Tritonymph Stage Research Articles

Prey life stages modulate effects of predation stress on prey lifespan, development, and reproduction in mites.

The non-consumptive effects of predator-induced stress can influence a variety of life-history traits. Many previous studies focused only on short-term effects such as development and reproductive rates. Recent studies have showed that long-term predation stress (given during the whole life of the prey) and short-term predation stress (provided during the immature stage of the prey) could generate completely opposite results: the former could decrease lifespan, whereas the later could increase lifespan. However, it is still unclear whether the advantage is because of the short duration of exposure or the early stage of life during which exposure was exerted. Thus, in this study, the prey (Tyrophagus putrescentiae) was exposed to predation stress from the predator (Neoseiulus cucumeris) during different life stages (larva, protonymph, tritonymph, first 5d of oviposition, the full lifespan or none of the above). The results showed that the predation stress supplied during larval and protonymphal stage delayed development, reduced fecundity and prolonged lifespan of the prey, while the stress given during tritonymphal stage only reduced lifespan slightly and the stress given during the first 5d of oviposition did not change lifespan but reduced fecundity. This study indicated that the effects of predation stress are dependent on prey life stage and the predation stress experienced in the early life stages is important to lifespan modulation.

<p class="Body">Existence of tritonymphal stage of Stigmaeus elongatus Berlese (Acari: Stigmaeidae), with numerical variations in some body setae in its adult stage

Tritonymphal stage of Stigmaeus elongatus Berlese (Stigmaeidae) has been described here. Distinguishing features among the adults and three nymphal stages of S. elongatus are presented. The presence of tritonymphal stage within the family is referred for the first time in this study. It is thought that this nymphal stage can occur optionally in response to certain circumstances. It is also given here information on intraspecific numerical variations in some body setae occurring in males and females of S. elongatus.

Contribution to the family Pseudocheylidae (Acari, Trombidiformes) from Thailand: one new species and one new record of Anoplocheylus Berlese, with observations on their ontogeny

We describe a new species of pseudocheylid mite in the genus Anoplocheylus Berlese, Anoplocheylus corticicola sp. nov., based on adults and immatures, and record the occurrence of A. aegypticus Baker & Atyeo, 1964 from Thailand. Immature (deutonymphal) dimorphism in A. corticicola sp. nov. is reported for the first time in Pseudocheylidae. The discovery of pharate females of A. corticicola sp. nov. in deutonymphal exuviae indicates that the tritonymphal stage is absent in the female ontogeny. Males presumably develop directly from the male deutonymphal morph, but we could not confirm this. The ontogeny of A. aegypticus is also described for the first time. Remarks on selected morphological characters of Anoplocheylus are given.http://zoobank.org/urn:lsid:zoobank.org:pub:8D0A1868-F4C0-45B9-982C-9123317B00BA

Effects of variation in nutrition on male morph development in the bulb mite Rhizoglyphus robini.

In male dimorphic species, growth influences morph expression and thereby the reproductive success of males. However, how variation in nutritional conditions affects male morph development and whether males can compensate for lost growth is poorly known. Here, we performed an experiment where males of the bulb mite (Rhizoglyphus robini)-which are fighters, able to kill other mites, or benign scramblers-were offered high quality food during the larval stage, but food of high or low quality during the protonymph and tritonymph (=final) stage. When food quality was low during the latter two stages, males matured smaller, later and were more likely to be a scrambler than when food quality was high. We found no evidence for compensatory growth: when males had low quality food only during the protonymph stage, they matured at the same age, but grew at a slower rate and matured at a smaller size than males that had high quality food throughout ontogeny. Furthermore, males that experienced this transient period of low food quality were less likely to mature as a fighter. Interestingly, scrambler increase in body size during the protonymph and tritonymph stages was always lower than that of fighters. Given the strong link between adult size and fitness, combined with the different development times and life histories of the male morphs, the lack of ability to compensate for a transient period of food deprivation during ontogeny is likely to have consequences for the dynamics of bulb mite populations.

