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"Swordfish Evolution."
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THE EVOLUTION OF THE SEXUALLY SELECTED SWORD IN XIPHOPHORUS DOES NOT COMPROMISE AEROBIC LOCOMOTOR PERFORMANCE
Sexual selection can increase morphological diversity within and among species. Little is known regarding how interspecific variation produced through sexual selection affects other functional systems. Here, we examine how morphological diversity resulting from sexual selection impacts aerobic locomotor performance. Using Xiphophorus (swordtail fish) and their close relatives (N = 19 species), we examined whether the evolution of a longer sexually selected sword affects critical swimming speed. We also examined the effect of other suborganismal, physiological, and morphological traits on critical swimming speed, as well as their relationship with sword length. In correlation analyses, we found no significant relationship between sword length and critical swimming speed. Unexpectedly, we found that critical swimming speed was higher in species with longer swords, after controlling for body size in multiple regression analyses. We also found several suborganismal and morphological predictors of critical swimming speed, as well as a significant negative relationship between sword length and heart and gill mass. Our results suggest that interspecific variation in sword length is not costly for this aspect of swimming performance, but further studies should examine potential costs for other types of locomotion and other components of Darwinian fitness (e.g., survivorship, life span).
Journal Article
Geographically Widespread Swordfish Barcode Stock Identification: A Case Study of Its Application
The swordfish (Xiphias gladius) is a cosmopolitan large pelagic fish inhabiting tempered and tropical waters and it is a target species for fisheries all around the world. The present study investigated the ability of COI barcoding to reliably identify swordfish and particularly specific stocks of this commercially important species.
We applied the classical DNA barcoding technology, upon a 682 bp segment of COI, and compared swordfish sequences from different geographical sources (Atlantic, Indian Oceans and Mediterranean Sea). The sequences of the 5' hyper-variable fragment of the control region (5'dloop), were also used to validate the efficacy of COI as a stock-specific marker.
This information was successfully applied to the discrimination of unknown samples from the market, detecting in some cases mislabeled seafood products.
The NJ distance-based phenogram (K2P model) obtained with COI sequences allowed us to correlate the swordfish haplotypes to the different geographical stocks. Similar results were obtained with 5'dloop. Our preliminary data in swordfish Xiphias gladius confirm that Cytochrome Oxidase I can be proposed as an efficient species-specific marker that has also the potential to assign geographical provenance. This information might speed the samples analysis in commercial application of barcoding.
Journal Article
Negotiating the coasts: status and the evolution of boat technology in California
For the Chumash of southern California, the plank canoe (tomol) played a crucial role in food acquisition, transport, exchange, and social integration, with significant consequences for status building and sociopolitical evolution. We present new data about plank canoe construction assemblages and new marine faunal data that help to pinpoint the date of the earliest appearance of the tomol, with the ultimate goal of situating this technological development in the broader sociopolitical evolution of coastal Chumash groups. Plank canoe manufacturing by-products, including asphaltum and redwood, and the remains of large open-ocean fish species such as swordfish provide new paths to understanding this symbolically and functionally important innovation.
Journal Article
Association preferences of unisexual Amazon mollies (Poecilia formosa): differential response to swords based on sex of the bisexual parental species
Most females exhibit preferences for certain males and females based on mating and social decisions. Unisexual females that reproduce by gynogenesis are also expected to express association preferences, which may have been inherited from parental species, or may have evolved in response to selection pressures associated with their unisexual mating system. The unisexual, gynogenetic Amazon molly (Poecilia formosa) is a hybrid of the Atlantic molly (P mexicana) and sailfin molly (P. latipinna). Although none of these three species have sword tails, the two parental species differ in preference for swords on conspecifics. We further examined the variation in pre-existing bias within this species complex by testing Amazon molly preference to associate with male and female sailfin mollies with artificially attached swords. Amazon mollies significantly avoided females with colored swords, but were indiscriminate towards swords on males. Thus, this hybrid species shares its lack of preference for swords on males with female Atlantic mollies and females from one population of sailfin mollies. Avoidance of females with swords by Amazon mollies is unique in this species complex. We discuss the implications and functions of association preferences expressed by Amazon mollies and propose hypotheses for the differential response towards swords based on sex.
Journal Article
Why Some Fishes are Hotheads
Of the 30,000 fish species, only a few dozen are warm-blooded. Animal physiologist Barbara Block has found evidence explaining the origins of endothermy. Her findings are discussed.
Journal Article
The Presence of a Copper/Zinc Superoxide Dismutase in the Bacterium Photobacterium leiognathi: A Likely Case of Gene Transfer from Eukaryotes to Prokaryotes
The free-living bacterium Photobacterium leiognathi is also known to be a symbiont of ponyfish. The presence of a copper/zinc superoxide dismutase in P. leiognathi has been considered to be a case of gene transfer from eukaryotes to prokaryotes because this form of superoxide dismutase is normally present only in higher eukaryotic species. However, the amino acid sequence of the enzyme from the bacterium exhibited low identities (25-30%) with the same enzyme from eukaryotes. When amino acid mutations are taken into consideration, the weighted sequence similarity increases significantly; furthermore, the bacterial enzyme has the same active site residues and similar predicted secondary structure as the eukaryotic enzymes. The possibility of convergence is ruled out and the case of divergence is considered unlikely because of the observed phylogenetic distribution of the enzyme. This indicates that the presence of the copper/zinc superoxide dismutase in P. leiognathi can indeed be considered a case of gene transfer from eukaryotic species to prokaryotic species.
Journal Article
Siokunichthys nigrolineatus (Syngnathidae) Found on Fungia sp
The Indo-Pacific pipefish genus Siokunichthys has recently been rediagnosed by Dawson (1983). Dawson has described S. nigrolineatus n. sp., which together with S. bentuvai is known to have a close association (possibly a commensal relationship) with certain corals. Observations on such relationships are rare. The purpose of this note is to publish the first photographs of S. nigrolineatus in situ on Fungia sp.
Journal Article