we report cells with the morphology of hatching gland cells in the rostral region of embryos at stages about to hatch. If not vestigial, these cells could assist the egg tooth, which is characteristic of terraranans, with chemical softening of the egg capsules during hatching.

Cryptic diversity in endoparasitic isopods (Bopyroidea: Entoniscidae) from mud crabs (Panopeidae) along the Atlantic coast of North America, with the description of a new genus and new species as revealed by molecular and larval characters: the long and the short of it

AbstractAlthough intertidal crabs from the western Atlantic coast are relatively well studied for some parasite fauna, their parasitic isopods are poorly known. We document two endoparasitic entoniscids (Cancrion carolinusPearse & Walker, 1939 and Cryptocancrion brevibrachiumn. gen., n. sp.) from mud (Brachyura: Panopeidae) and stone (Brachyura: Menippidae) crabs based on molecular and morphological data, including descriptions of their epicaridium larvae. Although these species cannot be distinguished based on adult female characters, molecular data and larval and male morphologies show that two species are present, sometimes sympatrically. The only other species of CancrionGiard & Bonnier, 1887 from the Atlantic coast of North America is Cancrion needleriPearse & Walker, 1939, described from adult specimens parasitizing Dyspanopeus sayi (Smith, 1869) from Prince Edward Island, Canada. Larvae of this species were never described and we consider it a species inquirenda. Cryptocancrion brevibrachiumn. gen., n. sp. is documented to have epicaridium larvae with a “short-armed” morphology (sixth pereopod subequal in length to pereopods 1–5), and the adults parasitize at least three mud crabs: D. sayi, Panopeus herbstiiH. Milne Edwards, 1834, and Rhithropanopeus harrisii (Gould, 1841). By contrast, Cancrion carolinus (originally described from P. herbstii collected in Beaufort, NC, USA) has epicaridium larvae with a “long-armed” morphology (sixth pereopod approximately twice the length of pereopods 1–5) and is found in at least four host species: Eurypanopeus depressus (Smith, 1869), P. herbstii, and R. harrisii and the stone crab Menippe mercenaria (Say, 1818). We describe C. brevibrachiumn. gen., n. sp. and redescribe C. carolinus based on type material and fresh specimens. The cryptic nature of these entoniscids indicates that examination of epicaridium larvae and/or molecular data are needed to properly identify species.

Cephalic anatomy highlights morphological adaptation to underground habitats in a minute lacewing larva of Dilar (Dilaridae) and conflicting phylogenetic signal in Neuroptera.

Dilaridae are a distinctive and phylogenetically ambiguous neuropteran family. So far, the anatomy of the immature stages remains largely unknown. We examined the 1st instar larvae of Dilar montanus in detail and present results of live observations for the first time. The minute, cryptic larvae display features correlated with their underground lifestyle: for instance, a strongly flattened head, stout antennae, eyelessness, and burrowing forelegs. In contrast to molecular data, several characters suggest a 'dilarid clade' combining Dilaridae with Mantispoidea, for instance a very thin and curved or reduced tentorial bridge, and an elongated postmentum. We found intrinsic antennal muscles and Johnston's organ, the first record of these structures in holometabolous larvae. This proves that the first 2 larval antennomeres are homologous with the scapus and pedicellus. The described characters are discussed and analyzed with an updated matrix of neuropteran larval characters. Alternative scenarios of character evolution are presented. Additionally, we show how the 1st-instar larvae move and feed in the substrate, and also provide a high-resolution video recording of the function of the elongate tubular ovipositor and the egg-laying behavior in an adult female under natural conditions.

The little-known larval morphology of two stoneflies of Styloperlidae (Insecta: Plecoptera) in China

The stoneflies are a relatively ancient group of aquatic insects. The larvae of stoneflies are exclusively aquatic and are important bioindicators for water quality changes. However, the identification and classification of stonefly larvae are much more difficult than the adults, due to the lack of sufficient descriptions for most stonefly taxa. Styloperlidae is an endemic stonefly family in South Asia. The larval morphology of this family remains less clear in comparison with their adults. In this paper, the larvae of Styloperla inae Chao, 1947 and Cerconychia flectospina Wu, 1962 are described and illustrated based on specimens from China. Their morphology corresponds with the proposed diagnostic larval characters of Styloperlidae in previous studies. Additional auxiliary characters useful for the identification of larvae in Styloperlidae are discussed. The larvae of S. inae and C. flectospina exhibit subtle morphological differences but can be easily distinguished by the presence or absence of dark sclerites on all the thoracic sternal pits.

