Evolutionary transitions in symbioses: dramatic reductions in bathymetric and geographic ranges of Zoanthidea coincide with loss of symbioses with invertebrates

Two fundamental symbiosis‐based trophic types are recognized among Zoanthidea (Cnidaria, Anthozoa): fixed carbon is either obtained directly from zooxanthellae photosymbionts or from environmental sources through feeding with the assistance of host‐invertebrate behaviour and structure. Each trophic type is characteristic of the suborders of Zoanthidea and is associated with substantial distributional asymmetries: suborder Macrocnemina are symbionts of invertebrates and have global geographic and bathymetric distributions and suborder Brachycnemina are hosts of endosymbiotic zooxanthellae and are restricted to tropical photic zones. While exposure to solar radiation could explain the bathymetric asymmetry it does not explain the geographic asymmetry, nor is it clear why evolutionary transitions to the zooxanthellae‐free state have apparently occurred within Macrocnemina but not within Brachycnemina. To better understand the transitions between symbiosis‐based trophic types of Zoanthidea, a concatenated data set of nuclear and mitochondrial nucleotide sequences were used to test hypotheses of monophyly for groups defined by morphology and symbiosis, and to reconstruct the evolutionary transitions of morphological and symbiotic characters. The results indicate that the morphological characters that define Macrocnemina are plesiomorphic and the characters that define its subordinate taxa are homoplasious. Symbioses with invertebrates have ancient and recent transitions with a general pattern of stability in host associations through evolutionary time. The reduction in distribution of Zoanthidea is independent of the evolution of zooxanthellae symbiosis and consistent with hypotheses of the benefits of invertebrate symbioses, indicating that the ability to persist in most habitats may have been lost with the termination of symbioses with invertebrates.     

Phylogeny‐based species delimitations and the evolution of host associations in symbiotic zoanthids (Anthozoa,Zoanthidea) of the wider Caribbean region

Zoanthids are marine cnidarians with simple morphologies that challenge our ability to delineate species. Phylogenetic analyses of internal transcribed spacer (ITS) sequences are consistent with six morphologically described species from the wider Caribbean region, and reveal four additional species that were not previously recognized. Histological examinations of unidentified species reveal cryptic Isozoanthus and Edwardsiidae (Actiniaria) species. Observations of zoanthids in situ reveal geographic distributions that range from regional to trans‐Atlantic. ITS and 16S data are consistent with hypotheses of paraphyly in some higher taxa of zoanthids; however, the clades of zoanthids recovered in both analyses can largely be defined by their host associations, thereby supporting phylogenetic conservatism in zoanthid–host association evolution. The single clear example of a zoanthid switching hosts was accompanied by a compensatory loss of endosymbiosis, which maintained the match in photosynthetic symbioses between zoanthids and sponge hosts. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 223–238.     

Transgenic cotton resistant to herbicide bialaphos

Resistance to bialaphos, a non-selective herbicide, was intro duced into cotton through genetic engineering. A gene encoding phosphinothric in acetyltransferase (bar) from Streptomyces hygroscopicus was inserted into elite varieties of cotton through particle bombardment. Based on the marker gene, -glucuronidase (gus) expression, a total of 18 Pima (Gossypium barbadense), 45 DP50 (G. hirsutum L.), 20 Coker 312 (G. hirsutum) and 2 El Dorado (G. hirsutum) transgenic plants were recovered. Integration of the bar gene into cotton genomic DNA was confirmed by Southern blot analysis and gene expression was confirmed by northern blot and enzyme assays. Herbicide (Basta®) tolerance up to 15 000 ppm was demonstrated in greenhouse trials. The newly introduced herbicide tolerance trait is inherited in a Mendelian fashion in the progenies of germline transformants. This study demonstrates the potential for particle bombardment to introduce commerically important genes directly into elite varieties of cotton. This mode of gene transfer can expedite the introduction of transgenic cotton products into world markets     

Onset of maturity in male southern rock lobsters Jasus edwardsii in Tasmania,Australia

