DIETS OF BAIRD'S BEAKED WHALES, BERARDIUS BAIRDII, IN THE SOUTHERN SEA OF OKHOTSK AND OFF THE PACIFIC COAST OF HONSHU, JAPAN

Stomach contents were analyzed from 127 Baird's beaked whales, Berardius bairdii , taken in coastal waters of Japan. During late July-August of 1985–1987, 1989, and 1991, 107 samples were collected from off the Pacific coast of Honshu. An additional 20 samples were collected from whales taken in the southern Sea of Okhotsk during late August—September of 1988 and 1989. Prey identification using fish otoliths and cephalopod beaks revealed the whales fed primarily on deep-water gadiform fishes and cephalopods in both regions. Prey species diversity and the percentage of cephalopods and fish differed between the two regions. Off the Pacific coast of Honshu the whales fed primarily on benthopelagic fishes (81.8%) and only 18.0% on cephalopods. Eight species of fish representing two families, the codlings (Moridae) and the grenadiers (Macrouridae), collectively made up 81.3% of rhe rotal. Thirty species of cephalopods representing 14 families made up 12.7%. In the southern Sea of Okhotsk, cephalopods accounted for 87.1% of stomach contents. The families Gonatidae and Cranchiidae were the predominant cephalopod prey, accounting for 86.7% of the diet. Gadiform fish accounted for only 12.9% of the diet. Longfin codling, Laemonema longipes , was the dominant fish prey in both regions. Depth distribution of the two commonly consumed fish off the Pacific coast of Honshu indicate the whales in this region fed primarily at depths ranging from 800 to 1,200 m.     

Renal organs of cephalopods: a habitat for dicyemids and chromidinids

The renal organs of 32 species of cephalopods (renal appendage of all cephalopods, and renal and pancreatic appendages in decapods) were examined for parasite fauna and for histological comparison. Two phylogenetically distant organisms, dicyemid mesozoans and chromidinid ciliates, were found in 20 cephalopod species. Most benthic cephalopods (octopus and cuttlefish) were infected with dicyemids. Two pelagic cephalopod species, Sepioteuthis lessoniana and Todarodes pacificus, also harbored dicyemids. Chromidinid ciliates were found only in decapods (squid and cuttlefish). One dicyemid species was found in branchial heart appendages of Rossia pacifica. Dicyemids and chromidinids occasionally occurred simultaneously in Euprymna morsei, Sepia kobiensis, S. peterseni, and T. pacificus. The small-sized cephalopod species, Idiosepius paradoxus and Octopus parvus, harbored no parasites. Comparative histology revealed that the external surface of renal organs varies morphologically in various cephalopod species. The small-sized cephalopod species have a simple external surface. In contrast, the medium- to large-sized cephalopod species have a complex external surface. In the medium- to large-sized cephalopod species, their juveniles have a simple external surface of the renal organs. The external surface subsequently becomes complicated as they grow. Dicyemids and chromidinids attach their heads to epithelia or insert their heads into folds of renal appendages, pancreatic appendages, and branchial heart appendages. The rugged and convoluted external surface provides a foothold for dicyemids and chromidinids with a conical head. They apparently do not harm these tissues of their host cephalopods.     

Intense ultrasonic clicks from echolocating toothed whales do not elicit anti-predator responses or debilitate the squid Loligo pealeii

Toothed whales use intense ultrasonic clicks to echolocate prey and it has been hypothesized that they also acoustically debilitate their prey with these intense sound pulses to facilitate capture. Cephalopods are an important food source for toothed whales, and there has probably been an evolutionary selection pressure on cephalopods to develop a mechanism for detecting and evading sound-emitting toothed whale predators. Ultrasonic detection has evolved in some insects to avoid echolocating bats, and it can be hypothesized that cephalopods might have evolved similar ultrasound detection as an anti-predation measure. We test this hypothesis in the squid Loligo pealeii in a playback experiment using intense echolocation clicks from two squid-eating toothed whale species. Twelve squid were exposed to clicks at two repetition rates (16 and 125 clicks per second) with received sound pressure levels of 199-226 dB re1 microPa (pp) mimicking the sound exposure from an echolocating toothed whale as it approaches and captures prey. We demonstrate that intense ultrasonic clicks do not elicit any detectable anti-predator behaviour in L. pealeii and that clicks with received levels up to 226 dB re1 microPa (pp) do not acoustically debilitate this cephalopod species.     

