Cocoon Construction Research Articles

The Role of Filippi's Glands in the Silk Moths Cocoon Construction.

Filippi’s glands (FGs), formerly also called Lyonet’s glands, are accessory secretory structures of the labial (silk) glands of lepidopteran caterpillars, which were implicated to play an important role in the maturation of the silk material and the construction of the cocoon. In our previous study, we have identified several species of giant silk moths that completely lack the FGs. Interestingly, the absence of FGs in these species correlates with the construction of a loose cocoon architecture. We investigated the functions of FGs by their surgical extirpation in the last instar larvae of the silkworm, Bombyx mori. We found that the absence of FGs altered the structure of the resulting cocoon, in which the different layers of silk were separated. In further experiments, we found no effects of the absence of FGs on larval cocoon formation behavior or on changes in cocoon mass or lipid content. Differential proteomic analysis revealed no significant contribution of structural proteins from FGs to silk cocoon material, but we identified several low abundance proteins that may play a role in posttranslational modifications of some silk proteins. Proteomic analysis also revealed a difference in phosphorylation of the N-terminal sequence of fibroin-heavy chain molecule. Thus, FGs appear to affect silk stickiness during spinning by regulating posttranslational modifications. This could also explain the link that exists between the absence of these glands and the formation of loose cocoons in some giant silk moth species.

The Filippi's Glands of Giant Silk Moths: To Be or Not to Be?

Simple SummaryIt is well documented that silkworms (Saturniidae) possess silk glands’ accessory glandular organs, the Filippi’s glands (FGs). These accessory glands are believed to play an important role in the cocoon construction. Unexpectedly, we have identified several silk moth species that are completely missing the FGs during the entire larval development and still produce fully functional cocoons. This finding suggests that the role of FGs is not crucial for the cocoon spinning.The Filippi’s glands (FGs), formerly “Lyonet’s glands”, are paired accessory organs associated with the silk glands. They are unique to Lepidoptera caterpillars and their exact role is not clear. The FGs are thought to be involved in the construction of a silk cocoon in bombycoid moths. FGs can differ in size and shape, therefore, in this study we attempt to find a correlation between FG morphology and phylogenetic position within the Bombycoidea. We use light and electron microscopy to examine the presence and morphology of FGs in a range of wild (giant) silk moths and several related species. Our results confirm that the majority of studied silk moth species have complex type of FGs that continuously increase in size during larval development. We identified several species of giant silk moths and two hawk moth species that completely lack FGs throughout their larval development. Finally, in several hawk moth species in which FGs are well developed during the first larval stage, these glands do not grow and remain small during later larval growth. Our results suggest that FGs are not critical for spinning and that loss of FGs occurred several times during the evolution of saturniids and sphingids. Comparison of FGs in different moths is an important first step in the elucidation of their physiological significance.

Phoretic association between Hisonotus chromodontus (Loricariidae: Hypoptopomatinae) and Ichthyocladius sp. (Diptera: Chironomidae) larvae in Amazonian streams

Abstract: Larvae of non-biting midges in the family Chironomidae can be found in association with several species of fish in the family Loricariidae. In this study, we describe the first record of phoretic interaction between larvae of Ichthyocladius sp. and the fish Hisonotus chromodontus in streams in the Amazon basin. Between July 2010 and March 2019, fish were collected from three streams of the Teles Pires River basin in the state of Mato Grosso, Brazil. We investigated the attachment site of chironomid larvae on the body of fish and the frequency of attachment. A total of 1.241 specimens of H. chromodontus were collected, among which nine hosts were found carrying in the ventral region a single Ichthyocladius sp. specimen. All Ichthyocladius sp. were attached to a spicule of fish between the pectoral and pelvic fins, in which they were observed at the fourth developmental stage at the beginning of the cocoon construction (1.50 mm). In addition, a pre-pupa larva (2.60 mm) and an empty cocoon (2.50 mm) were reported. The Loanda stream had the highest occurrence of this type of association (of 12 fish examined, three had larvae). The other two streams reported a lower occurrence: the Baixada Morena stream had three fish associated with larvae amongst 1105 fish examined, whereas the Selma stream had three out of 124 fish infested by larvae. The occurrence of only one larva per host can be related to the small body area of the host fish (average standard length = 26.60 mm and average weight = 0.31 g). We observed that the larvae prefer fixation sites in the vicinity of the pectoral and pelvic fin of the fish, which is presumably associated with the fact that chironomids feed on algae and debris suspended by the movement of loricariids. These streams differ with respect to the presence of riparian forests, which may affect resource availability and thereby influence ecological interactions between the species.

