Diapause in the pine processionary moth (Thaumetopoea pityocampa): ecological significance

Pine processionary moth (PPM, Thaumetopoea pityocampa) is an active range expanding pest species having significant economic impact in terms of tree growth and public health. A lot is known about its natural history although one important aspect of its life history, diapause, has been so far neglected in spite of its acknowledged importance in pest establishment and dynamics. A few questions related to diapause have been addressed in this PhD project. Although the existence of prolonged diapause (PD) was reported long ago, no study provided its maximum duration. We provide evidence of existence of at least 7 years of PD in one mountain population of PPM, and establish the importance of PD individuals in the sustenance of population density. This study underscores the importance of long-term surveillance of population for understanding the dynamics of PD. Although several studies have been conducted on the incidence of PD in PPM across it natural range, they were often published as forest service or forest health reports and not available to the large public. A collection of these reports, their validation and comparison with data from papers allowed to make a synthesis that included most of the pest range, including the sibling species Thaumetopoea wilkinsoni in the Near East. We suggest that winter conditions at the larval stage influence this decision. Data analysis suggests a strong U-shaped relationship between the incidence of PD and average winter temperature and a linear positive relationship between mortality and proportion of individuals in PD. The result contributes to the advancement of knowledge on the ecology, population dynamics and distribution of the PPM. Previous phenological models of PPM lack the description of dormant prepupal stage and its significance in synchronization of emergence. Besides, no study reported on the occurrence of diapause in PPM in a stage other than pupa. We show how with a weekly sampling during the two-month long procession period of pine processionary prepupae, it was possible to discover that prepupae differentially regulate their development time in such a way that moth emergence of short-lived adults resulted to be concentrated and synchronized in less than one month. Early descending individuals don’t pupate immediately, rather wait as diapausing prepupae for their late counterparts, whereas late-descending prepupae develop into pupae much faster. The finding of prepupal diapause and its significance in synchronization of emergence may improve the existing model of phenology and provide managers with a new tool to handle this pest. Diapause termination mechanism in both univoltine and prolonged diapausing individuals of PPM has been previously hypothesized based on the occurrence of a key period during the pupal stage. By using three proxies of metabolic activity, such as body temperature, O2 consumption, and weight loss, we confirm the hypothesis of existence of a key period (termination) in univoltine and prolonged diapausing individuals of PPM. This finding is a starting point for the study of diapause development in PPM from an ecological point of view. Compared to simple phenomenon of diapause, field of prolonged diapause in insects per se is not vast. A lot of questions regarding the regulation of prolonged diapause are still unresolved. When we consider PPM, the gap of knowledge in this regard is gigantic. Being an important pest of Mediterranean forests, PPM deploys diapause for its success. We know almost nothing about the regulation of diapause in this species. Despite that, this thesis attempted to start the effort of answering a few of thousands of questions on the regulation of diapause in PPM. This project has prepared the ground for several possible future works. Among them, some are: testing the findings in other populations, understanding genetic regulation of diapause and prolonged diapause, understanding the importance of climate change in regulating diapause, improving phenology models and using for predicting the effects of climate change under different scenarios.La processionaria del pino (PPM, Thaumetopoea pityocampa) è una specie in fase di espansione dell’areale e che causa perdite importanti di crescita degli alberi nonché problemi sanitari all’uoma e altri animali. Nonostante molti studi siano stati condotti su questa specie, alcuni aspetti relativi alla diapausa sono stati finora trascurati anche se riconosciuti come importanti per l’affermazione della specie. Questa tesi si pone l’obiettivo di chiarirne alcuni. La presenza di diapausa prolungata (PD) in Th. pityocampa è nota da tempo ma mancano dati precisi sull’effettiva durata del fenomeno. Con questo studio si è potuto dimostrare che in una valle alpina al limite dell’areale la diapausa si estende fino a 7 anni, con ripercussioni significative sulla dinamica di popolazione. Ciò indica la necessità di una sorveglianza estesa delle popolazioni dell’insetto. Nell’areale della processionaria del pino sono stati svolti vari studi in cui la presenza di diapausa è stata accertata e quantificata, e alcuni di questi sono stati inclusi in rapporti interni di difficile reperibilità. L’accesso a questa informazione e la sua verifica puntuale hanno consentito di produrre una sintesi dei risultati, includendo anche la specie sorella Th. wilkinsoni diffusa in Asia Minore. I risultati mostrano che un fattore importante è rappresentato dalle temperature invernali cui sono esposte le larve. E’ stata infatti trovata una relazione a U tra temperatura invernale e frequenza della diapausa, associata a una maggiore mortalità per gli individui diapausanti. Tale risultato rappresenta un passo in avanti nella documentazione dell’effetto dei fattori ecologici sull’ecologia e sulla dinamica dell’insetto. I modelli di sviluppo disponibili per la processionaria del pino non hanno mai considerato lo stadio di prepupa e l’esistenza di una quiescenza/diapausa che porti a una migliore sincronizzazione degli sfarfallamenti. Grazie a un campionamento settimanale durante il periodo delle processioni di interramento è stato possibile accertare che il periodo di discesa è lungo circa il doppio rispetto allo sfarfallamento, e che le prepupe presentano una diapausa mirata a sincronizzare l’uscita degli adulti e quindi gli accoppiamenti. Il meccanismo si basa su un arresto dello sviluppo nei primi individui che scendono al suolo, che si riduce progressivamente durante il periodo. Queste nuove conoscenze sono di notevole importanza nella definizione di modelli di sviluppo e di previsione delle popolazioni dell’insetto. La conclusione della diapausa pupale in individui univoltini o in diapausa prolungata è stata associata alla presenza di un periodo chiave durante il quale l’individuo decide se proseguire nello sviluppo ad adulto o se rimanere in diapausa. Grazie a misure di alcune variabili non distruttive (temperatura superficiale, consumo di ossigeno, peso corporeo) è stato possibile mettere in evidenza per la prima volta l’esistenza di tale periodo in individui mantenuti a varie condizioni ambientali. Questo risultato rappresenta un enorme passo in avanti nelle conoscenza sulla regolazione della diapausa in questa specie. Nonostante la diapausa degli insetti sia in generale ben nota, le informazioni sulla diapausa prolungata sono scarse e molte domande giacciono irrisolte. Nel caso specifico della processionaria del pino questo ritardo è notevole e allo stesso tempo importante per la regolazione della dinamica di popolazione e quindi dei danni a piante e animali. Questo lavoro contribuisce a chiarire alcune aspetti importanti e apre la strada a studi mirati a conoscere la regolazione genetica della diapausa, gli effetti del cambiamento climatico, e lo sviluppo di modelli in grado di prevedere con affidabilità l’andamento demografico

