Size distribution of individuals in the population of Asterias amurensis (Echinodermata: Asteroidea) and its reproductive cycle in China

Abstract

To obtain baseline information on the size distribution of individuals in the population and reproductive features of sea star Asterias amurensis, monthly surveys of the population were carried out from May to December 2010 and March to May 2015 in coastal waters off Yantai, China. Spawning period was predicted by gonad and pyloric caeca indices as well as anatomical and histological methods. In the A. amurensis population, both large individuals (>143 mm) and small ones (<42 mm) were present in all sampling months. The population size structure was driven by the appearance of big cohorts of individuals less than 55 mm from May to August. The appearance of small individuals in all months suggested a prolonged spawning period at other sites in this bay or sea stars growing slowly because of food shortage. An arm length is a good predictor to wet body weight for A. amurensis. The development of gonad was relative slow from May to September but rapidly reached a peak of 20.95 in October 2010, and then dropped remarkably, indicating its spawning lasted from October to November. The same phenomenon was found from March to May 2015, suggesting another spawning during March to May, which was also verified by the results of histologic analysis on ovary. The gonad index (GI) and pyloric caeca index (PCI) tended to show a negative relationship. Due to the poor food availability, the reproductive characteristics of sea star were most likely affected by the shellfish mariculturein Yantai coastal waters.

Chromosome-level genome assembly of the northern Pacific seastar Asterias amurensis

“…Asterias amurensis (class: Asteroidea), also known as the northern Pacific seastar, is widely distributed in the northwest and northeast Pacific, native to the coast of Alaska 1 , China 2 , Japan 3 , Korea 4 , and Russia 5 . As a benthic echinoderm with distinct evolutionary classification 6 , its reproduction mode includes not only dioecious but also asexual reproduction by arm regeneration 7 , 8 .…”

Management and Reduction Techniques Strategies of Ammonia Emission in Agricultural Sectors in China

“…From 1980 to 1999, the main concern was primary pollutants such as sulfur dioxide and nitrogen oxides from coal combustion, with little research on NH 3 emission inventories. The period was characterized by activity data from Statistical Yearbooks, using single emission factor methods to estimate NH 3 emission, emission factors reliant on foreign data, small field test results and descriptive evaluation of results [12,13,19]. However, regional and national NH 3 emission inventories have significantly increased in the last decade.…”

“…Estimates of NH 3 emissions rely primarily on the multiplication of activity levels of emission sources with emission factors [12]. Data on the activity level of a single source are easier to obtain, while data on local emission factors are more difficult to obtain.…”

“…The emission factor method, widely used in early research, often used a single emission source activity level, such as multiplying the year-end inventory of livestock and poultry, such as cattle and sheep, by the corresponding emission factor in the statistical yearbook. The emission factors are directly calculated using foreign data or the average values of multiple foreign ammonia emission factors [12,13]. The uncertainty in the results generated by this calculation method mainly comes from the differences between foreign and actual emission factors in various regions of China.…”