Population genetic substructure in blue whiting based on allozyme data

The genetic population structure of the pelagic gadoid blue whiting Micromesistius poutassou throughout its east Atlantic distribution range was explored using polymorphisms at the tissue enzyme loci IDHP-2 * and PGM-1 *. The study included 5025 individuals from 65 locations in the east Atlantic and the Mediterranean. Significant geographic heterogeneity in allele frequencies was demonstrated at both loci ( IDHP-2 *: P=0·030, PGM-1 *: P=0·005). The degree of genetic differentiation ( F _ST= 1·1%) in blue whiting appears to be at the same level as for the demersal gadoids cod and haddock. Several separate reproductive units were indicated at the fringes of the distribution range, i.e. in the Barents Sea, and in one Norwegian fjord (Romsdalsfjord).     

Anatomy and histology of the brain and sense organs of the Antarctic eel cod Muraenolepis microps (Gadiformes; Muraenolepididae)

Brain regions, cranial nerves, and sense organs in Muraenolepis microps, an Antarctic gadiform fish, were examined to determine which features could be attributed to a gadiform ancestry and which to habitation of Antarctic waters. We found that the central nervous system and sense organs are well developed, showing neither substantial regression nor hypertrophy. A detailed drawing of the brain and cranial nerves is provided. The rostral position of the olfactory bulbs and telencephalic size and lobation are common for the order. The optic tectum and corpus cerebelli are smaller than in most other gadiforms. The shape of the corpus cerebelli is not distinctive among gadiforms. The lateral line region is moderately well-developed, but not hypertrophied to the extent seen in deep-sea gadiforms. As is the case in gadids possessing barbels and elongated pelvic rays, Muraenolepis has well-developed facial lobes, although these are smaller and more laterally positioned. The vagal lobes are deeply placed in the rhombencephalon and project into the fourth ventricle. The brain of Muraenolepis resembles that of a phyletically derived gadoid, especially a phycid, more than it resembles the brain of a phyletically basal macrourid. Two histological features of the diencephalon of Muraenolepis appear to be unique among gadiforms: a well-organized thalamic central medial nucleus and subependymal expansions. Muraenolepis has a pure rod retina like many deep-sea species but lacks the superimposed layers of rod outer segments. The histology of the nonvisual sense organs, especially the olfactory and external taste systems, are well-developed in Muraenolepis but not hypertrophied. We relate our findings to what is known about neural morphology in other gadiforms and in phyletically distant notothenioids and liparids that are sympatric with Muraenolepis on the Antarctic shelf. The only feature that reflects an Antarctic existence is the diencephalic subependymal expansions, which within notothenioids mirror the habitation of cold waters and have been found in every Antarctic species examined to date. Although the waters of the Antarctic shelf are cold, dark, and deep, brain and sense organ morphology in Muraenolepis are remarkably free of extreme specialization.     

The palatine bone and its associations in gadoid fishes

The articulation of the palatine bone in gadoid fishes has been thought of as a specialization of that group. It is shown that there are, in fact, three principal types of articulation, two of which are shared with other gadiform groups. The type of palatine articulation in other paracanthopterygians is briefly described and compared with that of various acanthopterygians. The supposed relationships of some gadoids are commented upon in the light of the specialized nature of some types of palatine articulation.     

Seasonal changes in migratory and predatory activity of two species of gadoid preying on inshore northern shrimp Pandalus borealis

The interaction between two species of gadoid and a shrimp stock was studied in a 40 km long two-armed fjord in north-west Iceland. On the basis of acoustic and trawl surveys in 2005 and 2006, immature cod Gadus morhua and haddock Melanogrammus aeglefinus were found to migrate to the inner part of the fjord in late summer, concurrent with rising temperatures. At the same time, the local northern shrimp Pandalus borealis stock retreated into the north-east arm of the fjord. Vertical distribution of acoustic targets indicated that a significant and temporally variable fraction of the gadoids was inaccessible to the trawl. Shrimp was a significant part of the diet of immature G. morhua, except in June 2006 when euphausiids comprised most of the diet of both G. morhua and M. aeglefinus. Shrimp was only a minor part of the diet of M. aeglefinus. An on-off relationship was observed in the catches of gadoids and shrimp. In hauls with large catches of gadoids, few shrimp were found and vice versa, indicating avoidance reaction at this spatial scale. The cooling in winter may have driven the gadoids to the outer parts of the fjord, which in turn may have aided in the dispersal of the shrimp stock in the following months.     

