Social interactions of juvenile brown boobies at sea as observed with animal-borne video cameras.

While social interactions play a crucial role on the development of young individuals, those of highly mobile juvenile birds in inaccessible environments are difficult to observe. In this study, we deployed miniaturised video recorders on juvenile brown boobies Sula leucogaster, which had been hand-fed beginning a few days after hatching, to examine how social interactions between tagged juveniles and other birds affected their flight and foraging behaviour. Juveniles flew longer with congeners, especially with adult birds, than solitarily. In addition, approximately 40% of foraging occurred close to aggregations of congeners and other species. Young seabirds voluntarily followed other birds, which may directly enhance their foraging success and improve foraging and flying skills during their developmental stage, or both.

Production and characterization of an alloplasmic and monosomic addition line of Brassica rapa carrying the cytoplasm and one chromosome of Moricandia arvensis.

Intergeneric hybridization was performed between Moricandia arvensis and four inbred lines of Brassica rapa following embryo rescue. Three F(1) hybrid plants were developed from three cross combinations of M. arvensis × B. rapa, and amphidiploids were synthesized by colchicine treatment. Six BC(1) plants were generated from a single cross combination of amphidipolid × B. rapa 'Ko1-303' through embryo rescue. One BC(2) and three BC(3) plants were obtained from successive backcrossing with B. rapa 'Ko1-303' employing embryo rescue. Alloplasmic and monosomic addition lines of B. rapa (Allo-MALs, 2n = 21) were obtained from backcrossed progeny of three BC(3) plants (2n = 21, 22 and 23) without embryo rescue. An alloplasmic line of B. rapa (2n = 20) degenerated before floliation on 1/2 MS medium due to severe chlorosis. Allo-MALs of B. rapa (2n = 21) showed stable male sterility without any abnormal traits in vegetative growth and female fertility. Molecular analyses revealed that the same chromosome and cytoplasm of M. arvensis had been added to each Allo-MAL of B. rapa. This Allo-MAL of B. rapa may be useful material for producing cytoplasmic male sterile lines of B. rapa.