Rethinking trophic niches: Speed and body mass colimit prey space of mammalian predators

1. Realized trophic niches of predators are often characterized along a one‐dimensional range in predator–prey body mass ratios. This prey range is constrained by an “energy limit” and a “subdue limit” toward small and large prey, respectively. Besides these body mass ratios, maximum speed is an additional key component in most predator–prey interactions.
2. Here, we extend the concept of a one‐dimensional prey range to a two‐dimensional prey space by incorporating a hump‐shaped speed‐body mass relation. This new “speed limit” additionally constrains trophic niches of predators toward fast prey.
3. To test this concept of two‐dimensional prey spaces for different hunting strategies (pursuit, group, and ambush predation), we synthesized data on 63 terrestrial mammalian predator–prey interactions, their body masses, and maximum speeds.
4. We found that pursuit predators hunt smaller and slower prey, whereas group hunters focus on larger but mostly slower prey and ambushers are more flexible. Group hunters and ambushers have evolved different strategies to occupy a similar trophic niche that avoids competition with pursuit predators. Moreover, our concept suggests energetic optima of these hunting strategies along a body mass axis and thereby provides mechanistic explanations for why there are no small group hunters (referred to as “micro‐lions”) or mega‐carnivores (referred to as “mega‐cheetahs”).
5. Our results demonstrate that advancing the concept of prey ranges to prey spaces by adding the new dimension of speed will foster a new and mechanistic understanding of predator trophic niches and improve our predictions of predator–prey interactions, food web structure, and ecosystem functions.

     

1H, 13C and 15N resonance assignment of phage T4 endoribonuclease RegB

RegB is involved in the control of the phage T4 life cycle. It inactivates the phage early mRNAs when their translation is no more required. We determined its structure and identified residues involved in substrate binding. For this, all backbone and 90% of side-chain resonance frequencies were assigned.     

Hereditary retinoblastoma: can balanced insertion entirely explain the differences of expressivity among families?

Summary Although the retinoblastoma gene has been isolated and sequenced, the difference in penetrance and expressivity among families has not yet been fully explained. Balanced chromosomal insertion involving the 13q14 regions has been shown to account for some families with several unaffected carriers. Since there could be cases with karyotypically undetectable insertions, we tested whether this mechanism was general enough to explain the whole difference in expressivity among families. Using 166 pedigrees, reported in nine series available in the literature (including our own), we conclude that balanced insertion cannot entirely explain the familial data, even if we allow for a reduced viability of unbalanced gametes. Other mechanisms are proposed and discussed in this paper.     

Disentangling invasion processes in a dynamic shipping-boating network

The relative importance of multiple vectors to the initial establishment, spread and population dynamics of invasive species remains poorly understood. This study used molecular methods to clarify the roles of commercial shipping and recreational boating in the invasion by the cosmopolitan tunicate, Botryllus schlosseri. We evaluated (i) single vs. multiple introduction scenarios, (ii) the relative importance of shipping and boating to primary introductions, (iii) the interaction between these vectors for spread (i.e. the presence of a shipping-boating network) and (iv) the role of boating in determining population similarity. Tunicates were sampled from 26 populations along the Nova Scotia, Canada, coast that were exposed to either shipping (i.e. ports) or boating (i.e. marinas) activities. A total of 874 individuals (c. 30 per population) from five ports and 21 marinas was collected and analysed using both mitochondrial cytochrome c oxidase subunit I gene (COI) and 10 nuclear microsatellite markers. The geographical location of multiple hotspot populations indicates that multiple invasions have occurred in Nova Scotia. A loss of genetic diversity from port to marina populations suggests a stronger influence of ships than recreational boats on primary coastal introductions. Population genetic similarity analysis reveals a dependence of marina populations on those that had been previously established in ports. Empirical data on marina connectivity because of boating better explains patterns in population similarities than does natural spread. We conclude that frequent primary introductions arise by ships and that secondary spread occurs gradually thereafter around individual ports, facilitated by recreational boating.     

Structure and growth pattern of the bizarre hemispheric prominence on the rostrum of the fossil beaked whale Globicetus hiberus (Mammalia,Cetacea, Ziphiidae)

The rostrum of most ziphiids (beaked whales) displays bizarre swollen regions, accompanied with extreme hypermineralisation and an alteration of the collagenous mesh of the bone. The functional significance of this specialization remains obscure. With the voluminous and dense hemispheric excrescence protruding from the premaxillae, the recently described fossil ziphiid Globicetus hiberus is the most spectacular case. This study describes the histological structure and interprets the growth pattern of this unique feature. Histologically, the prominence in Globicetus is made up of an atypical fibro‐lamellar complex displaying an irregular laminar organization and extreme compactness (osteosclerosis). Its development is suggested to have resulted from a protraction of periosteal accretion over the premaxillae, long after the end of somatic growth. Complex shifts in the geometry of this tissue are likely to have occurred during its accretion and no indication of Haversian remodeling could be found. X‐ray diffraction and Raman spectroscopy indicate that the bone matrix in the premaxillary prominence of Globicetus closely resembles that of the rostrum of the extant beaked whale Mesoplodon densirostris: apatite crystals are of common size and strongly oriented, but the collagenous meshwork within bone matrix seems to be extremely sparse. These morphological and structural data are discussed in the light of functional interpretations proposed for the highly unusual and diverse ziphiid rostrum. J. Morphol. 277:1292–1308, 2016. © 2016 Wiley Periodicals, Inc.     

