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In light of their life-history characteristics, deep-sea fishes display a higher vulnerability to overfishing than most other groups of fish, and their exploitation may not be sustainable even at low levels. In the Falkland Islands, increasing efforts have been made to target deep-sea species, such as the ridge-scaled grenadier Macrourus carinatus, in the waters off the continental slope. Research findings relating to the age and growth of this species remain conflicting, largely as a result of non-representative sampling of the population, inappropriate ageing methods, and the absence of age validation. We show how M. carinatus display life-history characteristics typical of the deep-water fish community, such as a long life (53 years), late age at maturity (females = 14.00 years; males = 12.28 years), slow growth and low levels of natural mortality (females = 0.104 year−1; males = 0.117 year−1) that highlight the susceptibility of M. carinatus to overfishing. In particular, validated age estimates obtained using improved ageing criteria indicate that longevity is up to 28 years greater than previously reported estimates. M. carinatus were shown to be sexually dimorphic in size, with females growing larger (females = 31.49 cm pre-anal length [PAL]; males = 24.97 cm PAL) compared to males. Updated biological parameter estimates indicate M. carinatus are far more vulnerable to fisheries exploitation than previously thought. A precautionary approach must be followed and conservation measures put in place to ensure sustainable management of a directed fishery or bycatch of M. carinatus and other similar deep-sea species.

Although many factors have been identified and used to enhance the iPSC reprogramming process, its efficiency remains quite low. In addition, reprogramming efficacy has been evidenced to be affected by disease mutations that are present in patient samples. In this study, using RNA-seq platform we have identified and validated the differential gene expression of five transcription factors (TFs) (GBX2, NANOGP8, SP8, PEG3, and ZIC1) that were associated with a remarkable increase in the number of iPSC colonies generated from a patient with Parkinson's disease. We have applied different bioinformatics tools (Gene ontology, protein–protein interaction, and signaling pathways analyses) to investigate the possible roles of these TFs in pluripotency and developmental process. Interestingly, GBX2, NANOGP8, SP8, PEG3, and ZIC1 were found to play a role in maintaining pluripotency, regulating self-renewal stages, and interacting with other factors that are involved in pluripotency regulation including OCT4, SOX2, NANOG, and KLF4. Therefore, the TFs identified in this study could be used as additional transcription factors that enhance reprogramming efficiency to boost iPSC generation technology.

Diet analysis can provide an insight into the structure and function of an ecosystem, and can be used in ecosystem-based frameworks to inform management and conservation decisions. Diet composition...

An understanding of the mechanisms that determine host and parasite relationships is a central aim in parasitology. Association of a parasite species with a host species may be influenced primarily by phylogenetic constraints that cause parasite species to co-speciate with their host species, or predominantly by ecological parameters that influence all other co-evolutionary scenarios. This study aimed to investigate the role of co-speciation as well as other co-evolutionary scenarios in influencing the assemblages of tapeworm parasites (marine cestodes) in skate hosts (Rajiformes) using a modification of the PACo (Procrustean Approach to Cophylogeny) method. The study found that phylogeny and host ecology are both significant predictors of skate–tapeworm relationships, implying that co-speciation as well as other co-evolutionary scenarios are shaping these associations. The study also investigated the key ecological parameters influencing host-switching and found that host diet, distribution depth, average body size and geographical location have a combined effect. Given the importance of parasites in ensuring healthy and stable marine ecosystems, the findings of this study have implications for conservation management worldwide.

