• Journal of Forest and Environmental Science
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• 제32권2호
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• pp.113-119
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• 2016

The long lived iteroparous conifers produce male and female gametophyte for hundreds of years once they reach the reproductive stage, however, the production of seed is not frequent. This phenomenon of infrequent seed production in conifers is yet to be understood. An attempt to study this change in cone production in Cedrus deodara of Western Himalayas -a species reported to be mainly monoecious and rarely dioecious has been made. The observations recorded on selected trees of flowering/fruiting stage for four years at four different locations have shown the species to be dioecious with higher percentage of female trees during good seed year but with no definite or predictable pattern of reproduction in the trees. A decline in production of female trees was witnessed at all but one location immediately year after reaching the maximum (good seed year). The phenomenon of seed production has been observed to be cyclic and site specific. A change in the sexual behavior of the trees from male to female or vice-versa, male or female turning monoecious or vegetative and vegetative coming to reproductive was unpredictable.

• Ocean Science Journal
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• 제43권3호
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• pp.127-133
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• 2008

Reproductive patterns of an epifaunal amphipod, Pontogeneia rostrata, were studied on Dolsando sandy shore in Korea. The life history pattern was iteroparous, with recruitment mainly occurring from winter to spring. The sex ratio was malebiased, especially during breeding periods. The mean body length of females was significantly larger than that of males. Brood size and egg volume were positively related to the body length of ovigerous females. There was no significant difference in brood size between successive breeding periods, but egg volumes were significantly higher in early winter (December) than in late spring breeding (May and June), increasing the probability of survival to hatching. These traits contribute to more reproductive potential in early winter than in late spring breeding. The mean brood size of epifaunal P. rostrata was larger but the mean egg volume smaller than that of infaunal amphipods in this sampling area. We suggest that reproductive effort for epifaunal species may be proportionally greater than for infaunal species in risky environments.

• The Korean Journal of Ecology
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• 제12권3호
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• pp.171-182
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• 1989

The structure, clonal grwoth, shoot modules dynamics and rhizome respiratory rate of the Phragmites longivalvis circular patch were studied in a 15-year-old reclaimed land on Mado of the western Korea for two growing seasons. Clonal growth by P. longivalvis resulted in subpopulations of shoot modules which may be separated into pioneer, mature and senile growth phase. The radial growth of circular patch was 208 cm per a year. The shoot phytomass, shoot height and spike frequency were the lowest in the senile phase, and were the highest in the mature phase. The maximum shoot phytomass of pioneer, mature and senile phase in August was 347, 536 and 195g/$\m^2$ for the first year, and 609, 748 and 248g/$\m^2$ for the second year, respectively. The birth rates of shoot modules were the highest during the early spring. Of all modules, the percemtage of spring cohort of pioneer, mature and senile growth phase were 52, 82 and 70% for the first year, and 83, 88 and 85% for the second year, respectively. The flowering shoots were only derived from spring cohorts. The death rates of shoot modules of the pioneer and mature phase were the highest in October. The module is an annual semelparous plant though the genet is a perennial iteroparous plant. Their survivorship curve was negatively (Deevey type I). The density of shoot modules of the pioneer, mature and senile growth phase increased as much as 4.0, 1.6 and 2.3 times for one year, respectively. The respiratory rate was the highest in the lowest in the senile growth phase.

• 한국패류학회지
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• 제1권1호
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• pp.24-50
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• 1985