New data on distribution of Norwegian (Atlantic) pollock Theragra finnmarchica (Gadidae) in the Barents Sea

New data have been acquired on the biology, morphological features and distribution of Norwegian (Atlantic) pollock Theragra finnmarchica in the Barents Sea. Two individuals of this rare species gadoid (Gadidae) were caught in June and July 2012 in the south-eastern part of the Barents Sea, indicating a wider distribution area of this species than previously thought. It has been confirmed that a number of morphological features of Norwegian pollock is different from T. chalcogramma, and that it feeds on macroplankton (Euphausiidae, Hyperiidae).     

The food of five gadoid species during the pelagic O-group phase in the northern North Sea

The diets of five gadoid species in the northern North Sea are described: the cod, Gadus morhua (L.); haddock, Melanogrammus aeglefinus (L.); whiting, Merlangius merlangus (L.); saithe, Pollachius virens (L.); and the Norway pout, Trisopterus esmarkii (L.). The diet of each species was shown to be a gradual progression to different prey species as the predators increased in length. There were differences in the food taken by each species with respect to numbers, species and size. These differences in diet suggest that the degree of competition between pelagic O-group gadoids is not great.     

Findings of Andriashevs eel cod <Emphasis Type="Italic">Muraenolepis andriashevi</Emphasis> (Gadiformes: Muraenolepididae) at Discovery Seamount (South Atlantic)

Findings of a rare fish, Andriashevs eel cod Muraenolepis andriashevi Balushkin et Prirodina, 2005 (Muraenolepididae), from Discovery Seamount (South Atlantic) are described. The new findings extend the geographical distribution area and the range of morphological variability of this species previously known only from two type-specimens from the Agulhas Bank (South Africa).     

A molecular phylogeny of the patellid limpets (Gastropoda: Patellidae) and its implications for the origins of their antitropical distribution

The geographical distribution of the limpet family Patellidae is essentially antitropical, with 18 species in southern Africa, 10 in the northeastern Atlantic, and only 11 species elsewhere (although 4 of these do occur in the tropics). One possible explanation for this distribution is the suggestion of a recent, perhaps Early Pliocene, migration from southern Africa northward. We tested this hypothesis by constructing a molecular phylogeny, derived from partial sequences of the 12S and 16S mitochondrial genes, obtained from 34 of the 38 patellid species. Five species of Nacellidae and 3 of Lottiidae were included as potential outgroups. Analysis revealed that two patellid clades are represented in the northeastern Atlantic. The typical European patellids (Patella sensu stricto) form a single clade within which there is little molecular divergence, but are distant from all other patellids, thus refuting the idea of recent southern ancestry. From the limited fossil record and estimated rates of molecular divergence, we suggest that Patella s.s. may have originated at least as early as the Upper Cretaceous and that its northern distribution may have been achieved at the same time. The second patellid clade present in the northeastern Atlantic is the genus Cymbula, of which the single species Cymbula safiana extends from West Africa to the Mediterranean. In contrast to Patella s.s., C. safiana is indeed a member of an otherwise southern African clade and may have attained its present distribution more recently, during the Miocene. The geographical origin of the family remains unclear, but a Mesozoic radiation in southern Gondwana is possible. By optimizing morphological characters on our molecular tree, we consider the evolution of shell mineralogy and sperm ultrastructure. We also discuss the phylogenetic classification of the patellids and present some evidence that the family may not be monophyletic.     

Predation on northern shrimp (Pandalus borealis) by three gadoid species

Northern shrimp (Pandalus borealis) is targeted by commercial fisheries, but is also an important prey in the marine food web. In this study, stomach content data were used to study predation on shrimp by three gadoid species, cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus), in six inshore areas around Iceland. The results showed that shrimp was more important in the diet of cod compared with the other two predators. However, the overall predation pressure was similar for cod and haddock due to the high abundance of haddock. Therefore, even though shrimp is not the primary source of food for haddock, this species can have a substantial effect on shrimp stocks when haddock abundance is high. In addition, while cod and haddock did not select for any particular size of shrimp, whiting seemed to preferentially target juvenile shrimp. The results suggest that due to the overall effects of these three predators on shrimp stocks, gadoids need to be included in the management of shrimp stocks as predation is one of the major drivers in the development of this important prey stock.     

