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

INTRODUCTION

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 )

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.

MATERIALS AND

METHODS

The present study Induced

oviposition

Temperature and photoperiod

Ovarian development

瀨戶內海Seto Inland Sea

MATERIALS AND METHODS

Ovarian development

sample43 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 li

ght

Ovarian development ---histology

Fix after 24– 72 h Dehydrate Embed

sectioned 5-um thick

stained with Mayer’s hematoxylin–eosin

(V-12; Nikon Corp., Tokyo, Japan)

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)

Induced oviposition

7-kL (450 cm × 183 cm × 83 cm)=7000 L

10 cm

X 2~3

Induced oviposition

1987-1993

1991-1993

(trials no. 2 in 1991, no. 2 in 1992 and no. 3 in 1993)

5-47 females 16-38 females

21± 0.5℃(temperature-controlled 5~95

days)

natural temperatures

In one to three tanks In 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

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.

RESULTS

Ovarian development

Gonad index = (Gonad weight) X 107/CW3

15

57

overwintering period

Ovarian development

y =

Induced oviposition

†21, 21 ± 0.5oC; NC, not controlled.‡Carapace width; mean (range).§See Table 1.¶% = (number of females survived) X 102/(number of females reared).††% = (number of females oviposited) X 102/(number of females survived).‡‡% = (number of females survived until hatching) X 102/(number of females oviposited).

Cumulative percentage = (cumulative number of females oviposited) X 102/ (total number of females oviposited).See Table 2 for details ofculture trials of females.

Induced oviposition

Induced oviposition

Temperature and photoperiod

8.6℃

27.2℃－○－○ Temperature Photoperiod

DISCUSSION

DISCUSSION

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)

DISCUSSION

Temperature and photoperiod

showed no signs of development during the overwintering period under low temperatures below 12℃

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.

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.

Thanks