Observations of the Reproductive Cycle of Petrolisthes Title japonicas (de Haan) (Anomura: Porcellanidae) Author(s) Nakasone, Yukio 琉球大学理工学部紀要. 理学編 = Bulletin of Science & Citation Engineering Division, University of Ryukyus. Mathematics & natural sciences(15): 127-135 Issue Date 1972-03-01 URL http://hdl.handle.net/20.500.12000/23471 Rights 127 Observations of the Reproductive Cycle of Petrolisthes japonicus (de Haan) (Anornura: Porcellanidae) Yukio NAKASONE* Summary The reproductive cycle of Petrolisthes japonicus (de Haan) was studied in Fukuoka during 1966-67. 1) The ovigerous females were found in the crab population from the end of May to the beginning of November. The reproductive season was approximately fi ve months. 2) The females of the species produced three broods per year and the egg deposition occurred at every about six weeks during the reproductive season. The females had ova which will produce fourth brood., but their ova were not able to develop into eggs, probably because of low water temperature and were absorbed. 3) The start of maturity in the females occurred at about 4.1 mm in carapace length, although a single ovigerous female (3. 3mrn) less th.ln i.1 mm was found in the samples. Ovigerous females ranged from 3.8 to 8.5 mm in carapace length and from 30 to 381 in the number of eggs. 4) The females of the species may incubate in a year after hatching, Introduction The reproductive cycles of porcellanid crabs have been reported by some workers. Petrolisthes cinctipes from California reproduced throughout almost the entire year (Boolootian et al.) I,> Petrolisthes eriomerus found in Puget Sound, Washington had two broods of eggs during the reproductive season(Knudsen)2). Petrolisthes e/ongatus, which is common in New Zealand, reproduced throughout the year (Greenwood),3) while Wear') suggested that the most females of the species occurred at least two broods· of eggs per year. Petrolisthes japonicus (de Haan) (lap. nam. Iso-Kanidamashi) is one of the most common porcellanid crabs in Japan and the adults are usually found under stones in the intertidal zone. The reproductive cycle of the species is not known, but MiyakeS) stated that the ovigerous females were found in July and August. This paper is a record of field observations on the reproductive cycle of Iso-Kanidamashi. Materials and Methods The samples used in this study were captured by hand from under stones in the intertidal zone of Tsuyazaki, which is shown in Fig. 1, Fukuoka Prl,!fecture. All samples used for the annual reproductive cycle were several times collected from the Recei ved: Sept. 30, 1971 *General Education Division, University of the Ryukyus. 128 NAKASONE: Observations of the Reproductive Cycle of Pelrolislhes japonicus (de Hu n) (Anomura:Porcelianidae) Fig. 1. Showing stony shore exposed at low tide. Tsuyazakl. Pukuoka. population or thCl above locality monthly over a year f rom June 1966 10 May 1967 aDd they were preserved in 50/0 forma lin. Females arc easi ly distinguished by the presence of the g~nita l opening on the coxa of second wa lking leg. ~easurements were made with a .pai~ of dividers ~n d a ruler. Carapace le.ng th was measured from t he tip of the rostrum to the posterior margin. The size of eggs was measured using all-purpose projector. Ova described in this paper indicated those that had been able to confirm them under a low power binocular microscope and they were not observed histologically. The number of eggs removed from pleopods was counted with a counter. Result. and DIKussion Number of females collected monthly and its size ra nge, percentage of ovigerous females and size of the smallest ovigerous female, a nd size of the smallest female with ova are gi ven in Table 1. During the period frofY) April to November 1966, female crabs collected at each time of the survey were distinguished into four types, such as (1) non-ovigerous females with o va, (2) ovigerous females without ova, (3) ovigerous females with ova, (4) females with prehatch eggs a ttached 10 the pleopods. The results are shown in Fig. 2. Egg deposition began toward the end of May and increased rapidly unt il about July 20, when over 93.5% of females had ellS attached to the pleopods. AI the middle of August, the ovigerous females somewhat decreased and showed 