Gonads in Histiostoma mites (Acariformes: Astigmata): Structure and development

The development of male and female gonads in arrhenotokous and thelytokous species of Histiostoma was studied using transmission electron microscopy (TEM). All instars were examined: larvae, protonymphs, facultative heteromorphic deutonymphs (=hypopi), tritonymphs, and adults. In testis primordium, spermatogonia surrounding a testicular central cell (TCC) with a gradually enlarging, branched nucleus are present already at the larval stage. Spermatogonia and the TCC are connected via narrow, tubular intercellular bridges revealing that the TCC is a germline cell. Spermatocytes appear at the protonymphal stage. At the heteromorphic deutonymph stage, the testis primordium is similar to that of the protonymph, but in the tritonymph it is much larger and composed as in the adult: spermatids as well as sperm cells are present. The latter are congregated ventrally in the testis at the entrance of the deferent duct.In the larval ovary, an eccentrically located ovarian nutritive cell (ONC) is surrounded by oogonia which are connected with the ONC via tubular intercellular bridges. In later stages, the ovary grows and oocytes appear in the protonymph. Meiotic synaptonemal complexes in oocytes occur from the tritonymph stage. At about the time of the final molting, tubular intercellular bridges transform into peculiar diaphragm-crossed bridges known only in Histiostoma mites. In the adult female, growing oocytes at the end of previtellogenesis lose intercellular bridges and move ventro-laterally to the ovarian periphery towards the oviduct entrance. Vitellogenesis occurs in oviducts.Germinal cells in both the testis and ovary are embedded in a few somatic stroma cells which may be well discernible already in the larval ovary; in the testis, somatic stroma cells are evident not earlier than the end of the tritonymphal stage. The ovary has a thin wall of flat somatic cells, whereas the testis is covered by a basal lamina only.The obtained results suggest that gonads in Histiostoma and other Astigmata originate from two primordial cells only.

Travelling with tea: a Tuckerella’s tale

Tuckerella japonica Ehara appears strongly associated with tea (Camellia sinensis (L.) Kuntze, Theaceae) and, due to certain cultural practices in tea production, has in fact become a world traveller, accompanying the greatly coveted tea plant as it spread across the planet. The history of tea production and culture, and its arrival in the USA, provides the backdrop for this traveller's tale. Tuckerella japonica is morphologically similar to T. flabellifera Miller, described from Tasmania in Australia from Bedfordia salicina (Labill.) D.G. (Asteraceae). These two species have historically been misidentified as each other, creating inaccuracies in the collection records. The implications of this in terms of host plant lists and world distribution are discussed further, along with their morphological separation. The male and immature stages of T. japonica are described for the first time. Tuckerella xinglongensis Lin and Fu, from tea in China, is considered a junior synonym of T. japonica. The loss of the ancestral prostigmatan condition of three nymphal stages during ontogeny is confirmed for males of T. flabellifera, which do not retain a tritonymphal stage.

The first Paratydeidae (Trombidiformes: Paratydeoidea) in Turkey: Scolotydaeus anatolicus sp. nov.

A new species, Scolotydaeus anatolicus sp. nov., collected from a bird's nest and the decayed bark of a tree, is described and illustrated. This is the first time that the family Paratydeidae has been recorded from Turkey. The morphological development of life stages is reviewed and a larva, protonymph, deutonymph, tritonymph and adult life stage are likely present in all species. Accordingly, previous descriptions are reviewed and their probable life stage is reported. A key to the species of Scolotydaeus is also provided.

First Record of Pulaeus subterraneus Berlese, Male; with A Comparison between The Tritonymph Stage of The Two Sexes (Acri: Cunaxidae)

First Record of Pulaeus subterraneus Berlese, Male; with A Comparison between The Tritonymph Stage of The Two Sexes (Acri: Cunaxidae)

Hylomysobia gen. n. (Acari: Myobiidae), a new genus of mites parasitic on gymnures of the genus Hylomys (Eulipotyphla: Erinaceidae)