Sexual dimorphism of drumming muscles in European hake (<Emphasis Type="Italic">Merluccius merluccius</Emphasis>)

Dissections of mature and non-mature European hake males and females (N = 142) collected in waters off the western coast of Norway and in the Bay of Biscay (France) in 2004–2006 demonstrate for the first time that this gadoid species contains drumming muscles. There were differences in drumming muscles weight with body length, sex and maturity stage. This study shows that the difference between females and males is primarily manifested during the spawning season, seen both in the French and Norwegian samples. For the mature females the drumming muscles dry weight increases only slightly, if at all, with increase in total length. For mature males there is a corresponding rapid increase. There does not seem to be any consistent difference between the average dry weight of the drumming muscles in immature male and immature and mature female hake of the same length, tested on the Norwegian samples. Our results suggest that male hake, like the males of other gadoids studied, may produce sounds in the context of spawning.     

Climate impacts on transocean dispersal and habitat in gray whales from the Pleistocene to 2100

Arctic animals face dramatic habitat alteration due to ongoing climate change. Understanding how such species have responded to past glacial cycles can help us forecast their response to today's changing climate. Gray whales are among those marine species likely to be strongly affected by Arctic climate change, but a thorough analysis of past climate impacts on this species has been complicated by lack of information about an extinct population in the Atlantic. While little is known about the history of Atlantic gray whales or their relationship to the extant Pacific population, the extirpation of the Atlantic population during historical times has been attributed to whaling. We used a combination of ancient and modern DNA, radiocarbon dating and predictive habitat modelling to better understand the distribution of gray whales during the Pleistocene and Holocene. Our results reveal that dispersal between the Pacific and Atlantic was climate dependent and occurred both during the Pleistocene prior to the last glacial period and the early Holocene immediately following the opening of the Bering Strait. Genetic diversity in the Atlantic declined over an extended interval that predates the period of intensive commercial whaling, indicating this decline may have been precipitated by Holocene climate or other ecological causes. These first genetic data for Atlantic gray whales, particularly when combined with predictive habitat models for the year 2100, suggest that two recent sightings of gray whales in the Atlantic may represent the beginning of the expansion of this species' habitat beyond its currently realized range.     

Characteristic distribution of glycolipids in gadoid fish nerve tissues and its bearing on phylogeny.

Glycolipids were isolated from nerve tissues of gadoid fishes including Alaskan pollack and Pacific cod. Their chemical structures were determined by gas-liquid chromatography and gas chromatography-mass spectrometry, and their constituents were analyzed in detail and compared with those of glycolipids from other fish groups. The results revealed that gadoid fish nerve membranes contain peculiar glycolipid molecular species that are distinctly different from those in other teleostean fishes and higher vertebrates. The mole percentage ratio of the four major glycolipids (cerebroside-sulfatide-galactosylglyceride-sulfogalactosylglyce ride) was 48:12:25:15, indicating profound accumulation of glycoglycerolipids. Galactosylglyceride and sulfogalactosylglyceride were primarily of the diacyl type (greater than 90%), the major fatty acids being 16:0 and 18:1. An abundance of glucocerebroside (25 to 55% of cerebroside) and its fatty acid ester (37 to 47% of ester cerebroside) was noted. Cerebroside and sulfatide were characterized by the absence of hydroxy and odd numbered fatty acids, and 24:1 acid was a predominant component of both glucocerebroside and galactocerebroside. Subcellular fractionation revealed that myelin membranes comprised such unusual glycolipid constituents as those seen in whole nerve tissues. A vertebrate whose nerve membranes consist of such peculiar glycolipid molecules has not previously been reported. The characteristics of the glycolipid composition in gadoid fishes are discussed in relation to myelin functions, physicochemical properties of nerve membranes, and the phylogenic significance of this fish group.     

