Digging with ‘hands’: observations of food capture in the flying gurnard Dactylopterus volitans (Linnaeus, 1758)

ABSTRACT

Videofilms of a foraging flying gurnard (Dactylopterus volitans) were collected at Itaipu, Niterói, RJ, Brazil. Analysis revealed details of the use of anterior parts of the pectoral fins which act as digging ‘hands’ to access infaunal prey items that are subsequently captured by oral suction feeding. Each pectoral fin has two distinct sections articulated separately on the pectoral girdle. The digging ‘anterior pectoral fin’ mainly consists of segmented and flexible fin rays but has an anterior robust unsegmented ray that provides an edge to the ‘hand’, allowing penetration of the substratum. The huge ‘posterior pectoral fins’ are supported by unsegmented rays. Most digging episodes involved one ‘hand’ and consisted of 1–7 cycles of movement with frequencies 1.15–3.74 cycles s^?1. During a cycle, the ‘hand’ is moved forwards and medially above the substratum, then is twisted medially and simultaneously depressed so that the anterior unsegmented ray impacts and enters the substratum. The hand is then drawn backwards and laterally to disturb the substratum. To prevent upward pitching of the head during digging, the ‘posterior pectoral fins’ are both moved anteriorly and laterally to shift the centre of gravity forwards while the caudal and ?second dorsal fins continue to provide propulsive force.     

扰动对天敌有多食性模型稳定性的影响

本文主要讨论了扰动对天敌具有多食性模型 x_1=x_1(r_1-a_1y), x_2=x_2(r_2-a_2y), y=y(-r_3+b_1x_1+b_2x_2)稳定性的影响。利用Liapunov函数得到了昆虫种类内部的密度制约,将促使昆虫与天敌系统进一步稳定化,进而得出同一食饵水平上的竞争是不稳定化的结论。其中后一种情况与J.M,Smith的结论完全一致。     

一类具有时滞捕食-食饵系统的稳定性分析

研究了一类带有时滞和对食饵具有阶段结构的捕食-食饵系统，通过线性化得到了该系统平衡点的局部稳定的充分条件．给出了解的渐近性质和阶段结构对种群持续生存的负面影响、     

基于比率的离散型捕食系统的周期解

针对一类基于比率的离散型捕食系统，利用重合度理论给出了该系统正周期解的存在性判据．     

捕食者——食饵系统的稳定性

论证了具有种内相互作用，功能反应的一个公共食饵和两个互相竞争的捕食者系统，并得到了系统平衡态稳定性的两个定理，证明了扩散对系统具有稳定的效应，并且给出了两个了说明定量的应用，以此推广了文献（５）的结果。     

基于改进的Monte Carlo方法及其应用

建立了一个基于网格由狼羊草组成的生态系统模型，模型中对捕食者(狼)及被捕食者(羊)给予了相应的属性定义，把草界定为可再生资源，通过引入“超结构”的规则，解决了采用Monte Carlo。方法模拟时网格状态不能同步更新的问题。通过模拟，得到模型的三种典型结果：即捕食者灭绝，捕食者被捕食者都灭绝以及捕食者被捕食者共存，给出了三种结果出现的几率分布，而且只要捕食者的初始密度不太大，生态系统很容易达到共存状态，生态系统对应的网格规模越大，生态系统越容易达到共存。     

Microhabitat use and feeding habits of Crossodactylus bokermanni Caramaschi and Sazima, 1985 (Anura,Hylodidae) at a site in south‐eastern Brazil

We studied a population of Crossodactylus bokermanni in a stream at the Reserva Particular do Patrimônio Natural, Santuário do Caraça, south‐eastern Brazil, with respect to microhabitat use and diet. We characterized microhabitats based on substrate, distance to water and exposure level of the occupying individual (exposed or sheltered), and adjacent aquatic microhabitats (evaluated as potential nesting sites based on observed nests), according to water current (absent, slow or fast), substrate and depth. Calling males, silent males, ovigerous females, non‐ovigerous females and juveniles showed spatial niche overlap higher than that expected by chance, with calling males showing the strongest preference for microhabitats close to potential nesting sites (with intermediate depths, fast current and sandy bottom). Only 14 males out of 48 individuals examined for stomach contents had prey in their stomachs. The food items with the highest electivity values were Coleoptera and Diptera, but preys with both high and low mobility were exploited.     

一类捕食者－食饵系统的Hopf分枝

考虑一类具有偏食习惯的捕食者与被捕食者模型。分析了该系统的奇点类型及稳定性。利用中心流形定理和Ｈｏｐｆ分枝理论证明了该系统在一定条件下产生Ｈｏｐｆ分枝，得到了中心流形的具体表达式。     

一类食饵种群具有常数存放率的捕食者—被捕食者系统的定性分析

本文对具有 Holling 第二类功能性反应的食饵——捕食者两种群且食饵种群具有常数存放率的系统进行了定性分析.主要讨论了:平衡点的性态,可行平衡点的全局渐近稳定性,解的有界性,系统无极限环的条件和正平衡点周围存在唯一稳定极限环的条件.同时对这些结论的生态意义也给于了说明.     

三种群捕食者-食饵系统的持久性和全局渐进稳定性

用比较定理和极限理论研究了具有Holling Ⅱ类功能反应的三种群捕食者－食饵系统，证明了在某些条件下系统是持久的，而且在适当条件下系统的任意正解是全局渐进稳定的。