Journal of Experimental Biology - Latest Issue

• Exploring the mechanisms underlying the last male precedence in the North African houbara bustard

  ABSTRACT

  The last male precedence (LMP) effect refers to the competitive advantage of the last male in the mating sequence. We conducted in vitro and in vivo experiments to explore the mechanisms underlying LMP in the North African houbara bustard (Chlamydotis undulata). Ejaculates were stained with two nuclear fluorescent stains [Hoechst 33342 (HBlue) and NUCLEAR-ID^® Red DNA (NRed)] and a mitochondrial stain [MitoTracker™ Red FM (MRed)], and motility and velocity of stained and unstained sperm were compared. Given that NRed impaired sperm motility and velocity, HBlue and MRed were retained for in vivo experiments. In a first in vivo experiment, females were inseminated with HBlue-stained sperm and the sperm stored in tubules were counted at 24, 48 and 72 h post-insemination. The number of sperm counted at the three timings was not significantly different, suggesting no sperm loss over 72 h post-insemination. In a second in vivo experiment, we performed sequential inseminations where females were either first inseminated with HBlue-stained sperm and subsequently with MRed-stained sperm, or vice versa. Twenty-four hours after the second insemination, we counted the number of stored sperm and assessed their location within the tubules and their distribution across the tubules. The majority of tubules (79.1%) contained both HBlue and MRed sperm. However, tubules contained more sperm from the second insemination, and they were located significantly closer to the bottom of the tubule. We discuss these results in light of the possible mechanisms underlying the LMP.

• Plankton active response to turbulence enables efficient transport

  ABSTRACT

  Although plankton typically have slow swim speeds relative to ocean flows, they can potentially enhance their transport by exploiting certain flow features. For example, a theorized ‘surfing’ strategy describes how plankton can preferentially sample upwelling areas of the flow by simply sensing and actively reorienting in response to local velocity gradients. In this study, we present the first experimental evidence that real plankton may be able to surf turbulence. We studied the bottom-heavy, planktonic larval snail Crepidula fornicata as our model organism. By observing these plankton in a jet-stirred turbulence tank, we show that they indeed have complex responses to velocity gradients. In particular, we found that they actively rotate to oppose the local vorticity, which contrasts with the typical passive, gyrotactic response. We compared our observations with those of simulated surfing plankton to demonstrate the applicability of the surfing theory to our data, where we found good agreement. Finally, we observed that the real plankton can preferentially sample upwelling areas of the flow in some cases, enhancing their transport relative to their swimming speed alone, similar to the proposed surfing theory.

• Shaping of olfactory responses by taste in a new assay for operant learning in Drosophila melanogaster

  ABSTRACT

  Animals are driven to maximize food rewards and adjust their behavior to seek high-quality food and avoid low-quality options. This holds true for Drosophila melanogaster, which approaches food-associated odors and tastes while avoiding aversive ones. Despite its importance for understanding motivation, how voluntary olfactory and gustatory experiences shape fly interactions with these stimuli over time remains unclear. Here, we investigate how stimuli shape volitional behavior using our novel operant learning assay (Open-LA), which tracks individual flies as they enter/exit a region of stimuli self-administration. We analyzed the behaviors flies demonstrated when they control access to an aversive or appetitive odor or taste and analyzed how these behaviors were shaped by experience. As predicted, flies pursued apple cider vinegar and avoided benzaldehyde and showed rapid operant learning for both odors. Flies also self-administered both simulated sweet and bitter taste, which slightly altered aversive odor responses, but did not strongly enhance odor-based operant learning. These data suggest olfaction is the primary sense guiding volitional behaviors and provides a behavioral framework for examining how animals pursue positive and avoid negative stimuli.

• Celebrating 100 years of The Company of Biologists

  Summary: In this Editorial, The Company of Biologists’ team look back over our celebrations of the Company's 100-year anniversary and directions for the future.

• ECR Spotlight – Léna Meunier

  ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Léna Meunier is an author on ‘ Exploring the mechanisms underlying the last male precedence in the North African houbara bustard’, published in JEB. Léna is a Research assistant in the lab of Janaina Torres Carreira at Reneco International Wildlife Consultants, UAE, investigating Avian sperm competition and reproductive biology.