著者

Puneeta Pandey Vijai Dharmamony Yamamoto Jun Sakurai Yasunori

出版者

Inter-Research

雑誌

Marine ecology progress series (ISSN:01718630)

巻号頁・発行日

vol.551, pp.277-281, 2016-06-10

被引用文献数

5

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Batch spawning, intermittent spawning and multiple spawning represent common reproductive strategies among cephalopods. These flexible spawning strategies are also common in fishes, and are thought to be a female trait that is programmed depending on environmental parameters. The ommastrephid squid Todarodes pacificus, being a terminal spawner, is considered to have a single spawning event, extruding one large egg mass and dying soon thereafter. Females that are interrupted by males exhibiting mating behavior, while extruding the egg mass, spawn multiple egg masses over the course of 2-3 d instead of dying soon after spawning the first egg mass. We demonstrate that male mating behavior causes 'forced' intermittent spawning by females (i.e. more than one spawning event). We hypothesize that in T. pacificus, some males use this strategy to mate with females unable to repel advances while spawning, thus providing the male with the opportunity to contribute sperm and enhance gene flow.

著者

Shinomiya Yuichi Chiba Susumu Kanamori Makoto Hashizume Shigeyuki Yoshino Kenji Goshima Seiji

出版者

Inter-Research

雑誌

Marine ecology progress series (ISSN:01718630)

巻号頁・発行日

vol.570, pp.157-171, 2017-04-27

被引用文献数

14

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To understand the effects of patch attributes of seagrass beds on the persistence of an animal population, we examined shifts in patch utilization that occur with the life stages of a decapod crustacean, Hokkai shrimp Pandalus latirostris, inhabiting only eelgrass beds. The abundance of juveniles did not relate to the abundance of prey or patch size, but adult abundance decreased significantly when patches were smaller. Edge effects were suggested for adults. Since patch size and shoot density were inseparable structures at our study site, we conducted an experiment using artificial seagrass units (ASUs) to clarify structures that were effective as shrimp habitat. This experiment showed that while adults recruited mainly to the small patches regardless of shoot density, juveniles, though much smaller in number, recruited to all patch types. Adults frequently emerged from natural patches to bare spaces at night, while juveniles seldom used the bare spaces at all. When we experimentally released shrimps between ASUs at night, adults generally used the bare spaces while juveniles randomly moved to all habitat types. We tethered adults in the interior of seagrass patches and bare spaces during both daytime and nighttime, and found that the predation rate was high only in bare spaces during daytime. We demonstrated that the habitat functions of seagrass patches can vary with the life stages of this decapod crustacean, and suggest that spatial management of various sizes of patches is crucial for population persistence of Hokkai shrimp.

著者

Okuyama J Shimizu T Abe O Yoseda K Arai N

出版者

Inter-Research

雑誌

Endangered Species Research (ISSN:18635407)

巻号頁・発行日

vol.10, pp.181-190, 2010-03-03

被引用文献数

22

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To ensure the success of reintroduction programs, it is important to monitor the post-release behavior and survival of released animals. In this study, the post-release movement and behavior of 5 wild and 5 head-started hawksbill turtles Eretmochelys imbricata were monitored using ultrasonic telemetry. Their dispersal directions and recaptures may indicate that wild turtles perform homing migrations. However, the head-started turtles showed non-uniform patterns in dispersal movements. Four head-started turtles moved out of the monitoring area in various directions, whereas one turtle stayed within the monitoring area for approx. 10 mo. These results might indicate that head-started turtles wander aimlessly in their new surroundings. Signal reception patterns indicated that wild turtles were active in the daytime and rested under the coral at night. Although the head-started turtles also rest at night, their resting places did not seem to be sheltered from hazardous sea conditions or adequate for efficient resting. Therefore, head-started hawksbill turtles appear to need pre-release training such as exposure to structures or ledges in the rearing tank so they can utilize similar structures in the wild for shelter during rest periods and maximize their dive duration by employing these as a roof to counteract the positive buoyant effect of inhaled air. Prey analysis of a head-started turtle captured incidentally demonstrates that these turtles can make feeding adaptations to adjust to the natural environment. These findings provide constructive information for the implementation and improvement of head-start programs.