Development of 10 microsatellite loci in the ling (Molva molva)

We developed primers for two dinucleotide and eight tetranucleotide microsatellite loci in a marine fish, the ling (Molva molva). All markers were obtained from partial genomic DNA libraries and characterized in 55 unrelated individuals from one putative population. The number of alleles ranged from five to 24 (average 10.5) per locus, and the observed heterozygosity ranged from 0.218 to 0.981 (average 0.643). No loci amplified in two other gadoid species tested, the Atlantic cod (Gadus morhua) and the tusk (Brosme brosme).     

Identification of gadoid species (Pisces, Gadidae) by PCR-RFLP analysis

A rapid PCR-RFLP analysis was optimized to identify the presence of 3 closely related gadoid fish species: Alaska pollack Theragra chalcogramma, Pacific cod Gadus macrocephalus and Atlantic cod Gadus morhua in commercial seafood products. Gadoid universal primers were designed for PCR amplification of a 558-bp fragment encoding the mitochondrial cytochrome b gene. Without purification of the PCR products, double digestion with Eco32I and Eco105I restriction enzymes generated reproducible species-specific restriction patterns visualizing 3 fragments (106 bp, 161 bp and 291 bp) in Alaska pollack and 2 fragments (106 bp and 452 bp) in Pacific cod, whereas no cleavage was observed in Atlantic cod. This PCR-RFLP analysis is simple, rapid and reliable, and therefore can be routinely applied to discover fraudulent substitution among 3 economically important gadoid species in commercial seafood products.     

Observations on the size, dry weight and energy content of the eggs of some demersal fish species from British marine waters

The diameters, dry weights and calorific value of the eggs of seven gadoid species (cod, Gadus morhua , haddock, Melanogrammus aeglefinus , whiting, Merlangius merlangus , Norway pout, Trisopterus esmarkii , lythe. Pollachius pollachius , saithe, P. virens , ling. Molva molva ) and one pleuronectid (plaice, Pleuronectes platessa ) were measured. Ling eggs contain an oil globule; the eggs of the other species do not.
Preservation in formaldehyde solution caused a small (<4%) reduction in egg diameter but a large (15–30%) reduction in dry weight. There was no significant difference between the dry weights of unpreserved eggs weighed after (a) oven-drying at 60° C or (b) freeze-drying. Equations relating the dry weight of unpreserved eggs to unpreserved diameter and to preserved diameter are given for six species, and general equations that may apply to all North Sea gadoids whose eggs lack an oil globule are calculated. The calorific values of the dried, unpreserved eggs of all species except ling were similar (mean 23.19 kJ g⁻¹, S.D. 1.50) but the value for ling was higher (mean 26.92 kJ g⁻¹, S.D. 2.29). The estimated energy content (kJ 1000 eggs⁻¹) of eggs of each species are tabulated.     

A phylogeographic investigation of the kelp genus Laminaria (Laminariales,Phaeophyceae), with emphasis on the South Atlantic Ocean

The genus Laminaria has a wide distribution range compared with other kelp genera because it is found in both the North and the South Atlantic, on both sides of the North Pacific, as well as in the Mediterranean. Hypotheses behind this biogeographical pattern have been discussed by several authors but have not yet been fully evaluated with time‐calibrated phylogenies. Based on the analysis of four molecular markers (ITS2, rbcL, atp8 and trnWI), our goal was to reassess the Laminaria species diversity in South Africa, assess its relationship with the other species distributed in the South Atlantic and reconstruct the historical biogeography of the genus. Our results confirm the occurrence of a single species, L. pallida, in southern Africa, and its sister relationship with the North Atlantic L. ochroleuca. Both species belonged to a clade containing the other South Atlantic species: L. abyssalis from Brazil, and the Mediterranean L. rodriguezii. Our time‐calibrated phylogenies suggest that Laminaria originated in the northern Pacific around 25 mya, followed by at least two migration events through the Bering Strait after its opening (~5.32 mya). Today, the first is represented by L. solidungula in the Arctic, while the second gave rise to the rest of the Atlantic species. The colonization of the North Atlantic was followed by a gradual colonization southward along the west coast of Europe, into the Mediterranean (~2.07 mya) and two recent, but disconnected, migrations (~1.34 and 0.87 mya) across the equator, giving rise to L. abyssalis in Brazil and L. pallida in southern Africa, respectively.     