Cephalopod and Groundfish Landings: Evidence for Ecological Change in Global Fisheries?

Cephalopod fisheries are among the few still with some local potential for expansion; in fact, as groundfish landings have declined globally, cephalopod landings have increased. We propose the hypothesis that, although increased cephalopod landings may partly reflect increased market demand, overfishing groundfish stocks has positively affected cephalopod populations. Data from 15 key FAO areas reveal that, with the exception of the north- east Atlantic, cephalopod landings have increased significantly over the last 25 years while groundfish have risen more slowly, remained stable, or declined. In terms of volume, cephalopods have not replaced groundfish. This is hypothesized as owing to the shorter life cycle of cephalopods, and rapid turnover and lower standing stocks than for longer-lived finfish species. Under high fishing pressure, groundfish are probably poor competitors, having less opportunity for spawning and replacement. In West Africa, the Gulf of Thailand and Adriatic there is strong circumstantial evidence that fishing pressure has changed ecological conditions and cephalopod stocks have increased as predatory fish have declined. We recommend that this hypothesis be tested thoroughly in other areas where suitable data exist. Most coastal and shelf cephalopod fisheries are likely to be fully exploited or overexploited, and current annual fluctuations in cephalopod landings are probably largely environmentally-driven.     

Things that go bump in the night: evolutionary interactions between cephalopods and cetaceans in the tertiary

Echolocation has evolved independently in several vertebrate groups, and hypotheses about the origin of echolocation in these groups often invoke abiotic mechanisms driving morphological evolution. In bats, for example, the ecological setting associated with the origin of echolocation has been linked to global warming during the Palaeocene–Eocene; similarly, the origin of toothed whales (odontocetes) has been broadly correlated with the establishment of the circum-Antarctic current. These scenarios, and the adaptational hypotheses for the evolution of echolocation with which they are associated, neglect a consideration of possible biotic mechanisms. Here we propose that the origin of echolocation in odontocetes was initially an adaptation for nocturnal epipelagic feeding – primarily on diel migrating cephalopods. We test this hypothesis using data on the temporal, geographical, and water column distributions of odontocetes and cephalopods, and other global events from their respective tertiary histories. From this analysis, we suggest that echolocation in early odontocetes aided nocturnal feeding on cephalopods and other prey items, and that this early system was exapted for deep diving and hunting at depths below the photic zone where abundant cephalopod resources were available 24 h a day. This scenario extends to the evolution of other cephalopod feeding (teuthophagous) marine vertebrates such as pinnipeds and Mesozoic marine reptiles.     

Host defense mechanisms of cephalopods

Humoral and cellular mechanisms of defense have been described for cephalopods, a relatively advanced group of mollusks. Typical of other mollusks, cephalopod agglutinins are the most documented component of humoral immunity. Lectins, which have agglutinating properties, have been described and characterized from octopuses. Agglutinins from cephalopod hemolymph have also been shown to agglutinate a variety of vertebrate red blood cells, as well as potential bacterial pathogens. Hemocytes are the primary component of cellular immunity. Although the hemocyte role in phagocytosis has been extensively studied in other mollusks, the mechanisms of phagocytosis have not been described extensively for cephalopods. Cephalopod hemocytes have phagocytic capabilities and may function in encapsulation and neutralization of foreign substances; however, the effects of environmental factors and the full extent of phagocytic capabilities of cephalopod hemocytes have not been reported. Hemocytes from cephalopods have a role in wound healing and inflammation which have been reported in detail by several investigators.     

