De Loof A.,Zoological Institute
Journal of Insect Physiology | Year: 2011
The most prevalent hypothesis concerning the relationship between reproduction and longevity predicts that reproduction is costly, particularly in females. Specifically, egg production and sexual harassment of females by males reduce female longevity. This may apply to some short-lived species such as Drosophila, but not to some long-lived species such as the queens of ants and bees. Bee queens lay up to 2000 eggs a day for several years, but they nevertheless live at least 20 times longer than their sisters, the sterile workers. This discrepancy necessitates a critical reevaluation of the validity of both the trade-off concept as such, and of the current theories of aging. The widely accepted oxidative stress theory of aging with its links to metabolism and the insulin/IGF-I system has been disproven in Caenorhabditis elegans and mice, but not in Drosophila, necessitating other approaches. The recent spermidine/mitophagy theory is gaining momentum. Two major mechanisms may have been largely overlooked, namely epigenetic control of longevity by imprinting through DNA methylation as suggested by recent data in the honey bee, and especially, a mechanism of which the principles are outlined here, the progressive weakening of the " electrical dimension" of cells up to the point of total collapse, namely death. © 2010 Elsevier Ltd.
Bulyuk V.N.,Zoological Institute
Behavioral Ecology and Sociobiology | Year: 2012
Time of departure and landing of nocturnal migrants are of great importance for understanding migratory strategy used by birds. It allows us to estimate flying time and hence the distance that migrants cover during a single night. In this paper, I studied the temporal schedule of nocturnal departures of European robins during spring migration. The study was done on the Courish Spit on the Baltic Sea in 1998-2003 by retrapping 51 ringed birds in high mist nets during nocturnal migratory departure. Take-offs of individual birds occurred between the first and tenth hour after sunset (median 176 min after sunset). Departure time was not related to fuel stores at arrival and departure, stopover duration and progress of the season. The results suggest that one reason for temporal variation in take-off time was differential response of European robins with high and low motivation to depart to such triggers as air pressure and its trend. If these parameters reach a certain minimum threshold shortly before sunset, robins with a high migratory motivation take off in the beginning of the night. When air pressure or its trend reaches a maximum, it may trigger to take off later during the night birds with lower initial motivation for departure, including those that have low refuelling efficiency. In regulation of timing of take-offs of robins, an important role is also played by their individual endogenous circadian rhythm of activity which is related to the environment in a complex way. © 2011 Springer-Verlag.
Nassel D.R.,University of Stockholm |
Broeck J.V.,Zoological Institute
Cellular and Molecular Life Sciences | Year: 2016
Insulin, insulin-like growth factors (IGFs) and insulin-like peptides (ILPs) are important regulators of metabolism, growth, reproduction and lifespan, and mechanisms of insulin/IGF signaling (IIS) have been well conserved over evolution. In insects, between one and 38 ILPs have been identified in each species. Relatively few insect species have been investigated in depth with respect to ILP functions, and therefore we focus mainly on the well-studied fruitfly Drosophila melanogaster. In Drosophila eight ILPs (DILP1-8), but only two receptors (dInR and Lgr3) are known. DILP2, 3 and 5 are produced by a set of neurosecretory cells (IPCs) in the brain and their biosynthesis and release are controlled by a number of mechanisms differing between larvae and adults. Adult IPCs display cell-autonomous sensing of circulating glucose, coupled to evolutionarily conserved mechanisms for DILP release. The glucose-mediated DILP secretion is modulated by neurotransmitters and neuropeptides, as well as by factors released from the intestine and adipocytes. Larval IPCs, however, are indirectly regulated by glucose-sensing endocrine cells producing adipokinetic hormone, or by circulating factors from the intestine and fat body. Furthermore, IIS is situated within a complex physiological regulatory network that also encompasses the lipophilic hormones, 20-hydroxyecdysone and juvenile hormone. After release from IPCs, the ILP action can be modulated by circulating proteins that act either as protective carriers (binding proteins), or competitive inhibitors. Some of these proteins appear to have additional functions that are independent of ILPs. Taken together, the signaling with multiple ILPs is under complex control, ensuring tightly regulated IIS in the organism. © 2015 Springer Basel.
