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Social monogamy is a reproductive strategy characterized by pair living and defense of a common territory. Pair bonding, sometimes displayed by monogamous species, is an affective construct that includes preference for a specific partner, distress upon separation, and the ability of the partner to buffer against stress. Many seahorse species show a monogamous social structure in the wild, but their pair bond has not been well studied. We examined the gene expression of lined seahorses (Hippocampus erectus) during and after the process of pairing in the laboratory as well as color change (luminance), a potential form of social communication and behavioral synchrony between pair mates. When a seahorse of either sex was interacting with its pair mate, their changes in luminance ("brightness") were correlated and larger than when interacting with an opposite-sex stranger. At the conclusion of testing, subjects were euthanized, RNA was extracted from whole brains and analyzed via RNA sequencing. Changes in gene expression in paired males versus those that were unpaired included processes governing metabolic activity, hormones and cilia. Perhaps most interesting is the overlap in gene expression change induced by pairing in both male seahorses and male prairie voles, including components of hormone systems regulating reproduction. Because of our limited sample size, we consider our results and interpretations to be preliminary, and prompts for further exploration. Future studies will expand upon these findings and investigate the neuroendocrine and genetic basis of these behaviors.

Animals combine colour change and behavioural choices to enhance concealment and adapt to changes in habitat in time and space. However, non‐native and invasive habitat‐forming plants and seaweeds can change the landscape, challenging animals to remain camouflaged, especially when the colour of the new habitat differs from the native backgrounds.The chameleon prawn (Hippolyte varians) exhibits remarkable colour variation and effective camouflage against different native seaweeds in shallow tidepools. Individuals optimize crypsis by choosing colour‐matching seaweeds and changing colour over time. In some locations, the prawn's native habitats are now replaced by non‐native seaweeds of different coloration and structure, making it important to understand whether substrate choice and colour change facilitates the occupation of these seaweeds and enables prawns to camouflage against new backgrounds.Using image analysis and visual modelling of a fish predator, we assessed the colour variation and camouflage of chameleon prawns occupying the non‐native seaweeds brown wireweed (Sargassum muticum) and pink harpoon weed (Asparagopsis armata) in southwest UK. We performed laboratory trials to examine whether prawns maintain their preference for colour‐matching native substrates when given a choice between them and non‐native seaweeds, and if they can change their coloration to improve camouflage against non‐native substrates.Prawns exhibit phenotypic diversity and camouflage that varied with the non‐native seaweed species, with low colour variation and effective camouflage on pink harpoon weed, but high colour diversity and reduced concealment against brown wireweed. Prawns choose non‐native seaweeds when the alternative native substrate provides mismatching coloration, but they did not exhibit any preference between colour‐matching native and non‐native seaweeds. Once in non‐native habitats, prawns change their appearance over a few days to match the background, sometimes faster than when changing on native seaweeds of contrasting coloration.Although human activities considerably modify the coloration of marine landscapes by increasing the establishment of non‐native seaweeds, the impacts of those changes appear less severe for colour‐changing species, such as chameleon prawns, and will depend on the similarity between the colour of the new substrates and the original native backgrounds, and how animals use behaviour and physiology to match new habitats. [ABSTRACT FROM AUTHOR]

Trait-based differences among individuals are common and particularly important for polymorphic species in which alternative morphs exploit the same habitat types but occupy different trophic niches. The shrimp Hippolyte obliquimanus inhabits shallow-water vegetated habitats, particularly the seasonal and physically complex brown alga Sargassum furcatum and the less-structured but temporally stable red weed Galaxaura marginata. Two main colour morphs can be found in these habitats: homogeneous colour-changing shrimp that are able to match to their background and show little mobility, and transparent shrimp with coloured stripes, which cannot match their background, show lower habitat fidelity and are more evenly distributed between algal habitats. We used carbon and nitrogen stable isotopes and Bayesian mixing models to test whether morph-specific patterns of habitat use observed for H. obliquimanus living in Sargassum and Galaxaura meadows also influence trophic niche segregation. We observed morph-specific trophic differences that varied with habitat, with narrower niche space and lower niche overlap between morphs in Galaxaura meadows, and broader niche space and higher niche overlap between morphs in Sargassum habitat. Niche segregation between morphs occurred only in Galaxaura, where available resources are presumably less abundant than in Sargassum and the strength of competition between morphs is higher. Resource availability and habitat stability are likely driving dietary niche segregation between shrimp morphs, which can ultimately affect population dynamics and community composition in a spatially heterogeneous and seasonal habitat., Author(s): Rafael C. Duarte [sup.1] [sup.2] , Augusto A. V. Flores [sup.1] , Catarina Vinagre [sup.3] , Miguel C. Leal [sup.4] Author Affiliations: (1) Centro de Biologia Marinha, Universidade de [...]

