Juvenile Instars Research Articles

Description of juvenile instars of Scapheremaeus tonatiuh Palacios-Vargas, Ríos & Vázquez, 1998 (Acari, Oribatida, Cymbaeremaeidae)

The oribatid mite species Scapheremaeus tonatiuh (Oribatida, Cymbaeremaeidae) is recorded for the first time in the U.S.A. (initially described from Mexico). Its juvenile instars are described, based on materials collected from arboreal habitats in Florida, U.S.A. (Neotropical region). The larval instar is characterized by the presence of gastronotic setae с3, la, lm, lp long, lanceolate having setiform apex, and h1 very long, subflagellate; the nymphal instars are characterized by the presence of exuvial scalps, 12 pairs of gastronotic setae (da, dm, dp absent) of which setae с3, la, lm, lp, h1, h2 are long, phylliform but h3 is very long, subflagellate. The main morphological traits of the adult are summarized.

Ontogenetic instars of the oribatid mite Eupterotegaeus nortoni sp. nov. (Acari, Oribatida, Cepheusidae) from U.S.A.

A new species of the genus Eupterotegaeus (Oribatida, Cepheusidae) is described from the U.S.A., based on adult and juvenile instars. The revised generic diagnosis and an identification key to the known representatives of Eupterotegaeus are presented.

Juvenile instars of Sellnickia caudata (Michael, 1908) (Acari, Oribatida, Sellnickiidae)

Juvenile instars of Sellnickia caudata (Michael, 1908) are described, based on specimens collected from tree branches and leaves of Dipterocarpus alatus in Vietnam.

Ontogenetic instars of Basilobelba werneri Mahunka, 1982 (Acari, Oribatida, Basilobelbidae)

Basilobelba werneri (Oribatida, Basilobelbidae) was collected from an alpine cloud forest in Guatemala. This is the first representative of the family Basilobelbidae in the Guatemalan fauna. A supplementary description of adult B. werneri is presented along with summarized diagnostic morphological traits. The juvenile instars of B. werneri are described for the first time. The larva is characterized by the presence of 11 pairs of gastronotic setae, of which c1 (short), da and dm (medium-sized) slightly thickened, barbed, la, lm, lp, h1, and h2 long, thick, narrowed distally, heavily barbed, and c2, c3 and h3 short, setiform, roughened. The proto-, deuto- and tritonymph are characterized by the presence of 12 pairs of short, setiform gastronotic setae.

Variation in defensive spines across juvenile instars of Daphnia magna

Abstract Various species of freshwater zooplankton feature defensive spines, spikes or spinules across a comparatively wide size range. Among those is Daphnia magna, which has previously been found to express an enhanced spinescence in response to the predatory tadpole shrimp Triops cancriformis. This involves an elongated tail-spine, further protruding fornices and elongated, as well as further spread spinules along its carapace margins. Of these, the predator-induced trait changes concerning the spinules of D. magna at the age of first reproduction are known. However, their morphological development throughout the juvenile instars, in comparison to the changes of the prominent tail spine during the same periods, has thus far been unclear. Our study shows that D. magna expresses spinules across all investigated juvenile instars. Furthermore, during ontogeny, the development of D. magna’s rather small spinescence traits, i.e. the dorsal and ventral mean spinule length, as well as the dorsal spinules bearing area, in response to predation pressure, differs distinctly from that of the prominent tail-spine. Thus, our study provides further insight into the connectedness of traits contributing to the overall defensively enhanced spinescence of D. magna, with possible implications for the functional benefit of the traits at certain developmental periods.

Nematicidal effect of Canavalia ensiformis extract and its potentiation with nanoparticles against Meloidogyne incognita

The nematicidal effect of Canavalia ensiformis seed extract combined with silicon dioxide nanoparticles was evaluated on second instar juveniles of Meloidogyne incognita, a phytopathogenic nematode that affects tomato crops. In the first experiment, concentrations of the extract were tested at 2, 4, 6, 6, 8 and 10%, observing that the most effective concentration was 10%, with 90% mortality at 24 hours. In the second experiment, concentrations of the extract at 1.5, 2.0, 2.5 and 3.0% were combined with silicon dioxide nanoparticles at 0.06, 0.08, 0.10, 0.12 and 0.14%, where the most effective was 1.5% extract with 0.14% nanoparticles, which showed a mortality of 94% at 72 hours. These results suggest that the combination of C. ensiformis extract with NP's can be a strategy for the management of M. incognita in tomato crops

Functional Morphology of Leg Mechanosensory Organs in Early Postembryonic Development in the Stick Insect (Sipyloidea chlorotica).