Four antlion lacewings species and an owlfly one from two sister families have been studied and their chromosome number estimated:  Palpares libelluloides (2n = 26),  Distoleon tetragrammicus (2n = 18),  Myrmecaelurus trigrammus (2n = 16),  Macronemurus bilineatus (2n = 16), and owlfly (Ascalaphidae)  Bubopsis hamatus (2n = 18). Arrows point to X and Y sex chromosomes. Credit: Dr. Victor Krivokhatsky Varying between organisms, the number of chromosomes, the structures of organised and packaged DNA information, are normally a constant amount, thus allowing for the successful reproduction of a species. However, it may vary greatly even within a certain family. In the present study, conducted by Drs. Valentina Kuznetsova, Victor Krivokhatsky and Gadzhimurad Khabiev, Russian Academy of Sciences, four antlion lacewings species and an owlfly one from two sister families have been examined and their chromosome number estimated. The paper, published in the open-access journal ZooKeys, shows some patterns within the genera and suggests their common origin. The chromosome numbers of four antlion species (Myrmeleontidae) and an owlfly one (Ascalaphidae) from the Republic of Dagestan have been investigated in the Zoological Institute, Russian Academy of Sciences, St. Petersburg. When the data of the Myrmeleontoid lacewings were analyzed, some patterns emerged. It appears that the chromosome number is a preferential feature of the genera and few deviated from the modal value within the subfamily. While most antlions possess lower chromosome numbers, 2n = 14 and 2n = 16, which are encountered in all subfamilies, there is the exception of the Palparinae subfamily with the studied Palpares libelluloides species' chromosome number counting 2n = 26. The higher numbers, 2n = 22, 20 and 18, are also characteristic of the sister owlfly family Ascalaphidae. Since Palparinae lacewings represent one of basal phylogenetic lineage of the Myrmeleontidae, it is hypothesized that higher chromosome numbers are ancestral for antlions. The antlion subfamily along with the owlfly family have been registered with the the maximal modal values and have also been regarded as archaic taxa in relation to the rest of their close relatives. The higher chromosome numbers were inherited from the common ancestor of Myrmeleontidae + Ascalaphidae. It was preserved in the subfamily Palparinae (Myrmeleontidae) but changed via chromosomal fusions toward lower numbers, 2n = 18, 16 and 14, in other subfamilies. Explore further: Chromosome number changes in yeast More information: Valentina G. Kuznetsova et al. Chromosome numbers in antlions (Myrmeleontidae) and owlflies (Ascalaphidae) (Insecta, Neuroptera), ZooKeys (2015). DOI: 10.3897/zookeys.538.6655
News Article | March 15, 2016
Researchers have discovered the 90-million-year-old skeletal remains of a horse-sized dinosaur that is believed to be the missing piece that would complete the family tree of the fearsome tyrannosaurus rex. In a study featured in the journal Proceedings of the National Academy of Sciences, researchers from various scientific organizations, including the University of Edinburgh in the United Kingdom and the Smithsonian National Museum of Natural History in the United States, describe a set of dinosaur bones they found in a desert in Uzbekistan. The creature, which has been given the name Timurlengia euotica, showed characteristics that were similar to an earlier and a much smaller species of tyrannosaurus known as tyrannosauroids. However, the advanced ears and large brain outlined on the dinosaur's skull fragment suggest that it may have also shared traits with a later and much larger species, the tyrannosaurus rex. The team believes the Timurlengia euotica may very well hold the key to the secret of how the tyrannosaurus was able to grow so big. Scientists estimate that the first tyrannosaurs came into existence about 170 million years ago. Some of the early tyrannosauroids were merely the size of dogs. However, about 80 million years ago during the latter part of the Cretaceous Period, one species of tyrannosauroids, the tyrannosaurus rex, evolved into a large and menacing land predator. This creature had massive heads and very powerful jaws that produce a bite force of about 13,000 pounds. It can also grow to become as big as a full-sized bus. Tyrannosaurus rex was not only one of the largest creatures of its time, but it was a very capable hunter as well. Hans-Dieter Sues, a researcher from the Smithsonian National Museum and one of the authors of the study, said that contrary to what many people thought about the tyrannosaurus rex from the first "Jurassic Park" film, the creature was gifted with a keen sense of smell, hearing and even eyesight. The tyrannosaurus rex's killer instincts come from its two grapefruit-sized olfactory lobes that allowed it to smell objects very acutely. Its long, looped ear canals, on the other hand, allowed it to hear even low-frequency sounds generated by the footsteps of their prey from a distance. "It was sort of a superpredator," Sues pointed out. Finding out exactly how tyrannosaurs became quite the gifted predators, however, remained an elusive achievement for paleontologists over the years. This was because they did not have enough data on 100-million-year-old fossil records that pertain to the earlier and smaller tyrannosauroids. With the dissolution of the Soviet Union, researchers from different parts of the world now had access to territories where tyrannosauroids remains could be found. In 2004, a team of scientists unearthed a braincase fragment that was believed to be owned by some sort of dinosaur. It was kept in storage at the Zoological Institute of the Russian Academy of Sciences, until one of the members of the current research team, Steve Brusatte, came across the bone fragment in 2014. Brusatte and his colleagues made use of CT scans in order to better understand the structure of the braincase fragment. They discovered that the Timurlengia euotica had elongated inner ear canals, much like those seen on the tyrannosaurus rex. These would have given the creature an acute sense of hearing. The size of the braincase fragment, however, showed that the Timurlengia euotica lacked the knobs and recesses that a tyrannosaurus rex would likely have. This means that the Timurlengia also shared some physical similarities with the earlier tyrannosaur known as Xiongguanlong. The researchers believe that tyrannosaurs were able to develop their brain structure and keen hunting senses first before they became gigantic creatures. Their smarts for hunting prey made them more than capable of becoming the apex predators of their time.