Summary

The reproductive contribution of male southern rock lobsters Jasus edwardsii has recently become of interest for managing this fishery as changes to the length of seasonal closures have shifted fishing effort towards males. To assess size at onset of maturity, a total of 387 male southern rock lobsters Jasus edwardsii were collected using baited traps from four of the eight fishery regions around the Tasmanian coast during July and August 2000. Sizes at onset of maturity in these samples were estimated by examining the vasa deferentia for evidence of the commencement of spermatid production. In addition, the total combined weight of the vasa deferentia and testis was compared with body size (as a gonad somatic index, GSI). Estimates of size at onset of maturity from the two methods were similar, although estimates from GSI appeared to have broader confidence limits. Although these physiological indices of maturity do not necessarily translate to functional maturity, they indicate that maturity is well below that of the legal minimum size of 110 mm carapace length used for managing the fishery (all estimates by either method for length at 50% sample maturity ≤70 mm carapace length). Production of sperm by males occurs below the size at onset of maturity of females from the same region and spatial patterns in maturity estimated by onset of spermatid production were similar to those of females.     

Measurement and interpretation of sedimentary pigments

SUMMARY.

• 1 The factors that control the concentrations of pigments in lake sediments are examined using data from (i) transects across lake basins, (ii) surface samples from logographic and atrophic lakes, and (iii) two ²¹⁰Pb-dated short cores. Methods for the rapid non-chromatographic analysis of percent native chlorophyll and the blue-green algal pigments oscillaxanthin and myxoxanthophyll are described.
• 2 The concentrations of chlorophyll derivatives, total arytenoids, oscillaxanthin and myxoxanthophyll, and percent native chlorophyll, are higher under conditions along the transects favorable for preservation. Chlorophyll degrades at about the same rate as total carotenoids, and oscillaxanthin degrades at about the same rate as myxoxanthophyll. Therefore, both the ratio of chlorophyll to arytenoids (CD/TC) and the ratio of oscillaxanthin to myxoxanthophyll (OSC/MYX) are mostly determined by the quality of autochthonous production rather than by preservation conditions.
• 3 CD/TC values are higher in logographic lakes than in atrophic lakes, apparently as a result of differences in production of the two pigment types. Calculations show that CD/TC shifts in these two cores cannot be a record of the allochthonous-autochthonous Baltic in the systems. Instead, the CD/TC values shift with large changes in the kinds of plants dominating primary production.
• 4 The stratigraphy of percent native chlorophyll appears to record the hypohmnetic oxygen concentrations at the time of deposition.
• 5 No obvious reason exists why a eutrophic lake should produce more pigment per gram organic matter than should an oligotrophic lake. However, several correlated mechanisms tend to produce higher sedimentary pigment concentrations in eutrophic lakes. Most of these mechanisms, such as hypolimnetic oxygen consumption, indirectly translate greater primary productivity into greater sedimentary pigment concentration. Therefore, pigment concentrations are sometimes misleading, and pigment accumulation rate may be a better indicator of past primary production.

     

Preliminary Studies on the Optimum Shape of Dental Bridges

Several pre-existing anterior and posterior dental bridge models using Finite elements and the new ceramic material In-Ceram have been developed. The mechanical behaviour of these models has been compared with optimised profiles obtained from a newly developed evolutionary algorithm known as Evolutionary Structural Optimisation (ESO).

The results show that the mechanical behaviour of the bridges was mainly restricted by the properties of the porcelain veneer and the design of the bridges themselves. For the case of the anterior bridge, it was found that there existed a specific thickness of veneer that minimised the maximum principal stress. This was related to peak stresses that occurred at the bridge surface. Peak stresses also occurred in the material interface between the In-Ceram and the veneer. These extreme stresses were attributed to the notch size and shape. For the case of the posterior bridge, it was concluded that the shape of the bottom of the Pontic tooth is crucial in reducing the magnitude of the maximum principal tensile stress. The ESO process produced bridge designs which have uniformly stressed bridge surfaces, and which also have significantly lower maximum principal tensile stresses compared to the pre-existing designs (up to 44%).