The subgenual organ complex of stick insects has a unique neuroanatomical organisation with two elaborate chordotonal organs, the subgenual organ and the distal organ. These organs are present in all leg pairs and are already developed in newly hatched stick insects. The present study analyses for the first time the morphology of sensory organs in the subgenual organ complex for a membrane connecting the two sensory organs in newly hatched insects (Sipyloidea chlorotica (Audinet-Serville 1838)). The stick insect legs were analysed following hatching by axonal tracing and light microscopy. The subgenual organ complex in first juvenile instars shows the sensory organs and a thin membrane connecting the sensory organs resembling the morphology of adult animals. Rarely was this membrane not detected, where it is assumed as not developed during embryogenesis. The connection appears to influence the shape of the subgenual organ, with one end extending towards the distal organ as under tension. These findings are discussed for the following functional implications: (1) the physiological responses of the subgenual organ complex to mechanical stimuli after hatching, (2) the influence of the membrane on the displacement of the sensory organs, and (3) the connection between the subgenual organ and distal organ as a possible functional coupling.

Catalogue of juvenile instars of oribatid mites (Acari: Oribatida)the next decade (20142023).

In its traditional, paraphyletic context (sans Astigmata), oribatid mites comprise more than 11,000 known species (Subas 2022). They are largely fungivores and decomposers in organic horizons of soil and have a plesiotypic ontogeny that includes four active, free-living juvenile instars. In a taxonomically organized 2014 catalogue, we summarized literature resources concerning the 805 species for which ontogenetic data (mainly morphological) were available. Herein, we supplement that catalogue with all data known to us that were published during the intervening decade. These relate to 267 species, of which 165 were described prior to 2014. As in the 2014 catalogue, representation is strongest among: the middle-derivative hyporder Nothrina; brachypyline superfamilies that are affiliated with aquatic, semiaquatic or intertidal environments (Limnozetoidea, Ameronothroidea); some eupheredermous groups (Plateremaeoidea, Damaeoidea); and Ceratozetoidea. Also as in 2014, groups that are underreprented, based on their high known diversity, are the ptyctimous Mixonomata (Euphthiracaroidea, Phthiracaroidea) and the brachypyline superfamilies Oppioidea and Oripodoidea.

Laboratory Evaluation of Efficiency of some Normal and Nano Amino Acids in Hatching Eggs and Vitality of J2 Second Instar Juveniles in Root-knot Nematode Meloidogyne spp.

Tomato affected by several pathogenic factors, including root-knot nematodes (Meloidogyne spp.). This research was conducted to evaluate the efficacy of three amino acid Arginine, Serine, and Leucine, in their normal and Nano forms, at three different concentrations (10, 20, 30 ppm). The evaluation was performed under laboratory conditions to assess their effectiveness in inhibiting egg hatching and the viability Second stage Juveniles (J2) of the targeted nematode species. The laboratory results demonstrated the efficiency of all treatments in reducing the percentage of unhatched eggs, particularly at higher concentrations. The Nano-form of the three amino acids at a concentration of 30 ppm exhibited the highest efficacy compared to the normal form and showed significant superiority over the control treatment. After 72 hours, the percentage of unhatched eggs for Arginine, Serine, and Leucine Nano-amino acids was (21.00, 31.33, and 30.67), respectively, with a kill rate of (79%, 68.88%, and 69.33%) compared to the control treatment, which recorded 75% unhatched eggs and a kill rate of 25%. The impact of these treatments on the viability Second stage juveniles(J2) also varied significantly with different concentrations, showing a dose-dependent effect over time and significant differences compared to the control group. The highest concentration of 3000 ppm was the most effective, resulting in the highest kill rate for Arginine, Serine, and Leucine Nano-amino acids, which reached (95.27%, 90.27%, 88.89%), respectively, compared to the control treatment, which had a kill rate of 48.60%.

