Macrofaunal communities of threatened subtidal maёrl seabeds on Tenerife (Canary Islands, north-east Atlantic Ocean) in summer

This study contributes with the first data on physical and taxonomical structure of macrofaunal assemblages of maerl beds from the Canary Islands. Maerl beds and Cymodocea nodosa meadows of the Canary Islands are considered biodiversity hot-spots in terms of taxonomic and functional biodiversity with a broad geographical and depth ranges. The authors have studied the structure of the macrofaunal assemblages on different habitat types （Cymodocea, Caulerpa, sabellid field, garden eel and maerl beds）. Samples were taken at a range of depths between 14 and 46 m. Correlations were performed among abiotic variables （granulometry, organic matter, nitrogen and phosphates） and the most abundant taxa. Similarity analysis was performed to explore the patchiness of seabeds at a local scale. Significant differences were found in macrofaunal assemblages among seabed types, with highest abundances and lowest biodiversity in sabellid fields, where the sabellid Bispira viola dominated. The polychaetes Aponuphis bilineata and Chone filicauda and the mollusc Turritella brochii were the most abundant taxa on maerl beds. The mosaic of granulometric conditions would explain the associated macroinfaunal community structure and contribute to the creation of diversity on these relatively well preserved seabeds at a local scale.

The qqsQ(q=u,d;Q=c,b)tetraquark system in a chiral quark model

The S-wave qqsQ(q=u,d;Q=c,b)tetraquarks,with spin-paritiesJ^(P)=0^(+),1^(+),and 2^(+),in both isoscalar and isovector sectors,are systematically studied using a chiral quark model.The meson-meson,diquark-antidiquark,and K-type arrangements of quarks and all possible color wave functions are comprehensively considered.The four-body system is solved using the Gaussian expansion method,a highly efficient computational approach.Additonally,a complex-scaling formulation of the problem is established to disentangle bound,resonance,and scattering states.This theoretical framework has already been successfully applied in various tetra-and penta-quark systems.For the complete coupled channel and within the complex-range formulation,several narrow resonances of qqsC and qqsb systems are obtained,in each allowed I(J^(P))-channel,within the energy regions of 2.4-3.4 GeV and 5.7-6.7GeV,respectively.The predicted exotic states,which indicate a richer color structure when going towards multiquark systems beyond mesons and baryons,are expected to be confirmed in future high-energy particle and nuclear experiments.

Triply heavy baryons in the constituent quark model

The constituent quark model is used to compute the ground and excited state masses of QQQ baryons containing either c or b quarks.The quark model parameters previously used to describe the properties of charmonium and bottomonium states were used in this analysis.The non-relativistic three-body bound state problem is solved by means of the Gaussian expansion method which provides sufficient accuracy and simplifies the subsequent evaluation of the matrix elements.Several low-lying states with quantum numbers J^P=1/2^±,3/2^±,5/2^±and 7/2^+are reported.We compare the results with those obtained by the other theoretical formalisms.There is a general agreement for the mass of the ground state in each sector of triply heavy baryons.However,the situation is more puzzling for the excited states,and appropriate comments about the most relevant features of our comparison are given.