Morphological phylogeny of alpheid shrimps: parallel preadaptation and the origin of a key morphological innovation, the snapping claw

The Alpheidae-possibly the most diverse family of recent decapod crustaceans-offers attractive opportunities to study the evolution of many intriguing phenomena, including key morphological innovations like spectacular snapping claws, highly specialized body forms, facultative and obligate symbioses with many animal groups, and sophisticated behaviors like eusociality. However, studies of these remarkable adaptations remain hampered by insufficient phylogenetic information. We present the first phylogenetic hypothesis of relationships among 36 extant genera of alpheid shrimps, based on a cladistic analysis of 122 morphological characters from 56 species, and we use this hypothesis to explore evolutionary trends in morphology and species diversity. Our results strongly supported a monophyletic Alpheidae that included two hitherto difficult-to-place genera (Yagerocaris and Pterocaris). Of 35+ nodes among genera, all were supported by at least one morphological character (24 were supported by two or more) and 17 received greater than 50% jackknife support. Unfortunately, many basal nodes were only weakly supported. Six genera appeared nonmonophyletic, including the dominant genus Alpheus (paraphyletic due to inclusion of one clade with three minor genera). Evolutionary trends in alpheid claw form shed some revealing light on how key innovations evolve. First, several functionally significant features of the cheliped (claw bearing leg) evolved independently multiple times, including: asymmetry, folding, inverted orientation, sexual dimorphism, adhesive plaques that enhance claw cocking, and tooth-cavity systems on opposing claw fingers, a preadaptation for snapping. Many conspicuous features of alpheid claw form therefore appear prone to parallel evolution. Second, although tooth-cavity systems evolved multiple times, a functional snapping claw, which likely facilitated an explosive radiation of over 550 species, evolved only once (in Synalpheus + [Alpheus + satellite genera]). Third, adhesive plaques (claw cocking aids) also evolved multiple times, and within snapping alpheids are associated with the most diverse clade (Alpheus + derivative genera). This pattern of parallel preadaptation-multiple independent evolutionary origins of precursors (preadaptations) to what ultimately became a key innovation (adaptation)-suggests alpheid shrimp claws are predisposed to develop features like tooth-cavity and adhesive plaque systems for functional or developmental reasons. Such functional/developmental predisposition may facilitate the origin of key innovations. Finally, moderate orbital hoods-anterior projections of the carapace partly or completely covering the eyes-occur in many higher Alpheidae and likely evolved before snapping claws. They are unique among decapod crustaceans, and their elaboration in snapping alpheids suggests they may protect the eyes from the stress of explosive snaps. Thus one key innovation (orbital hoods) may have facilitated evolution of a second (snapping claws).     

Response of extracellular zinc in the ventral hippocampus against novelty stress

An extensive neuronal activity takes place in the hippocampus during exploratory behavior. However, the role of hippocampal zinc in exploratory behavior is poorly understood. To analyze the response of extracellular zinc in the hippocampus against novelty stress, rats were placed for 50 min in a novel environment once a day for 8 days. Extracellular glutamate in the hippocampus was increased during exploratory behavior on day 1, whereas extracellular zinc was decreased. The same phenomenon was observed during exploratory behavior on day 2 and extracellular zinc had returned to the basal level during exploratory behavior on day 8. To examine the significance of the decrease in extracellular zinc in exploratory activity, exploratory behavior was observed during perfusion with 1 mm CaEDTA, a membrane-impermeable zinc chelator. Locomotor activity in the novel environment was decreased by perfusion with CaEDTA. The decrease in extracellular zinc and the increase in extracellular glutamate in exploratory period were abolished by perfusion with CaEDTA. These results suggest that zinc uptake by hippocampal cells is linked to exploratory activity and is required for the activation of the glutamatergic neurotransmitter system. The zinc uptake may be involved in the response to painless psychological stress or in the cognitive processes.     

Testing Someone Else’s Intelligence: From Regimentation to Freedom1

This article discusses the trend in the development of testing from maximum regimentation of the test-takers’ activity (where they solve problems clearly formulated by the creator with a single correct answer) to diagnostic problematic situations that are very new and indefinite with an open beginning and an open end. With increasing frequency, the open beginning used in testing presupposes a freedom of independent formulation of one’s own research questions of the reality being studied and a search for answers while interacting with that reality. The emergence of mass testing of exploratory behavior is a reflection of the conviction that one of the key abilities that will be required in the very near future is the ability to cope with uncertainty and novelty, including by actively investigating them.

The discussion deals with the problems of testing intelligence and creativity in conditions of novelty and uncertainty, including the “judging problem.” It is pointed out that any thinking test, especially a test of creative thinking, is also an implicit (albeit perhaps not conscious) claim by its developers that their wisdom is virtually unsurpassed. After all, it is assumed that any person’s intelligence and creativity that unfold in a new situation may be described in the context of the model produced by the creative intellect of the test’s developer and, hence, by a more powerful “superintellect.” The errors that are practically inevitable with such an approach can be corrected in a dialog among various groups of researchers or, to the contrary, may be deepened if criticism is shut off.

