A new coordinating model for green supply chain and batch delivery scheduling with satisfaction customers

Environment, Development and Sustainability - Scheduling an integrated, detailed SC (supply chain) at the operational level is a crucial aspect of SCM (supply chain management). Simultaneous...     

Chemically mediated burrow recognition in the Mexican tarantula <Emphasis Type="Italic">Brachypelma vagans</Emphasis> female

Chemically mediated communication is common in spiders but has been poorly studied in burrowing tarantulas. This study aimed to determine whether chemical cues influence the behaviour of females of Brachypelma vagans, a Mexican species of tarantula, during encounters with previously inhabited burrows or with extracts from the silk of conspecific females. In laboratory choice tests, female tarantulas entered a burrow that had previously been inhabited by a conspecific female significantly more frequently than a burrow that had never been inhabited. The identity of the previous inhabitant also affected the number of spiders that chose to enter a burrow. Spiders were quicker to choose and enter a burrow previously inhabited by themselves than a burrow previously inhabited by a conspecific or a burrow that had not been previously inhabited. Hexane, methanol and dichloromethane extracts of conspecific silk elicited different responses from female tarantulas when extracts were placed on filter paper disks at one end of an experimental arena with a control filter paper disk, on to which the corresponding solvent alone had been pipetted, placed on the other end of the arena. Spiders showed the strongest responses to hexane extracts of silk, with a significant preference to move towards the hexane extract and a significantly greater period of time spent in proximity to the hexane extract compared to the control disk. Overall and in contrast to expectations, tarantulas were most strongly attracted to the cues left by other conspecific females. As encounters between B. vagans females usually lead to aggression and mortality of one of the participants, we conclude that chemical cues are not signals that are deliberately released by burrow-inhabiting females but may inadvertently escape and cannot be easily suppressed.     

Between introgression events and fragmentation, islands are the last refuge for the American crocodile in Caribbean Mexico

Habitat loss and degradation in the Mexican Caribbean, caused by the development of tourism, have decreased the potential nesting area for the American crocodile (Crocodylus acutus) and have fragmented the populations of the Yucatan peninsula. Our study investigated five populations (three continental: North, South, Sian Ka’an, and two insular: Cozumel, Banco Chinchorro) of C. acutus in the Mexican Caribbean using seven different inter simple sequence repeat (ISSR) markers as tools for genetic variability and population differentiation. Three classification methods were tested and compared: distance analysis, self-organizing map, and Bayesian methods, to evaluate the resolution of each method with ISSR markers. The 77 loci selected revealed a high variability between populations (polymorphism from 17% for Sian Ka’an to 75% for Banco Chinchorro) with a total polymorphism of 84% and a global coefficient of gene differentiation (G _ST ) of 0.296, but low values of Nei’s Gene diversity (from 0.065 for Sian Ka’an to 0.233 for Banco Chinchorro). Our results suggest elevated inbreeding in all local populations with higher indices for Banco Chinchorro and lower indices for Sian Ka’an. Three independent classification methods gave similar results, and suggested that most continental individuals are admixtures, with different levels of introgression, with the sympatric species Crocodylus moreletii. We propose that the islands/atolls remain the sole areas with genetically “pure” American crocodiles and we discuss these results for future conservation of this endangered crocodile species.