The effects of dietary amino acid balance on post-embryonic development in a lubber grasshopper

Effects of dietary protein quality on insect development (not just growth) are unclear. Dietary amino acid blends matching yolk proteins support reproduction and juvenile development in Drosophila melanogaster. We matched amino acids to vitellogenin and tested development of juvenile male lubber grasshoppers, which do not produce vitellogenin. Last instars were fed classic dry diets with amino acids substituted for proteins. Matching amino acids to vitellogenin allowed molting to adulthood, while an unmatched isonitrogenous diet did not. Health on dry diets was poor, so we developed wet diets with agar, horse feed, and amino acids. Juveniles fed these diets matched to vitellogenin developed comparably to juveniles fed lettuce. However, wet diets with amino acids dissimilar to vitellogenin (low-quality) slowed development but maintained size at adulthood. We observed no compensatory feeding on low-quality diets. Theory suggests accumulation of proteins permits development. To detect a threshold, we started last juvenile instars on high-quality diets, then abruptly switched them to low-qualities diets. When switched to the poor-quality diet at 6d, grasshoppers molted at a similar age (∼17d) to grasshoppers continuously on the high-quality diet. Total hemolymph proteins levels were unaffected by the timing of diet switches. Last, methionine is essential but can be noxious at high levels. Diets with low-quality protein except for methionine slowed growth early but did not alter the time or size at molt. Overall, the feeding threshold is solely due to essential amino acids, and low-quality protein diets slowed development but did not affect adult size.

Is there a downside to plant ecological services in the city? Influences of particulate matter on the two-spotted spider mite (Tetranychus urticae) foraging on the small-leaved lime in urban conditions

The aim of this research was to examine how particulate matter (PM) pollution affects the life history of the two-spotted spider mite (TSSM), Tetranychus urticae (Trombidiformes: Tetranychidae), in modelled urban conditions. For this purpose, experimental populations of TSSM were cultured on the foliage of small-leaved lime (Tilia cordata) contaminated with PM at intensities corresponding to differing city zones such as a park, a busy road and an industrial area. The control samples in the study were washed, unpolluted leaves. The spider mite was selected as a model organism due to its cosmopolitan distribution, broad host spectrum, resistance to a variety of pesticides and food-intake mode involving cell-content sucking, while T. cordata is widely planted in cities and has demonstrated a considerable capability for PM capture. Data on the longevity and mortality of particular instars and on female fecundity at different pollution levels were collected and statistically evaluated. Concentrations of PM typical for roads and industrial city zones significantly reduced total female fecundity (avg. 53.9 and 55.9 eggs/female, respectively, vs 79.2 in control), which entailed a slower population increase, while the survival rate of particular developmental instars (P = 0.52) and fertility curves (P = 0.19) remained unchanged. The presence of PM caused physiological effects in the mites, despite the lack of direct consumption of the pollutant by adult and juvenile instars. Considering the incomparable resilience of TSSM to unfavourable environmental factors, it is predicted that the detrimental influence of PM on other representatives of urban arthropods may be even more severe. The results suggest that there is a need for further investigations into the ecological ramifications of air purification provided by urban green spaces.

Ontogenetic instars of Zygoribatula excavata, with remarks on juveniles of Oripodoidea (Acari: Oribatida)

Information on the morphological ontogeny of oribatid mites of the family Oribatulidae is very scarce, and the juveniles of most species are unknown yet. In this work, the ontogenetic instars of the semicosmopolitan species, Zygoribatula excavata Berlese, 1916 are studied. The juvenile instars of this species are morphologically similar to those of the other species of Zygoribatula, and this genus can be included among those in which species are difficult to distinguish based on juvenile characteristics alone. As information on the morphological ontogeny of most species of Oribatulidae is still insufficient or unknown, a comparison on the juvenile characteristics of the families belonging to the superfamily Oripodoidea is given based on our own data and available literature sources. The major characteristics of juvenile instars of 10 families and 21 genera are presented. There are few characters, such as body shape and size, pattern of cuticle, excentrosclerites at gastronotic setae, size and morphology of setiform organs, such as bothridial as well as gastronotic setae that distinguish the families or genera of Oripodoidea.

Ontogenetic instars of the oribatid mite Spatiodamaeus kalugaensis sp. nov. (Acari, Oribatida, Damaeidae) from Russia.