The beta-1, 4-N-acetylglucosaminidase 1gene, selected by domestication and breeding, is involved in cocoon construction of Bombyx mori.

Holometabolous insects have distinct larval, pupal, and adult stages. The pupal stage is typically immobile and can be subject to predation, but cocoon offers pupal protection for many insect species. The cocoon provides a space in which the pupa to adult metamorphosis occurs. It also protects the pupa from weather, predators and parasitoids. Silk protein is a precursor of the silk used in cocoon construction. We used the silkworm as a model species to identify genes affecting silk protein synthesis and cocoon construction. We used quantitative genetic analysis to demonstrate that β-1,4-N-acetylglucosaminidase 1 (BmGlcNase1) is associated with synthesis of sericin, the main composite of cocoon. BmGlcNase1 has an expression pattern coupled with silk gland development and cocoon shell weight (CSW) variation, and CSW is an index of the ability to synthesize silk protein. Up-regulated expression of BmGlcNase1 increased sericin content by 13.9% and 22.5% while down-regulation reduced sericin content by 41.2% and 27.3% in the cocoons of females and males, respectively. Genomic sequencing revealed that sequence variation upstream of the BmGlcNase1 transcriptional start site (TSS) is associated with the expression of BmGlcNase1 and CSW. Selective pressure analysis showed that GlcNase1 was differentially selected in insects with and without cocoons (ω1 = 0.044 vs. ω2 = 0.154). This indicates that this gene has a conserved function in the cocooning process of insects. BmGlcNase1 appears to be involved in sericin synthesis and silkworm cocooning.

A re-evaluation of silk measurement by the cecropia caterpillar (Hyalophora cecropia) during cocoon construction reveals use of a silk odometer that is temporally regulated.

The late 5th instar caterpillar of the cecropia silk moth (Hyalophora cecropia) spins a silken cocoon with a distinct, multilayered architecture. The cocoon construction program, first described by the seminal work of Van der Kloot and Williams, consists of a highly ordered sequence of events. We perform behavioral experiments to re-evaluate the original cecropia work, which hypothesized that the length of silk that passes through the spinneret controls the orderly execution of each of the discrete events of cocoon spinning. We confirm and extend by three-dimensional scanning and quantitative measurements of silk weights that if cocoon construction is interrupted, upon re-spinning, the caterpillar continues the cocoon program from where it left off. We also confirm and extend by quantitative measurements of silk weights that cecropia caterpillars will not bypass any of the sections of the cocoon during the construction process, even if presented with a pre-spun section of a cocoon spun by another caterpillar. Blocking silk output inhibits caterpillars from performing normal spinning behaviors used for cocoon construction. Surprisingly, unblocking silk output 24-hr later did not restart the cocoon construction program, suggesting the involvement of a temporally-defined interval timer. We confirm with surgical reductions of the silk glands that it is the length of silk itself that matters, rather than the total amount of silk extracted by individuals. We used scanning electron microscopy to directly show that either mono- or dual-filament silk (i.e., equal silk lengths but which vary in their total amount of silk extracted) can be used to construct equivalent cocoons of normal size and that contain the relevant layers. We propose that our findings, taken together with the results of prior studies, strongly support the hypothesis that the caterpillar uses a silk “odometer” to measure the length of silk extracted during cocoon construction but does so in a temporally regulated manner. We further postulate that our examination of the anatomy of the silk spinning apparatus and ablating spinneret sensory output provides evidence that silk length measurement occurs upstream of output from the spinneret.

