Collective behavior emerges from genetically controlled simple behavioral motifs in zebrafish

Since Darwin, coordinated movement of animal groups has been believed to be essential to species survival, but it is not understood how changes in the genetic makeup of individuals might alter behavior of the collective. Here we find that even at the early larval stage, zebrafish regulate their proximity and alignment with each other. Two simple visual responses, one that measures relative visual field occupancy and the other global visual motion, suffice to account for the group behavior that emerges. We analyze how mutations in genes known to affect social behavior of humans perturb these simple reflexes in larval zebrafish and thereby affect their collective behaviors. We use model simulations to show that changes in reflexive responses of individual mutant animals predict well the distinctive collective patterns that emerge in a group. Hence group behaviors reflect in part genetically defined primitive sensorimotor “motifs”, which are evident even in young larvae.Long AbstractCoordinated movement of animal groups is essential to species survival. It is not clear whether there are simple interactions among the individuals that account for group behaviors, nor when they arise during development. Zebrafish at the early larval stage do not manifest obvious tendencies to form groups, but we find here that they have already established mechanisms to regulate proximity and alignment with respect to their neighbors, which are the two key ingredients of shoaling and schooling. Specifically, we show that two basic reflexes are sufficient to explain a large part of emerging collective behaviors. First, young larvae repel away from regions of high visual clutter, leading to a dispersal of the group. At later developmental stages, this dispersal reflex shifts to attraction and aggregation behaviors. Second, larvae display a strong tendency to move along with whole field motion stimuli, a well-described behavior known as the optomotor reflex (OMR). When applied to individuals swimming within a group, this reflex leads to an emergence of mutual alignment between close neighbors and induces collective motion of the whole group. The combined developmental maturation of both reflexes can then explain emergent shoaling and schooling behavior.In order to probe the link between single genetic mutations and emergent collective motion, we select fish with mutations in genes orthologous to those associated with human behavioral disorders and find that these mutations affect the primitive visuomotor behaviors at a very young age and persist over development. We then use model simulations to show that the phenotypic manifestations of these mutations are predictive of changes in the emergent collective behaviors of mutant animals. Indeed, models based solely on these two primitive motor reflexes can synergistically account for a large fraction of the distinctive emergent group behaviors across ages and genetic backgrounds. Our results indicate that complex interactions among individuals in a group are built upon genetically defined primitive sensorimotor “motifs”, which are evident even in young larvae at a time when the nervous system is far less complex and more directly accessible to detailed analysis.

An atlas of neural crest lineages along the posterior developing zebrafish at single-cell resolution

Neural crest cells (NCCs) are vertebrate stem cells that give rise to various cell types throughout the developing body in early life. Here, we utilized single-cell transcriptomic analyses to delineate NCC-derivatives along the posterior developing vertebrate, zebrafish, during the late embryonic to early larval stage, a period when NCCs are actively differentiating into distinct cellular lineages. We identified several major NCC/NCC-derived cell-types including mesenchyme, neural crest, neural, neuronal, glial, and pigment, from which we resolved over three dozen cellular subtypes. We dissected gene expression signatures of pigment progenitors delineating into chromatophore lineages, mesenchyme cells, and enteric NCCs transforming into enteric neurons. Global analysis of NCC derivatives revealed they were demarcated by combinatorial hox gene codes, with distinct profiles within neuronal cells. From these analyses, we present a comprehensive cell-type atlas that can be utilized as a valuable resource for further mechanistic and evolutionary investigations of NCC differentiation.

Phalonidia manniana (Fischer von Röslerstamm, 1839) (Lepidoptera: Tortricidae): apparently previously unrecorded observations on the early larval stage

An account is given of finding the early instar larvae of Phalonidia manniana (Fischer von Röslerstamm, 1839) feeding in the tips of the stems of Mentha aquatica L., eating both the pith and adjoining leaves, being hitherto unrecorded observations. Larval descriptions and foodplants are considered as well as voltinism. The larva appears to differ in colour from that of the closely related Phalonidia udana (Guenée, 1845). A hymenopterous parasitoid was reared and details given.

Development of a culture tank to improve the survival rate in the early larval stage

Aquaculture is a method of producing fish, crustaceans, molluscs, aquatic plants, algae and other organisms in a sustainable manner. As the global population continues to grow, so too has demand and, as a result, many marine species have become severely depleted. Aquaculture is a means of sustainably addressing this demand, replenishing wild stocks and rebuilding populations of endangered species. Assistant Professor Yuki Takahashi, from the Graduate School of Fisheries Sciences at Hokkaido University in Japan, is working as part of a collaborative team of researchers from across academia and industry in Japan to adress this issue of sustainability of demand, by developing an aquaculture tank designed to improve the survival rate in the early larval stage.

Fast, easy and early (larval) identification of transparent mutant zebrafish using standard fluorescence microscopy

The availability of transparent zebrafish mutants (either TraNac: trab6/b6; nacw2/w2 or casper: roya9/a9; nacw2/w2) for live imaging studies together with the ease of generating transgenic lines are two of the strengths of the zebrafish model organism. The fact that transparent casper (roya9/a9;nacw2/w2) and silver nacre (nacw2/w2) mutants are indistinguishable by eye at early stages (1-5 days post-fertilization; dpf) means many fish must be raised and later culled if they are not transparent. To identify translucent mutants early and easily at the early larval stage (≤5 dpf) before they are classified as protected animals, we developed a simple screening method using standard fluorescence microscopy. We estimate that this procedure could annually save 60,000 animals worldwide.

An atlas of neural crest lineages along the posterior developing zebrafish at single-cell resolution

ABSTRACTNeural crest cells (NCCs) are vertebrate stem cells that give rise to various cell types throughout the developing body in early life. Here, we utilized single-cell transcriptomic analyses to delineate NCC-derivatives along the posterior developing vertebrate, zebrafish, during the late embryonic to early larval stage, a period when NCCs are actively differentiating into distinct cellular lineages. We identified several major NCC/NCC-derived cell-types including mesenchyme, neural crest, neural, neuronal, glial, and pigment, from which we resolved over three dozen cellular subtypes. We dissected gene expression signatures of pigment progenitors delineating into chromatophore lineages, mesenchyme subtypes, and enteric NCCs transforming into enteric neurons. Global analysis of NCC derivatives revealed they were demarcated by combinatorial hox gene codes, with distinct profiles within neuronal cells. From these analyses, we present a comprehensive cell-type atlas that can be utilized as a valuable resource for further mechanistic and evolutionary investigations of NCC differentiation.

Pre-imaginal conditioning alters adult sex pheromone response in Drosophila

Pheromones are chemical signals that induce innate responses in individuals of the same species that may vary with physiological and developmental state. In Drosophila melanogaster, the most intensively studied pheromone is 11-cis-vaccenyl acetate (cVA), which is synthezised in the male ejaculatory bulb and is transferred to the female during copulation. Among other effects, cVA inhibits male courtship of mated females. We found that male courtship inhibition depends on the amount of cVA and this effect is reduced in male flies derived from eggs covered with low to zero levels of cVA. This effect is not observed if the eggs are washed, or if the eggs are laid several days after copulation. This suggests that courtship suppression involves a form of pre-imaginal conditioning, which we show occurs during the early larval stage. The conditioning effect could not be rescued by synthetic cVA, indicating that it largely depends on conditioning by cVA and other maternally-transmitted factor(s). These experiments suggest that one of the primary behavioral effects of cVA is more plastic and less stereotypical than had hitherto been realised.