Social preferences and network structure in a population of reef manta rays

Understanding how individual behavior shapes the structure and ecology ofpopulations is key to species conservation and management. Like manyelasmobranchs, manta rays are highly mobile and wide ranging species threatened byanthropogenic impacts. In shallow-water environments these pelagic rays often formgroups, and perform several apparently socially-mediated behaviors. Group structuresmay result from active choices of individual rays to interact, or passive processes.Social behavior is known to affect spatial ecology in other elasmobranchs, but this isthe first study providing quantitative evidence for structured social relationships inmanta rays. To construct social networks, we collected data from more than 500groups of reef manta rays over five years, in the Raja Ampat Regency of West Papua.We used generalized affiliation indices to isolate social preferences from non-socialassociations, the first study on elasmobranchs to use this method. Longer lastingsocial preferences were detected mostly between female rays. We detectedassortment of social relations by phenotype and variation in social strategies, with theoverall social network divided into two main communities. Overall network structurewas characteristic of a dynamic fission-fusion society, with differentiated relationshipslinked to strong fidelity to cleaning station sites. Our results suggest that fine-scaleconservation measures will be useful in protecting social groups of M. alfredi in theirnatural habitats, and that a more complete understanding of the social nature of mantarays will help predict population response

Periodontal ligament cells secrete the factor that inhibits osteoclastic differentiation and function: the factor is osteoprotegerin/osteoclastogenesis inhibitory factor

Published in Journal of Periodontal Research, 2001; 36 (1):56-63 at www.interscience.wiley.comNaohisa Wada, Hidefumi Maeda, Kazunari Tanabe, Eisuke Tsuda, Kazuki Yano, Hiroyoshi Nakamuta and Akifumi Akamin

Lymphoepithelioma-Like Carcinoma of the Colon

A 70-year-old female underwent follow-up colonoscopy after colonic polypectomy. The colonoscopy revealed the presence of a 7-mm submucosal tumor in the sigmoid colon. The tumor surface was smooth and covered with normal mucosa. It was diagnosed as a submucosal tumor, and polypectomy was performed. Histopathological examination of the resected specimen revealed moderately to poorly differentiated adenocarcinoma measuring 2 × 5 × 3 mm with marked peritumoral lymphocytic infiltration and lymphoid follicle formation. It was diagnosed as carcinoma with lymphoid stroma (lymphoepithelioma-like carcinoma), SM (1,800 μm), ly2, v0, budding; grade 1. We confirmed the indication for noncurative additional surgical resection and performed laparoscopic sigmoid colectomy. No metastases were observed in the dissected lymph nodes