6 research outputs found
Ischnura praematura sp. nov. (Odonata: Zygoptera: Coenagrionidae): a species from Yunnan (China) whose females mate in the teneral state
Ischnura praematura sp. nov. (Holotype ♂, China, Yunnan, Lijiang, 26º31´03.54”N, 100º13’38.89”E, 2396 m, 04 xii 2015, I. Sanmartín-Villar & H. Zhang leg.) is morphologically described, illustrated and compared with close species of the genus. Ischnura praematura can be mainly distinguished from its congeners I. aurora, I. rubilio and I. asiatica by its abdominal and thoracic morphology and colouration. The posterior lobe of the prothorax is elevated in I. praematura and the mesostigmal plates possess dorsal triangular protuberances. Ischnura praematura shows pointed paraprocts, internalised wide cerci and lacks a dorsal tuberculum in the tenth abdominal segment. The blue abdominal colouration is present in the last three segments (incomplete for segment eight and ten in some individuals). No female polychromatism was detected and all females observed possessed different colouration than male (gynochrome). Morphological distinctiveness of the species is supported by genetic analyses, which show that I. praematura forms a well-supported, monophyletic clade, with I. asiatica, I. ezoin and I. pumilio as the most closely related species. In the field, mature females show strong reluctance to mate, and males were observed mating with newly emerged females.
Ministerio de Economía y Competitividad | Ref. BES-2012-052005Ministerio de Economía y Competitividad | Ref. EEBB-I-15- 09382Ministerio de Ciencia e Innovación | Ref. CGL2014-53140-PMinisterio de Ciencia e Innovación | Ref. PGC2018-096656-B-I0
The evolution and diversity of intra-male sperm translocation in Odonata: a unique behaviour in animals
Behavioural diversity is a basic component of biodiversity, with implications in ecological interactions at the intra- and interspecific levels. The reproductive behaviour of Odonata (dragonflies and damselflies) is unique among insects and conditioned by the anatomical separation between the male’s reproductive organs and the intromittent organ. Prior to mating, males must translocate sperm from the genital pore in the ninth abdominal segment to the seminal vesicle located ventrally in the second abdominal segment. This behaviour, exclusive to odonates, is known as intra-male sperm translocation (ST). Here, we review the literature on ST and use phylogenetic comparative analyses to investigate the evolution of ST within the Odonata. Information on ST was compiled for 176 species, with the commonest variant being ST once per mating, after tandem formation (66%). Other variants found were ST involving precopulatory genital touching (10%), ST by the male alone before tandem (16%) or after copulation (5%), and repetition of ST during the same copulation (3%). The precopulatory genital touching might have evolved to detect female receptivity. ST before tandem formation might be favoured when mating opportunities are scarce and copulations are brief. ST after mating might be favoured if males need to be ready to copulate fast. Finally, repeated ST could have evolved through postcopulatory sexual selection in males with limited sperm removal ability, as a means to improve their sperm competition. The most plausible scenario for the evolution of ST is that the ancestors of the Odonata produced a spermatophore and attached it to the body, leading towards the evolution of the secondary genitalia in males. Our study emphasises the role of behavioural diversity to understand behavioural evolution.Ministerio de Economía y Competitividad | Ref. BES-2015-071965Ministerio de Economía y Competitividad | Ref. CGL2014-53140-
Sexual conflict and the evolution of monandry: the case of the damselfly Ischnura hastata (Odonata: Coenagrionidae) in the Galápagos Islands
Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG1. Sexual selection favours the evolution and maintenance of polygamy, which is the dominant reproductive strategy in insects. Monogamy can evolve in very short-lived species due to time constraints. Here we study adult activity and mating behaviour of a population of the damselfly Ischnura hastata, a species rarely seen mating, and which has been suggested to be monandric, in wetlands of Isabela Island, Galápagos.
2. By means of mark-recapture methods we estimated that the daily survival rate was low, ranging from 0.385 to 0.876, yielding average life expectancies of mature individuals of only 1.2-3.2 days. Adults showed very low activity before 7:00, indicating that mating does not occur early. The number of male-female interactions and mating attempts was extremely low, with only 44 copulations recorded on over 230 h of observations. 3. Copulations were brief, with a mean duration of 11 minutes (but only two observed from the start). Males showed clear preference to attempt to grasp in tandem females of intermediate age (in 94.3% of cases), rather than young (31.3%) or mature females (24.0%). Males were very persistent once a tandem was achieved, retaining females for up to 139 min, but most females resisted and did not copulate.
