Life-history parameters and vertical distribution of Maurolicus muelleri in Masfjorden in summer

Population characteristics, individual life-history variables, feeding and vertical distribution of the mesopelagic fish Müller's pearlside Maurolicus muelleri collected in 1990 in Masfjorden, western Norway, are reported as well as environmental variables from the fjord. Minimum size at maturity was far smaller than reported from previous investigations in the same region. Fecundity was size-dependent and total egg numbers were higher than reported from other investigations of M. muelleri world wide, while the number of maturing eggs was far lower than observed in the same region earlier. Food concentration in the fjord was an order of magnitude lower than previous early summer observations, and several factors indicated that feeding opportunities may have been low for a long period. Daily feeding rate (g prey g^-1 fish) decreased with increasing fish size. These observations fit well with a model of maximizing fitness by means of a flexible size at maturity. Minimum age at maturity seems to be achieved at the expense of fecundity. M. muelleri was concentrated in a 20 to 30 m deep sound scattering layer (SSL). The SSL stayed close to the surface during the night and at 100 to 180 m during the daytime. The vertical position of the SSL varied instantaneously with changes in surface light intensity, remaining at 10^-3 to 10^-4 mol m^-1 s^-1 at the top of the SSL. Stomach fullness was highest during the night; feeding intensity seems to have been peaked at dusk. Cladocerans were the main prey ranked by number, copepods by biomass. Intake of large copepods increased with fish size.     

A biological paleoindicator for early lake acidification: Mallomonadacean (Chrysophyceae) scale abundance in sediments

The Science of Nature -     

Phthalide als Hauptbestandteile des ätherischen Öls der Früchte vonMeum athamanticum Jacq.

The Science of Nature -     

Insektenpheromone

Pheromones — semiochemicals used by insects for intraspecific chemical communication — can be isolated and with special analytical techniques their chemical structure elucidated. With stereoselective synthesis methods, presented by the preparation of sex attractants and aggregating pheromones of moths and beetles, respectively, a synthetic access to compounds is given which can be used for behavior manipulation of insects. Aside the importance of these compounds for investigations of the sensoric process the possibility of their application in an integrated and biological pest control is discussed.     

A new type of infrared organ in the Australian "fire-beetle" Merimna atrata (Coleoptera: Buprestidae)

 The Australian buprestid beetle Merimna atrata (Coleoptera: Buprestidae) approaches forest fires because its larvae develop in freshly burnt wood. So far nothing is known about possible sensory systems enabling the beetles to detect fires and to cope with the thermal environment close to the flames. We found that M. atrata has two pairs of infrared (IR) organs on the ventrolateral sides of the abdomen. Each IR organ consists of a specialized IR-absorbing area which is innervated by one thermosensitive multipolar neuron. The primary dendritic branches ramify into more than 800 closely packed terminal endings which contain a large number of mitochondria. We called the special morphology of the dendritic region a terminal dendritic mass. The type of IR receptor found in M. atrata is unique in insects and can best be compared with the IR organs of boid snakes. Received: 14 August 2000 / Accepted in revised form: 18 October 2000