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1. Effect of Salinity on DMSP Production in Gambierdiscus belizeanus (Dinophyceae)

   https://doi.org/10.1111/jpy.12923  

   Gwinn, Jessica K. ; Robertson, Alison ; Kiene, Ronald P. ( October 2019 , Journal of Phycology)

   Dimethylsulfoniopropionate (DMSP) is produced by many species of marine phytoplankton and has been reported to provide a variety of beneficial functions including osmoregulation. Dinoflagellates are recognized as majorDMSPproducers; however, accumulation has been shown to be highly variable in this group. We explored the effect of hyposaline transfer inGambierdiscus belizeanusbetween ecologically relevant salinities (36 and 31) onDMSPaccumulation, Chla, cell growth, and cell volume, over 12 d. Our results showed thatG. belizeanusmaintained an intracellularDMSPcontent of 16.3 pmol cell⁻¹and concentration of 139 mMin both salinities. Although this intracellular concentration was near the median reported for other dinoflagellates, the cellular content achieved byG. belizeanuswas the highest reported of any dinoflagellate thus far, owing mainly to its large size.DMSPlevels were not significantly affected by salinity treatment but did change over time during the experiment. Salinity, however, did have a significant effect on the ratio ofDMSP:Chla, suggesting that salinity transfer ofG. belizeanusinduced a physiological response other thanDMSPadjustment. A survey ofDMSPcontent in a variety ofGambierdiscusspecies and strains revealed relatively highDMSPconcentrations (1.0–16.4 pmol cell⁻¹) as well as high intrageneric and intraspecific variation. We conclude that, althoughDMSPmay not be involved in long‐term (3–12 d) osmoregulation in this species,G. belizeanusand otherGambierdiscusspecies may be important contributors toDMSPproduction in tropical benthic microalgal communities due to their large size and high cellular content.

    

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2. Stripes, jewels and spines: further investigations into the evolution of defensive strategies in a chemically defended gecko radiation ( Strophurus , Diplodactylidae)

   https://doi.org/10.1111/zsc.12181  

   Nielsen, Stuart V. ; Oliver, Paul M. ; Laver, Rebecca J. ; Bauer, Aaron M. ; Noonan, Brice P. ( May 2016 , Zoologica Scripta)

   The geckos in the genusStrophurus(Diplodactylidae) are one of only two squamate lineages with specialized caudal defensive glands. Many species in this genus also have distinctive caudal ornamentation combined with bright and/or contrasting colour pattern elements on the iris, tail and especially the lining of the mouth that are hypothesized to be adaptations for specialized (e.g. deimatic) defensive functions. We present the first multilocus, phylogenetic analysis of the biogeography and evolution of all recognized taxa ofStrophurus. Contrary to previous phenotypic and ecological assessments, our phylogenetic analyses delineate four divergent lineages. Three lineages are relatively small (snout‐vent length [SVL] 40–60 mm), species‐poor (<5 recognized taxa), cryptically coloured (either striped or spotted) and lack precloacal pores (a secondary sexual trait) and putative deimatic elements. In contrast, the remaining lineage is comparatively species rich (at least 14 taxa), attains a larger body size (SVL60–90 mm), possesses precloacal pores and shows extensive variation in caudal ornamentation and often bright and/or contrasting eye, tail and mouth colouration. The three less diverse lineages have smaller distributions and tend to be associated with spinifex (e.g.Triodia) hummock grasses or rocks, whereas the fourth lineage is much more widespread (including multiple biomes) and consistently reported to utilize more exposed diurnal microhabitats on shrubs and trees. Biogeographical analyses also indicate that – in contrast to many other Australian radiations – the arid biome is the ancestral area of occupation forStrophurus, with multiple inferred shifts into surrounding sclerophyll and monsoon biomes. This study emphasizes that – independent of caudal defensive glands – it appears to be a shift in microhabitat use that correlates with the accumulation of bright and contrasting colouration elements, secondary sexual characters and the widest geographic distribution.

    

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3. Ankle structure of the Tokay gecko ( Gekko gecko ) and its role in the deployment of the subdigital adhesive system

   https://doi.org/10.1111/joa.13511  

   Higham, Timothy E. ; Zhuang, Minga ; Russell, Anthony P. ( July 2021 , Journal of Anatomy)