Xenos vesparum(Strepsiptera: Xenidae)—A New Insect Model and Its Endoparasitic Secondary Larva

AbstractXenos vesparum of the highly specialized Strepsiptera is a new insect model in the context of host-parasite relationships. The endoparasitic female and male secondary larvae were studied using µCT, 3D-reconstructions, histology, and photomicrography. The infectious primary larva is followed by a trophic and endoparasitic secondary larval stage. In contrast to immature stages of other holometabolous groups, the second instar increases dramatically in size. Compound eyes and external wing anlagen are present in male larvae before the pupal stage. In contrast to the females, the brain of males bears well-developed optic neuropils and retinula cells are present. The cephalothorax is comparatively simple in the female larvae, yet distinctly more complex than in the adult, where most muscles are reduced. Large testes are present in male larvae and numerous oocytes in the females, but they are still immature. The larval features are discussed in the context of holome­tabolous development and heterochronic processes. Unique features of Strepsiptera are the early differentiation of the sexes and the occurrence of compound eyes and external wing anlagen in male secondary larvae. The phylogenetic position of Strepsiptera suggests that this is a secondary feature and thus an autapomorphy. To address mature females of Stylopidia as neotenic adults is an oversimplification. They display a mosaic pattern of paedomorphic characters such as features of the nervous system and the presence of stemmata, but also non-paedomorphic structures, such as the spiracles.

A widespread new genus of Baetidae (Baetidae, Ephemeroptera) from Southeast Asia.

A reinvestigation of type and other material of Baetisjavanicus Ulmer, 1913 and Baetissabahensis Müller-Liebenau, 1984, together with new material from Southeast Asia revealed a new genus, Branchiobaetis gen. nov. The above species are formally assigned to the new genus Branchiobaetis gen. nov. It is characterized by the presence of accessory gills ventrally near fore coxa and at the base of maxillae, a peculiar folding of the gonostyli developing under the cuticle of last instar male larvae, together with a unique combination of other larval characters. Besides the two formerly described species, five new species are identified using a combination of morphology and molecular characters (COI, Kimura 2-parameter distances), four species from Sumatra and one from the Philippines. They are described and illustrated at the larval stage. Additionally, a complementary description of larva and adult stages of the generic type species B.javanicus comb. nov. as well as the first description of the eggs are provided. Furthermore, new reports of B.javanicus comb. nov. and B.sabahensis comb. nov. are indicated. The distribution of Branchiobaetis gen. nov. includes the Indonesian Sunda Islands, Borneo, and the Philippines. A key to the larval stage of all species is provided.

Larval morphology of the Madagascan endemic diving beetle genus Hovahydrus Biström, 1982 (Coleoptera: Dytiscidae) and phylogenetic comparison with other known Hyphydrini

We describe for the first time the instar III larva of the diving beetle genus Hovahydrus Biström, 1982, based on H. praetextus (Guignot, 1951) and a new species yet to be described (identified here as Hovahydrus sp. near H. minutissimus (Régimbart, 1903)). We include detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi in order to discover useful characters for distinguishing Hovahydrus larvae from those of other known Hyphydrini (Coleoptera: Dytiscidae, Hydroporinae). A provisional parsimony analysis based on larval characteristics of 11 Hyphydrini species in eight genera was conducted using the program TNT. Larval morphology supports a close relationship between Hovahydrus, Hyphydrus Illiger, 1802, and the endemic South Africa genera Andex Sharp, 1882, Coelhydrus Sharp, 1882, Darwinhydrus Sharp, 1882 and Primospes Sharp, 1882.