Pelagic cephalopods from eastern Australia: species composition, horizontal and vertical distribution determined from the diets of pelagic fishes

The distribution and relative biomass of cephalopods from pelagic waters off eastern Australia was examined between 1997 and 2004 from stomach contents of swordfish, yellowfin tuna and dolphinfish taken in the domestic longline fishery. A total of 38 taxa from 19 families were identified. Comparison of the species composition of the three predators indicated pronounced differences in cephalopod species composition. In swordfish, species of the family Ommastrephidae, particularly Ommastrephes bartramii (Lesueur 1821) and Nototodarus gouldi (McCoy 1888) dominated, whereas a more diverse mix of species was identified from yellowfin-sampled cephalopods. Todaropsis eblanae (Ball 1841) was the main cephalopod sampled from the surface-dwelling dolphinfish. For swordfish-sampled cephalopods, significant relationships were found between biomass and season, fluorescence and year. In yellowfin tuna, cephalopod biomass was significantly correlated with season, area and sea surface temperature. Significant factors differed between predator-sampler, possibly reflecting the limits of the predator, but could also give insights into individual cephalopod species distributions. However, the increase in cephalopod biomass over summer in both swordfish and yellowfin tuna suggested cephalopod biomass was higher over summer in the region.     

Approaches to resolving cephalopod movement and migration patterns

Cephalopod movement occurs during all phases of the life history, with the abundance and location of cephalopod populations strongly influenced by the prevalence and scale of their movements. Environmental parameters, such as sea temperature and oceanographic processes, have a large influence on movement at the various life cycle stages, particularly those of oceanic squid. Tag recapture studies are the most common way of directly examining cephalopod movement, particularly in species which are heavily fished. Electronic tags, however, are being more commonly used to track cephalopods, providing detailed small- and large-scale movement information. Chemical tagging of paralarvae through maternal transfer may prove to be a viable technique for tracking this little understood cephalopod life stage, as large numbers of individuals could be tagged at once. Numerous indirect methods can also be used to examine cephalopod movement, such as chemical analyses of the elemental and/or isotopic signatures of cephalopod hard parts, with growing interest in utilising these techniques for elucidating migration pathways, as is commonly done for fish. Geographic differences in parasite fauna have also been used to indirectly provide movement information, however, explicit movement studies require detailed information on parasite-host specificity and parasite geographic distribution, which is yet to be determined for cephalopods. Molecular genetics offers a powerful approach to estimating realised effective migration rates among populations, and continuing developments in markers and analytical techniques hold the promise of more detailed identification of migrants. To date genetic studies indicate that migration in squids is extensive but can be blocked by major oceanographic features, and in cuttlefish and octopus migration is more locally restricted than predictions from life history parameters would suggest. Satellite data showing the location of fishing lights have been increasingly used to examine the movement of squid fishing vessels, as a proxy for monitoring the movement of the squid populations themselves, allowing for the remote monitoring of oceanic species.     

The ecological role of cephalopods and their representation in ecosystem models

Cephalopods, especially squids, are believed to have a structuring role in marine ecosystems as a link between different trophic levels, primarily due to their voracious prey consumption and high production rate. Cephalopod ecology, however, is still poorly understood as observational studies often give highly uncertain and variable results due to the peculiarities of cephalopod behaviour and biology, and their responsiveness to external drivers. This review evaluates our representation of cephalopods in ecosystem models and the insights given by these models on the role of cephalopods in our oceans. We examined ecosystem models from 13 regions to analyse the representation of cephalopods and compared their results to local trophic studies. Our analysis indicated that most ecosystem models inadequately include cephalopods in terms of model structure and parametrization; although some models still have the capacity to draw valuable conclusions regarding the impact and role of cephalopods within the system. Oceanic squid species have a major role linking trophic levels and food webs from different habitats. The importance of neritic species varies locally, but generally cephalopods have a substantial impact via their consumer role. To better understand the ecological role of cephalopods, improved representation of these species in ecosystem models is a critical requirement and could be achieved relatively easily to more accurately articulate the mechanisms regulating the ecological role of cephalopods.