Developmental Biology among Corbiculate Bees: Bombus impatiens, Including Observations on Its Egg Eclosion

This contribution results from an investigation of four commercially obtained colonies of Bombus (Pyrobombus) impatiens Cresson in an attempt to understand the functional anatomy and behavior of its immature stages. Eggs are described in detail, and their chorionic microstructure is contrasted with that of Bombus (Cullumanobombus) griseocollis (De Geer). They are deposited in groups consisting of a few to more than nine eggs into a single chamber. The study confirms that larvae pass through four instars. Although increasing in size dramatically from one instar to the next, larval anatomy and behavior change little during the first three instars. The last instar is the one that commences defecation and production of silk resulting in cocoon construction. In contrast to most bees, its larval activities result in substantial changes in size and shape of its brood chamber, whereas brood chambers of most bees are constructed by the female and modified little by the offspring. This study is a part of a series of investigations into the similarities and differences in the developmental biologies among corbiculate bees.

Food Consumption and Growth Rates with Certain Biological Aspects of Red Palm Weevil, Rhynchophorus ferrugineus Olivier Rearing on Sugarcane Stems

The rearing of red palm weevil, Rhynchophorus ferrugineus Olivier on sugarcane stems, as substitutive host, to study each of food consumption, growth rates and some biological aspects, detected that the larvae undergo ten instars from egg hatching until construction of cocoon, the total duration after hatching of these instars reached 66.1days, ranged between 58 to 74 days. The lengths of larvae at 10th instars were ranged 47 -56mm, with a mean of 52 + 3.03mm. The weight of last larval instar reached 6.61 g (ranged 5.8- 7.4 g). Larval growth rate recorded 0.096g/day, adult weevil remains stable through the 1st four weeks of feeding (mean, 1.244 g) and decreased afterward during the 5th and 6th weeks of feeding (mean, 1.128 and 0.956 g, respectively). The acquired weight of larvae has differed with the variation in weight of larvae. The percentage of larval weight gain varied from 49.76 (for 2 g / larva) to 7.93% (for 5 g / larva). Total weight of food consumption during successive growth periods (55days) recorded 83.18 g / larva. Daily consumption recorded 10.37 g during the feeding period, with a rate of 1.5 g / larva.

Suppression of orb-web building behavior of the spider Metazygia laticeps (O. Pickard-Cambridge, 1889) (Araneae: Araneidae) by a new parasitoid wasp

Parasitoids may change host behavior in order to improve their survival during the pupal stage. This has been observed in some ichneumonid wasps (Polysphincta genus group), which are able to induce modifications in the movements of host spiders during web construction. These changes usually result in web patterns distinct from those of normal webs of spiders. In this study, we describe the behavioral change in the orb-weaver spider Metazygia laticeps (Araneidae), parasitized by a new species of parasitoid wasp, Polysphincta sinearaneasp. n. (Ichneumonidae), which has a high prevalence in M. laticeps populations. This parasitoid induces behavioral changes in M. laticeps that result in the complete suppression of the normal orb-web structure. The absence of the orb probably reduces accumulation of debris and interception of insects by the webs (factors that could result in the rupture of threads that hold the shelter of the web) during the period from cocoon construction to the emergence of the adult wasp. Also, the suppression of the normal orb-web structure implies that resources that would have been invested in the web will be available to the larva wasp.

Changes in Silk Feedstock Rheology during Cocoon Construction: The Role of Calcium and Potassium Ions.

