42 research outputs found
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)
2-[4-Chloro-3-(4-ethoxybenzyl)phenyl]-1,3-dithiane
In the title compound, C19H21ClOS2, the dithiane ring adopts a chair conformation. The dihedral angle between the benzene rings is 87.88 (4)°. In the crystal, inversion dimmers linked by pairs of C—H...O interactions occur
Two Routes to 4‑Fluorobenzisoxazol-3-one in the Synthesis of a 5‑HT<sub>4</sub> Partial Agonist
A potent 5-HT<sub>4</sub> partial agonist, <b>1</b> (PF-04995274),
targeted for the treatment of Alzheimer’s disease and cognitive
impairment, has been prepared on a multi-kilogram scale. The initial
synthetic route, that proceeded through a 4-substituted 3-hydroxybenzisoxazole
core, gave an undesired benzoxazolinone through a Lossen-type rearrangement.
Route scouting led to two new robust routes to the desired 4-substituted
core. Process development led to the efficient assembly of the API
on a pilot plant scale under process-friendly conditions with enhanced
throughput. In addition, crystallization of a hemicitrate salt of
the API with pharmaceutically beneficial properties was developed
to enable progression of clinical studies
Long, Directional Interactions in Cofacial Silicon Phthalocyanine Oligomers
Single crystal structures have been determined for the three cofacial, oxygen-bridged, silicon phthalocyanine oligomers, [((CH<sub>3</sub>)<sub>3</sub>SiO)<sub>2</sub>(CH<sub>3</sub>)SiO](SiPcO)<sub>2–4</sub>[Si(CH<sub>3</sub>)(OSi(CH<sub>3</sub>)<sub>3</sub>)<sub>2</sub>], and for the corresponding monomer. The data for the oligomers give structural parameters for a matching set of three cofacial, oxygen-bridged silicon phthalocyanine oligomers for the first time. The staggering angles between the six adjacent cofacial ring pairs in the three oligomers are not in a random distribution nor in a cluster at the intuitively expected angle of 45° but rather are in two clusters, one at an angle of 15° and the other at an angle of 41°. These two clusters lead to the conclusion that long, directional interactions (LDI) exist between the adjacent ring pairs. An understanding of these interactions is provided by atoms-in-molecules (AIM) and reduced-density-gradient (RDG) studies. A survey of the staggering angles in other single-atom-bridged, cofacial phthalocyanine oligomers provides further evidence for the existence of LDI between cofacial phthalocyanine ring pairs in single-atom-bridged phthalocyanine oligomers
Long Directional Interactions (LDIs) in Oligomeric Cofacial Silicon Phthalocyanines and Other Oligomeric and Polymeric Cofacial Phthalocyanines
Crystal structures have been determined for the three-member
set of cofacial silicon phthalocyanines, ((<i>n</i>-C<sub>6</sub>H<sub>13</sub>)<sub>3</sub>SiO)[SiPcO]<sub>1–3</sub>(Si(<i>n</i>-C<sub>6</sub>H<sub>13</sub>)<sub>3</sub>).
The staggering angles between adjacent rings in the dimer and trimer
of this set are ∼16°. The interactions leading to these
angles have been investigated by the atoms-in-molecules (AIM) and
reduced-density-gradient (RDG) methods. The results show that long
directional interactions (LDIs) are responsible for these angles.
A survey of the staggering angles in various cofacial phthalocyanines
described in the literature has revealed the existence of significant
LDIs in a number of them. It is apparent that in many cases the ability
of LDIs to dominate the forces giving rise to the staggering angles
observed in cofacial phthalocyanines depends on their inter-ring separations