     

Palaeoecology and palaeogeography of Late Ordovician (Katian–Hirnantian) cephalopods of the Boda Limestone,Siljan district,Sweden

The carbonates associated with the Late Ordovician (Katian–Hirnantian) Boda mounds of the Siljan district, Sweden, contain a rich cephalopod fauna. Cephalopods are rare in the micritic stromatactis facies of the Katian Boda Core Member, but are concentrated together with other molluscs and trilobites in synsedimentary fillings of caves and crevices of the lithified mound limestone. More than 60 cephalopod species are known from these fillings. The assemblage is dominated in richness and abundance by small orthoconic proteoceratids of the genus Isorthoceras and by curved barrandeocerids, and is considerably less endemic than the benthic fauna of the Boda mounds. Similarities are remarkable at the species level with assemblages from elsewhere in Baltica, with Avalonia and south‐western Kazakhstan. A genus‐level comparison reveals affinities with Laurentia. However, the genus‐level similarities are interpreted as reflecting mainly similarities of the depositional environment and of physicochemical conditions. The presence of calcareous algae in the Boda Limestone and maximum hydrostatic septal strength of cephalopods indicate a depositional depth of <100 m, well within the euphotic zone. The dominance and diversity of cephalopods with vertical migrant lifestyle and the absence of actinocerids indicate a cool, nutrient‐rich deeper neritic environment. The post‐Katian sediments contain a drastically reduced diversity, dominated by orthocerids. The maximum hydrostatic septal strength of the Hirnantian cephalopods and sedimentological features indicate a shallowing during the Hirnantian, but a continuation of high food availability for cephalopods in the water column.     

Ethical and welfare considerations when using cephalopods as experimental animals

When using cephalopods as experimental animals, a number of factors, including morality, quality of information derived from experiments, and public perception, drives the motivation to consider welfare issues. Refinement of methods and techniques is a major step in ensuring protection of cephalopod welfare in both laboratory and field studies. To this end, existing literature that provides details of methods used in the collection, handling, maintenance, and culture of a range of cephalopods is a useful starting point when refining and justifying decisions about animal welfare. This review collates recent literature in which authors have used cephalopods as experimental animals, revealing the extent of use and diversity of cephalopod species and techniques. It also highlights several major issues when considering cephalopod welfare; how little is known about disease in cephalopods and its relationship to senescence and also how to define objective endpoints when animals are stressed or dying as a result of the experiment.     

Cannibalism in cephalopods

Cannibalism refers to the action of consuming a member of the same species and is common in many taxa. This paper reviews the available literature on cannibalism in cephalopods. All species of the class Cephalopoda are predators and cannibalism is common in most species whose diet has been studied. Cannibalism in cephalopods is density-dependent due to their aggressive predatory and in case of the octopuses territorial nature. It also depends upon local and temporal food availability and of the reproductive season. Cannibalistic behaviour is positively related to the size of both cannibal and victim. It can affect population dynamics of cephalopods in periods of low food availability and/or high population abundance. Cephalopods are generally restricted in their ability to store energy. It is thus assumed that cannibalism is part of a population energy storage strategy enabling cephalopod populations to react to favourable and adverse environmental conditions by increasing and reducing their number. Finally, we propose five orientation points for future research on cannibalism in cephalopods.     

Pelagic cephalopods of the central Mediterranean Sea determined by the analysis of the stomach content of large fish predators

The pelagic cephalopod fauna of the central Mediterranean Sea was investigated through stomach content analyses of large fish predators. A total of 124 Xiphias gladius, 22 Thunnus thynnus, 100 Thunnus alalunga, and 25 Tetrapturus belone were analyzed. Overall, 3,096 cephalopods belonging to 23 species and 16 families were identified. The cephalopod fauna in the study area is dominated by Sepiolidae, Ommastrephidae, and Onychoteuthidae. The sepiolid Heteroteuthis dispar was the most abundant species (n?=?1,402) while the ommastrephid Todarodes sagittatus showed the highest biomass. They can be considered key-species in the pelagic food web of the study area. The neutrally buoyant Histioteuthis bonnellii, H. reversa, and Chiroteuthis veranyi seem to characterize the deeper water layers. Given the difficulty in sampling pelagic cephalopods, the presence of cephalopod beaks in the stomach of predators represents a fundamental tool to assess the biodiversity and the ecological importance of these taxa in the marine ecosystem.     

