Demographic characteristics of Lytechinus variegatus (Echinoidea: Echinodermata) from three habitats in a North Florida Bay, Gulf of Mexico
Demographic characteristics of Lytechinus variegatus (Echinoidea: Echinodermata) from three habitats in a North Florida Bay, Gulf of Mexico
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DOI：
10.1046/j.1439-0485.2000.00688.x
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发表时间：
2000-05-01
期刊：
影响因子：
--
通讯作者：
McClintock, JB
中科院分区：
文献类型：
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作者：
Beddingfield, SD;McClintock, JB
对杂色绿海胆（Lytechinus variegatus）的种群密度、空间分布、大小频率、生长速率、寿命和繁殖活动进行了为期两年的研究。海胆在圣约瑟夫湾，佛罗里达，这是在其分布的北方范围内的三个栖息地进行了检查。海胆的密度，其中不等高达35个人。m（-2）随季节变化，在海樽藻（Thalassia testudinum）组成的海草床中的m（-2）高于丝状丁香（Syringelephaliforme）或砂坪。一个冷锋造成大规模的，灾难性的死亡率成人，特别是少年，海胆在近岸栖息地的海湾在1993年的春天，导致海胆密度急剧下降的Thalassia海草网站。该研究中心的种群在6个月内恢复，这归因于新成虫的迁入。少年招聘表现出年际和特定地点的变化，与招聘是最高的海草栖息地在秋季和春季。1993年秋季在Thalassia场址发生了最明显的补充事件。在海草床中，按月确定的成虫的空间分布不随随机性而变化。testudinum和S.丝状）或在春季、夏季或秋季在沙滩上。尽管如此，成年海胆聚集在沙滩上观察到在冬季的几个月，并与植物食物资源的斑块分布。幼海胆（< 25毫米测试直径）在所有网站和67%的10毫米测试直径以下的所有青少年（91 165个人观察）被发现在成年人的脊椎檐篷下聚集。产卵诱导的测量表明在春季和夏季的所有三个亚群的配子成熟的高峰。性腺指数不同的栖息地和年份，但不同的最大值被检测到，特别是在1993年春季和1994年夏末。1993年春季，在丁香海草站点的个体的平均性腺指数比其他站点高2- 4倍，1993年春季所有站点的性腺指数都比1994年高得多。根据大小频率队列的变化以及灯笼形金字塔上生长手的测量，对生长的估计表明L。在圣约瑟夫湾的三个栖息地的variegatus有相似的增长率，并达到约35毫米的平均测试直径在一年。在该物种的中央地理范围内的种群，这可能会达到测试直径达90毫米，在圣约瑟夫湾记录的最大的个人是60毫米的测试直径，几乎所有的个人不超过45毫米的测试直径或两岁。人口统计L.在其分布的北方界限，斑翅小蠹似乎受到纬度驱动的低温事件的强烈影响，其次受到当地非生物因素的影响，特别是春季低盐度，这可能对幼虫的发育和补充产生不利影响。
The population densities, spatial distributions, size frequencies, growth rates, longevity and reproductive activities of sub-populations of the sea urchin Lytechinus variegatus were investigated over a two-year period. Sea urchins were examined in three habitats in Saint Joseph Bay, Florida, which is within the northern limits of their distribution. Densities of sea urchins, which ranged as high as 35 individuals . m(-2) fluctuated seasonally at all sites and were higher in seagrass beds comprised of Thalassia testudinum than Syringodium filiforme or on a sand flat. A cold front caused large-scale, catastrophic mortality among adult, and especially juvenile, sea urchins in nearshore habitats of the Bay in the spring of 1993, leading to a dramatic decline in sea urchin densities at the Thalassia seagrass site. The population recovered over 6 months at this site and was attributable to immigration of new adults. Juvenile recruitment displayed both interannual and site-specific variability, with recruitment being highest in seagrass habitats in fall and spring. The most pronounced recruitment event occurred in fall 1993 at the Thalassia site. Spatial distributions of adult individuals ascertained monthly never varied from random in the seagrass beds (T. testudinum and S. filiforme) or during spring, summer or fall months on the sand flat. Nonetheless, aggregations of adult sea urchins were observed on the sand flat in the winter months and were associated with patchy distributions of plant food resources. Juvenile sea urchins (< 25 mm test diameter) exhibited aggregations at all sites and 67% of all juveniles under 10 mm test diameter (91 of 165 individuals observed) were found under the spine canopies of adults. Measurements of the inducibility of spawning indicated peak gametic maturity in all three sub-populations in spring and summer. Gonad indices varied between habitats and years, but distinct maxima were detected, particularly in spring 1993 and late summer 1994. The mean gonad index of individuals at the Syringodium seagrass site was 2- to 4-fold higher than the other sites in spring 1993 and gonad indices were much higher at all sites in spring of 1993 than 1994. Estimates of growth based on changes in size frequency cohorts coupled with measurements of growth hands on lantern demipyramids indicated that L. variegatus in three habitats of Saint Joseph Bay have similar growth rates and attain a mean test diameter of approximately 35 mm in one year. In contrast to populations within the central biogeographical range of the species, which may attain test diameters up to 90 mm, the largest individuals recorded in Saint Joseph Bay were 60 mm in test diameter, and almost all individuals were no more than 45 mm in test diameter or two years of age. The demographics of L. variegatus in the northern limits of their distribution appear to be strongly influenced by latitudinally driven, low-temperature events and secondarily by local abiotic factors, especially springtime low salinities, which may negatively impact larval development and recruitment.