As a part of a comprehensive survey of macroparasites of commercially exploited fish species off the coast of Otago, New Zealand, the parasite fauna of the New Zealand sole Peltorhamphus novaezeelandiae Günther was recently studied. Steringotrema robertpoulini n. sp. is described from this host and compared with known species of Steringotrema Odhner, 1911. The new species is readily distinguished from all of its congeners, except for S. divergens (Rudolphi, 1809) Odhner, 1911, by having the follicular vitellarium divided in four zones rather than two, and can be differentiated from S. divergens mainly by the posterior extent of the intestinal caeca in the hindbody, as well as by host association and geographical distribution. DNA sequences of the 28S ribosomal gene were generated and phylogenetic analyses were undertaken using maximum likelihood and Bayesian inference to assess the phylogenetic position of the new species within the family Fellodistomidae Nicoll, 1909. Analyses included the available sequences for 14 species of the family distributed among eight genera, along with nine species of other members of the order Plagiorchiida La Rue, 1957 as outgroups. The resulting topology shows that the new species of Steringotrema is nested as the sister species of Steringophorus dorsolineatus (Reimer, 1985) Bray, 1995. However, low nodal support indicates that relationships among these species are not fully resolved and require further revision and denser taxon sampling for more detailed molecular work. More information is required to draw further conclusions about the taxonomic status of the genera Steringotrema and Steringophorus Odhner, 1905.

The notothenid Patagonotothen ramsayi is one of the most abundant fin fish species on the Patagonian Shelf and it is an important prey species and central to the trophic ecology of the shelf ecosystem of the region. 353 otoliths and the parasites analysed from 80 fishes collected in January 2010, and 2004 and 2006, respectively, from the Falkland Islands Shelf and in an area north of the Falkland Islands on the high seas, were used to gain insights into the stock discrimination using elemental signatures and parasitology. Multivariate analyses (Quadratic Discriminant Function Analysis (QDFA)) of trace elements in the edges of the otolith was extremely well resolved indicating samples taken from the southern (SS), northern Falkland Islands shelf (NS) and the high seas (HS) to the north are clearly separated. Analyses of the otoliths cores were less well resolved, but showed good separation. However, there was overlap with the samples taken on the SS / NS, NS / HS, but no overlap between the samples taken on the SS / HS, indicating some intermixing during larval dispersal. Univariate and multivariate analyses of parasite communities showed a clear separation of samples taken from the SS and HS. In addition, this study has added to the biogeography and knowledge of host specificity of the parasites inhabiting the Patagonian Shelf. Our results demonstrate that the multi-pronged approach of using both otolith trace elemental analyses and parasites can be a powerful tool to resolve stock discrimination in P. ramsayi.

Understanding the spatial and temporal dynamics in marine fish populations is essential for the development of effective adaptive management strategies. Many marine fish species undergo ontogenetic shifts in abundance, with the utilization of productive shelf-based habitats during early life-history stages. For instance, in the shelf ecosystem around the Falkland Islands, a dynamic Patagonian toothfish population undertakes an early life-history ontogenetic migration after recruitment from spawning areas off southern Chile and the Burdwood Bank. To better understand the spatial-temporal dynamics for this species, Bayesian species distribution models were used to (1) identify oceanographic drivers of recruitment success; (2) assess the spatial-temporal distribution patterns; and (3) describe the habitat preferences and ecological interactions during a six-year study period (2015–2020) on the Patagonian Shelf. The presence of seasonal mesoscale eddies linking the Sub-Antarctic Front with the Falkland Current appear to be of primary importance for the survival of toothfish eggs and larvae on the shelf after transport from offshore spawning areas over the Burdwood Bank and southern Chile. Results indicate persistent recruitment hotspots for newly-settled Patagonian toothfish to the north-east, along with opportunistic areas to the south and west of the Falkland Islands, coinciding with the main areas of upwelling and high productivity. During years of low recruitment, juveniles are largely constrained to sheltered inshore regions to the north-west of the Falkland Islands. Spatial distribution patterns during post-settlement ontogenetic migrations are progressive, characterised by age-structured hotspots that differ according to depth, current velocity, oxygen, mixed-layer thickness, the abundance of competitors (icefish – Champsocephalus esox) and prey (rock cod – Patagonotothen ramsayi). The temporal shift in the range and intensity of hotspots is linked to levels of recruitment and subsequent cohort strength, which in turn appears to be driven by oceanographic processes. Understanding the environmental influences on recruitment dynamics is a key step in assessing connectivity within these discrete spatial groups on the Patagonian Shelf, and how their variability can influence the adult population over time.