Cephalopod embryonic shells as a tool to reconstruct reproductive strategies in extinct taxa

An exhaustive study of existing data on the relationship between egg size and maximum size of embryonic shells in 42 species of extant cephalopods demonstrated that these values are approximately equal regardless of taxonomy and shell morphology. Egg size is also approximately equal to mantle length of hatchlings in 45 cephalopod species with rudimentary shells. Paired data on the size of the initial chamber versus embryonic shell in 235 species of Ammonoidea, 46 Bactritida, 13 Nautilida, 22 Orthocerida, 8 Tarphycerida, 4 Oncocerida, 1 Belemnoidea, 4 Sepiida and 1 Spirulida demonstrated that, although there is a positive relationship between these parameters in some taxa, initial chamber size cannot be used to predict egg size in extinct cephalopods; the size of the embryonic shell may be more appropriate for this task. The evolution of reproductive strategies in cephalopods in the geological past was marked by an increasing significance of small‐egged taxa, as is also seen in simultaneously evolving fish taxa.     

A lateral line analogue in cephalopods: water waves generate microphonic potentials in the epidermal head lines ofSepia andLolliguncula

Summary Many cephalopods have lines of ciliated cells on their head and arms. In the cuttlefishSepia and the squidLolliguncula, electrophysiological recordings clearly identify these epidermal lines as an invertebrate analogue to the mechanoreceptive lateral lines of fish and aquatic amphibians and thus as another example of convergent evolution between a sophisticated cephalopod and vertebrate sensory system. Stimulation of the epidermal lines with local water displacements, generated by a vibrating sphere, causes receptor potentials that have many features known from lateral line microphonic potentials. The minimal threshold of the head lines is 0.2 m peak-to-peak water displacement (calculated at the skin surface) at 75–100 Hz.     

浙南近海头足类种类组成及生态位分析

在浙南海域布设42个调查站位,于2015年1 1月、2016年2月、5月和8月进行了4个航次的系统调查.针对获得的头足类样品,运用相对重要性指数、生态位宽度和生态位重叠等生态指标,结合非度量多维标度法(nMDS)和典范对应分析(CCA)对生态位的重叠和分化进行分析.结果 表明:调查海域有头足类14种,优势种为剑尖枪乌贼...     

PYGMY SPERM WHALES KOGIA BREVICEPS IN THE NORTHEAST ATLANTIC: NEW INFORMATION ON STOMACH CONTENTS AND STRANDINGS

Little is known about the feeding ecology of pygmy sperm whales ( Kogia breviceps ) in the Northeast Atlantic. Results are presented on the stomach contents of five whales stranded on the Galician coast (NW Spain) between 1995 and 2002 and seven whales stranded on the French Atlantic coast between 1984 and 2001. These results are compared with those obtained from the stomach contents of two pygmy sperm whales (a pregnant female and her calf ) stranded on the Scottish (UK) coast in 1999, the first records of the species in Scotland. In 13 out of 14 cases, food remains consisted almost entirely of cephalopod beaks, although some crustacean and fish remains were also present. In all the Spanish specimens, the identified prey were oceanic species: the cephalopods Histioteuthis reversa , H. bonnellii , Todarodes sagittatus , the viperfish Chauliodus sloani , and the giant mysid Gnatophausia sp. The same cephalopod species were found in the stomachs of the whales stranded in Scotland, although both whales had also consumed neritic cephalopod species such as Rossia macrosoma and other sepiolids. In the French specimens, almost all prey identified were oceanic cephalopods ( H. reversa , Brachioteuthis riseii , T. sagittatus , Taonius pavo , etc. ), but remains of crustaceans and a neritic squid ( Loligo forbesi ) were also found. One whale from France had eaten mainly Henslow's swimming crab ( Polybius henslowi ). Results from the present study are consistent with those found by other authors in the Azores and the Canary Islands in that pygmy sperm whales appear to be mainly teuthophagous, with histioteuthid squids forming an important part of the diet. Strandings records suggest that occurrence of pygmy sperm whales in the NE Atlantic may be seasonal, with most strandings occurring in autumn and winter.     

