A study of abundance of planktonic organisms in Lekan-Are Lake, Ogun State, Nigeria

A study of the plankton abundance in the shore, surface and bottom of Lake Lekan-Are Abeokuta, Ogun State, Nigeria was carried out between January 2007 and August 2008 at three stations along the entire stretch of the lake. The numerical abundance of the plankton in this lake was investigated. There were marked seasonal variations in the zooplankton and phytoplankton of the lake. Four major groups of phytoplankton were identified Baccilariophyceae (diatoms), Chlorophyceae (green algae) and Cyanophyceae (blue green). The green algae dominated the phytoplankton constituting 63.3% in the surface and 54.8% in the bottom zone of the lake. The phytoplankton density was at its peak in sunny months of January to early June that coincided with the period of high temperature. The three major groups of zooplankton observed in the lake were Cladocera, Copepoda and Rotifera. The Copepoda dominated the three habitats 83.37% (shore), 82.73% (surface) and 80.26% (bottom). Copepoda also dominated at the three stations of the lake. The  seasonality of zooplankton followed a similar pattern with that of the phytoplankton reaching a peak between February and May.Keywords: Numerical abundance, plankton Lekan Area, Nigeri

Factors modifying the association between birth weight and blood pressure

Contains fulltext : 88632.pdf (publisher's version ) (Closed access)1 december 201

Female cuckoo calls misdirect host defences towards the wrong enemy

Prey are sensitive to even subtle cues of predation risk which provides the evolutionary potential for parasites to exploit host risk perception. Brood parasitic common cuckoos (Cuculus canorus) lay their eggs in the nests of host species and their secretive laying behaviour enables them to evade host defences. Therefore, it seems paradoxical that female cuckoos often give a conspicuous “chuckle” call after parasitizing a host’s clutch. Here we show that this hawk-like chuckle call increases the success of parasitism by diverting host parents’ attention away from the clutch and towards their own safety. Our field experiments reveal that reed warbler (Acrocephalus scirpaceus) hosts paid no more attention to the “cuck-oo” call of the male common cuckoo than to the call of a harmless dove. However, the chuckle call of the female cuckoo had the same effect as the call of a predatory hawk in distracting the warblers’ attention and reducing rejection of a foreign egg. Our results show that the cuckoo enhances her success by manipulating a fundamental trade-off in host defences between clutch- and self-protection

Cognition and the brain of brood parasitic cowbirds.

Cowbirds are brood parasites. Females lay their eggs in the nests of other species, which then incubate the cowbird eggs and raise the young cowbirds. Finding and returning to heterospecific nests presents cowbirds with several cognitive challenges. In some species, such as brown-headed cowbirds (Molothrus ater), females but not males search for and remember the locations of potential host nests. We describe recent research on sex differences in cognition and the hippocampus associated with this sex difference in search for host nests. Female brown-headed cowbirds perform better than males on some, but not all, tests of spatial memory and females show a pattern of adult hippocampal neurogenesis not found in males or in closely related non-parasitic birds. Because of the apparent specialization of the hippocampus, brown-headed cowbirds may be a good model in which to examine spatial information processing in the avian hippocampus and we also describe recent research on the spatial response properties of brown-headed cowbird hippocampal neurons

Relationships between egg-recognition and egg-ejection in a grasp-ejector species

