Pterostichus Nigrita Research Articles

Ecology, biology and conservation of Pterostichus rhaeticus Heer, 1837 (Coleoptera: Carabidae) at the edge of its distribution range, in the Western Balkans

Pterostichus rhaeticus is widely distributed in northern and central Europe and has now been recorded for the first time in Croatia, and this record represents its southeasternmost distribution point. This species was only recently separated from the very common and widespread Pterostichus nigrita Paykull, 1790. These two sibling species differ in a few morphological features and can be certainly distinguished by the form of male and female genitalia. Therefore, we measured a few morphometric features, e.g. body length, elytrae length and width, male right paramere and female eighth abdominal sternite. In general, P. rhaeticus is significantly smaller and narrower than P. nigrita. However, in mixed populations, the differences in body size, length and width of elytrae were not observed and the overlap in sizes is considerable. Additionally, we noticed that the range edge individuals of P. rhaeticus are larger compared to individuals in central Europe. Most of the individuals of both species can be clearly and immediately identified by the shape of their genitalia, but in mixed populations these differences are possibly not so obvious, and measurements are necessary. P. rhaeticus is a tyrphophilous species that was exclusively found at three peatlands in Croatia. It was found in the open peat bog centre and adjacent shaded habitats, in both acidic peaty and alkaline soils with high soil humidity. According to present knowledge, this species can be considered an indicator species of peatland habitats in Croatia. These distinctive habitats are highly endangered in the Western Balkans, and therefore the survival of this and other bog-specific species depends on active conservation and protection measures.

Structure of the male reproductive accessory glands of Pterostichus nigrita (Coleoptera: Carabidae), their role in spermatophore formation

Accessory gland secretions of male insects have many important functions including the formation of spermatophores. We used light and electron microscopy to investigate the structure of the accessory glands and posterior vasa deferentia of the carabid beetle Pterostichus nigrita to try to determine where spermatophore material is produced. Each accessory gland and posterior vas deferens had an outer layer of longitudinal muscle, beneath which was a layer of connective tissue and a thin band of circular muscle, all of which surrounded a layer of epithelial cells lining the lumen of the ducts. Based on the ultrastructure of the epithelial cells, and their secretory products, we identified two epithelial cell types in each region (distal and proximal) of the accessory glands and four types in the posterior vas deferens. Most secretory products, which stained positively for proteins and some mucins, were released into the lumen of the ducts by apocrine secretion. The accessory glands produced one type of secretory product whereas in posterior vasa deferentia, four types of secretory products were found layered in the lumen. Our results suggest that most of the structural material used to construct a spermatophore is produced by the cells of the posterior vasa deferentia.

Formation of sperm bundles in Pterostichus nigrita (Coleoptera: Carabidae)

The formation and structure of sperm bundles (spermiozeugmata), and the structure of the vas deferens where bundles are formed, in Pterostichus nigrita is described by light and electron microscopy. The spermiozeugmata are of the sheet-like type consisting of a central rod (about 3 mm long) of electron-dense material (the spermatostyle), to which two bundles of spermatozoa (about 95 per bundle) are attached. The spermatostyle has a spoon-shaped head, and the rod material is differentiated into an electron-dense core and a more electron-lucent cortex. Spermatozoa (about 340 µm long) are attached to the anterior portion of the rod only. Spermiozeugma formation occurs in the upper vas deferens (before the seminal vesicle region) with the secretion of rod material by epithelial cells, which are characterized by well developed rough endoplasmic reticulum with distended cisternae, abundant mitochondria and Golgi bodies. Some cells contain numerous myeloid structures thought to be precursors of rod material, and coated vesicles. During spermiozeugma development, the heads of spermatozoa become embedded in the developing rod material, the anterior of which sits in one of the many diverticula of the mid-region of the vas deferens. Elongation of the rod proceeds by addition of material posteriorly.

Chromosomes and identification of the sibling species Pterostichus nigrita (Paykull) and P. rhaeticus Heer (Coleoptera: Carabidae)

SummaryThe karyotypes of Pterostichus nigrita (Paykull) and P. rhaeticus Heer are described. Both species have eighteen pairs of autosomes, sex chromosomes which are XO (♂) and XX (♀), plus a variable number of totally heterochromatic B chromosomes. Males may be identified by the form of the inflated endophallus, but the shape of the right paramere is not a reliable character. Females may be identified by the form of the eighth abdominal sternite.

Latitude Dependent Circadian Rhythms of Carabid Beetles

Abstract Comparative studies of circadian activity rhythms were performed with three stocks of the species Pterostichus rhaeticus Heer (from Southern Europe, Central Europe, and the Subarctic) and with one Central European stock of the sibling species Pterostichus nigrita Paykull. The hehaviour was investigated in various LD conditions, constant conditions including LL with changes of the illumination intensity and constant darkness with light pulses. The data were analysed with the program system “Timesdia” containing various techniques like power spectrum estimation, periodogram analysis and complex demodulation. This allowed to reveal the time course of rhythms and to determine the number of phase jumps as a measure for precision. With the help of these methods, the activity patterns are classified in different types of behaviour: synchronization, temporarily synchronization, aperiodic behaviour, free run, temporarily free run, relative entrainment, and relative coordination. Besides graduated differences between the populations in south-to-north direction (e.g. in the tendency to rhythmic behaviour) the analysis revealed splitting of rhythms into two or even three components of different frequencies and transitions from rhythmic to aperiodic behaviour or vice versa after arbitrarily chosen light pulses in constant darkness. This behaviour cannot be explained by a system which is composed of one single limit cycle oscillator, but the results rather support a multi-oscillator model.