Despite the fact that tapeworms comprise the bulk of parasite communities of sharks in marine ecosystems, little is known about their life cycles and, more specifically, about the potential intermediate hosts they utilize as transmission routes. In the absence of morphological features required for specific identification of larval tapeworms from potential intermediate hosts, recent molecular advances have contributed to linking larval and adult parasites and, in some instances, uncovering unknown trophic links. Host–parasite checklists are often the first source of information consulted to assess the diversity and host specificity of parasites, and provide insights into parasite identification. However, these host–parasite checklists are only useful if they encompass the full spectrum of associations between hosts and parasites. A checklist of New Zealand fishes and their parasites has been published, but recent parasitological examinations of commercial fish species reveal that the checklist appears to be far from complete. We focused our current study on a comprehensive survey of macroparasites of a commercial species, the New Zealand sole (Peltorhamphus novaezeelandiae) off the coast of Otago, New Zealand. Specifically, we were expecting to recover marine tapeworms using sharks as their definitive hosts that are generally underreported in parasite surveys. The parasites recovered included tapeworms, flukes, round worms and thorny-headed worms. Surprisingly, a large proportion of the non-tapeworm parasites we recovered were not previously reported from this fish species. A discussion on the potential ecological roles played by this fish species in the transmission of parasites is included.

Despite their very different historical origins as scientific disciplines, parasitology and marine ecology have already combined successfully to make important contributions to our understanding of the functioning of natural ecosystems. For example, robust assessments of the contribution of parasites to ecosystem biomass and energetics, and of their impact on community-wide biodiversity and food web structure, have all been made for the first time in marine systems. Nevertheless, for the marriage between parasitology and marine ecology to remain fruitful, several challenges must first be overcome. We discuss seven such challenges on the road to a greater synergy between these disciplines: (1) Raising awareness of parasitism as an ecological force by increasing the proportion of articles about parasites and diseases in marine ecology journals; (2) Making greater use of theory and conceptual frameworks from marine ecology to guide parasitological research; (3) Speeding up or at least maintaining the current rate at which marine parasites are found and described; (4) Elucidating a greater proportion of life cycles in all major groups of marine parasites; (5) Increasing the number of host–parasite model systems on which our knowledge is based; (6) Extending parasitological research offshore and into ocean depths; and (7) Developing, as needed, new epidemiological theory and transmission models for the marine environment. None of these challenges is insurmountable, and addressing just a few of them should guarantee that parasitology and marine ecology will continue to join forces and make further substantial contributions.

Most parasites from known host species are yet to be discovered and described, let alone those from host species not yet known to science. Here, we use tapeworms of elasmobranchs to identify factors influencing their discovery and explaining the time lag between the descriptions of elasmobranch hosts and their respective tapeworm parasites. The dataset included 918 tapeworm species from 290 elasmobranch species. Data were analysed using linear mixed-effects models. Our findings indicated that we are currently in the midst of the greatest rate of discovery for tapeworms exploiting elasmobranchs. We identified tapeworm size, year of discovery of the type host, host latitudinal range and type locality of the parasite influencing most on the probability of discovery of tapeworms from elasmobranchs and the average time lag between descriptions of elasmobranchs and their tapeworms. The time lag between descriptions is decreasing progressively, but, at current rates and number of taxonomic experts, it will take two centuries to clear the backlog of undescribed tapeworms from known elasmobranch species. Given that the number of new elasmobranch species described each year is on the rise, we need to re-assess funding strategies to save elasmobranchs (and, thus, their tapeworm parasites) before they go extinct.