79.6%. The percenlage of the ovigerous females during the period from about August 20 to the end of September showed an approximately steady peak. though the most high peak was 92 .0% at the middle of September, and then the percentage of the ovigerous females decrea~ed rap idly and came to almost zero in Ihe fi rst weekof·November. Thedaia' Sullest "tha t the rep'roductive sei$on ' c~ntinues from June 10 October in the populalie:n, L c-, approximately rive months. The field records Bull, Sciences '" Engineering Div" Univ, of the Ryukyus, (Math, &; Nat, Sci,) 129 Table I, Showing number of females, size range, percentage of ovigerous females., the smalJe~t size of females, and sex ratio in the samples of PetTolisthes japonicus collected monthly at Tsuyazaki" from June 1966 to May 1961. Month No, of Size range % of Size of Size of females (in mm) ovig, ~ smallest smallest ¥ examined ovig, ~ with ova (I n mm) (in mm) 1966 June 180 2,8-8.5 31,1 '.7 '.7 1/1,1 July 405 3,5-8,3 83.7 3.8 '.4 1/ 1,1 Aug, 313 4.3-7.8 77 ,3 '.3 4.1 1/1,7 Sept, 679 4. 3-8.3 82,2 '.3 '.3 1/2.1 Oct, ". 4.1-8.3 21,6 '.7 5.1 1/1,4 Nov. 618 3.1-8.0 0.2 6.' 6.2 1/ 1.5 0.,. 302 3.3-7.6 o o o 1/1.6 1967 Jan. 654 2.1-7.8 o o o 1/1,3 Feb, 396 2.9-7.6 o o o 1/1.4 Mar, 71. 2,8-7.8 o o o 1/1.7 Apr, 869 2.5-8.1 o o 5.2 1/2.3 Mo, 73. 3.1-1,9 0.5 6.6 4.1 1/1.8 from about July 10 to the end of September showed t hat between 80 and 93% of the females were reproductively active (Pig, 2) . During the reproductive season 2020 ovigerous females were captured. 1729 of them (about 85010 ) had ova which were large and bright orange. This supports the idea that t wo or more broods may be produced by the females in the population during the reproductive season. Fig. 2 shows the season of egg deposition or hatching for fi rst, second, and third broods as far as the data will permit, '00 f ~ ," ".. f ~ < ,... Fig. 2. Reproductive cycle of Petrolisthes japonicu$. Ts uyazaki. Fukuoka, 1966. As shown in Fig. 2. non-ovigerous females began havi ng ova early in April and reached the peak on May 25 and then came to nearly zero at the midd le of July. Egg deposition for the first brood began toward the end of May and continued until about July 20, when a large number of females (about 93%) were in berry. At this 130 NAKASONE: Observations of the Reproductive Cycle of Petrolisthes japonicus (de Haan) (Anomura: Porcellanidae) time over 58% of the ovigerous females had prehatch eggs. Eye pigment of the embryo of the first brood became visible at about June 20, when a few ovigerous females again began having ova which will produce the second brood. The ovigerous females with second brood of ova showed a minimum value of 23% at the middle of July. In the early part of July, a fact that the ovigerous females with second brood of ova decreased and the ovigerous females without ova increased suggests that some individuals begin the hatching of the first brood of eggs. But, a large number of individuals begin the hatching after July 20, for a sharp falling-off in the percentage of individuals with prehatch eggs is noticed, and continues until about the middle of August. Judging from the fact that ova within the ovaries of females bearing the first brood of eggs showed a considerable degree of maturity, it seems that the egg deposition of the second brood occurs very shortly after the hatching of the first brood begins and that time is probably about the middle of July. That is, the egg deposition of the second brood begins about the middle of July. The peak of females bearing the second brood of eggs is evident at about August 20, when over 84% of the ovigerous females also had ovaries swollen with large bright orange ova which Oct. 5 ~ l l- • 10 • I L I 1 Sept. - - ~ 20 - <IS > J I 0 - -9 10 I ·i - J Aug. n -; - I 1 8 .d.... G) CI '- 10 ~ 0 '- I Jul. 0 ~ I ~ Q) bO I L- <IS d G) I- () 10 '"'G) Jun. ~ ~ I I I 10 I- ---I May l- I .- I 5 I- Apr. , L I t • • • • I .~ 3.9 4.3 4.7 5.1 5.5 5.9 6.3 6.7 7.1 7.S 7.9 Carapace length (mm) Fig. 3. Size distribution of females bearing ova collected from the crab population at Tsuyazaki from June 1966 to May 1967. Bull. Sciences &. Engineering Div., Univ. of the R)'uk)'us.{Math. &. Nat. Sci.) 131 22 18 - - 2 J ~ 3.9 4.3 4.7 5.1 5.5 5.9 6.3 6.7 7.1 7.5 7.9 8.3 Carapace length (mm) Fig.