Diapause in the pine processionary moth (Thaumetopoea pityocampa): ecological significance

Pine processionary moth (PPM, Thaumetopoea pityocampa) is an active range expanding pest species having significant economic impact in terms of tree growth and public health. A lot is known about its natural history although one important aspect of its life history, diapause, has been so far neglected in spite of its acknowledged importance in pest establishment and dynamics. A few questions related to diapause have been addressed in this PhD project. Although the existence of prolonged diapause (PD) was reported long ago, no study provided its maximum duration. We provide evidence of existence of at least 7 years of PD in one mountain population of PPM, and establish the importance of PD individuals in the sustenance of population density. This study underscores the importance of long-term surveillance of population for understanding the dynamics of PD. Although several studies have been conducted on the incidence of PD in PPM across it natural range, they were often published as forest service or forest health reports and not available to the large public. A collection of these reports, their validation and comparison with data from papers allowed to make a synthesis that included most of the pest range, including the sibling species Thaumetopoea wilkinsoni in the Near East. We suggest that winter conditions at the larval stage influence this decision. Data analysis suggests a strong U-shaped relationship between the incidence of PD and average winter temperature and a linear positive relationship between mortality and proportion of individuals in PD. The result contributes to the advancement of knowledge on the ecology, population dynamics and distribution of the PPM. Previous phenological models of PPM lack the description of dormant prepupal stage and its significance in synchronization of emergence. Besides, no study reported on the occurrence of diapause in PPM in a stage other than pupa. We show how with a weekly sampling during the two-month long procession period of pine processionary prepupae, it was possible to discover that prepupae differentially regulate their development time in such a way that moth emergence of short-lived adults resulted to be concentrated and synchronized in less than one month. Early descending individuals don’t pupate immediately, rather wait as diapausing prepupae for their late counterparts, whereas late-descending prepupae develop into pupae much faster. The finding of prepupal diapause and its significance in synchronization of emergence may improve the existing model of phenology and provide managers with a new tool to handle this pest. Diapause termination mechanism in both univoltine and prolonged diapausing individuals of PPM has been previously hypothesized based on the occurrence of a key period during the pupal stage. By using three proxies of metabolic activity, such as body temperature, O2 consumption, and weight loss, we confirm the hypothesis of existence of a key period (termination) in univoltine and prolonged diapausing individuals of PPM. This finding is a starting point for the study of diapause development in PPM from an ecological point of view. Compared to simple phenomenon of diapause, field of prolonged diapause in insects per se is not vast. A lot of questions regarding the regulation of prolonged diapause are still unresolved. When we consider PPM, the gap of knowledge in this regard is gigantic. Being an important pest of Mediterranean forests, PPM deploys diapause for its success. We know almost nothing about the regulation of diapause in this species. Despite that, this thesis attempted to start the effort of answering a few of thousands of questions on the regulation of diapause in PPM. This project has prepared the ground for several possible future works. Among them, some are: testing the findings in other populations, understanding genetic regulation of diapause and prolonged diapause, understanding the importance of climate change in regulating diapause, improving phenology models and using for predicting the effects of climate change under different scenarios

Diapause in the pine processionary moth (Thaumetopoea pityocampa): ecological and applied significance