A new genus of Myobiidae, Hylomysobia gen. n. with two new species, H. mikhailzaitzevi sp. n. (type species) and H. chinensis sp. n., is described from gymnures of the genus Hylomys Müller (Eulipotyphla: Erinaceidae). The two species parasitize Hylomys suillus Müller from Cambodia and Vietnam, and Hylomys sinensis (Trouessart) from China, respectively. These species represent the first records of myobiid mites from species in the family Erinaceidae. The new genus differs from the closely related Eutalpacarus Jameson, 1949 by the following features: in both sexes, coxae I have a triangular process, setae ve are about three times wider than sce and c2, and coxae II bear two pairs of setae; in females, setae sci are lanceolate, setae ag1 and ag3 are absent, and the vulvar lobes are weakly developed; in males, setae e2 are absent, and setae c1, d1, d2 and e1 are situated on the genital shield. The life cycle of Hylomysobia spp. includes egg, larva, protonymph, deutonymph, and adults, male and female. In contrast to the most other myobiid genera possessing the tritonymphal stage, the deutonymphs of Hylomysobia moult directly to adults, and the tritonymphs are absent. Based on the restricted distribution of Hylomysobia species on hosts of this family (only on species of the genus Hylomys) and close morphological similarities to myobiids from Soricidae and Talpidae, it is suggested that the ancestor of this genus secondarily colonized the ancestor of Hylomys from moles or shrews.

First copulation increases longevity and fecundity of Histiostoma feroniarum (Acari: Astigmata: Acaridida) females

I investigated the influence of insemination at different life stages on female fitness in the mite Histiostoma feroniarum. In this species, males guard immature females at the tritonymph stage to inseminate them immediately after the last moulting. Four groups of females were studied (1) females inseminated 'naturally', i.e. mating occurred immediately after guarding, and then the male was removed (IF/0M), (2) 'naturally' inseminated females, where after insemination the male was replaced by two additional males (IF/2M), (3) virgin females reared without males (VF/0M) and (4) mature, virgin females to which two virgin males were added 3 days after last moulting (VF/2DM). The results show that females inseminated 'naturally' (IF/0M) have higher longevity and fecundity than either virgin (VF/0M) or late-inseminated females (VF/2DM). Furthermore, longevity and fecundity of the former (IF/0M) was also greater than that of females 'naturally' inseminated and subsequently exposed to males (IF/2M). One may suggest that seminal fluids have a positive effect on female fitness. When delayed insemination occurs, such positive effect may not be observed due to a change in features of the sperm access system. Harassment may explain decreased longevity and fecundity of females inseminated 'naturally' compared to females that received additional males.

Mating and fecundity of Dermatophagoides farinae.

Studies of the life cycle of cultured Dermatophagoides farinae found that after an initial mating D. farinae females lived for 63.3+/-64.6 (SD) d after their egg production period ended (Arlian and Dippold 1996). The long period after cessation of egg production for D. farinae suggested D. farinae females could mate multiple times and produce eggs continuously for a longer period. The purpose of this study was to determine if female D. farinae could mate at least two times, and subsequently increase the production of viable eggs over a longer period of time compared to a single mating. Female D. farinae were randomly selected from thriving cultures and isolated in cages. When the females had ceased to lay eggs a male was added to the cage. Fifty-seven percent of the isolated females mated again and produced a second batch of viable eggs. In natural or culture populations, females have continuous availability of males. Therefore, in another experiment, females that emerged from the tritonymphal stages were continuously exposed to fresh males and fecundity and lengths of the reproductive and post reproductive periods were determined. These females had a 11 d longer reproductive period and produced 30.7% more eggs compared to females that only mated one time after they emerged from the tritonymphal stage. However, the post reproductive period was still long (58.6+/-11.4 [SE] d) the significance of which is not clear. In conclusion, this study revealed that D. farinae females are capable of more than one successful mating that results in increased egg production compared to that of a single mating. It is likely that females mate multiple times in natural and culture populations. It was observed that females actively attract males during the reproductive period but not afterward even though she continues to live a long time.

Ultrastructure of the integument during moulting of the quiescent tritonymphal instar of trombiculid mite Hirsutiella zachvatkini (Acariformes: Trombiculidae).

The ultrastructure of the integument of the quiescent reduced tritonymph of the trombiculid mite Hirsutiella zachvatkini (Schluger) was investigated by means of transmission electron microscopy. Mites were investigated daily during the 14-16 day tritonymphal period (imagochrysalis). This period includes the deutonymphal moult (1-3 days), the quiescent tritonymph period (2-4 days), and the tritonymphal moult into the adult mite (6-10 days). A distinct recognizable feature of the tritonymphal moulting cycle is a sequence of events independent of precise time intervals. This process involves partial destruction and reorganization of the hypodermis of the previous instar, and formation of a new hypodermis of the subsequent instar from islands of rudimentary hypodermal cells. The integument of the reduced tritonymph differs greatly from that of both larva and active deutonymph and adult. It consists of a simply organized hypodermal layer of varying thickness and a thick clear poorly lamellate cuticle with curved pore canals, and lacking setae. The epicuticle is very thin and without a clear protein layer. The tritonymphal instar as such with its own cuticle situated near the hypodermis is encased within the detached covering of the previous active deutonymph, and may be considered a calyptostasic and entirely pharate instar. There is a tendency for reduced tritonymphal stage to be eliminated from ontogenesis and this stage is not homologous to the pupa of insects.

