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A Study of the Marine Spiny Crayfish Jasus lalandii (Milne-Edwards) Including Accounts of Autotomy and Autospasy

First Appearance of Eggs and Duration of the "Berried" Season

First Appearance of Eggs and Duration of the "Berried" Season

Females may be conveniently divided into three classes:

(i)

Those with eggs attached to setae on the pleopods. Von Bonde (1936, p. 12) says: "There are a few plumose setae on the pleopods, but in no single instance have any eggs been noticed attached to them." In contradistinction to this, I have found that the eggs of the Wellington crayfish are always attached to these setae. Indeed, it is hard to conceive of any other manner of attachment. The setae page 15 are also present to the extent of more than a "few" on the pleopods. They form a rather thick fringe to the endopodite. Herrick (1909) states: "In the lobster the ova adhere principally to certain setae of the appendages of the five anterior segments of the abdomen."

(ii)

Those with no eggs but with setae present. This is the normal state for a mature female except in the "berry" season.

(iii)

Those with neither eggs nor setae. These are caught in small numbers all the year round, and are considered to be immature (see page 12).

Females carrying eggs make their first appearance in the catches in May. Nearly 100% of the females caught in May are in this condition. It is probable that egg-extrusion begins in April because of the large number "in berry" by May. Hickman (1945, p. 33) found the first berried female, over a period of five years, on 26th April. Unfortunately, in the present investigation, data for April was unobtainable owing to the suspension of fishing operations.

It is unlikely that any commence egg-extrusion earlier than April; certainly none have been observed "in berry" earlier than this. The eggs on the specimen reported by Hickman as having been caught on 26th April were at the morula stage. Von Bonde (1936, p. 13) has shown that this stage is reached three days after laying. Accordingly, the eggs were probably laid about 23rd April.

Fig. 7: Percent of Females with Eggs vs with Setae

page 16

The percentage of females with eggs and the percentage with setae only are graphed in Fig. 7. The percentage with eggs is high from May to September. In October a significant decrease occurs. This agrees with Hickman, who says: "After September there is a rapid falling-off in the number of the 'berried' females caught." In November and December, the percentage is very small, and in January no females are carrying eggs. Hickman says "only three females in berry were taken in October, none in November, and one in December"—this from observations over a period of five years, involving the examination of 572 females. It may be said, then, that release of larvae from most of the females occurs in October, leaving only a few to hatch in November and December. This is supported by the fact that a tagged specimen released in the "berried" condition on 6th June, 1947, and another released on 12th July, 1948 were free of eggs when recaptured on 24th October, 1947, and 16th October, 1948, respectively.

Hickman says: "At Wedge Bay, laying takes place mainly during April, May, and June, and hatching during July, August, and September." He found that three out of 66 females taken in July carried eggs which were ready to hatch. Since oviposition seems to begin about the same time in Tasmania and Wellington, it seems probable that hatching in Wellington may also begin in a few specimens as early as July. This means that the eggs are carried for about three months, which agrees with Von Bonde and Marchand (1935, p. 14), who state: "In the aquarium experiments the female carried her eggs for about three to four months, under artificial conditions. It may be taken that, on a general average, the berried season last for two to three months."

From May to September, only a small number of females were without eggs but with the setae present to winch eggs are normally attached (see Fig. 7). In October, there is a significant increase in the number of females in this condition, and the increase continues through to December. The number in this condition between May and September is small, because almost all of the females are carrying eggs. The increase from October onwards is the result of extensive hatching leaving the pleopods free from eggs but with the setae present. Reference to Fig. 7 will show that this is the time when the percentage of "berried" females shows a sharp decline.

Failure of the sum of "berried" and "setae only" females to reach 100% each month is due to the presence of a number of small specimens which have neither setae nor eggs. These are all between 17 cm. and 26.1 cm. in total length, with most of them between 17 cm. and 23 cm. These are considered to be immature, since there are no setae to which eggs could be attached, and this is supported by the fact that no female crayfish larger than 26.1 cm. lacked the setae. The presence of a thick fringe of setae on the endopodites of the pleopods is considered to be an index of maturity. This is further discussed on page 12.

It is interesting to correlate the hatching period with the temperature curve (Fig. 3). The bottom and surface temperatures begin to increase in August, and page 17 this increase continues through to January. That is, hatching occurs during a period of increasing temperature.

Table 2 gives the smallest and largest berried females in each month's sample.

Table 2
Month Number of berried females examined Smallest berried female Largest berried female
May 9 24.5 30.4
June 55 21 37.3
July 127 19.1 36
August 70 21.4 35.2
September 53 22.7 33.8
October 5 22.2 25.8
November 1 24.7 24.7
December 3 20 26.6

It appears that, from October on, none of the largest females are "in berry." This suggests that large crayfish may "come into berry" before small ones, and consequently be free of eggs earlier. This has been recognized by local fishermen.