International audienceDiapause has been rarely considered in the ecophysiology of the pine processionary moth (Thaumetopoea pityocampa) despite its acknowledged importance in pest establishment and dynamics. A review study indicated a U-shaped relationship between incidence of prolonged diapause and winter temperature, and a negative correlation between overall pupal survival and the proportion of diapausing individuals. Based on observations of anatomical changes in diapausing pupae, it has been proposed in the literature that the mechanism of diapause termination occurs at a key period not only in univoltine (emerging the same year) individuals, but also in those that will eventually enter prolonged diapause . By using two separate and real-time measures of metabolic activity, body temperature and O2 consumption, the existence of a transient restoration of activity (termination) has been confirmed in both univoltine and prolonged diapausing pupae. Both methods clearly detected simultaneous diapause termination through increased metabolic rate in both types of pupae before any morphological or behavioural changes could be observed, but univoltine individuals were characterized by a continuous increase until emergence while prolonged diapause individuals later returned to previous low activity levels. This finding is a starting point for the study of diapause development in the pine processionary moth from an ecological point of view. In addition to pupal diapause, there is evidence of a prepupal dormant stage implicated in synchronizing emergences. Through a weekly sampling spanning a two-month procession period, prepupae were found to differentially regulate their development time in such a way that adult emergences were concentrated and synchronized in less than one month. The new findings on diapause and their significance in synchronizing emergences may improve phenological models in a climate change perspective

Termination of pupal diapause in the pine processionary moth Thaumetopoea pityocampa

International audienceDiapause development is a complex process involving several eco-physiological phases. Understanding these phases, especially diapause termination, is vital for interpreting the life history of many insect species and for developing suitable predictive models of population dynamics. The pine processionary moth is a major defoliator of pine and a vertebrate health hazard in the Mediterranean region. This species can display either univoltine or semivoltine development, with a pupal diapause extending from a few months to several years, respectively. Although the ecological and applied importance of diapause is acknowledged, its physiological regulation in either case remains obscure. In the present study, we characterize pre-termination, termination and post-termination phases of pupae developing as univoltine or remaining in prolonged diapause. Changes in metabolic activity are monitored continuously using thermocouples, comprising a novel method based on direct calorimetry, and periodically by use of O-2 respirometry. The two methods clearly detect diapause termination in both types of pupae before any visible morphological or behavioural changes can be observed. Univoltine individuals are characterized by an increase in metabolic activity from pre-termination through to termination and post-termination, ultimately resulting in emergence. Remarkably, a synchronous termination is observed in individuals that enter prolonged diapause instead of emerging; however, in these pupae, the increased metabolic activity is only transient. The present study represents a starting point toward understanding the eco-physiology of diapause development processes in the pupae of the pine processionary moth

Winter temperature predicts prolonged diapause in pine processionary moth species across their geographic range

Prolonged diapause occurs in a number of insects and is interpreted as a way to evade adverse conditions. The winter pine processionary moths (Thaumetopoea pityocampa and Th. wilkinsoni) are important pests of pines and cedars in the Mediterranean region. They are typically univoltine, with larvae feeding across the winter, pupating in spring in the soil and emerging as adults in summer. Pupae may, however, enter a prolonged diapause with adults emerging one or more years later. We tested the effect of variation in winter temperature on the incidence of prolonged diapause, using a total of 64 individual datasets related to insect cohorts over the period 1964-2015 for 36 sites in seven countries, covering most of the geographic range of both species. We found high variation in prolonged diapause incidence over their ranges. At both lower and upper ends of the thermal range in winter, prolonged diapause tended to be higher than at intermediate temperatures. Prolonged diapause may represent a risk-spreading strategy to mitigate climate uncertainty, although it may increase individual mortality because of a longer exposure to mortality factors such as predation, parasitism, diseases or energy depletion. Climate change, and in particular the increase of winter temperature, may reduce the incidence of prolonged diapause in colder regions whereas it may increase it in warmer ones, with consequences for population dynamics

Bioactive-Based Cosmeceuticals: An Update on Emerging Trends

Cosmetic-containing herbals are a cosmetic that has or is claimed to have medicinal properties, with bioactive ingredients purported to have medical benefits. There are no legal requirements to prove that these products live up to their claims. The name is a combination of “cosmetics” and “pharmaceuticals”. “Nutricosmetics” are related dietary supplements or food or beverage products with additives that are marketed as having medical benefits that affect appearance. Cosmetic-containing herbals are topical cosmetic–pharmaceutical hybrids intended to enhance the health and beauty of the skin. Cosmetic-containing herbals improve appearance by delivering essential nutrients to the skin. Several herbal products, such as cosmetic-containing herbals, are available. The present review highlights the use of natural products in cosmetic-containing herbals, as natural products have many curative effects as well as healing effects on skin and hair growth with minimal to no side effects. A brief description is given on such plants, their used parts, active ingredients, and the therapeutic properties associated with them. Mainly, the utilization of phytoconstituents as cosmetic-containing herbals in the care of skin and hair, such as dryness of skin, acne, eczema, inflammation of the skin, aging, hair growth, and dandruff, along with natural ingredients, such as for hair colorant, are explained in detail in the present review