A new species of the genus Spatiodamaeus (Oribatida, Damaeidae) is described from Russia, based on adult and juvenile instars collected from bark of Acer platanoides and soil-litter of mixed and broadleaf forests in European part of Russia and Western Siberia. The adult of Spatiodamaeus kalugaensis sp. nov. is similar to S. nortoni (Bayartogtokh, 2004) comb. nov. in having epimeral neotrichy but differs from the latter by the presence of the parastigmatic tubercle Sa, the form of the parastigmatic tubercle Sp and the notogastral setae c1, c2, and the barbulation of the rostral, epimeral, anogenital, and notogastral setae of p-series. Comparisons between juvenile instars of the new species and the known juveniles of Spatiodamaeus and Epidamaeus are presented.

Ontogenetic instars of the oribatid mite Tyrphonothrus digeluensis sp. nov. (Acari, Oribatida, Malaconothridae) from Ethiopia.

A new species of the genus Tyrphonothrus (Oribatida, Malaconothridae) is described from Ethiopia, based on adult and juvenile instars; it is collected from mosses on the swamp at the top of the mountain in Arsi Mountains National Park. Tyrphonothrus digeluensis sp. nov. differs from the related species Tyrphonothrus obesus (Yamamoto & Coetzee, 2004) and T. rectus (Yamamoto & Coetzee, 2004) by the pubescence of exobothridial, epimeral, anoadanal, and some notogastral setae. Comparison between juvenile instars of the new species and the known juveniles of Malaconothridae is presented.

First data on ontogeny of the oribatid mite family Caloppiidae (Acari, Oribatida), with description of juvenile instars of the representative of the genus Zetorchella.

Juvenile instars of Zetorchella arsiensis (Oribatida, Caloppiidae) are described, based on specimens collected from mosses on the swamp at the top of the mountain in Arsi Mountains National Park, Ethiopia. It is the first data on ontogeny for the family Caloppiidae. Main morphological differences between juveniles of Caloppiidae with other families in Oripodoidea are presented.

After chemo-metamorphosis: p-menthane monoterpenoids characterize the oil gland secretion of adults of the oribatid mite, Nothrus palustris

The oil gland secretion of the oribatid mite Nothrus palustris is known to show the phenomenon of juvenile–adult polymorphism, i.e., juvenile instars produce secretions predominated by geranial, whereas adults secrete dehydrocineole along with a number of chemically unidentified compounds. We here re-analyzed the secretions of adult N. palustris by GC–MS and NMR spectroscopy, eventually identifying the unknown compounds as p-menthane monoterpenoids. The major components were two isomeric 6-isopropenyl-3-methyl-cyclohex-3-en-1-yl formates (= p-1,8-menthadien-5-yl formates), which accounted for about 75% of the secretion. These were accompanied by five additional, only partly identified p-menthanes (or p-methane-derivatives), all of which represented minor or trace components. In addition, adult secretions contained two C21-hydrocarbons, 1,12-heneicosadiene (major) and a heneicosatriene (minor). Menthane monoterpenoids represent a novel sub-class of terpene compounds in the oil gland secretions of Oribatida. In case of N. palustris, we assume that both geranial and p-menthane monoterpenoids arise via the mevalonate pathway which obviously shows a split at the level of geranyl pyrophosphate, leading to geranial in juveniles and to p-menthanes in adults. The significance of methane occurrence in oil glands as well as the taxonomic distribution of juvenile–adult polymorphism in oribatid oil gland secretions is discussed. The latter phenomenon—i.e., “chemo-metamorphosis” of secretions—is not known from early- and middle-derivative Oribatida nor from Astigmata, but appears to be more common in some derivative desmonomatan and brachypyline oribatid groups.

Systematic, synonymic and biogeographical list of ptyctimous mites (Acari, Oribatida) in the world (1799-2022).

