1. Ovarian development and induced oviposition of the overwintering swimming crab Portunus trituberculatus (Brachyura: Portunidae) reared in the laboratory Katsuyuki HAMASAKI, Hideyuki IMAI, Nobuhiko AKIYAMA AND Kyohei FUKUNAGA FISHERIES SCIENCE 2004; 70: 988–995 在研究室飼育三齒梭子蟹觀察 越冬期間卵巢發育及引誘產卵之研究 報告人：王崧華

2. INTRODUCTION

3. Portunus trituberculatus (Miers, 1876) Arthropoda ( 節肢動物門 ) Crustacea ( 甲殼亞門 ) Malacostraca ( 軟甲綱 ) Decapoda ( 十足目 ) Portunidae ( 梭子蟹科 ) Portunus ( 梭子蟹屬 )

4. objective For several crustaceans, studies have revealed that temperature and photoperiod play an important role in regulating ovarian development and oviposition. Information on the reproductive biology of P. trituberculatus is very limited to reliably control its ovarian development and oviposition for seed production; it is only reported briefly that ovipositions were induced under high temperature conditions. The present study examined ovarian development and oviposition of laboratory reared P. trituberculatus. we analyzed the relationship between the beginning times (early February to late April) of culture of females under high temperature regimes and the number of days to oviposition.

5. MATERIALS AND METHODS

6. The present study Induced oviposition Temperature and photoperiod Ovarian development 瀨戶內海 Seto Inland Sea MATERIALS AND METHODS

7. Ovarian development sample 43 from October–December 1991 and 10 in October 1992 148–235 mm in CW (mean, 183 mm) 7-kL (450 cm × 183 cm × 83 cm) =7000 L (in outdoor) 10 cm numbered vinyl tape (shade efficiency, 90%) Sand-filtered seawater was supplied using a flow-through system (15–24 L/min; salinity, 31–32 psu) and water temperatures were not regulated natural light

8. Ovarian development ---histology Fix after 24– 72 h DehydrateEmbed sectioned 5-um thick stained with Mayer’s hematoxylin– eosin (V-12; Nikon Corp., Tokyo, Japan)

9. Ovarian development 1.Yolk granule stag (YGS) 2.Primary yolk globule stage (PYGS) 3.Secondary yolk globule stage (SYGS) 4.Prematuration stage (PMS) 5.Maturation stage (MS)

10. Induced oviposition 7-kL (450 cm × 183 cm × 83 cm) =7000 L 10 cm X 2~3

11. Induced oviposition 1987-1993 1991-1993 (trials no. 2 in 1991, no. 2 in 1992 and no. 3 in 1993) 5-47 females16-38 females 21± 0.5 ℃ (temperature-controlled 5~95 days) natural temperatures In one to three tanksIn tanks 4-kL (450 cm × 150 cm × 50 cm) =4000 L 10 cm flow-through systems (8–14 L/min; salinity, 31–32 psu) in an experimental room with windows that admitted natural light

12. Temperature and photoperiod Natural temperatures in tanks were measured each morning (09.00–10.00 hours) from December 1986 to June 1993 and the mean temperatures for every 10 days were calculated using these data. The natural photoperiod was calculated from the hours between sunrise and sunset at Tamano city (34°29’N, 133°53’E) where our institute is located, as reported by the Japan Weather Association, plus 30 min before sunrise and sunset according to the method of Aiken and Waddy.

13. RESULTS

14. Ovarian development Gonad index = (Gonad weight) X 10 7 /CW 3 15 57 overwintering period

15. Ovarian development y =

16. Induced oviposition †21, 21 ± 0.5 o C ; NC, not controlled. ‡Carapace width; mean (range). §See Table 1. ¶% = (number of females survived) X 10 2 /(number of females reared). ††% = (number of females oviposited) X 10 2 /(number of females survived). ‡‡% = (number of females survived until hatching) X 10 2 /(number of females oviposited).

17. Cumulative percentage = (cumulative number of females oviposited) X 10 2 / (total number of females oviposited). See Table 2 for details of culture trials of females. Induced oviposition

19. Temperature and photoperiod 8.6 ℃ 27.2 ℃ －○－○ Temperature Photoperiod

20. DISCUSSION

21. Temperature and photoperiod are important environmental factors controlling the reproductive cycle of crustacean species. Panulirus japonicus all test temperatures (13, 19, 25 ℃ ) under the long photoperiod (14 h) developmental rate increased with increasing temperature 13 ℃  ovarian development progressed slowly 19 and 25 ℃  prevented or delayed considerably under the short photoperiod (10 h)

22. DISCUSSION Temperature and photoperiod showed no signs of development during the overwintering period under low temperatures below 12 ℃

23. DISCUSSION P. trituberculatus females reared at natural temperatures began to oviposit from mid–late April when tank temperatures exceeded 12 ℃. Females reared under high temperature regimes (21 ℃ ) oviposited earlier than those reared at natural temperatures. These facts suggest that temperature is also the prominent environmental factor controlling oviposition in P. trituberculatus, however, final maturation of ovaries and oviposition might be affected by the photoperiod because the number of days to oviposition tended to decrease with increasing calendar days of beginning times of heating culture, but the ovarian developmental stage did not change significantly during the overwintering period; induced ovipositions seem to be easier with increasing photoperiod from c. 12 h in early February to c. 14 h in late April.

24. To develop reliable control measures of egg production of P. trituberculatus, we should culture the females under conditions combining various temperatures and photoperiods in appropriate seasons during the reproductive cycle to examine their effects on ovarian development and oviposition.

25. Thanks