Structural studies on cyanobacterial photosystem I

The cyanobacterial photosystem, I complex from Synechococcus sp. PCC6301 contains polypeptides of apparent M_r of 70,000, 18,000, 17,700, 16,000 and 10,000. Procedures were developed for the purification of the M_r 17,700 and 10,000 polypeptides. Amino acid analyses showed the absence of cystine and cysteine from these polypeptides. Amino-terminal sequences of 98 residues for the M_r 17,700 polypeptide and of 42 residues for the M_r 10,000 polypeptide were determined. Studies of pigment distribution within the photosystem I complex indicated that the binding of chlorophyll a and -carotene is in part dependent on the presence of these polypeptides.Abbreviations PSI photosystem I - P700 reaction center of PSI - SDS sodium dodecylsulfate - TBS tris-buffered saline - TTBS TBS containing Tween-20     

Effect of noradrenaline chronic administration on brown fat phospholipids

Chronic cold exposure of rats (9 days at 5°C) induces an alteration of the fatty acid composition of phospholipids in brown adipose tissue. The alteration is due to an increase of the unsaturation degree of these lipids. The phenomenon can be reproduced by 10^–7 mole. h^–1 administration of noradrenaline for 9 days in rats kept at 25°C. Thus, phospholipid alteration in brown fat of cold exposed rats is most probably a consequence of the increase of sympathetic tone which occurs in this tissue during exposure to cold.     

NCI-H716 cells as a model for endocrine differentiation in colorectal cancer

In colonic neoplasms, endocrine differentiation is encountered not only in carcinoid tumors but also in adenocarcinomas, where endocrine cells may represent a distinct line of differentiation in the tumor. The significance of endocrine differentiation in colorectal cancer is not well established, partly because of the paucity of tumor cell lines which can serve as a model for studying endocrine differentiation. In this report we describe the properties of NCI-H716 cells, a cell line derived from a poorly differentiated adenocarcinoma of the caecum, under various in vitro conditions and as xenografts in athymic mice. Phenotypical properties were immunohistochemically assessed using a panel of differentiation related antibodies, and also by Northern blot analysis and by electron microscopy. Receptors for biogenic amines and peptide hormones were analyzed by ligand binding assay. These studies show that:

Plant regeneration from haploid cell suspension-derived protoplasts of Mediterranean rice (Oryza sativa L. cv. Miara)

More than 750 plants were regenerated from protoplasts isolated from microspore callus-derived cell suspensions of the Mediterranean japonica rice Miara, using a nurse-feeder technique and N6-based culture medium. The mean plating efficiency and the mean regeneration ability of the protocalluses were 0.5% and 49% respectively. Flow cytometric evaluation of the DNA contents of 7 month old-cell and protoplast suspensions showed that they were still haploid. Contrastingly, the DNA contents of leaf cell nuclei of the regenerated protoclones ranged from 1C to 5C including 60% 2C plants. This was consistent with the morphological type and the fertility of the mature plants. These results and the absence of chimeric plants suggest that polyploidization occurred during the early phase of protoplast culture.Abbreviations BAP 6-benzylamino purine - 2,4-D 2,4-dichlorophenoxyacetic acid - FDA fluorescein diacetate - GA3 gibberellic acid - NAA -naphthaleneacetic acid - PAS periodic acid Schiff - PCM protoplast culture medium - PCV packed cell volume     

Expression of a Rhizobium phaseoli Sym plasmid in R. trifolii and Agrobacterium tumefaciens: incompatibility with a R. trifolii Sym plasmid

Identification of the Sym plasmid in Rhizobium phaseoli strain RCC3622 is described. Introduction of this plasmid into R. trifolii or Agrobacterium tumefaciens strains resulted in bacteria capable of forming characteristic spherical root nodules on beans. This Sym plasmid, designated pSym9, was characterized as 275 MDa and nonconjugative. pSym9 was incompatible with the R. trifolii Sym plasmid pSym5, and carries genes determining a melanin-like black pigment. A second plasmid of 135 MDa, pRph3622a, was also transferred from R. phaseoli to R. trifolii and A. tumefaciens. Transconjugants carrying this plasmid did not form root nodules on beans. In contrast to other Rhizobium plasmids, pRph3622a was unstable in A. tumefaciens.