왜우렁(Parafossarulus manchouricus)은 우리 나라와 중국대륙(中國大陸), 일본(日本), 대만등지(臺灣等地)에 널리 만연(蔓延)되어 있는 간흡충증(肝吸蟲症)(clonorchiasis)의 원인기생충(原因寄生蟲)인 간흡충(肝吸蟲)(Clonorchis sinensis)의 제일중간숙주(第一中間宿主)로서 Bithyniidae 과(科)에 속(屬)하는 담수권패(淡水卷貝)의 일종(一種)이다. 우리나라의 청평(淸平), 진주(晋州), 군산(群山) 및 일본(日本), 대만등지(臺灣等地)에서 채집(採集)된 왜우렁과 공주지역(公州地域)에서 채집(採集)된 Bithynia(Gabbia) misella, 그리고 미국(美國)의 Michigan 호(湖)와 독일(獨逸)의 Bodensee 근역(近域)에서 채집(採集)된 Bithyniatentaculata를 대상(對象)으로 이들의 산난특성(産卵特性), 형태(形態), 세포학적(細胞學的) 특성(特性), 흡충류(吸蟲類)의 자연감염실태(自然感染實態)와 서식지(棲息地)의 생태등(生態等)을 상호비교관안(相互比較觀案)하여 주로 우리나라에 분포(分布)되어 있는 왜우렁의 패류학적(貝類學的) 근거(根據)를 마련하고저 본(本) 연구(硏究)가 수행(遂行)되었다. 왜우렁의 배양(培養)에 있어 중요(重要)한 요소(要素)는 먹이로서 유패(幼貝)인 경우 Navicula나 Gomphonema와 같은 Benthic diatoms가 필수적(必須的)임을 알았고 알에서 부화(孵化)하여 성패(成貝)가 될 때까지는 54日, 그리고 산난(産卵)할때까지는 약(約) 150日이 소요(所要)됨을 알았다. 왜우렁뿐만 아니라 같은 Bithyniidae科에 속(屬)하는 B.(G.) misella나 B. tentaculata도 년(年) 1회(回) 산난(産卵)함을 보았다. 왜우렁의 패곡(貝穀)에는 나선형(螺線形) 육기(陸起)(spiral ridges)가 있음이 타종(他種)과 구별(區別)되는 점(點)이였고 B.(G.) misella의 성패(成貝)의 크기는 7.5mm를 초과하지 않았다. 왜우렁 유패(幼貝)의 주사전자현징경적(走査電子顯徵鏡的) 관내(觀奈)에서 나선형(螺線形) 주름만이 보였을 뿐이여서 Hydrobiidae科에 속(屬)하는 권원류(卷員類)와는 상이(相異)한 형태(形態)를 나타내었다. 왜우렁의 설치(舌齒)는 B. tentaculata와 비숫한 형태(形態)를 보였으나 B.(G.) misella는 cusps가 일반적으로 크고 날카로웠으며 비교(比較)된 삼종(三種) 모두의 치형(齒型)은 2:1:1:1:2이었다. 또한 한국산(韓國産) 왜우렁과 대만산(臺灣産) 왜우렁에 었어 곡고대곡구비(穀高對穀口比)가 서로 통계학적(統計學的)으로 유의(有意)하게 상이(相異)한 것은 지역적환경(地域的環境)의 차리(差異)때문인 것으로 사료(思料)되었다. 왜우렁의 세포분열상(細胞分裂相)은 타종(他種)과 차리(差異)가 없었으나 염색체수(染色體數)는 B. tentaculata와 마찬가지로 n=17이었고 B.(G.) misella는 n=18이었다. 왜우렁의 핵형(核型)은 지역간(地域間)에 그 차리(差異)를 볼 수 없었으며 성염색체(性染色體)는 확인(確認)할 수 없었다. 왜우렁의 간흡충유충감염율(肝吸蟲幼蟲感染率)은 진주산(晋州産) 0.14%, 군산산(群山産) 1.25%이었으나 청평산(淸平産)에서는 0%였으며, 공주산(公州産) B.(G.) misella 亦是 자열감염(自熱感染)을 인정(認定)할 수 없어 간흡충(肝吸蟲)의 중간숙주(中間宿主)가 될 수 없음을 확인(確認)하였다. 왜우렁의 서식처(棲息處)는 수류(水流)가 완만(緩慢)하거나 정체(停滯)될 수계(水系)였으나 비교적(比較的) 오염(汚染)이 적고 용존산소량(溶存酸素量)이 높은 곳에 서식(棲息)하고 있있으며 서식처(棲息處)의 calcium ion양(量)이 타지역(他地域)보다 월등(越等)히 높았음을 알 수 있었다.