Variation in silk feedstocks is a barrier both to our understanding of natural spinning and biomimetic endeavors. To address this, compositional changes are investigated in feedstock specimens from the domesticated silkworm (Bombyx mori). It is found that the feedstock viscosity decreased systematically by over two orders of magnitude during cocoon construction. Potential factors such as protein concentration, molecular weight, pH, or the presence of trehalose are excluded, whereas a clear correlation appear between viscosity and the relative concentrations of Ca2+ and K+ ions. It is expected that Ca2+ ions would favor "salt bridges" between acidic (Asp and Glu) amino acids, leading to an increased viscosity, whereas K+ ions would compete for these sites, thereby reducing viscosity. Thus, these findings suggest a simple, systematic yet sophisticated control of feedstock viscosity in the silkworm, which in turn can be applied to future industrial silk production.

When a little is enough: cocoon web of Kapogea cyrtophoroides (Araneae: Araneidae) induced by Hymenoepimecis heidyae (Ichneumonidae: Pimplinae)

The final instar larvae of the koinobiont ectoparasitoids in the Polysphincta group of genera induce their host spiders to construct webs that protect the wasp pupa during its development. It has been hypothesized that changes in structure and design in the cocoon web correlate with the duration and characteristics of the normal web. Kapogea cyrtophoroides (Araneidae) construct long-lived, strong normal webs; the cocoon web induced by Hymenoepimecis heidyae (Ichneumonidae) is nearly identical to the normal web, providing support for the hypothesis. The larva constructs its cocoon in the centre of the host's dense web, connecting it to the spider web and following the same behavioural pattern of construction described for other wasp species in the same group. The behaviour induced in the spider as well as the cocoon construction is very stereotypic, and consistent with other species, but modifications in the cocoon web seem to be strongly determined by the characteristics and design of the spiders' normal web.

Orientation Inside Linear Nests by Male and Female Osmia bicornis (Megachilidae).

Numerous species of solitary bees and wasps build linear nests with only one entrance. Developing insects must orient themselves inside their nest to choose the correct direction in which to emerge. Misorientation and chewing towards the dead end of the nest can result in significant mortality. Most insects position themselves towards the nest entrance during cocoon construction; however, some individuals are misoriented. We tested whether imagines can examine and possibly correct their orientation after emerging from their cocoons. Males were usually able to correct their misoriented position based on the shape of the cell wall and emerged through the correct entrance, whereas most females pursued the direction that they faced in their cocoons. We suggest that there can be more than one time point during development when bees can control their position in relation to the nest entrance and that the importance of these time points varies between sexes.

Developmental ecdysteroid titers and DNA puffs in larvae of two sciarid species, Rhynchosciara americana and Rhynchosciara milleri (Diptera: Sciaridae).

Ecdysteroid titers, developmental landmarks and the presence of prominent amplifying regions (DNA puffs) have been compared during late larval to pupal development in four groups of Rhynchosciara americana larvae and in R. americana and Rhynchosciara milleri. Three prominent DNA puffs (B2, C3 and C8) expand and regress sequentially on the rising phase of the 20-hydroxyecdysone (20E) titer in R. americana as a firm, cellular cocoon is being constructed. A sharp rise in 20E coincides with the regression of these puffs. The shape of the 20E curve is similar in R. milleri, a species that does not construct a massive cocoon, but the behavior of certain DNA puffs and their temporal relationship to the curve differs. Regions corresponding to B2 and C3 can be identified in R. milleri by banding pattern similarity with R. americana chromosomes and, in the case of B2, by hybridization to an R. americana probe. A B2 puff appears in R. milleri as the 20E titer rises but remains small in all gland regions. A puff similar to the R. americana C3 puff occurs in posterior gland cells of R. milleri (C3(Rm)) after the B2 puff, but this site did not hybridize to R. americana C3 probes. C3(Rm) incorporated (3)H-thymidine above background, but showed less post-puff DNA accumulation than C3 of R. americana. R. americana C8 probes hybridized to a more distal region of the R. milleri C chromosome that did not appear to amplify or form a large puff. These differences can be related to developmental differences, in particular differences in cocoon construction between the two species.