Variability in the life history of Unionicola crassipes, a sponge-associated water mite (Acari: Unionicolidae)

The life history of a member of the widely distributed Unionicola crassipes complex (Acari: Unionicolidae) in a foothills pond in Alberta, Canada, differs from those previously described for this taxon. Two years are required for a female to develop from an egg to an ovipositing adult. Fertilized females overwinter and oviposit in the sponge Eunapius fragilis in early May. Larvae emerge in late May to early June and parasitize chironomids of the genus Tanytarsus. Engorged larvae drop from their insect hosts and return to sponges for the protonymph resting stage. Active, predaceous deutonymphs develop from protonymphs in early summer. Deutonymphs overwinter and enter the tritonymph resting stage, also in sponges, in early May. Summer adults emerge from the tritonymph stage in late May to early June. Males emerge first, but there is an overall female bias to the sex ratio of emerging adults. Growth of sclerotized and unsclerotized parts occurs in adults over the summer, during which time females appear to suffer greater mortality than males, because the sex ratio is 1:1 in September. It is primarily mated females that overwinter for a second time. A population decline in the summer of 1987 was correlated with degeneration of sponges; variation in the life histories of sponge-associated water mites is discussed in light of this correlation.

Transformation of hypopodes ofRhizoglyphus robini (Acari: Astigmata: Acaridae) on cultures of three soil fungi

Cultures of three soil plant pathogens were tested for their influence on transformation of hypopodes ofRhizoglyphus robini Claparede to the tritonymphal stage. Potato-dextrose agar (PDA) substrate was used to growBotrytis gladiolorum Timmermans,Curvularia trifolii f. sp.gladioli Parmelee and Latterell, andFusarium oxysporum f. sp.perniciosum (Hepting) Toole. Hypopodes were placed directly on the agar cultures of these fungi and on plain PDA. No significant differences were found in total number of hypopodes transformed or in rate of transformation.

Precopulatory Pairing and Mating of Psoroptes Mites (Acari: Psoroptidae)

Adult males of 2 species of Psoroptes formed attachment pairs with both nymphal stages of the female. However, more female nymphs of both species were paired while in the tritonymph stage than as protonymphs. This attachment behavior is compared to the “guarding” behavior of male Tetranychus mites on female deutonymphs. It is argued that the probability of successful mating by adult males of both species is increased by the long attachment period. Copulation between the sexes occurred after the tritonymph female molted to the adult stage. Microscopic examination of nymphal and adult females showed that only adults possessed the bursa copulatrix, which was on the anal plate of both species. When females of either species were separated from males as nymphs, they developed to the adult stage but produced no eggs or offspring. Female nymphs paired with adult males mated and produced eggs after developing to the adult stage. The mating process between adult males and females is described.

Influence of Temperature and Photoperiod on Development and Oviposition of the Pecan Leaf Scorch Mite, Eotetranychus hicoriae1, 3

The life cycle of the pecan leaf scorch mite (PLSM), Eotetranychus hicoriae (McGregor), was studied at 15.5°, 21.1°, 26.7°, and 32.2°C and 30-50% RH on pecan leaf discs. Initial studies at constant illumination (24:0 LD) demonstrated a negative correlation between developmental time and temperature. No eggs hatched at 15.5°C. At a photoperiod of 10:14 and 21.1°C, females exhibited diapause morphology and did not oviposit. Shortening of the photophase resulted in an increase in developmental time for both sexes. Oviposition studies on pecan seedlings at the above temperature regimes showed maximum daily oviposition occurred at 26.7°C. There was no significant difference between oviposition on seedlings and leaf discs. No significant difference was found in the total eggs deposited by mated vs. virgin females. The presence of a tritonymph stage was not confirmed.