title: Variations in body size of the lancelet Branchiostoma belcheri at different depths in the Seto Inland Sea: effect of food supply on the growth rate.
abstract: Variations in body size of the suspension-feeding lancelet Branchiostoma belcheri were examined from April 2001 to December 2001 at different water depths of 10-80 m. The lancelets were abundantly collected (220 indiv./dredge) at water depth of 10 m. The maximum size, ranging from 36.8 to 50.4 mm BL, decreased with increasing water depth. However, the minimum size of 7.4-7.8 mm BL, which corresponds to settling size, did not different with water depth. From seasonal changes in the length-frequency histograms, five cohorts were observed at every water depth. The lancelets grew to 44 mm BL at water depths of 10-20 m and to 34 mm BL at water depth of 80 m with four years of life span. Developmental stages of the gonads at an age of two years showed that no individuals had undeveloped gonads at water depth of 10 m, but 82% of them did at water depth of 80 m. The analysis of the stepwise multiple regressions of monthly growth rate on environmental variables showed that chlorophyll a was the best explanatory variable and showed a significant positive correlation with the growth of 1-2 years age groups. These results suggested that variations in the body length were mainly fluctuated by phytoplankton supply.
authors.affiliation: Graduated School of Biosphere Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima 739-8528, Japan. saito@hiroshima-u.ac.jp
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Saito
authors.forename: Keisuke
authors.initials: K
authors.lastname: Mimura
authors.forename: Akira
authors.initials: A
authors.lastname: Doi
authors.forename: Eiso
authors.initials: E
authors.lastname: Inoue
authors.forename: Koichiro
authors.initials: K
authors.lastname: Kawai
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Imabayashi
mesh_terms: D000367:Age Factors; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D049628:Body Size; D002816:Chordata, Nonvertebrate / Q000254:growth & development*; D006066:Gonads / Q000254:growth & development; D007564:Japan; D008386:Marine Biology; D012044:Regression Analysis; D012621:Seasons