Filling gaps in the life history of the snapping shrimp Alpheus petronioi: morphology of the first post-embryonic stages reared in laboratory

ABSTRACT Larval characteristics play an important role in life history, phylogenetic and systematic studies. The morphology of the first post-embryonic stages (zoeae I–III) of the snapping shrimp Alpheus petronioi were described in detail and illustrated based on laboratory-hatched larvae. The morphological characteristics of the species were compared with available descriptions of other Alpheus species with known first zoeal stages. We provided a combination of characteristics useful for the diagnosis of the early zoeal stages of A. petronioi. The species can be separated from the first zoeal stage of the other species of the genus using the following structures: basial endite of maxillule with 2 stout spines (both without rows of spinules), and 2 small plumose setae; endopod of maxillule with 1 terminal denticulate seta, 1 short terminal simple seta and 1 subterminal spine; basial endite of maxilla bilobed, with 4 and 5 simple setae on proximal and distal lobe, respectively and basis of second maxilliped with 5 (3 strong and 2 slender) simple setae arranged (2 + 2 + 1). This is the first study on the biology of A. petronioi after its description, adding new information on its life history.

Knockdown of Ecdysone-Induced Protein 93F Causes Abnormal Pupae and Adults in the Eggplant Lady Beetle.

Ecdysone-induced protein 93F (E93) plays triple roles during post-embryonic development in insects whose juvenile instars are more than four. However, it only acts as a specifier of adult structures in Drosophila flies whose larval instars are fixed at three. In this study, we determined the functions of E93 in the eggplant lady beetle (Henosepilachna vigintioctopunctata), which has four larval instars. We uncovered that E93 was abundantly expressed at the prepupal and pupal stages. A precocious inhibition of the juvenile hormone signal by RNA interference (RNAi) of HvKr-h1 or HvHairy, two vital downstream developmental effectors, at the penultimate instar larval stage increased the expression of E93, Conversely, ingestion of JH by the third-instar larvae stimulated the expression of HvKr-h1 but repressed the transcription of either HvE93X1 or HvE93X2. However, disturbance of the JH signal neither drove premature metamorphosis nor caused supernumerary instars. In contrast, depletion of E93 at the third- and fourth-instar larval and prepupal stages severely impaired pupation and caused a larval-pupal mixed phenotype: pupal spines and larval scoli were simultaneously presented on the cuticle. RNAi of E93 at the pupal stage affected adult eclosion. When the beetles had suffered from a dsE93 injection at the fourth-instar larval and pupal stages, a few resultant adults emerged, with separated elytra, abnormally folded hindwings, a small body size and short appendages. Taken together, our results suggest the larval instars are fixed in H. vigintioctopunctata; E93 serves as a repressor of larval characters and a specifier of adult structures during the larval-pupal-adult transition.

Life-history traits in the Pacific oysterCrassostrea gigasare robust to ocean acidification under two thermal regimes

AbstractOcean acidification and warming (OAW) are pressing contemporary issues affecting marine life and specifically calcifying organisms. Here, we investigated the direct effects of OAW on life-history traits of the Pacific oyster Crassostrea gigas, the most cultivated bivalve species worldwide. We also tested whether parental conditioning history shaped the phenotypic characters of their progenies (intergenerational carryover effects). Adult oysters and their offspring were exposed to two temperatures (18°C, +3°C) under ambient pH conditions or under an end-of-century acidification scenario (−0.33 pH unit). In adults, we monitored standard biometric and reproductive parameters, stress response by quantifying neuroendocrine metabolites and gamete quality. In larvae, we measured hatching rate, size, biochemical quality, and behavior. We found that reducing pH reduced growth rate and activated the serotonin system, but increasing temperature attenuated these effects. There was no effect of pH on reproduction at either temperature, and no intergenerational carryover effects. Larval characteristics were similar between treatments, regardless of parental conditioning history. Thus, the Pacific oyster seems robust to changes in pH, and increasing temperature is not an aggravating factor. We emphasize that the use of neuroendocrine indicators holds promise for revealing sublethal impacts of environmental changes.

Description of the immature and mature larvae of Bocchus scobiolae Nagy (Hymenoptera: Dryinidae)

The last immature instar and the mature larva of Bocchus scobiolae are described and illustrated for the first time. The affinities of both immature and mature larvae of Bocchus scobiolae and Mystrophorus formicaeformis are discussed to define larval characters of the subfamily Bocchinae.