Parasites are important components of natural systems, and among their various roles, parasites strongly influence the flow of energy between and within food webs. Over 1000 tapeworm species are known to parasitise elasmobranchs, although full life cycles are resolved for fewer than 10 of them. The lack in resolution stems from the inability to distinguish larval from adult stages using morphology alone. Molecular elucidation of trophic transmission pathways is the next step in understanding the role of hosts and parasites within food webs. We investigated the parasite assemblage of New Zealand’s rough skate, Zearaja nasuta. Skates and their prey items (obtained from the skates’ stomachs) were dissected for the recovery of adult and larval tapeworms, respectively. A fragment of the 28S rDNA region was amplified for worm specimens with the aim to confirm species identity of parasites within rough skates and to uncover trophic transmission pathways that exploit the predation links between rough skates and their prey. We identified seven species of tapeworms from four tapeworm orders. Four trophic transmission pathways were resolved between three prey items from skates stomachs and skates, and one pathway between larval tapeworm sequence from a New Zealand sole and skate, i.e. a genetic match was found between larval tapeworms in prey and adult worms in skates. We report the first case of an adult trypanorhynch parasitising rough skate. These findings contribute to our limited understanding of cestode life cycles as well as providing insights into the importance of predator-prey relationships for parasite transmission.

SUMMARYHost-parasite checklists are essential resources in ecological parasitology, and are regularly used as sources of data in comparative studies of parasite species richness across host species, or of host specificity among parasite species. However, checklists are only useful datasets if they are relatively complete, that is, close to capturing all host–parasite associations occurring in a particular region. Here, we use three approaches to assess the completeness of 25 checklists of metazoan parasites in vertebrate hosts from various geographic regions. First, treating checklists as interaction networks between a set of parasite species and a set of host species, we identify networks with a greater connectance (proportion of realized host–parasite associations) than expected for their size. Second, assuming that the cumulative rise over time in the number of known host–parasite associations in a region tends toward an asymptote as their discovery progresses, we attempt to extrapolate the estimated total number of existing associations. Third, we test for a positive correlation between the number of published reports mentioning an association and the time since its first record, which is expected because observing and reporting host–parasite associations are frequency-dependent processes. Overall, no checklist fared well in all three tests, and only three of 25 passed two of the tests. These results suggest that most checklists, despite being useful syntheses of regional host–parasite associations, cannot be used as reliable sources of data for comparative analyses.

Information about the parasite fauna of spectacled porpoises and cetaceans from New Zealand waters in general is scarce. This study takes advantage of material archived in collections of the Otago Museum in Dunedin and Massey University in Auckland, sampled from cetacean species found stranded along the New Zealand coastline between 2007 and 2014. Parasites from seven species of cetaceans (spectacled porpoise, Phocoena dioptrica (n = 2 individuals examined); pygmy sperm whale (n = 1); long-finned pilot whale, Globicephala melas (n = 1); Risso’s dolphin, Grampus griseus (n = 1); short-beaked common dolphin, Delphinus delphis (n = 7); striped dolphin, Stenella coeruleoalba (n = 3) and dusky dolphin, Lagenorhynchus obscurus (n = 2)) from the respiratory and gastro-intestinal tract, cranial sinus, liver, urogenital and mammary tract, fascia and blubber were investigated. Ten parasite species were identified, belonging to the Nematoda (Stenurus minor, Stenurus globicephalae, Halocercus sp. (Pseudaliidae), Anisakis sp. (Anisakidae), Crassicauda sp. (Crassicaudidae)), Cestoda (Phyllobothrium delphini and Monorygma grimaldii (Phyllobothriidae)), Trematoda (Brachicladium palliata and Brachicladium delphini (Brachicladiidae)) and Crustacea (Scutocyamus antipodensis (Cyamidae)). Some of the parasite species encountered comprises new records for their host. Although the material was not sampled within a systematic parasitological survey, the findings contain valuable new information about the parasite fauna of rare, vagile and vulnerable marine wildlife from a remote oceanic environment.