A comparative microscopic and ultrastructural study of perichondrial tissue in cartilage of Octopus vulgaris (Cephalopoda, Mollusca)

The microscopic and submicroscopic structures of perichondrial tissues in the head cartilages of Octopus vulgaris were studied by polarized light and transmission electron microscopy. The orbital cartilages possess a birefringent layer parallel to the surface of the cartilage; ultrastructurally, this layer, which may be considered perichondrial tissue, has the typical organisation of connective tissue but does not possess the stratification of collagen laminae found in vertebrate perichondria. Perichondrial extracellular matrix is clearly distinct from that of cartilage because its collagen fibrils are of a larger diameter than collagen fibrils from cartilage. In addition, perichondrial fibroblasts are characteristically located at the center of collagen fibers. In the cerebral cartilage, the perichondrium is absent or discontinuous in relation to complex interconnections between cartilage and connective fibres, muscle fibres, blood vessels and nerve. Distinctive cartilage-lining cells, rich in electron dense cytoplasmatic granules, are stratified either along the cartilage surface or along vessels and muscle fibres that penetrate within the cartilage. The perichondrium of cephalopod cartilage, whose structure varies according to the location and function of its skeletal segments, mimics that of vertebrate perichondrium, exemplifying the high level of tissue differentiation attained by cephalopods.     

Surface-feeding on cephalopods by procellariiform seabirds in the southern Benguela region, South Africa

Cephalopod beaks recovered from stomach samples taken from 14 seabird species in the southern Benguela region off Southern Africa and from one species at Sub-Antarctic Marion Island, were identified as far as possible, counted and the lower rostral lengths (LRLs) measured. Dorsal mantle lengths (DMLs) and body masses of the cephalopods eaten were estimated. The results of analyses by percentage frequency of occurrence and numerical abundance are discussed with reference to present knowledge of the distribution of cephalopods eaten by seabirds in the areas studied. Division of the cephalopod component of seabird diets into species which float, and species which sink, after death indicates that the birds forage on dead or moribund cephalopods on the surface, rather than catching live bioluminescent cephalopods at night.     

Comparative visual ecology of cephalopods from different habitats

Previous investigations of vision and visual pigment evolution in aquatic predators have focused on fish and crustaceans, generally ignoring the cephalopods. Since the first cephalopod opsin was sequenced in late 1980s, we now have data on over 50 cephalopod opsins, prompting this functional and phylogenetic examination. Much of this data does not specifically examine the visual pigment spectral absorbance position (λ_max) relative to environment or lifestyle, and cephalopod opsin functional adaptation and visual ecology remain largely unknown. Here we introduce a new protocol for photoreceptor microspectrophotometry (MSP) that overcomes the difficulty of bleaching the bistable visual pigment and that reveals eight coastal coleoid cephalopods to be monochromatic with λ_max varying from 484 to 505 nm. A combination of current MSP results, the λ_max values previously characterized using cephalopod retinal extracts (467–500 nm) and the corresponding opsin phylogenetic tree were used for systematic comparisons with an end goal of examining the adaptations of coleoid visual pigments to different light environments. Spectral tuning shifts are described in response to different modes of life and light conditions. A new spectral tuning model suggests that nine amino acid substitution sites may determine the direction and the magnitude of spectral shifts.