Growth and Physiology of Foraminifera in the Laboratory; Part 4 — Monoxenic Culture of an Allogromiid with Notes on its Morphology

SYNOPSIS. A polymorphic allogromiid (our strain NF) was isolated in monoxenic culture but attempts at its axenic culture failed. Growth of monoxenic cultures was stimulated by various metals and vitamins. The morphology and life cycle of this allogromiid with a prominent collar have been studied in detail. It varied in form from ovoid to elongate bioral "Shepheardella-like" forms and to irregular polyoral organisms. The organisms ranged in length from 56–385 μ (118 μ± 50.54) and in width from 35–385 μ (99 μ± 39.34). The number of nuclei per organism averaged 8.9 ± 6.3 (range 1–40). Reproduction of " Shepheardella -like" forms was by binary fission. Three types of budding have been observed and, rarely, schizogony. No evidence for sexual reproduction has thus far been seen.     

Response of littoral invertebrates to reduction of fish density: simultaneous experiments in ponds with different fish assemblages

1. We experimentally reduced densities of predatory fish in replicated 2 m² areas of the littoral zone in two ponds to test whether density and biomass of invertebrates would respond to release from fish predation. The ponds are of similar size and in close proximity, but support different fish assemblages: bluegills ( Lepomis macrochirus Rafinesque) and largemouth bass ( Micropterus salmoides (Lacepede)) in one pond, and bluespotted sunfish ( Enneacanthus gloriosus (Holbrook)) and chain pickerel ( Esox niger Lesueur) in the other. Fish densities were reduced to less than 15% of ambient levels in both experiments.
2. In the bluegill–bass pond, density and biomass of most invertebrate taxa and size classes were unaffected by the fish manipulation. Total invertebrate densities did not differ significantly between fish treatments, but total invertebrate biomass was significantly greater where fish density was reduced, averaging 30% higher over the course of the study. Likewise, manipulation of fish in the bluespotted sunfish–pickerel pond had few significant effects on individual taxa and size classes. There were no significant effects on total invertebrate abundance in the bluespotted sunfish–pickerel pond.
3. Our results provide direct experimental evidence consistent with the collective evidence from previous work, suggesting that the impact of fish predation on density and biomass of invertebrate prey in littoral habitats is variable, but generally weak. Invertebrates that coexist successfully with fish in littoral systems probably are adept at taking advantage of refugia offered by the structurally complex physical environment.     

Asymmetric priority effects influence the success of invasive forest insects

1. Settlement timing is often an important factor in interspecific herbivore interactions, as early‐arriving species may encounter higher resource availability and/or avoid induced defences. Despite the general importance of priority effects to the outcome of herbivore interactions, there has been little exploration of such interactions on woody host plants where their impact can only be measured over multiple years. 2. In the eastern U.S.A., two invasive species, the hemlock woolly adelgid Adelges tsugae and the elongate hemlock scale Fiorinia externa, share a native host, eastern hemlock Tsuga canadensis. Their interaction and its consequences were investigated for plant growth – hemlock saplings that had been inoculated with either A. tsugae or F. externa, starting in spring 2007, were cross‐infested with the other insect in spring 2009. A set of uninfested trees was simultaneously infested with A. tsugae, F. externa, both, or neither insect (= control), and insect density and plant growth was assessed in all treatments. 3. Adelges tsugae settlement rates did not differ if it settled alone or simultaneously with F. externa, but were ～45% lower on trees previously infested with F. externa. There was no difference in F. externa settlement rates, and plant growth did not differ substantively between any of the herbivore treatments. 4. At a temporal scale (i.e. multiple growing seasons) appropriate to interactions between woody plants and their herbivores, this work demonstrates that plant‐mediated priority effects can substantially affect herbivore settlement and thus the outcome of interspecific competition.     

Lack of compensation by final instar larvae of the myrmecophilous lycaenid butterfly,Jalmenus evagoras,for the loss of nutrients to ants

Abstract Larvae and pupae of the Australian lycaenid butterfly, Jalmenus evagoras Donovan (Lepidoptera; Lycaenidae), are protected from parasites and predators by attendant ants. In return, the juveniles of J. evagoras secrete to the ants a solution containing substantial amounts of sugars and amino acids. Larvae of J. evagoras were reared from hatching until adult eclosion either with or without ants. Experiments were performed to examine whether fifth (final) instar larvae attempt to compensate for the nutrient loss to ants, by consuming more food, digesting food more efficiently, or extending development time. The presence or absence of ants had no effect on the feeding rate, efficiency of digestion or development time of fifth instar larvae. Larvae with ants converted a smaller proportion of ingested food into biomass, and consequently grew less than their counterparts without ants. Thus fifth instar larvae of J. evagoras do not appear to compensate for the nutrient loss to ants. Possible reasons for the failure to compensate are discussed.