Plasticity of male mating behaviour in a marine bioluminescent ostracod in both time and space

Marine eukaryote bioluminescence: a review of species and their functional biology

Bioluminescence, the ability of organisms to produce visible light, has intrigued scientists for centuries. Studies have examined bioluminescence, using a wide range of approaches and organisms, from its ecological role to its underlying molecular mechanisms, leading to various applications and even a Nobel prize. Over the last ten years, an increasing amount of data has been collected leading to a growing number of recognized marine bioluminescent species. This review provides and describes a referenced listing of the eukaryotic luminous marine species, including information related to: (i) intrinsic versus extrinsic source of the bioluminescence, (ii) the color and maximum wavelength of emission, (iii) the bioluminescent system (substrate and enzyme) and the associated molecules, (iv) the availability of light organ/cell(s) pattern and histological structure, (v) the physiological control of the light production, and (vi) the demonstrated or suggested bioluminescent function(s). This listing provides basic information and references for researchers in or entering in the field of marine bioluminescence. Using a semi-quantitative approach, we then highlight major research gaps and opportunities and reflect on the future of the field.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-024-00250-0.

Social mates dynamically coordinate aggressive behavior to produce strategic territorial defense

Negotiating social dynamics among allies and enemies is a complex problem that often requires individuals to tailor their behavioral approach to a specific situation based on environmental and/or social factors. One way to make these contextual adjustments is by arranging behavioral output into intentional patterns. Yet, few studies explore how behavioral patterns vary across a wide range of contexts, or how allies might interlace their behavior to produce a coordinated response. Here, we investigate the possibility that resident female and male downy woodpeckers guard their breeding territories from conspecific intruders by deploying defensive behavior in context-specific patterns. To study whether this is the case, we use correlation networks to reveal how suites of agonistic behavior are interrelated. We find that residents do organize their defense into definable patterns, with female and male social mates deploying their behaviors non-randomly in a correlated fashion. We then employ spectral clustering analyses to further distill these responses into distinct behavioral motifs. Our results show that this population of woodpeckers adjusts the defensive motifs deployed according to threat context. When we combine this approach with behavioral transition analyses, our results reveal that pair coordination is a common feature of territory defense in this species. However, if simulated intruders are less threatening, residents are more likely to defend solo, where only one bird deploys defensive behaviors. Overall, our study supports the hypothesis that nonhuman animals can pattern their behavior in a strategic and coordinated manner, while demonstrating the power of systems approaches for analyzing multiagent behavioral dynamics.

Collective synchrony of mating signals modulated by ecological cues and social signals in bioluminescent sea fireflies

Individuals often employ simple rules that can emergently synchronize behaviour. Some collective behaviours are intuitively beneficial, but others like mate signalling in leks occur across taxa despite theoretical individual costs. Whether disparate instances of synchronous signalling are similarly organized is unknown, largely due to challenges observing many individuals simultaneously. Recording field collectives and ex situ playback experiments, we describe principles of synchronous bioluminescent signals produced by marine ostracods (Crustacea; Luxorina) that seem behaviorally convergent with terrestrial fireflies, and with whom they last shared a common ancestor over 500 Mya. Like synchronous fireflies, groups of signalling males use visual cues (intensity and duration of light) to decide when to signal. Individual ostracods also modulate their signal based on the distance to nearest neighbours. During peak darkness, luminescent 'waves' of synchronous displays emerge and ripple across the sea floor approximately every 60 s, but such periodicity decays within and between nights after the full moon. Our data reveal these bioluminescent aggregations are sensitive to both ecological and social light sources. Because the function of collective signals is difficult to dissect, evolutionary convergence, like in the synchronous visual displays of diverse arthropods, provides natural replicates to understand the generalities that produce emergent group behaviour.