Cocoon orientation in the nests of red mason bees (Osmia bicornis) is affected by cocoon size and available space

Proper orientation of cocoons in linearly structured nests can be crucial for the survival of hatching bees. Nevertheless, misoriented cocoons appear in nature in notable proportions. A detailed analysis of sex, space available for cocoon spinning, cocoon size, and nest diameter in the red mason bee (Osmia bicornis) showed that smaller males are more prone to misorientation than larger females. Generally, smaller individuals of both sexes are more often misoriented because smaller larvae disregard the direction of the entrance during cocoon construction. Moreover, cocoons in stems of smaller diameter are less often misoriented than bees in wider nests. Our results suggest that cocoon size and available space are the most important traits affecting cocoon orientation.

Description of immature stages of Phelypera schuppeli (Boheman, 1834) with comments on natural history (Coleoptera: Curculionidae: Hyperinae)

Immatures of the Phelypera schuppeli (Boheman, 1834) (Curculionidae; Hyperinae; Cepurini) are described, illustrated and compared with available descriptions of larvae and pupae of Hyperini. Immatures and adults from midwest (Dourados, Mato Grosso do Sul; Pirenópolis, Goiás) and southeast Brazil (Bauru, São Paulo) were found on leaves of the host plant, Pachira aquatica Aubl. ( Malvaceae, formerly Bombacaceae), a tree used as an ornamental plant in many Brazilian frost-free cities. Larvae of P. schuppeli are exophytic, brightly colored, eruciform and possess abdominal ambulatory ampullae, resembling larvae of Lepidoptera. Mature larvae can spin globular lattice-like cocoons where pupation takes place. Data in the field and under laboratory conditions confirmed previously published biological observations on P. schuppeli. Additional information about defensive behaviors, process of cocoon construction and natural enemies, such as the larval predator Supputius cinticeps (Stål, 1860) (Hemiptera: Pentatomidae) and the prepupal and pupal parasitoid Jaliscoa nudipennis Bouček, 1993 (Hymenoptera: Pteromalidae), are reported.

Hospicidal Behavior of the Cleptoparasitic Wasp Sapyga luteomaculata And Investigation into Ontogenetic Changes in Its Larval Anatomy (Hymenoptera: Vespoidea: Sapygidae)

Abstract This study describes the nesting biology of the Egyptian cleptoparasitic wasp Sapyga luteomaculata Pic, which attacks the nests of two species of bees, Osmia submicans Morawitz and Megachile minutissima Radoszkowski, both belonging to the Megachilidae. We include descriptions of the egg/mature oocyte and of the first and last larval instars. We also identify the anatomical changes in the larva that take place as it transforms through intermediate instars from a host-killing first instar to a form adapted to feeding on the stored provisions supplied by the host. Biological subjects treated are egg deposition, ovariole statistics, eclosion, larval behavior including cocoon construction and defecation, and competition with other cleptoparasites. Comparisons are made throughout with accounts of other Sapyginae. Many biological and larval anatomical similarities between Sapyga and cleptoparasitic bees are recognized, and only a few possible cleptoparasitic novelties are identified.

Maternal Influence on Spiderlings' Emergence from the Cocoon: Observations in a Subsocial Spider