Modular organization provides flexibility for colonial animals to deal with variable and unpredictable environmental conditions since each module has specific tasks within the colony, such as feeding, defending or reproducing. Depending on the selecting pressures, sessile organisms may phenotypically adjust the morphology of each module or modify their density, increasing individual fitness. Here we used the marine bryozoan Schizoporella errata (Cheilostomata, Schizoporellidae) to test how the divergent conditions between two artificial habitats, the location inside a marina (IM) and the external wall of the breakwater (BW), affect colony size and the density of the distinct modules. The density of avicularia and ovicells, modules related to defense and reproduction, respectively, did not differ between habitats. However, colonies growing in the turbulent waters of BW were, in general, larger and had higher density of feeding autozooids than those at IM. Reciprocal transplants of bryozoan clones indicated that trait variation is genotype‐dependent but varies according to the environmental conditions at the assigned location. The occurrence of larger colonies with more zooids in BW is probably linked to the easier feeding opportunity offered by the small diffusive boundary layer around the colony at this location. Since in colonial polymorphic organisms each module (zooid) performs a specific function, the phenotypic response is not uniform across colonies, affecting only those modules that are susceptible to variations in the main selective pressures. Understanding the importance of colony‐level plasticity is relevant to predict how modularity will contribute to organisms to deal with human‐induced environmental changes in coastal habitats. Research Highlights: Artificial habitats induce phenotypic plasticity in the marine bryozoan Schizoporella errata.Phenotypic response differs across colony modules.Colony size and autozooid density, but not ovicells and avicularia were affected by the habitat. [ABSTRACT FROM AUTHOR]

Animals frequently exhibit great variation in appearance, especially in heterogeneous habitats where individuals can be concealed differentially against backgrounds. Although background matching is a common anti-predator strategy, gaps exist in our understanding of within- and among-species variation. Specifically, the drivers of changes in appearance associated with habitat use and occurring through ontogeny are poorly understood. Using image analysis, we tested how individual appearance and camouflage in two intertidal crab species, the mud crab Panopeus americanus and the mottled crab Pachygrapsus transversus , relate to ontogeny and habitat use. We predicted that both species would change appearance with ontogeny, but that resident mud crabs would exhibit higher background similarity than generalist mottled crabs. Both species showed ontogenetic changes; the mud crabs became darker, whereas mottled crabs became more green. Small mud crabs were highly variable in colour and pattern, probably stemming from the use of camouflage in heterogeneous habitats during the most vulnerable life stage. Being habitat specialists, mud crabs were better concealed against all backgrounds than mottled crabs. Mottled crabs are motile and generalist, occupying macroalgae-covered rocks when adults, which explains why they are greener and why matches to specific habitats are less valuable. Differential habitat use in crabs can be associated with different coloration and camouflage strategies to avoid predation. [ABSTRACT FROM AUTHOR]

Polymorphism may allow individuals to expand habitat use through morph-specific resource demands. However, the underlying mechanisms maintaining different morphotypes in nature are difficult to identify. We sampled populations of the shrimp Hippolyte obliquimanus in the macroalgae Sargassum furcatum and Galaxaura marginata to examine morph-specific distribution patterns, population structure and female reproductive output, as an initial step to understand polymorphism in this species. Two main colour morphotypes were identified: homogeneous shrimps (H), which change their colour, mostly from pink to greenish-brown tones, and striped translucent shrimps (ST), whose colour remain unaltered. Distribution of individuals between habitats was clearly morph-specific. H shrimps occupied colour-matching substrates, mainly Sargassum, where they can attain large densities, and ST individuals were evenly distributed in both algae. Brood production and size-fecundity relationships were similar between morphs and habitats, suggesting these are relatively fixed traits in the population. However, sex proportions, defined as the male to female ratio, were different between morphs and macroalgae. H shrimps were chiefly females (1:2.04) and ST shrimps mostly males (1:0.30). Given the likely polygynic pure-search mating system in H. obliquimanus, the female-biased sex ratio observed in Sargassum is apparently more advantageous than the Mendelian proportion found in Galaxaura habitat. Clustering on vegetated habitat, the female-biased H morph may be relatively cryptic and sedentary, compared with the male-biased ST morph which apparently combines a more neutral camouflage strategy to a generalized habitat use. Altogether, results suggest that selection for sex-specific traits favours the maintenance of polymorphism in H. obliquimanus. [ABSTRACT FROM PUBLISHER]

Benthic conspecific cues are used by competent larvae of many marine invertebrates to locate and settle on suitable habitat. However, aggregations of conspecifics can generate strong intraspecific competition and inter-cohort cannibalism. We investigated the effects of adult conspecific cues on general fitness parameters of juvenile Carcinus maenas (stages J1–J5), and used geometric morphometrics to investigate patterns of allometric growth indicative of life-history strategies and resource use potential. Cues induced faster metamorphosis and slightly shortened intermolt time in J2 individuals, at the expense of acute mortality in J1 crabs. These effects are cumulative but compensatory processes nullify differences by the end of the experiment. Allometric carapace change toward the adult standard remained unchanged, but conspecific cues induced first a change in size (J1) and then in shape (J5) of claws. In both control and cued juveniles, heterochely was incipient but apparent in J5 crabs. Independently of body side, conspecific cues triggered a very marked increase of the propodus posterior margin, presumably enhancing general strength. Therefore, early benthic stages may grow slightly faster to a size refuge, and develop stronger claws providing competitive advantage for the use of high-value food items when population density-dependent processes are more probable. [ABSTRACT FROM AUTHOR]