The article analyzes a fundamental methodological error of creativity testing—the “standard list of creative answers” drawn up by the test-maker in advance, against which the participants’ solutions are checked. This error is explored in the case of an invention-oriented task in the international scholastic test PISA 2012, based on which the education ratings of countries are constructed.

An optimistic thesis is offered: no matter how successful testing is, humankind will never be fully prepared to determine its creative potential, due to its forward development. Without diagnostic tools, however, it will be far less prepared; they are a new and important part of that potential.     

Individual differences in the effect of social defeat on anhedonia and histone acetylation in the rat hippocampus

Major depression is a growing problem worldwide with variation in symptoms and response to treatment. Individual differences in response to stress may contribute to such observed individual variation in behavior and pathology. Therefore, we investigated depressive-like behavior following exposure to repeated social defeat in a rat model of individual differences in response to novelty. Rats are known to exhibit either high locomotor activity and sustained exploration (high responders, HR) or low activity with minimal exploration (low responders, LR) in a novel environment. We measured anhedonia using the sucrose preference test in HR and LR rats following exposure to social defeat stress or in basal, non-defeated conditions. We then compared histone acetylation in the hippocampus in HR and LR defeat and non-defeated rats and measured mRNA levels of histone deacetylases (HDAC) 3, 4, 5, and Creb binding protein (CBP). We found that basally, HR rats consumed more sucrose solution than LR rats, but reduced consumption after exposure to defeat. LR rats' preference was unaffected by social defeat. We found that HR rats had higher levels of histone acetylation on H3K14 and H2B than LR rats in non-stress conditions. Following defeat, this acetylation pattern changed differentially, with HR rats decreasing acetylation of H3K14 and H2B and LR's increasing acetylation of H3K14. Acetylation on histone H4 decreased following defeat with no individual variation. Basal differences in CBP expression levels may underlie the observed acetylation pattern; however we found no significant effects of defeat in levels of HDACs 3, 4, 5 in the hippocampus.     

Novel trophic niches drive variable progress towards ecological speciation within an adaptive radiation of pupfishes

Adaptive radiation is recognized by a rapid burst of phenotypic, ecological and species diversification. However, it is unknown whether different species within an adaptive radiation evolve reproductive isolation at different rates. We compared patterns of genetic differentiation between nascent species within an adaptive radiation of Cyprinodon pupfishes using genotyping by sequencing. Similar to classic adaptive radiations, this clade exhibits rapid morphological diversification rates and two species are novel trophic specialists, a scale‐eater and hard‐shelled prey specialist (durophage), yet the radiation is <10 000 years old. Both specialists and an abundant generalist species all coexist in the benthic zone of lakes on San Salvador Island, Bahamas. Based on 13 912 single‐nucleotide polymorphisms (SNPs), we found consistent differences in genetic differentiation between each specialist species and the generalist across seven lakes. The scale‐eater showed the greatest genetic differentiation and clustered by species across lakes, whereas durophage populations often clustered with sympatric generalist populations, consistent with parallel speciation across lakes. However, we found strong evidence of admixture between durophage populations in different lakes, supporting a single origin of this species and genome‐wide introgression with sympatric generalist populations. We conclude that the scale‐eater is further along the speciation‐with‐gene‐flow continuum than the durophage and suggest that different adaptive landscapes underlying these two niche environments drive variable progress towards speciation within the same habitat. Our previous measurements of fitness surfaces in these lakes support this conclusion: the scale‐eating fitness peak may be more distant than the durophage peak on the complex adaptive landscape driving adaptive radiation.     

Trait decoupling promotes evolutionary diversification of the trophic and acoustic system of damselfishes

Trait decoupling, wherein evolutionary release of constraints permits specialization of formerly integrated structures, represents a major conceptual framework for interpreting patterns of organismal diversity. However, few empirical tests of this hypothesis exist. A central prediction, that the tempo of morphological evolution and ecological diversification should increase following decoupling events, remains inadequately tested. In damselfishes (Pomacentridae), a ceratomandibular ligament links the hyoid bar and lower jaws, coupling two main morphofunctional units directly involved in both feeding and sound production. Here, we test the decoupling hypothesis by examining the evolutionary consequences of the loss of the ceratomandibular ligament in multiple damselfish lineages. As predicted, we find that rates of morphological evolution of trophic structures increased following the loss of the ligament. However, this increase in evolutionary rate is not associated with an increase in trophic breadth, but rather with morphofunctional specialization for the capture of zooplanktonic prey. Lineages lacking the ceratomandibular ligament also shows different acoustic signals (i.e. higher variation of pulse periods) from others, resulting in an increase of the acoustic diversity across the family. Our results support the idea that trait decoupling can increase morphological and behavioural diversity through increased specialization rather than the generation of novel ecotypes.     