Brood parasitism frequently leads to a total loss of host fitness, which selects for the evolution of defensive traits in host species. Experimental studies have demonstrated that recognition and rejection of the parasite egg is the most common and efficient defence used by host species. Egg-recognition experiments have advanced our knowledge of the evolutionary and coevolutionary implications of egg recognition and rejection. However, our understanding of the proximate mechanisms underlying both processes remains poor. Egg rejection is a complex behavioural process consisting of three stages: egg recognition, the decision whether or not to reject the putative parasitic egg and the act of ejection itself. We have used the blackbird (Turdus merula) as a model species to explore the relationship between egg recognition and the act of egg ejection. We have manipulated the two main characteristics of parasitic eggs affecting egg ejection in this grasp-ejector species: the degree of colour mimicry (mimetic and non-mimetic, which mainly affects the egg-recognition stage of the egg-rejection process) and egg size (small, medium and large, which affects the decision to eject), while maintaining a control group of non-parasitized nests. The behaviour of the female when confronted with an experimental egg was filmed using a video camera. Our results show that egg touching is an indication of egg recognition and demonstrate that blackbirds recognized (i.e., touched) non-mimetic experimental eggs significantly more than mimetic eggs. However, twenty per cent of the experimental eggs were touched but not subsequently ejected, which confirms that egg recognition does not necessarily mean egg ejection and that accepting parasitic eggs, at least sometimes, is the consequence of acceptance decisions. Regarding proximate mechanisms, our results show that the delay in egg ejection is not only due to recognition problems as usually suggested, given that experimental eggs are not touched significantly more often. Thus, the delay in egg ejection is mainly the consequence of a delay in the decision to eject, probably triggered by mechanical constraints imposed by eggs that are harder to eject (i.e. larger). Our results offer important information on the relationships between recognition and ejection and contribute to a better understanding of host defences against brood parasites.Financial support was provided by the Junta de Andalucía (research project CVI-6653). JDI is funded by a postdoctoral contract (TAHUB-104) from the “Andalucía Talent Hub” program (co-funded by the European's Union Seventh Framework Program Marie Skłodowska-Curie actions (COFUND) and the regional Government of Andalucía)

Observed Reductions in Schistosoma mansoni Transmission from Large-Scale Administration of Praziquantel in Uganda: A Mathematical Modelling Study

To date schistosomiasis control programmes based on chemotherapy have largely aimed at controlling morbidity in treated individuals rather than at suppressing transmission. In this study, a mathematical modelling approach was used to estimate reductions in the rate of Schistosoma mansoni reinfection following annual mass drug administration (MDA) with praziquantel in Uganda over four years (2003-2006). In doing this we aim to elucidate the benefits of MDA in reducing community transmission.Age-structured models were fitted to a longitudinal cohort followed up across successive rounds of annual treatment for four years (Baseline: 2003, TREATMENT: 2004-2006; n = 1,764). Instead of modelling contamination, infection and immunity processes separately, these functions were combined in order to estimate a composite force of infection (FOI), i.e., the rate of parasite acquisition by hosts.MDA achieved substantial and statistically significant reductions in the FOI following one round of treatment in areas of low baseline infection intensity, and following two rounds in areas with high and medium intensities. In all areas, the FOI remained suppressed following a third round of treatment.This study represents one of the first attempts to monitor reductions in the FOI within a large-scale MDA schistosomiasis morbidity control programme in sub-Saharan Africa. The results indicate that the Schistosomiasis Control Initiative, as a model for other MDA programmes, is likely exerting a significant ancillary impact on reducing transmission within the community, and may provide health benefits to those who do not receive treatment. The results obtained will have implications for evaluating the cost-effectiveness of schistosomiasis control programmes and the design of monitoring and evaluation approaches in general

Egg rejection in blackbirds Turdus merula: a by-product of conspecific parasitism or successful resistance against interspecific brood parasites?

Traditional theory assumes that egg recognition and rejection abilities arise as a response against interspecific brood parasitism (IBP). However, rejection also appears in some species that are currently not exploited by interspecific parasites, such as Turdus thrushes. Recent evidences suggest that rejection abilities evolved in these species as a response to conspecific brood parasitism (CBP). To test these two alternative hypotheses, we performed an experimental study by parasitizing nests of the common blackbird (Turdus merula) with conspecifics or heterospecific eggs under different risk of parasitism (presence of interspecific or conspecific parasites near the nest). Common blackbird is a potential host of the common cuckoo (Cuculus canorus) but suffers low levels of CBP too. Results: We found that blackbirds were able to recognize and eject heterospecific eggs at high rates whereas most of conspecifics eggs were not recognized and, therefore, accepted. Ejection rates of conspecific eggs did not exceed 13 %, even in situations of high risk of CBP (blackbird female placed near the nest), which contradict the main prediction derived from the CBP hypothesis. Conversely, ejection rates of experimental eggs simulating IBP were much higher (80–100 %). Furthermore, female blackbirds were more aggressive towards cuckoos than towards blackbird dummies. Conclusions: Our results considered together support the IBP hypothesis, indicating that recognition and rejection of parasitic eggs in blackbirds have probably evolved due to previous cuckoo parasitism. The current absence of IBP in blackbirds may be due to the highly efficient rejection abilities in this species. Thus, these abilities have been retained in absence of brood parasitism as a consequence of the low costs involved for blackbirds, resulting in a successful resistance against interspecific brood parasitism.Financial support has been provided by the Consejería Economía, Innovación, Ciencia y Empleo. Junta de Andalucia (research project CVI-6653)