The global biodiversity of some taxonomic groups is poorly described, but thought to be decreasing rapidly. Surprisingly, this holds for a group of the world's most iconic large-bodied animals: sharks. Our analysis shows rapid and steep contemporary population declines in sharks coinciding with an increasing rate in species discovery. Larger sharks occupying lower trophic positions with wide geographic distributions (latitudinal ranges) found in shallow waters tend to be discovered first. In light of this increasing trend in species discovery and a cumulative description record far from reaching an asymptote, models cannot predict the global number of sharks. Our results highlight that while our knowledge of shark diversity improves at an accelerating rate, this diversity is under threat and declining rapidly; most shark species are vulnerable to declines, especially smaller-bodied sharks. This surprising finding may relate to mesopredator declines following periods of rapid expansion due to the demise of large sharks (apex predators). Furthermore, shark population declines are structured by phylogeny and, to a lesser extent, geography. Decline in sharks are likely to influence other species as well, e.g. via trophic cascades. The net result may be a greater loss of biodiversity in the oceans and could potentially explain why fewer extinction events are observed than predicted by models. Likewise, it is not inconceivable that species may be lost prior to their discovery.

SUMMARYFrom hundreds of independent transitions from a free-living existence to a parasitic mode of life, separate parasite lineages have converged over evolutionary time to share traits and exploit their hosts in similar ways. Here, we first summarize the evidence that, at a phenotypic level, eukaryotic parasite lineages have all converged toward only six general parasitic strategies: parasitoid, parasitic castrator, directly transmitted parasite, trophically transmitted parasite, vector-transmitted parasite or micropredator. We argue that these strategies represent adaptive peaks, with the similarities among unrelated taxa within any strategy extending to all basic aspects of host exploitation and transmission among hosts and transcending phylogenetic boundaries. Then, we extend our examination of convergent patterns by looking at the evolution of parasite genomes. Despite the limited taxonomic coverage of sequenced parasite genomes currently available, we find some evidence of parallel evolution among unrelated parasite taxa with respect to genome reduction or compaction, and gene losses or gains. Matching such changes in parasite genomes with the broad phenotypic traits that define the convergence of parasites toward only six strategies of host exploitation is not possible at present. Nevertheless, as more parasite genomes become available, we may be able to detect clear trends in the evolution of parasitic genome architectures representing true convergent adaptive peaks, the genomic equivalents of the phenotypic strategies used by all parasites.

Metacestodes are often found in the body cavity of the common bully (Gobiomorphus cotidianusMcDowall), from freshwater habitats in Otago, New Zealand. Identification of metacestodes relies only on the number, size and shape of the rostellar hooks. To attempt species determination, we cultivated metacestodesin vitrofor up to 23 days, during which they matured to at least the male stage of development, although female organs were not discernable. Identified as members of the genusParadilepisHsü, 1935 (family Gryporhynchidae), these specimens are compared to previously described species, in particularP. minima(Goss, 1940), from Australia, the closest species, both geographically and morphologically. Although the size of scolex, suckers and proglottids differ significantly from those ofP. minima, we are cautious about interpreting ‘adults’ grownin vitro, because we are unsure whether the artificial conditions alter development. For this reason, and because of the lack of female organs, we refrain from erecting a new species, and refer to the specimens asParadilepiscf.minimauntil such time as the adults are found in the definitive host. With this proviso we present here a description of thein vitro-grown worms and the metacestodes as a preliminary study of this cestode. A molecular analysis of small subunit (SSU) rDNA sequences, shows the position ofP.cf. minimaand another gryporhynchid,Neogryporhynchus cheilancristrotus(Wedl, 1855), to be equivocal, but confirms their exclusion from the Dilepididae and Hymenolepididae. This is the first record of a gryporhynchid from New Zealand, and the first from the fish family Eleotridae.

