Geographic Variation in the Central Pacific Halfbeak, Hyporhamphus acutus (Gunther)

Hyporhamphus acutus (Gunther) is distinguished from other Central Pacific species of Hyporhamphus by its long upper jaw, long anal fin base (longer than dorsal base), and shape of its preorbital lateral line canal. Two subspecies are recognized: Hyporhamphus acutus acutus (Gunther) with fewer vertebrae and fin rays inhabits the chain of islands from Wake Island and the Marshall Islands in the northwest to the Tuamotu Archipelago and Easter Island in the southeast; Hyporhamphus acutus paciftcus (Steindachner) with more vertebrae and fin rays is found in the Hawaiian Islands and at Johnston Island. Hemiramphus furcatus Philippi from Easter Island and Odontorhamphus chancellori Weed from the Cook Islands are placed in the synonymy of Hyporhamphus acutus acutus

Global Phylogeography Of Mackerels Of The Genus Scomber

Inter- and intraspecific genetic relationships among and within three species of mackerels of the genus Scomber were investigated by restriction site analysis of the whole mitochondrial (mt) DNA genome and direct sequence analysis of the mitochondrial cytochrome b gene. A total of 15 samples, averaging 19 individuals each, were collected from geographically isolated populations throughout the ranges of S. scombrus (two samples), S, australasicus (five samples), and S. japonicus (eight samples). Restriction site analysis with 12 restriction enzymes revealed substantial genetic variation within each species. Sample haplotype diversities ranged from 0.28 to 0.95, and nucleotide sequence diversities from 0.13% to 0.76%. Spatial partitioning of genetic variation was observed in each of the species. Eastern and western North Atlantic samples of S. scombrus exhibited significant heterogeneity in the distribution of mtDNA haplotypes, but no fixed restriction site differences were observed between samples. Similarly, no fixed restriction site differences occurred among samples of S. japonicus in the Atlantic Ocean, although there were significant differences in the distribution of haplotypes among samples. In contrast, samples of S. japonicus from within the Pacific Ocean were characterized by fixed restriction site differences. North and South Pacific samples of S. australasicus were highly divergent, and one of two divergent mtDNA matrilines was restricted to samples from the South Pacific. A 420-bp segment of the cytochrome b gene was sequenced for representatives of each of the major mtDNA lineages identified by restriction site analysis. Scomber scombrus differed from S. australasicus and S. japonicus by more than 11% net nucleotide sequence divergence, considerably greater than the 3.5% sequence divergence between S. australasicus and S. japonicus. Levels of interspecific genetic divergences based on restriction site data were similar in pattern, but were approximately 20% lower in magnitude when based on the cytochrome b sequences. Parsimony analysis and neighbor-joining of restriction site data, and parsimony analysis of cytochrome b sequences showed similar paraphyletic patterns in both S, japonicus and S. australasicus. Levels of divergence among samples of S. japonicus were similar to those between samples of S. australasicus and S. japonicus. Complete partitioning of halpotypes among some samples of S. japonicus that are morphologically distinct suggests that Atlantic and Indo-Pacific populations of S. japonicus may need to be recognized as separate species

Corrected Numbers for fish on Red List

(First paragraph) Kelly Swing gives inaccurate numbers for marine fish species on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. He also mistakenly conflates the scientific process of species assessment for the Red List with the separate political process of IUCN member voting (Nature 494, 314; 2013)

Unstable and Stable Classifications of Scombroid Fishes

Many cladists believe that a classification should strictly reflect a cladistic hypothesis. Consequently, they propose classifications that often differ markedly from existing ones and are potentially unstable due to phylogenetic uncertainty. This is problematic for economically or ecologically important organisms since changing classifications can cause confusion in their management as resources. The classification of the 44 genera of scombroid fishes (the mackerels, tunas, billfishes, and their relatives) illustrates this problem of instability. Previous cladistic analyses and analyses presented in this paper, using different data sets, result in many different cladistic hypotheses. In addition, the inferred cladograms are unstable because of different plausible interpretations of character coding. A slight change in coding of a single character, the presence of splint-like gill rakers, changes cladistic relationships substantially. These many alternative cladistic hypotheses for scombroids can be converted into various cladistic classifications, all of which are substantially different from the classification currently in use. In contrast, a quantitative evolutionary systematic method produces a classification that is unchanged despite variations in the cladistic hypothesis. The evolutionary classification has the advantage of being consistent with the classification currently in use, it summarizes anagenetic information, and it can be considered a new form of cladistic classification since a cladistic hypothesis can-be unequivocally retrieved from an annotated form of the classification