The primitive ptyctimous mites are one of the most important groups of oribatid mites (Acari), with almost cosmopolitan distribution, except for the Arctic and the Antarctic regions. These mites occur especially in places where there is decaying organic matter. In this study, a detailed catalogue of all known ptyctimous mite species in the world is presented. The catalogue provides information about the zoogeographical distribution of each species, discusses important nomenclatural issues and addresses some remarks. Besides this, it also contains useful data on known juvenile instars of 47 species. The catalogue also presents a classification of the higher taxa of eight families, four subfamilies, 42 genera, 15 subgenera, the taxonomic characteristics and the information about the zoogeographical distribution of 1458 valid known species from all over the world. Among them, 231 species and one genus are enumerated as synonyms, nine homonyms, one rejected name, one genus inquirenda, 41 species inquirendae, four subspecies inquirendae, one genus incertae sedis, 39 species incertae sedis, 12 species nomina nuda, two species mistakenly identified, one species without the author's name, and one non-ptyctimous mite species are included in the catalogue. Furthermore, the DNA sequence data of 53 ptyctimous species (belonging to eight families, 15 genera) can be found in the GenBank. Finally, the attached appendix contains important corrections referring to the published monographs published by the first author, and a list of new species described after the publication of these monographs. SEM photos of some typical ptyctimous mites showing their diversity are attached.

Juvenile Dungeness crab foraging behavior and lipid composition is altered more by food quantity than seawater pH in a multi-stressor experiment

Increases in atmospheric, anthropogenic carbon are driving reductions in seawater pH, a process referred to as ocean acidification. Reduced seawater pH can influence behavior of marine animals, but little is currently known about how juvenile crustaceans will respond. We conducted lab experiments to improve our understanding of the consequences of pH exposure and food quantity on juvenile Dungeness crab (Metacarcinus magister, (Dana, 1852)) behavior and nutritional condition. To understand the foraging and pH sensing behavior of juvenile crab, and how this interacts with their nutritional status, we exposed recently settled second instar juveniles to either ambient pH or reduced pH for 42-d, crossed with either a ‘maintenance’- or low-quantity ‘challenge’ diet treatment. After the experimental exposure period, we introduced crab into foraging and sensing pH behavior experiments. In the foraging experiment, we placed crab in a behavior arena with unidirectional flow, where we measured the food discovery time and time allocation of activities in 300-s trials for all individual crab. Food quantity and pH exposure influenced both the speed with which juvenile crab identified and allocation of activities but there was no interactive effect of experimental factors. For our pH sensing experiment, we used a two-current flume plumbed with both ambient and reduced pH seawater. This flow-through flume provided a choice between the pH treatment waters and allowed us to measure the amount of time individuals spent on either side of the arena in 300-s trials. There was no effect of prior diet or pH exposure on the amount of time juvenile crab spent in either seawater pH condition. In addition to the behavior trials, we evaluated crab nutritional condition by quantifying the total lipid content of whole-body tissues and fatty acid profile composition of juvenile crab fed either the maintenance or low-quantity diet during the experimental pH exposure period. The proportional fatty acid profiles differed for crab based on their diet and pH exposure, with no interactive effects. However, we did not detect differences in the concentrations of key summary categories of fatty acids (e.g., saturated, monounsaturated, or polyunsaturated) based on pH exposure. Our results indicate that reduced food availability has a greater impact on juvenile Dungeness crab foraging behavior and nutritional condition than reduced seawater pH exposure representing the 0.3 pH unit decrease predicted by 2100.

Ontogenetic instars of Phyllhermannia bimaculata Hammer, 1979 (Acari, Oribatida, Hermanniidae)

The morphology of juvenile instars (larva, proto-, deuto- and tritonymph) of the Oriental oribatid mite species Phyllhermannia bimaculata Hammer, 1979 (Oribatida, Hermanniidae) is studied, based on arboreal material from southern Vietnam. The SEM micrographs and morphological traits summarized for adults of P. bimaculata are presented. Juveniles of P. bimaculata are compared to those of other known species of the genus.

A new species of Scatoglyphus Berlese (Acariformes: Astigmata: Scatoglyphidae) associated with nests of the fungus growing ants Acromyrmex lundi (Guérin-Méneville) (Formicidae: Myrmicinae: Attini)

Scatoglyphus myrmecophilus sp. nov. (Astigmata: Scatoglyphidae), is described based on material collected in ant nests in Buenos Aires city, Argentina, the second species of the genus and family. Juvenile instars are described for the first time in this family. The new species presents some unexpected traits, representing putatively ancestral states of some characters.