Phenotypic evolution shaped by current enzyme function in the bioluminescent courtship signals of sea fireflies

Mating behaviours are diverse and noteworthy, especially within species radiations where they may contribute to speciation. Studying how differences in mating behaviours arise between species can help us understand how diversity is generated at multiple biological levels. The bioluminescent courtship displays of cypridinid ostracods (or sea fireflies) are an excellent system for this because amazing variety evolves while using a conserved biochemical mechanism. We find that the evolution of one aspect in this behavioural phenotype-the duration of bioluminescent courtship pulses-is shaped by biochemical function. First, by measuring light production from induced bioluminescence in 38 species, we discovered differences between species in their biochemical reactions. Then, for 16 species for which biochemical, phylogenetic and behavioural data are all available, we used phylogenetic comparative models to show that differences in biochemical reaction are nonlinearly correlated with the duration of courtship pulses. This relationship indicates that changes to both enzyme (c-luciferase) function and usage have shaped the evolution of courtship displays, but that they differentially contribute to these phenotypic changes. This nonlinear dynamic may have consequences for the disparity of signalling phenotypes observed across species, and demonstrates how unappreciated diversity at the biochemical level can lead to inferences about behavioural evolution.

Age and aggregation trigger mating behaviour in the small hive beetle, Aethina tumida (Nitidulidae)

This study aimed to investigate the poorly documented reproductive behaviour of the small hive beetle, Aethina tumida (Nitidulidae), a honey bee (Apis mellifera) parasite. We described the mating behaviour in detail and tested the hypothesis that beetle aggregation plays a vital role in mating in this species. Gender preference was examined in the context of age-dependency and possible chemical communication. Beetles started mating at a high frequency 18 days after emergence from the soil but only if they were aggregated (p < 0.001); mating was infrequent when beetles were paired. Males in aggregation also tried to copulate with males and only copulated more frequently with females at 18 days after emergence from soil (p < 0.001) in contrast to newly emerged, 7-day-old and 60-day-old beetles. Males and females spent more time in social contact with the opposite sex (p < 0.01) when they were 18 days old in contrast to 7-day-old beetles. Filter papers which had been in contact with 21-day-old beetles were highly attractive to similar-aged beetles of the opposite sex (p < 0.01). This suggests that chemical substances produced by the beetles themselves play a role in mating. Mating behaviour was characterised by a short pre-copulation courtship and female aggression towards other females and copulating couples. Both behaviours may be indicative of cryptic female choice. Delayed onset of reproductive behaviour is typical of many polygamous species, whilst the indispensability of aggregation for onset of sexual behaviour seems to be a feature unique to A. tumida. Both strategies support mass reproduction in this parasitic species, enabling A. tumida to overcome its honey bee host colony, and are probably triggered by chemotactic cues..

The relative cost of using luminescence for sex and defense: light budgets in cypridinid ostracods

Luminescent signals can be used by animals for a number of purposes, including courtship and defense, sometimes by the same individual. However, the relative costs of producing these different behaviors are largely unknown. In the marine ostracod Photeros annecohenae, males utilize extracellular luminescence for complex courtship displays, and both males and females luminesce as a predation defense. We compared the relative luminescent output of courtship with that of defensive displays and also with respect to their total luminescent stores. Courtship displays are relatively inexpensive compared with defensive displays, with an average defensive display releasing 50 times more luminescence than the average courtship display. Furthermore, in order to completely exhaust its stores, a male would have to produce 450 typical courtship displays or approximately 10 average defensive displays. Both courtship pulses and defensive displays show first-order decay kinetics, yet courtship pulses decay three times faster than defensive displays, suggesting that there is differential release of the luciferin, luciferase and mucus in order to control the reaction kinetics.

Bioluminescence in the sea

Bioluminescence spans all oceanic dimensions and has evolved many times--from bacteria to fish--to powerfully influence behavioral and ecosystem dynamics. New methods and technology have brought great advances in understanding of the molecular basis of bioluminescence, its physiological control, and its significance in marine communities. Novel tools derived from understanding the chemistry of natural light-producing molecules have led to countless valuable applications, culminating recently in a related Nobel Prize. Marine organisms utilize bioluminescence for vital functions ranging from defense to reproduction. To understand these interactions and the distributions of luminous organisms, new instruments and platforms allow observations on individual to oceanographic scales. This review explores recent advances, including the chemical and molecular, phylogenetic and functional, community and oceanographic aspects of bioluminescence.