Ownership-dependent mating tactics of minor males of the beetle Librodor japonicus (Nitidulidae) with intra-sexual dimorphism of mandibles

Intra-sexual dimorphism is found in the weapons of many male beetles. Different behavioral tactics to access females between major and minor males, which adopt fighting and alternative tactics, respectively, are thought to maintain the male dimorphism. In these species major males have enlarged weapons that they use in fights with rival males. Minor males also have small weapons in some of these species, and it is unclear why these males possess weapons. We examined the hypothesis that minor males might adopt a fighting tactic when their status was relatively high in comparison with that of other males (e.g., ownership of a territory). We observed the behavioral tactics of major and minor males of the beetle Librodor japonicus, whose males have a dimorphism of their mandibles. Major males fought for resources, whereas minor males adopted two status-dependent tactics, fighting and sneaking, to access females, depending on their ownership of a sap site. We suggest that ownership status-dependent mating tactics in minor males may maintain the intra-sexual dimorphism in this beetle.</p

Social relationships in a cooperatively polyandrous group of tamarins ( Saguinus fuscicollis )

This paper presents detailed data on the social relationships among the adults, and between the adults and young, of a cooperatively polyandrous saddle-back tamarin ( Saguinus fusciollis ; Callitrichidae) group studied for one year. Some data are also presented from groups studied in other years. Adult males in the study groups gave more grooming than they received, while the opposite was true for females (e.g. Fig. 1). The two polyandrous males in the main study group were very rarely aggressive to each other, rarely tried to disrupt each others' copulations, groomed each other, and occasionally shared food, suggesting that their relationship was more affiliative than agonistic. Data on grooming (Fig. 2), spatial relationships, and the initiation of copulations suggest that the males of this group, may have been somewhat more responsible than the female for the maintenance of male-female relationships. Both males and females performed all forms of parental care except lactation. In the main study group each of the males groomed the offspring and remained in close proximity to them more than did the female (Figs.3 and 4). These data are compared with existing data on social relationships in bird species that exhibit cooperative polyandry.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46887/1/265_2004_Article_BF00299639.pd

Egg Eviction Imposes a Recoverable Cost of Virulence in Chicks of a Brood Parasite

Background: Chicks of virulent brood parasitic birds eliminate their nestmates and avoid costly competition for foster parental care. Yet, efforts to evict nest contents by the blind and naked common cuckoo Cuculus canorus hatchling are counterintuitive as both adult parasites and large older cuckoo chicks appear to be better suited to tossing the eggs and young of the foster parents. Methodology/Principal Findings: Here we show experimentally that egg tossing imposed a recoverable growth cost of mass gain in common cuckoo chicks during the nestling period in nests of great reed warbler Acrocephalus arundinaceus hosts. Growth rates of skeletal traits and morphological variables involved in the solicitation of foster parental care remained similar between evictor and non-evictor chicks throughout development. We also detected no increase in predation rates for evicting nests, suggesting that egg tossing behavior by common cuckoo hatchlings does not increase the conspicuousness of nests. Conclusion: The temporary growth cost of egg eviction by common cuckoo hatchlings is the result of constraints imposed by rejecter host adults and competitive nestmates on the timing and mechanism of parasite virulence.Michael G. Anderson, Csaba Moskát, Miklós Bán, Tomáš Grim, Phillip Cassey and Mark E. Haube