4. We conclude that females of I. hastata show a very short time window to mate, exactly when they change colour from juvenile to mature, and live only enough to mate once. Short lifespan has selected for female monandry in I. hastata, creating an intense sexual conflict over mating rates.Ministerio de Economía y Competitividad | Ref. CGL2014-53140-PAgencia Estatal de Investigación | Ref. PGC2018-096656-B-I0
Variation in intraspecific sperm translocation behaviour in a damselfly and its consequences for sperm viability
Sperm quality and viability affect both male and female fitness. Most dragonfly and damselfly males translocate sperm from the testis to the seminal vesicle before each copulation, a behaviour known as intramale sperm translocation (ST). However, some published observations indicate that odonate males can occasionally skip ST prior to copulation. Our aim was to determine the circumstances under which males skip ST and how this might affect sperm viability. We allowed males of the damselfly Ischnura graellsii to perform ST (interrupting the copulation at this stage) and we studied ST behaviour during subsequent copulation. Males were randomly assigned to four treatments, which consisted of allowing the experimental male to copulate again 15 min or 1–3 days after his last ST. Fertility of females mated with the experimental males was analysed as a proxy for sperm viability. All males used the sperm that they translocated previously when the second mating took place 15 min after the manipulation, while the proportion of males that repeated ST increased steadily over time. Both treatment (time elapsed since last ST) and the interaction between treatment and ST (yes/no) had a significant effect on fertility, which decreased only in males that did not perform ST immediately before copulation. Additional experiments with damselflies of the genus Calopteryx showed also that males did not repeat ST when the time to the next copulation was less than a day. Our results suggest that sperm quality decays over time in odonates, and that males can choose whether to keep and reuse the sperm in the seminal vesicle or to discard it. We conclude that the special anatomical disposition of odonate males might increase selective pressures to maximize sperm viability and/or repeated intramale ST behaviour.Ministerio de Economía y Competitividad | Ref. BES-2015-071965Ministerio de Economía y Competitividad | Ref. CGL2014-53140-
Water toxicity in reservoirs after freshwater algae harvest
Blooms of microalgae and cyanobacteria increase every year, presenting great problems for the environment. Finding a way of harvesting these microalgae could be useful for water governance. Furthermore, the method should not cause cell lysis and should thus avoiding discharging toxins into the water. Three reservoirs were studied, two of them with eutrophication problems (As Conchas and A Baxe) and another (Salas) with no such problems. Three different harvesting methods were studied; electroflocculation (EF) with the application time being varied; centrifugation, with application times and speeds being varied; and finally, natural sedimentation. The highest efficiency was obtained in the culture from A Baxe, which had a higher initial absorbance value (1.664), using EF (90.64% for an application time of 2 min and 30 s) and centrifugation at 4000 rpm (92.25% for2 minutes, 92.73% for 5 min). Electrofloculation can obtain up to 84% more biomass than natural sedimentation alone. Sample toxicity was studied before and after harvesting using Microcystest and found to be higher after harvesting. It was observed that for the same sample, the higher the yield was the greater the toxicity was. For the A Baxe culture with an application time of 2 min, a speed of 2000 rpm and a yield of 87.02%, a toxicity figure of 0.94 μg/L was obtained, while for a speed of 4000 rpm the yield was 92.25% and the toxicity was 1.05 μg/L. The toxicity limit set by the World Health Organization (WHO) is 1 μg/L, and this small difference seems to be key. With these results, this study concludes that chlorophyll levels may interfere with the test used. Future tests or analyses should be developed so as to avoid such interference, which may alter the toxin values. Electroflocculation seems to be a promising method since it does not cause the lysis of "Microcystis aeruginosa", whereas the centrifugation method could give problems. Finally, it is worth highlighting the importance of performing toxin measurements after harvesting the microalgae to check that the method is viable in natural ecosystems
Genetic divergence and aggressiveness within a supercolony of the invasive ant Linepithema humile
Biological invasions constitute an opportunity to study the evolutionary processes behind species’ adaptations. The invasive potential of some species, like the Argentine ant (Linepithema humile), has likely been increasing because they show low intraspecific competition. However, multiple introductions over time or genetic divergence could increase the probability of intraspecific competition, constituting barriers for their dispersal and thus, decreasing invasive success. Here, we studied the genetic and behavioural variability of L. humile workers collected at six locations on the NW coast of the Iberian Peninsula, a possible scenario for multiple introductions and population divergence, due to its high level of maritime traffic and complex coastal geography. We analysed behaviours related to spatial navigation (exploration, wall-following), resources acquisition, and competition (inter and intraspecific aggressiveness) through two relevant seasons for the nest ecology: spring and autumn. Genetic analyses using microsatellites indicated that the nests studied belonged to the most spread supercolony in South Europe. However, we identified the existence of two genetically differentiated clusters in Galiza. Lethal interactions were found between workers from different and similar genetic clusters, but a trend suggests higher agonistic behaviours between the two genetic groups. Genetic differences were positively correlated with the geographical distance, but aggressiveness was not correlated with any of them. Ants from each of the tested nests expressed different behaviours with high plasticity through time. Ants from all nests showed more exploration and aggressiveness, less wall-following and faster detection of food in autumn than in spring, with no intraspecific aggressiveness observed in spring. Our findings suggest competition between nests of the same supercolony and behavioural seasonal variability, supporting the hypothesis of divergent evolutionary processes. The results of our work question the assumed unity of supercolonies of this species and offer insights for understanding the future adaptation of L. humile in the introduced areas