Nutrition as a facilitator of host‐race formation: the shift of a stem‐boring beetle to a gall host

1. The importance of host‐race formation to herbivorous insect diversity depends on the likelihood that successful populations can be established on a new plant host. A previously unexplored ecological aid to success on a novel host is better nutritional quality. The role of nutrition was examined in the shift of the stem‐boring beetle Mordellistena convicta to fly‐induced galls on goldenrod and the establishment there of a genetically distinct gall host race. 2. First, larvae of the host race inhabiting stems of Solidago gigantea were transplanted into stems and galls of greenhouse‐grown S. gigantea plants. At the end of larval development, the mean mass of larvae transplanted to galls was significantly greater than the mass of larvae transplanted to stems, indicating a likely nutritional benefit during the shift. This advantage was slightly but significantly diminished when the gall‐inducing fly feeding at the centre of the gall died early in the season. Additionally, there was a suggestion of a trade‐off in the increased mortality of smaller beetle larvae transplanted into galls. 3. In a companion experiment, S. gigantea gall‐race beetle larvae were likewise transplanted to S. gigantea stems and galls. Besides the expected greater mass in galls, the larvae also exhibited adaptations to the gall nutritional environment: larger inherent size, altered tunnelling behaviour, and no diminution of mass pursuant to gall‐inducer mortality. 4. In a third line of inquiry, chemical analyses of field‐collected S. gigantea plants revealed higher levels of mineral elements important to insect nutrition in galls as compared with stems.     

The consumption of rainbow trout (Salmo gairdneri Richardson) eggs by macroinvertebrates in the field

SUMMARY. 1. Perforated boxes containing live, dead or no eggs of the rainbow trout, Salmo gairdneri Richardson, were buried in a natural spawning redd in a stream in North Wales for the duration of the natural incubation period.
2. A significant difference ( P <0.001) was found between the mean number of invertebrates colonizing perforated boxes containing live eggs, dead eggs and no eggs.
3. The number of eggs retrieved from boxes originally containing dead eggs decreased as the number of invertebrates colonizing the boxes increased.
4. Using a serological method of prey identification it was demonstrated that Leuctra hippopus (Kempny), Gammarus pulex (L.) and Ptychopter-idae sp. scavenged on trout eggs in the field.
5. There was some evidence that Rhyacophila dorsalis (Curtis) and Diura bicaudata (L.) preyed on trout eggs, but in view of their scarcity, it is suggested that they were a minor mortality factor.     

The Patterning of Neuronal Connections

SYNOPSIS. The final level of development in the vertebrate nervoussystem concerns the patterning, or modelling, of the connectionsof the postmitotic neurons at target tissues. The growth oftarget tissue and the sprouting of newly-arrived axons is followedby a regulated distribution of the sprouts, and often the developmentof specific contacts (synapses). Usually there are more sproutsthan can be accommodated; the result is competition for targetsites and regression of unsuccessful endings, leading to thecharacteristic pattern of connections. Studies particularlyof the reinnervation of denervated skin in salamanders and ratshave revealed a number of conditions and processes that influencecompetition. Spatial and temporal constraints restrict the sproutingof certain nerves but not others. Substances conveyed to nerveterminals by fast axoplasmic transport can "neutralize" sproutinginfluences believed to derive from target tissues, and can "mask"target features that nerves recognize; other substances areneeded for sprouting to occur at all. Increased impulse activityin certain nerves accelerates their sprouting. Intriguingly,regenerating nerves will recapture targets from sprouted endings.Most of the identified conditions and processes occur in theadult animal; they could therefore provide a basis for remodellingof neuronal connections. Remodelling occurs when the characteristicearly hyperinnervation of target tissues converts after birthto the adult pattern; in cutaneous "touch domes" targets areeliminated in addition to endings. Perhaps remodelling playsa role in the development of behaviour even in mature animals.     

Intraspecific Variation and Phylogenetic Relationships in the Genus Entamoeba as Revealed by Riboprinting

ABSTRACT. Eighty-seven isolates of amebae assigned to the genus Entamoeba have been studied by riboprinting (restriction enzyme polymorphism analysis of polymerase chain reaction amplified small subunit ribosomal RNA genes). Twenty-four distinct patterns were obtained, most of which corresponded to previously described species. In three species ( Entamoeba coli, Entamoeba gingivalis and Entamoeba moshkovskii ) intraspecific variation was detected that led to the grouping of isolates into 'ribodemes' (populations of amebae that share the same riboprint pattern). The riboprint data were used to estimate genetic distances among and within species for the construction of phylogenetic trees based on parsimony and distance analyses. The trees obtained with the two methods are largely congruent. In some cases the estimated distances between species were greater than the upper limit recommended for the fragment comigration method of analysis indicating unusually deep branches within this genus. However, it appears that those species producing cysts with eight nuclei, those producing cysts with one nucleus, and those producing cysts with four nuclei form morphologically based groups that are supported by the riboprint data. The oral parasite Entamoeba gingivalis , which does not encyst, clusters with the third group indicating secondary loss of this ability.     

Cryopreservation and Storage of Parasitic Protozoa in Liquid Nitrogen

ABSTRACT. In 1961 I reported the first successful attempt to cryopreserve and store protozoa in liquid nitrogen. In this presentation, drawing on more than 30 years of personal experience, I discuss the factors which I consider to be most critical to the successful preservation and long term storage of several species of parasitic protozoa in liquid nitrogen. I then present my most successful protocol for cryopreservation of these parasites. Finally. I cite some longevity records for a variety of protozoa stored in liquid nitrogen vapor at the Laboratory of Parasitic Diseases. The oldest record is for a monoxenic culture of Entamoeha histolytica grown in association with Crithidia fasciculata that was frozen on January 6, 1961. Thirty-two years and 11 months later both parasites were recovered and used to initiate new culture lines.