The clock gene Period1 regulates innate routine behaviour in mice

Laboratory mice are well capable of performing innate routine behaviour programmes necessary for courtship, nest-building and exploratory activities although housed for decades in animal facilities. We found that in mice inactivation of the clock gene Period1 profoundly changes innate routine behaviour programmes like those necessary for courtship, nest building, exploration and learning. These results in wild-type and Period1 mutant mice, together with earlier findings on courtship behaviour in wild-type and period-mutant Drosophila melanogaster, suggest a conserved role of Period-genes on innate routine behaviour. Additionally, both per-mutant flies and Period1-mutant mice display spatial learning and memory deficits. The profound influence of Period1 on routine behaviour programmes in mice, including female partner choice, may be independent of its function as a circadian clock gene, since Period1-deficient mice display normal circadian behaviour.     

Neophobia and Dietary Conservatism:Two Distinct Processes?

Birds show distinct hesitation when approaching novel food and this has been termed ‘neophobia’. In laboratory-held birds like domestic chicks this effect lasts for a matter of a few minutes at most, but hesitant attack of novel foods can last for weeks or even months in wild birds. This effect, called ‘dietary conservatism’, seems to be a different type of learning process from neophobia as first described and has hitherto been largely overlooked. This paper presents some evidence for the view that the processes may be fundamentally different. We outline results from laboratory chicks that show neophobia to be easily deactivated by experience, which renders it unlikely to be an important force in wild birds. We also report evidence that the process of incorporation of novel food into the diet is not a simple one-stage process but includes at least four steps of assessment. The paper concludes with an outline of the importance of dietary conservatism in our understanding of the evolution of aposematism and the workings of mimicry. This revised version was published online in July 2006 with corrections to the Cover Date.     

Invasion windows for a global legume invader are revealed after joint examination of abiotic and biotic filters

• Successful alien plant invasion is influenced by both climate change and plant–plant interactions. We estimate the single and interactive effects of competition and extreme weather events on the performance of the global legume invader Lupinus polyphyllus (Lindl.).
• In three experimental studies we assessed (i) the stress tolerance of seedling and adult L. polyphyllus plants against extreme weather events (drought, fluctuating precipitation, late frost), (ii) the competitive effects of L. polyphyllus on native grassland species and vice versa, and (iii) the interactive effects of extreme weather events and competition on the performance of L. polyphyllus.
• Drought reduced growth and led to early senescence of L. polyphyllus but did not reduce adult survival. Fluctuating precipitation events and late frost reduced the length of inflorescences. Under control conditions, interspecific competition reduced photosynthetic activity and growth of L. polyphyllus. When subjected to competition during drought, L. polyphyllus conserved water while simultaneously maintaining high assimilation rates, demonstrating increased water use efficiency. Meanwhile, native species had reduced performance under drought.
• In summary, the invader gained an advantage under drought conditions through a smaller reduction in performance relative to its native competitors but was competitively inferior under control conditions. This provides evidence for a possible invasion window for this species. While regions of high elevation or latitude with regular severe late frost events might remain inaccessible for L. polyphyllus, further spread across Europe seems probable as the predicted increase in drought events may favour this non‐native legume over native species.

     

Mate Preference for Novel Phenotypes: A Fresh Face Matters

Conspicuous polymorphism in sexually selected traits is usually attributed to processes such as frequency‐dependent selection that can maintain genetic variation. Recent evidence indicates that dramatic variation of male coloration in guppies (Poecilia reticulata) is promoted by a form of frequency‐dependent selection in which males bearing rare or novel color patterns achieve higher mating success than males bearing common patterns. Active female preference for unfamiliar or rare color patterns has been implicated in generating this rare‐phenotype advantage, but the behavioral processes responsible for the preference remain unclear. To determine whether familiarity that is developed over a very short timescale can lead to a rare‐male mating advantage, we measured female response to courtship by males with color patterns that were the same as or different from that of the previous male to court. Females showed two types of short‐term preference variation in this experiment. On the first trial day, females shifted their preferences on a timescale of minutes, showing strong preference for males bearing a color pattern different from that of the immediately previous male to court. Twenty‐four hours later, females were less responsive to male courtship overall, and there was no difference in females’ response to different‐ and same‐morph males. Females also preferred males with more orange coloration on both trial days, but this color preference was independent of the preference for ‘different’ color patterns. These data suggest that the behavioral process underlying rare‐male advantage in guppies is that females prefer males bearing unfamiliar color patterns and that familiarity is determined over a very short timescale.