Brood caring behavior was observed in Amaurobius ferox (Araneae, Amaurobiidae), a semelparous subsocial spider, from cocoon construction until the emergence of spiderlings from the cocoon. Unlike most spiders, which emerge from cocoon by their own means, A. ferox mothers intervene in the process of the emergence of their young. I manipulated broods by removing the mother prior to emergence to determine the effects of maternal behavior on the emergence of spiderlings. My results showed that maternal intervention making the cocoon expansion and its exit, is not absolutely necessary for the emergence of A. ferox spiderlings from the cocoon. Nine clutches out of ten were able to get out of the cocoon by their own means without their mother`s help. There was no difference between control groups (`with mother`) and experimental groups (`without mother`) in the number of spiderlings that emerged ( vs. , respectfully) and in the time from the beginning to the end of emergence ( vs. hours). Time from eclosion until the emergence of the first individual in a clutch, however, was greater in the mother-absent group (3.5 days) than in the control group (2.0 days). The construction of the cocoon by the mother required always occurred in the same area within the retreat, and took approximately 6 hours, and the mother guarded the eggs during the incubation period. The emergence of the spiderlings followed a sigmoidal pattern. After emergence, the spiderlings formed a very compact group on the cocoon, which may be important in securing maternal care. The absence of cribellum and calamistrum, structures likely involved in their survival, observed in individuals of the first instar suggests that in the first stage of life, the spiderlings are dependent on their mother.

An Unlikely Silk: The Composite Material of Green Lacewing Cocoons

Spiders routinely produce multiple types of silk; however, common wisdom has held that insect species produce one type of silk each. This work reports that the green lacewing ( Mallada signata, Neuroptera) produces two distinct classes of silk. We identified and sequenced the gene that encodes the major protein component of the larval lacewing cocoon silk and demonstrated that it is unrelated to the adult lacewing egg-stalk silk. The cocoon silk protein is 49 kDa in size and is alanine rich (>40%), and it contains an alpha-helical secondary structure. The final instar lacewing larvae spin protein fibers of approximately 2 microm diameter to construct a loosely woven cocoon. In a second stage of cocoon construction, the insects lay down an inner wall of lipids that uses the fibers as a scaffold. We propose that the silk protein fibers provide the mechanical strength of the composite lacewing cocoon whereas the lipid layer provides a barrier to water loss during pupation.

Histochemical and ultrastructural evidence of lipid secretion by the silk gland of the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae)

The silk gland in Lepidoptera larvae is responsible for the silk production used for shelter or cocoon construction. The secretion of fibroin and sericin by the different silk gland regions are well established. There are few attempts to detect lipid components in the insect silk secretion, although the presence of such element may contribute to the resistance of the shelter to wet environment. This study characterizes the glandular region and detects the presence of lipid components in the secretion of the silk gland of Diatraea saccharalis(Fabricius). The silk gland was submitted to histochemical procedure for lipid detection or conventionally prepared for ultrastructural analyses. Lipid droplets were histochemically detected in both the apical cytoplasm of cell of the anterior region and in the lumen among the microvilli. Ultrastructural analyses of the anterior region showed lipid material, visualized as myelin-like structures within the vesicular Golgi complex and in the apical secretory globules, mixed up with the sericin; similar material was observed into the lumen, adjacent to the microvilli. Lipids were not detected in the cells neither in the lumen of the posterior region. Our results suggest that the silk produced by D. saccharalis has a minor lipid content that is secreted by the anterior region together with the sericin.

The order of technology: Complexity and control in a connected world

This paper examines some of the implications associated with the growing complexity of the contemporary world, consequent upon the expanding economic and organizational involvement of ICT-based systems and artefacts. Drawing on Luhmann, traditional forms of technological control are analyzed in terms of functional simplification and closure. Functional simplification involves the demarcation of an operational domain within which the complexity of the world is reconstructed as a simplified set of causal or instrumental relations. Functional closure implies the construction of a protective cocoon that is placed around the selected causal sequences to ensure their recurrent unfolding. While possible to analyze in similar terms, current developments, as manifested in the diffusion of large-scale information systems and mostly the internet spin a web of technological relations that challenge the strategies of functional simplification and closure and the organizational practices that have traditionally accommodated them.

The Relationship between Silkworm Spinneret Positions during Cocoon Construction and Movement of Cocoons in the Reeling Bath

The Relationship between Silkworm Spinneret Positions during Cocoon Construction and Movement of Cocoons in the Reeling Bath