Studying resource specialization at the individual level can identify factors constraining the evolution of generalism. We quantified genotypic and phenotypic variability among infective stages of 20 clones of the parasitic trematode Maritrema novaezealandensis and measured their infection success and post-infection fitness (growth, egg output) in several crabs and amphipods. First, different clones varied in their infection success of different crustaceans. Second, neither genetic nor phenotypic traits had consistent effects on infection success across all host species. Although the results suggest a relationship between infection success and phenotypic variability, phenotypically variable clones were not better at infecting more host species than less variable ones. Third, genetic and phenotypic traits also showed no consistent correlations with post-infection fitness measures. Overall, we found no consistent clone-level specialization, with some clones acting as specialists and others, generalists. The trematode population therefore maintains an overall generalist strategy by comprising a mixture of clone-level specialists and generalists.

The lack of information on marine tapeworm life cycles can be addressed with knowl- edge derived from trophic interactions in marine environments. These trophically transmitted para- sites exploit transmission routes involving predator-prey interactions. Porbeagle sharks Lamna nasus are apex predators feeding on a wide range of organisms, including teleosts and cephalopods. Although the biology of this shark species is relatively well studied, there is a surprising lack of infor- mation about the trophic interactions involving this species that lead to the acquisition of tapeworms. Recently, the use of molecular tools, combined with phylogenetics, has proven useful in identifying trophic links involved in the transmission of marine tapeworms. In the present study, we used sequence data from the D2 domain of the large subunit ribosomal DNA to link adult tapeworms of the species Clistobothrium cf. montaukensis and Dinobothrium sp. parasitising porbeagle sharks to lar- vae recovered from the squid Doryteuthis gahi. To the best of our knowledge, it is the first to provide empirical evidence for a trophic link between porbeagle sharks and D. gahi as a definitive route for the successful transmission of these tapeworms. Furthermore, our data suggest an ontogenetic shift in diet away from squid. Parasite abundance data in D. gahi indicate that the abundance of porbea- gle sharks can be significant in some years.

Parasitism is increasingly recognized as an important determinant of population dynamics, productivity and community structure in intertidal ecosystems, and yet there is very little known about the effect of parasites on polychaetes, which represent a major component of the benthic fauna. We surveyed 11 polychaete species from a mudflat in Otago Harbour, New Zealand, and found that seven of these were infected by five parasite species: four trematodes and one apicomplexan gregarine. The gregarine found in Spirobranchus cariniferus and a strigeid trematode using Streblosoma toddae as its first intermediate host are both likely to have negative fitness impacts on their hosts. Other trematodes found were at the metacercarial stage and thus use polychaetes as second intermediate hosts. The most common, an opecoelid, infected the polychaetes Heteromastus filiformis and Abarenicola affinis at relatively high abundance. There was no indication of parasite-induced mortality in these two hosts based on the relationship between host size and infection intensity. However, a comparison of intact H. filiformis individuals with those that fragmented during collection revealed a significantly higher number of opecoelid metacercariae per segment in the fragments than in the complete individuals, suggesting that infection may compromise the structural integrity of the polychaetes. These results suggest that there exists a great diversity of both trematodes and host–trematode associations within the polychaete fauna, whose ecological impact remains to be quantified.

The great white shark Carcharodon carcharias Linnaeus, 1758 is a versatile and fierce predator (and responsible for many shark attacks on humans). This apex predator feeds on a wide range of organisms including teleosts, other elasmobranchs, cephalopods, pinnipeds, and cetaceans. Although much is known about its diet, no trophic links have been empirically identified as being involved in the transmission of its tapeworm parasites. Recently, the use of molecular tools combined with phylogenetics has proven useful to identify larval and immature stages of marine tapeworms; utilization of the technique has been increasing rapidly. However, the usefulness of this approach remains limited by the availability of molecular data. Here, I employed gene sequence data from the D2 region of the large subunit of ribosomal DNA to link adults of the tapeworm Clistobothrium carcharodoni Dailey and Vogelbein, 1990 (Cestoda: Tetraphyllidea) to larvae for which sequence data for this gene are available. The sequences from the adult tapeworms were genetically identical (0% sequence divergence) to those available on GenBank for "SP" 'small' Scolex pleuronectis recovered from the striped dolphin (Stenella coeruleoalba) and Risso's dolphin (Grampus griseus). This study is the first to provide empirical evidence linking the trophic interaction between great white sharks and cetaceans as a definitive route for the successful transmission of a tetraphyllidean tapeworm. Using the intensity of infection data from this shark and from cetaceans as proxies for the extent of predation, I estimate that this individual shark would have consumed between 9 to 83 G. griseus , fresh, dead, or both, in its lifetime.