A new look at geographic and phylogenetic relationships within the species group surrounding Octopus vulgaris (Mollusca, Cephalopoda): indications of very wide distribution from mitochondrial DNA sequences

The distribution of Octopus vulgaris has not yet been completely clarified. For a long time, a cosmopolitan distribution with unknown distribution limits had been assumed. This assumption has recently been questioned and it has been postulated that the distribution is restricted to the Mediterranean and the northeastern Atlantic. However, as our previous studies show, the existence of O. vulgaris can be confirmed for the Mediterranean and the whole eastern Atlantic, and evidence is provided for its occurrence in the western Atlantic. The aim of the present work is to extend our previous data matrix and to clarify whether O. vulgaris exists in the northwestern Pacific. Therefore, the sequence variation in ostensible O. vulgaris from 13 localities in the Mediterranean (France), the Atlantic Ocean [Lanzarote, Senegal, South Africa (Atlantic, Indian Ocean), Tristan da Cunha, north, middle and south Brazil], the Caribbean Sea (Venezuela) and the Pacific Ocean (Taiwan, Japan and Costa Rica) was examined using the mitochondrial genes coding for the 16S rRNA and cytochrome oxidase subunit III (COIII). Sequence divergence was relatively low between populations of O. vulgaris from the Mediterranean, the eastern and western Atlantic (except north Brazil), Venezuela, Taiwan and Japan compared with other species of the genus Octopus . Trees constructed by using maximum likelihood, neighbour joining and maximum parsimony algorithms (PAUP) show the above-mentioned populations from the Mediterranean, the western and eastern Atlantic, Venezuela and the northwestern Pacific (Japan and Taiwan) as a monophyletic cluster. Thus, even if the Octopus vulgaris -like octopus from north Brazil should turn out a cryptic species, the data of this work not only support our hypothesis of the distribution of O. vulgaris in the Mediterranean, the eastern and western Atlantic but also show that O. vulgaris is present in the northwestern Pacific, namely in the waters of Taiwan and Japan.     

KLEPTOPARASITISM OF SANDWICH TERNS STERNA SANDVICENSIS BY BLACK-HEADED GULLS LARUS RIDIBUNDUS

The parasitic behaviour of Black-headed Gulls in a mixed colony of terns and gulls at the Sands of Forvie on the northeast coast of Scotland is described in some detail. Food-stealing occurred with varying frequency throughout the breeding season. Less than 6% of the terns were attacked during incubation and when their chicks were a few days old, but up to 29% were attacked thereafter. At the same time the percentage of successful attacks rose from 1% or less to 6.5%.
Food items brought back to the ternery were predominantly sandeels, clupeids and gadoids. Only a small proportion of terns carrying fish shorter than 7 cm were attacked whether they were sandeels, clupeids or gadoids.
Robbing success was higher with clupeids and gadoids than with sandeels.
The effect of the Black-headed Gulls' kleptoparasitism on the Sandwich Terns' breeding success is thought to have been negligible during incubation and early chick-life, but might have influenced fledging weight and ultimately post-fledging survival.     

Allozyme analyses of the genus Trisopterus: taxonomic status and population structure of the poor cod

Genetic analysis of the four Trisopterus (Gadidae) taxa suggests that the interrelationships of the two morphs of poor cod ( T. minutus minutus in the Atlantic and T. minutus capelanus in the Mediterranean) should be reconsidered. The Mediterranean poor cod T. m. capelanus is more closely related to bib T. luscus than to the Atlantic poor cod, so the population structure in the Atlantic and Mediterranean poor cod must be considered separately. Among 635 Atlantic individuals there was some evidence of poor cod population differentiation (allele frequency heterogeneity test P <0·0005; F _ST=0·0135, P ≤0·0005). Levels of genetic variation were similar to those reported for related gadoid species. Some differentiation was present on the Norwegian coast (samples from Trondheimsfjord) and between the Faeroe Islands (Faeroe Bank) and the adjacent European coastal location. In contrast no statistically significant population differentiation was evident in Mediterranean poor cod, but fewer samples and individuals were screened.