Tubercles and contact organs

p. 145-216 : ill. ; 27 cm.Includes bibliographical references (p. 204-216)

First record of the flat needlefish Ablennes hians (Belonidae) in central Mediterranean waters (western Ionian Sea)

Two specimens of Ablennes hians (Valenciennes, 1846) were collected between 2018 and 2020 in nearshore waters off the island of Malta. The first occurrence of the flat needlefish in the central Mediterranean, almost contemporary to its first record in the eastern Levantine Sea, is briefly discussed.peer-reviewe

Climatic change drives dynamic source–sink relationships in marine species with high dispersal potential

While there is now strong evidence that many factors can shape dispersal, the mechanisms influencing connectivity patterns are species‐specific and remain largely unknown for many species with a high dispersal potential. The rock lobsters Jasus tristani and Jasus paulensis have a long pelagic larval duration (up to 20 months) and inhabit seamounts and islands in the southern Atlantic and Indian Oceans, respectively. We used a multidisciplinary approach to assess the genetic relationships between J. tristani and J. paulensis, investigate historic and contemporary gene flow, and inform fisheries management. Using 17,256 neutral single nucleotide polymorphisms we found low but significant genetic differentiation. We show that patterns of connectivity changed over time in accordance with climatic fluctuations. Historic migration estimates showed stronger connectivity from the Indian to the Atlantic Ocean (influenced by the Agulhas Leakage). In contrast, the individual‐based model coupled with contemporary migration estimates inferred from genetic data showed stronger inter‐ocean connectivity in the opposite direction from the Atlantic to the Indian Ocean driven by the Subtropical Front. We suggest that the J. tristani and J. paulensis historical distribution might have extended further north (when water temperatures were lower) resulting in larval dispersal between the ocean basis being more influenced by the Agulhas Leakage than the Subtropical Front. As water temperatures in the region increase in accordance with anthropogenic climate change, a southern shift in the distribution range of J. tristani and J. paulensis could further reduce larval transport from the Indian to the Atlantic Ocean, adding complexity to fisheries management

Restricting Dosage Compensation Complex Binding to the X Chromosomes by H2A.Z/HTZ-1

Dosage compensation ensures similar levels of X-linked gene products in males (XY or XO) and females (XX), despite their different numbers of X chromosomes. In mammals, flies, and worms, dosage compensation is mediated by a specialized machinery that localizes to one or both of the X chromosomes in one sex resulting in a change in gene expression from the affected X chromosome(s). In mammals and flies, dosage compensation is associated with specific histone posttranslational modifications and replacement with variant histones. Until now, no specific histone modifications or histone variants have been implicated in Caenorhabditis elegans dosage compensation. Taking a candidate approach, we have looked at specific histone modifications and variants on the C. elegans dosage compensated X chromosomes. Using RNAi-based assays, we show that reducing levels of the histone H2A variant, H2A.Z (HTZ-1 in C. elegans), leads to partial disruption of dosage compensation. By immunofluorescence, we have observed that HTZ-1 is under-represented on the dosage compensated X chromosomes, but not on the non-dosage compensated male X chromosome. We find that reduction of HTZ-1 levels by RNA interference (RNAi) and mutation results in only a very modest change in dosage compensation complex protein levels. However, in these animals, the X chromosome–specific localization of the complex is partially disrupted, with some nuclei displaying DCC localization beyond the X chromosome territory. We propose a model in which HTZ-1, directly or indirectly, serves to restrict the dosage compensation complex to the X chromosome by acting as or regulating the activity of an autosomal repellant