Interspecific variation in parasite species richness among host species has generated much empirical research. As in comparisons among geographical areas, controlling for variation in host body size is crucial because host size determines resource availability. Recent developments in the use of species–area relationships (SARs) to detect hotspots of biodiversity provide a powerful way to control for host body size, and to identify ‘hot’ and ‘cold hosts’ of parasite diversity, i.e. hosts with more or fewer parasites than expected from their size. Applying SAR modelling to six large datasets on parasite species richness in vertebrates, we search for hot and cold hosts and assess the effect of other ecological variables on the probability that a host species is hot/cold taking body size (and sampling effort) into account. Five non-sigmoid SAR models were fitted to the data by optimisation; their relative likelihood was evaluated using the Bayesian information criterion, before deriving an averaged SAR function. Overall, the fit between the five SAR models and the actual data was poor; there was substantial uncertainty surrounding the fitted models, and the best model differed among the six datasets. These results show that host body size is not a strong or consistent determinant of parasite species richness across taxa. Hotspots were defined as host species lying above the upper limit of the 80% confidence interval of the averaged SAR, and coldspots as species lying below its lower limit. Our analyses revealed (1) no apparent effect of specific ecological factors (i.e. water temperature, mean depth range, latitude or population density) on the likelihood of a host species being a hot or coldspot; (2) evidence of phylogenetic clustering, i.e. hosts from certain families are more likely to be hotspots (or coldspots) than other species, independently of body size. These findings suggest that host phylogeny may sometimes outweigh specific host ecological traits as a predictor of whether or not a host species harbours more (or fewer) parasite species than expected for its size.

Parasite species richness is a fundamental characteristic of host species and varies substantially among host communities. Hypotheses aiming to explain observed patterns of richness are numerous, and none is universal. In this study, we use tapeworm parasites of elasmobranch fishes to examine the phylogenetic and environmental influences on the variation in species richness for this specific system. Tapeworms are the most diverse group of helminths to infect elasmobranchs. Elasmobranchs are cosmopolitan in distribution and their tapeworm parasites are remarkably host specific; therefore, making this an ideal system in which to examine global patterns in species diversity. Here, we 1) quantify the tapeworm richness in elasmobranch fishes, 2) identify the host features correlated with tapeworm richness, and 3) determine whether tapeworm richness follows a latitudinal gradient. The individual and combined effects of host size, factors associated with water temperatures (influenced by latitude and depth), host habitat, and type of elasmobranch (shark or batoid) on measures of species diversity were assessed using general linear models. These analyses included tapeworm host records for 317 different elasmobranch species (124 species were included in our analyses) and were conducted with and without taking into account phylogenetic relationships between host species. Since sharks and batoids differ substantially in body form, analyses were repeated for each host subset. On average, batoids harboured significantly more tapeworm species than shark hosts. Tapeworm richness in sharks was influenced by median depth, whereas no predictor variable included in our models could adequately account for interspecific variation in tapeworm richness in batoid hosts. The taxonomic diversity of tapeworm assemblages of sharks and batoids was influenced by median depth and median latitude, respectively. When the influence of host phylogeny is accounted for, larger hosts harbour a greater tapeworm richness, whereas hosts exploiting wider latitudinal ranges harbour more taxonomically distinct tapeworm assemblages. Species richness and taxonomic diversity of tapeworm assemblages in elasmobranch fishes are influenced by different evolutionary pressures, including host phylogenetic relationships, space constraints and geographical area. Our results suggest that ca 3600 tapeworm species have yet to be described from elasmobranch fishes.

