한국 연근해에 서식하는 깨다시꽃게(Ovalipes punctatus)의 자원생태학적 연구

Abstract

Ovalipes punctatus larvae and environmental data were collected from a total of 119 stations in Korean waters. The average of sea surface temperature (SST) was the lowest at 12.9℃ in February and the highest at 26.6℃ in September, and the sea surface salinity (SSS) was lowest at 31.0 psu in September and highest at 34.4 psu in March. The average concentration of sea surface chlorophyll a (SSC) was the highest in September at 1.59 μg/L. O. punctatus larvae mainly appeared from April to June, and total density was particularly high in the South Sea and coastal zone of Jeju area in May. As the larvae developed to the later stages, they appeared in higher densities at the coastal stations, and in the Megalopal stages, as swimming ability increased, they dispersed to wider area. In addition, Megalopal stages appeared in a wider range of SST and SSS than Zoea stages, which are considered to be response of environmental tolerance to settle down before metamorphosis to Juvenile. In the results of redundancy analysis (RDA) and Spearman's rank correlation analysis between larval density and environmental factors, it shows a correlation with SST as the larvae developed, which may be related to the abundance of prey. SSS may be related to physiological actions that occurred when larvae are dispersed, and SSC is considered that it is related with growth to the later stage as larvae produced in coastal waters (high chlorophyll a concentration) and transported offshore (low chlorophyll a concentration) by ocean currents and tides. Therefore, it is considered that O. punctatus undergoes ontogenetic migration during the larval stage. The gonads of female O. punctatus were present in 4 developmental stages (immature, maturing, mature and ripe) and spent stages. Gonadosomatic index (GSI) increased serially after the increase in condition factor (K), and appeared high from May to July when the SST was high. It suggested that this period was the spawning period of this species. Relationship between abdominal width and GSI at each gonadal stage showed correspondence, and maturity could be infer according to abdominal width (AW). In the histological analysis of female gonads, the developmental process of oocytes at each stage was clear. Monthly variation of oocyte long diameter was similar to monthly variation of GSI and oocytes were synchromous developmental form that developed simultaneously. In addition, the 50% group maturity size of female Ovalipes punctatus estimated to be 75.6 mm. In the results of the growth for O. punctatus, the allometric growth between the sexes of all morphometric measurements were significant and indicating sexual dimorphism. Male chela showed positive allometric growth which is suitable for mating behavior, and abdominal flap of all sexes also showed positive allometric growth which is suitable for spawning in the allometry type analysis. In addition, the orbital spine width (OW) showed a negative relative growth in all sexes, which is suggested to be a negative allometric growth to prevent the occurrence of blind spots due to distance between the eyes as grow. In the results of length frequency, cohort were separated into 2 modes from September to December, but in order to separate cohort more accurately, it was necessary to collect Juveniles and analyze a large number of samples for various length frequency. The growth equation of O. punctatus was estimate by the modified von Bertalanffy growth function (VBGF) considering the season, and it showed an asymptotic pattern of growth. This pattern of growth graph was due to the crustacean growth characteristics (molting). Growth between the sexes, estimated by the parameters, indicated that males grow faster than females, males and females grow slower around December and August, respectively. This difference is a reproductive strategy, in which males who grow mainly on body growth slow down as the water temperature decreases in winter, and females who use more energy to develop internal reproductive organs slow down to spawn. In addition, the main recruitment period of O. punctatus were in September, after the spawning period. To identify O. punctatus populations and establish management units for each population, mtDNA COI regions were analyze. As a result, the clades of O. punctatus in Korea were separated 2 clades and the genetic distance of the mtDNA COI region between the clades was 0.17–2.08%, which was not significantly different. There was no significant difference in the pairwise FST value, which represent genetic differentiation among the sampling areas, and no geographical separation found in the distribution of haplotypes and the results of the haplotype network. This result suggests that O. punctatus larvae were dispersed for a long time by the ocean current by suffering meroplanktonic period for a month, and increased the gene flow due to the development of the swimming legs for the increase in mobility. Therefore, in the results of mtDNA COI region analysis of O. punctatus in the East Sea, Yellow Sea, South Sea and East China Sea (Ieodo) of Korea, no clear intraspecies differentiation were found. However, it is necessary to conduct microsatellite DNA (msDNA) and single nucleotide polymorphism (SNP) analyzes in order to understand the recent gene flow of this species and the genetic differentiation intraspecies by each sampling area.