The carabid communities on peat and upland grasslands in northern England

During a two year period 13498 individuals of 66 species of carabids were taken from 44 sites on peat and upland grasslands over an altitude range of 11‐847 m in the north of England. The similarities between the carabid faunas of each site have been assessed using a modified form of the Sørensen's Index and the sites clustered according to their similarities. Five carabid communities on peat and three on mineral soils have been identified and the more abundant species have been used to characterise them. Peat Community I occurs on dry heath and is characterised by peat associated species such as Trichocellus cognatus and Bradycellus ruficollis together with widespread open habitat species such as Pterostichus madidus, Notiophilus aquaticus, Calathus melanocephalus and Nebria salina. Peat Community II is found on areas where dry heath and deep wet peat are adjacent and is characterised by the species already mentioned together with typical wet habitat species such as Pterostichus diligens, P. nigrita, Patrobus assimilis. Agonum fuliginosum. Peat Community III is found on blanket bog and is characterised by the wet habitat species in the absence of the species present on the dry heath. Peat Community IV found on the lowland oligotrophic mires is characterised by the small number of species present and the addition of Pterostichus niger and Agonum ericeti to the few wet habitat species present. Peat Community V, on the scarp slope of Dun Fell, consists of the wet habitat species of Peat Community III together with Pterostichus madidus. Nebria salina, Notiophilus aquaticus and Calathus melanocephalus.Grassland Community I, on the fell tops, is characterised by the presence of Nebria gyllenhali, Notiophilus germinyi and Patrobus assimitis. Grassland Community II and III are less clearly defined but Grassland Community II may be present on wetter sites than III and is characterised by the presence of Pterostichus nigrita, P. diligens and P. strennus together with Notiophilus biguttatus. N. aquaticus, Pterosfichus madidus and Patrobus afrorufus. Grassland Community III consists of the latter group of species together with Nebria salina, Calathus melanocephalus and Notiophilus aestuans. The number of grassland sites studied was small and there may be further communities on the upland grasslands.

Effect of the photoperiod on corpus allatum activity in vitro in the beetle,Pterostichus nigrita F

In the carabid beetlePterostichus nigrita reproduction is controlled by photoperiods and the corpus allatum hormone. Corpora allata were incubated in vitro and the release of juvenile hormone was quantified. Short-day conditions induced low activity of the corpora allata; long days, after short-day treatment, stimulate high corpus allatum activity, while long days alone have no effect.

Analysis and comparison of circadian rhythms of subarctic and central European beetles of the Carabid speciesPterostichus nigritaPaykull (Coleoptera, Carabidae)∗∗

Abstract The entrainment of the circadian locomotor activity of subarctic and Central European beetles of the Carabid species Pterostichus nigrita to different Zeitgeber conditions was studied. Various light‐dark cycles such as artificial light, Central European natural light illumination in Cologne, and simulated subarctic light conditions during midsummer were used. A time series analysis of the data was performed with the computer program system “Timesdia”;. In various 24‐h LD cycles with artificial light as well as under natural Central European light illumination the Central European beetles are generally stably entrained to the Zeitgeber with activity during the dark phase. In contrast to this behaviour subarctic beetles show: larger and more frequent changes of phase and amplitude, different phase relations and a higher amount of activity during the light phase. Under simulated subarctic midsummer light conditions the entrainment of the activity rhythms of the subarctic beetles is even less stable ...

Two-step photoperiodic and hormonal control of reproduction in the female beetle, Pterostichus nigrita

The carabid P. nigrita is a short-day/long-day insect. Short days with less than 15.0 hr of light per day induce pre-vitellogenesis. Vitellogenesis only takes place in subsequent long days with more than 13,1 hr of light. In the range from ld 13:11 to ld 16:8 egg production is possible without a change in photoperiod. Pre-vitellogenesis is induced by the corpus allatum hormone. Implantation of active corpora allata or injection of juvenile hormone substitutes for short-day photoperiods. Histological investigations and implantation experiments revealed that for vitellogenesis some neurosecretion is necessary. Ecdysterone cannot replace this neurosecretion.

Differences in measurement of day-length and photoperiodism in two stocks from subarctic and temperate climates in the Carabid beetle Pterostichus nigrita F.