   The remarkable ability of geckos to adhere to smooth surfaces is often thought of in terms of external structures, including the branching setae that make contact with the surface producing van der Waals forces. Some geckos also exhibit unique movements of the distal segments of the limbs during locomotion and static clinging, including active digital hyperextension and considerable pedal rotation. During static clinging, geckos can exhibit considerable adduction/abduction of the pes while the crus and thigh remain firmly adpressed to the substratum. This decoupling of pedal adduction/abduction from ankle flexion/extension and pedal long‐axis rotation is a significant departure from pedal displacements of a typical lizard lacking adhesive ability. The structure of the ankle is likely key to this decoupling, although no detailed comparison of this complex joint between pad‐bearing geckos and other lizards is available. Here we compare the configuration of the mesotarsal joint of nongekkotan lizards (IguanaandPristidactylus) with that of the Tokay gecko (Gekko gecko) using prepared skeletons, scanning electron microscopy, and micro‐computed tomographic (µCT) scans. We focus on the structure of the astragalocalcaneum and the fourth distal tarsal. The mesotarsal joint exhibits a suite of modifications that are likely associated with the secondarily symmetrical pes of pad‐bearing geckos. For example, the lateral process of the astragalocalcaneum is much more extensive inG.geckocompared with other lizards. The mesotarsal joint exhibits several other differences permitting dissociation of long‐axis rotation of the pes from flexion–extension movement, including a reduced ventral peg on the fourth distal tarsal, an articulatory pattern dominated by a well‐defined, expansive distomesial notch of the astragalocalcaneum, and an associated broad proximodorsal articulatory facet of the fourth distal tarsal. Pad‐bearing geckos are capable of effectively deploying their intricate adhesive system across a broad array of body angles because of this highly modified ankle. Future research should determine whether the differences encountered inG.gecko(and their extent) apply to the Gekkota as a whole and should examine how the elements of the ankle move dynamically during locomotion across a range of taxa.

    

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4. Development and the effects of extended parenting in the cold‐breeding burying beetle Nicrophorus sayi

   https://doi.org/10.1111/een.12670  

   Benowitz, Kyle M. ; Amukamara, Ashley U. ; Mckinney, Elizabeth C. ; Moore, Allen J. ( August 2018 , Ecological Entomology)

   1. Burying beetles (Nicrophorusspp.) provide an excellent model system to test predictions about the relationships between environment, life‐history and behaviour. All species in the genus display similar natural histories, breeding on vertebrate carcasses and providing parental care to developing offspring. However, variations in other aspects of species' ecologies provide a rich framework to examine the evolution of parental behaviours and other traits.

   2. One little‐studied species,N. sayi, breeds in substantially colder temperatures than its congeners, creating a potentially harsh environment for offspring. Here, we examined the timing of reproductive and developmental events in this species, and also investigated the effects of removing parents on offspring performance.

   3. We find that development is not only extremely slow in this species, but it is also delayed even in comparison to other burying beetles reared at similar temperatures. However, the presence of parents reduces the time that offspring take to leave the carcass. This decrease in development time does not appear to result in a trade‐off with mortality or body size.

   4. From these results, we suggest that very slow development may be advantageous when living in a particularly cold environment. Additionally, one role of extended parental care may be to assist offspring in dealing with these harsh conditions, and to mitigate the potentially negative consequences of adopting such a slow life‐history strategy.

    

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5. The Arabidopsis heterotrimeric G‐protein β subunit, AGB 1, is required for guard cell calcium sensing and calcium‐induced calcium release

   https://doi.org/10.1111/tpj.14318  

   Jeon, Byeong Wook ; Acharya, Biswa R. ; Assmann, Sarah M. ( April 2019 , The Plant Journal)

   Cytosolic calcium concentration ([Ca²⁺]_cyt) and heterotrimeric G‐proteins are universal eukaryotic signaling elements. In plant guard cells, extracellular calcium (Ca_o) is as strong a stimulus for stomatal closure as the phytohormone abscisic acid (ABA), but underlying mechanisms remain elusive. Here, we report that the sole Arabidopsis heterotrimeric Gβ subunit,AGB1, is required for four guard cell Ca_oresponses: induction of stomatal closure; inhibition of stomatal opening; [Ca²⁺]_cytoscillation; and inositol 1,4,5‐trisphosphate (InsP3) production. Stomata in wild‐type Arabidopsis (Col) and in mutants of the canonical Gα subunit,GPA1, showed inhibition of stomatal opening and promotion of stomatal closure by Ca_o. By contrast, stomatal movements ofagb1mutants andagb1/gpa1double‐mutants, as well as those of theagg1agg2 Gγ double‐mutant, were insensitive to Ca_o. These behaviors contrast withABA‐regulated stomatal movements, which involveGPA1 andAGB1/AGG3 dimers, illustrating differential partitioning of G‐protein subunits among stimuli with similar ultimate impacts, which may facilitate stimulus‐specific encoding.AGB1knockouts retained reactive oxygen species andNOproduction, but lostYC3.6‐detected [Ca²⁺]_cytoscillations in response to Ca_o, initiating only a single [Ca²⁺]_cytspike. Experimentally imposed [Ca²⁺]_cytoscillations restored stomatal closure inagb1. Yeast two‐hybrid and bimolecular complementation fluorescence experiments revealed thatAGB1 interacts with phospholipase Cs (PLCs), and Ca_oinduced InsP3 production in Col but not inagb1. In sum, G‐protein signaling viaAGB1/AGG1/AGG2 is essential for Ca_o‐regulation of stomatal apertures, and stomatal movements in response to Ca_oapparently require Ca²⁺‐induced Ca²⁺release that is likely dependent on Gβγ interaction withPLCs leading to InsP3 production.

    

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