Über den bau der eischale von bulimus (Helicidae)

Zusammenfassung Der kohlensaure Kalk der untersuchten Helicideneischalen — Bulimus maximus (Durchmesser der Schale 23,6 x 25,1 mm, Dicke 0,25 mm), nicht näher bestimmte Schneckeneischale aus Sta. Catharina Brazil (Durchmesser 22,5 x 16,3 mm, Dicke 0,15 mm) — ist Calcit gemäß Optik (negativ einachsiges Konoskopbild) and Meigenscher Reaktion (in Übereinstimmung mit Kellys Beobachtungen bei Bulimus oblongus). Der Phosphatgehalt der Schale ist äuBerst gering trotz reichlichen Vorkommens der KELLyschen Phosphatkörnehen; diese sind in Wirklichkeit Gaseinschüisse. Erhitzen von Schalenstiicken braunt den Kalk bei Verkohlung der organischen Substanz durch and durch ; these durchsetzt also die Calcitkristalle, in Übereinstimmung mit Kellys Erfahrungen beim Entkalken. Erhitzen his zum Verbrennen der organischen Substanz (Wiederweißwerden der Schalenstücke) hebt die Doppelbrechung auf (Umwandlung des Calciumcarbonats in -oxyd); zugleich erscheint bräunliche Trübung im durchfallenden Licht wohl infolge des Austretens der Kohlensäure.Die Mammillenschicht auf der Innenseite der Schale besteht aus einzelnen Calcitindividuen oder Gruppen von solchen; diese Kristallkörnchen wachsen (zum Teil) zu den annähernd senkrecht stehenden Prismen aus, deren optische Achse rneist gegen die Schalenfläche geneigt ist. Vor allem bei Bulimus maximus lassen die Prismen eine innere grobgeschichtete and eine äußere feinstreifige Lage unterscheiden; die erste enthält die Gaseinschliisse, die sich bei der Schneckeneischale aus Sta. Catharina Brazil bis in die Mammillen hinein finden, and von rundlicher Form sind, während she bei Bulimus maximus zum Teil spaltenartig erscheinen. An manchen Stellen der Eischale aus Sta. Catharina Brazil tragen die Mamillen an ihrem freien Ende Scheiben aus radial gestellten Kalknadeln oder Rosetten aus größeren Kristallen, die bis zur Berührung benachbarter auswachsen können.     

Ecosystem function and species loss – a microcosm study

There are too many kinds of organisms to be able to study and manage each, yet the loss of a single species can sometimes unravel an ecosystem. Such `fusewire species'– critical in the same sense that an electrical fuse can cut out a whole circuit – would be a rewarding focus for research and management effort. However, this approach can only be effective if these `fusewires' represent but a small proportion of the number of species in the system.  

Aim

To demonstrate methods for measuring what proportion of the species in a system are critical to ecosystem function.  

Methods

The prevalence of fusewire species was measured in manipulative experiments on an aquatic microcosm.  

Results

No single genus deletion caused changes in key characteristics of the system.  

Main conclusions

Comparison of these results with other published studies shows that the proportion of critical fusewire species varies amongst different ecosystems. The oxidation pond microcosms were shown to contain no single species indispensable to system function. They appear to be ill-suited to a management strategy which focuses on priority eukaryote species. However, a single study provides no evidence that this result is general or even typical of other kinds of ecosystems; it is presented here as an empirical model. Other methods of investigation are available; they are less experimentally rigorous but more practical. These could provide important guidance in planning an approach to management in a particular ecosystem.     

The haemagglutination activity in the different developmental stages and changes of this activity caused by analogues of insect hormones in two members of the Culex pipiens complex of mosquitoes

Abstract. Haemagglutination activity was studied in last larval instars, pupae and adults of both sexes of the Culex pipiens mosquito complex. In females of Culex pipiens quinquefasciatus Say, an anautogenous member of C. pipiens complex, activity was detected in the homogenate of the head‐thorax complex, gut and remaining abdomen (after removing the gut), before and after sucking water, glucose solution or blood. Similar investigations were made in females of autogenous Culex pipiens molestus Forskal, a member of the same mosquito complex. The results were compared with data obtained for males of these subspecies, plus the larvae and pupae. The results show that haemagglutination activity in adult females depends not on the sucking of blood, but on the age of the females. In newly emerged females, the level of activity was very low, but after 24 h or 48 h of activity was highly enhanced, even in females that had no possibility to suck water or other liquids including blood. Furthermore, in C. p. molestus, the haemagglutination activity does not change in hungry or engorged females, and a high level of activity was found in the gut of last larval instars, a developmental stage that never takes blood. Treatment with methoprene reduces haemagglutination activity in both sexes, but 20‐hydroxycdysone application decreased activity in the gut of females. It is suggested that haemagglutination activity may be regulated indirectly by the endocrine system. The possibility that haemagglutination activity may depend on some aspect of the digestive system that has no direct connection to blood uptake is discussed. In addition, the activity may be important not only for the elimination of infections, but also for the processing of food and the utilization and transport of nutrients.