Experiments on the measurement of day-length as a basis for photoperiodism were made with a stock of the carabid Pterostichus nigrita from the Subarctic in Swedish Lapland (64-66° N). Results were compared with those of earlier investigations on a Central European stock (51° N). P. nigrita from Lapland reacted differently from the Central European ones in experiments with abnormal photoperiods (cycle durations from 12 to 72 h; light period in all cases 8 h). Whereas, in the Central European stock, short-day induced reactions (previtellogenesis in the females, maturation of the male gonads) could only be observed if those cycles represented multiples of 24 h in whole numbers, 'short-day" reactions in the Lapland stock were inducible with all cycles in nearly 100% of the specimens investigated (only in LD 8:4 was this percentage slightly diminished). Experiments with "dark breaks" of 2 h in extreme long-day (LD 20:4) revealed nearly 100% short-day maturation, irrespective of the temporal location of these dark breaks in beetles from the Lapland stock, whereas in Central European beetles only dark breaks during certain scotophile phases had such an effect. In the Central European P. nigrita, two hour light breaks during the night phase of an LD 14:10 had a destructive effect on short-day maturation processes; in the Lapland stock, these were possible in spite of 1 h light breaks during the night of an LD 19:5. In the Lapland stock, developmental processes which in the Central European stock are confined to short-day conditions could occur in all types of experiments, provided that about 3 to 4 h of darkness were given during each 24 h cycle, whether uninterrupted or not.Light break experiments revealed that the long-day process for ovarian development (vitellogenesis) is induced in the same way as with the Central European P. nigrita. It occurs if light falls into a photosensitive phase during the second half of the 24 h cycle.Thus, for the Subarctic population, a model is proposed in which short-day is measured by means of an hour-glass timer, whereas long-day is perceived by means of a circadian oscillator.

Measurement of day-length as a basis for photoperiodism and annual periodicity in the Carabid beetle Pterostichus nigrita F.

Pterostichus nigrita undergoes a gonad dormancy which is overcome by the sequence of short-day/long-day in females and by short-day in males. Experiments with abnormal photoperiods showed that only photoperiods of 24 h and their multiples in whole numbers allowed the processes of gonad maturation, which are normally bound to short-day (i.e., previtellogenesis in the females, bundling of sperms to spermiozeugmata in the males). They were mostly suppressed by photoperiods which represent uneven multiples of 12 h (12, 36, 60). These results permit the conclusion that the short-day measurement is based on an oscillatory (circadian) process. Experiments with "dark breaks" in an extreme long-day (LD 20:4) resulted in two peaks of "short-day" effects. From these findings a model of short-day measurement was derived. It postulates that there are two dark sensitive phases every 24 h during which the beetles require darkness in order for the short-day processes to occur. One of these phases is set by dawn, reaching its peak 15 h thereafter. The other phase is set by dusk and reaches its maximum about 7 h afterwards. Thus, the steps of gonad development bound to short-day are induced if the night is at least about 8-9 h long. The two scotophile phases represent two systems of short-day measurement, which complement each other and strengthen their effects.Light break experiments revealed that the long-day process of ovarian development (vitellogenesis in the females) is induced if light falls into a photosensitive phase during the second half of the day with its maximum about 15 h after "light on."

Photoperiodic and hormonal control of reproduction in male beetles, Pterostichus nigrita

After metamorphosis the development of males of Pterostichus nigrita is controlled by photoperiods. Development is free of any dormancy in short day conditions (photoperiods with less than 16·9 to 15·1 hr of light per day). This type of dormancy can be called ‘photoperiodic quiescence’. Short days promote the aggregation of spermatozoa to spermiozeugma. Long day conditions suppress the development of spermiozeugma reversibly. The optimum temperature for the production of spermiozeugma is 15°C. Photoperiods must be perceived by means of the compound eyes. Extirpation of both eyes results in a development of the gonads just as occurs in continuous darkness. Short days activate the corpora allata. The volume of these glands is correlated with the state of sexual maturity (formation of spermiozeugma, growth and filling of the accessory glands). Intra- and intersexual transplantations of active corpora allata into undeveloped male beetles maintained in long day photoperiods replace the short day influence. Very probably the gonadotropic hormone is a juvenile hormone. By injection of 10,11-farnesyl-methyl-ester or a synthetic juvenile hormone, sexual maturity can be initiated.

Neuro-endocrine control of diapause and oöcyte maturation in the beetle, Pterostichus nigrita

This paper deals with the study of the histology of the neuroendocrine system of Pterostichus nigrita females: Changes in the amount of neurosecretory material in the A-cells of the pars intercerebralis, the axons of nervi corporis cardiaci and nervi corporis allati, in the corpora cardiaca (CC), and changes in the volume of the corpora allata (CA) are described and correlated to ovarian diapause and development, the latter consisting of a two-step process. During diapause, induced by long-days, the neurosecretory cells and CA seem to function only at a very low level. During the first step of ovarian maturation (previtellogenesis), induced by short-days and characterized by the lack of yolk deposition, the production of stainable material and the transport along the axons are increased, but the activity of the CA does not yet reach its climax. A high level of activity of CA is associated with the final termination of diapause and yolk deposition in oöcytes (vitellogenesis), induced only by long-days after a sufficient period of short-days. The neuro-endocrine control of this very interesting and rare two-step process of breaking of diapause and of ovarian development is discussed as a basis of experimental studies.