An analysis of patterns in otolith shape is an effective tool for discriminating among fish stocks. Otolith shapes of Patagonian toothfish (Dissostichus eleginoides) and Antarctic toothfish (D. mawsoni) were investigated for geographic variability within seven regions across the Patagonian Shelf, and South Georgia and the South Sandwich Islands (SGSSI). Otolith shape was characterised by its elliptical Fourier coefficients (EFCs), corrected for fish length before being analysed, using multivariate methods. Non-metric multidimensional scaling analysis suggested the following three main groupings: Patagonian Shelf, SGSSI, and the third for Antarctic toothfish. This result was supported by ANOVA-like permutation tests, indicating significant (P

The objectives of this study were to (1) describe the host range for 6 tetraphyllidean species and quantify their host specificity using 5 specificity indices; (2) determine the role of morphological determinants in the host specificity of tetraphyllideans by comparing villar and bothridial measurements of species examined herein; and (3) determine the role of a physiological component in the host specificity of tetraphyllideans by exposing tetraphyllideans to blood sera from different fish species and other solutions. Our results indicate that Echeneibothrium dubium abyssorum (ex Amblyraja radiata), Echeneibothrium canadensis (ex A. radiata), and Zyxibothrium kamienae (ex Malacoraja senta) exhibit the highest degree of specificity, followed by Echeneibothrium vernetae (ex Leucoraja erinacea and Leucoraja ocellata), Pseudanthobothrium hanseni (ex A. radiata and M. senta), and Pseudanthobothrium purtoni (ex Leucoraja erinacea and L. ocellata). However, these results vary based on the specificity index used. Compatible bothridial and villar measurements indicate that there is no morphological determinant of host specificity but that there is a morphological determinant to attachment site specificity. Our data indicate that attachment site specificity may also be phylogenetically determined. Additionally, the exposure of parasites to blood sera from various hosts confirms that host specificity in this system has a physiological determinant. Therefore, host specificity in this system is determined, at least in part, by physiological factors, whereas attachment site specificity is an extension of host specificity and is phylogenetically determined.

The impact of parasites on host population dynamics depends on local abundance of the parasites, which may vary considerably across spatial scales. In sand hopper populations, mermithid parasites have major impacts on host dynamics, which may vary among spatially separated populations due to the sand hopper’s wide, patchy distribution. The present study compared the abundance and biomass of a mermithid parasite (Thaumamermis zealandica Poinar et al., 2002) in sand hoppers (Bellorchestia quoyana (Milne-Edwards)) both within and among disconnected beaches. In addition, several variables were measured and tested as potentially important predictors of the parasite abundance and biomass. It was found that geographic isolation may only be responsible for minor differences in parasite populations compared with other factors. Host size was identified as the most important predictor of mermithid parasite abundance, but epibiont abundance, kelp patch mass and host density were poor predictors of abundance. These factors were also poor predictors of parasite biomass in hosts. This study further supports the notion that studies aiming to elucidate population dynamics or patterns should sample thoroughly across both spatial and temporal scales.

SUMMARYThe range of hosts used by a parasite is influenced by macro-evolutionary processes (host switching, host–parasite co-evolution), as well as ‘encounter filters’ and ‘compatibility filters’ at the micro-evolutionary level driven by host/parasite ecology and physiology. Host specialization is hypothesized to result in trade-offs with aspects of parasite life history (e.g. reproductive output), but these have not been well studied. We used previously published data to create models examining general relationships among host specificity and important aspects of life history and reproduction for nematodes parasitizing animals. Our results indicate no general trade-off between host specificity and the average pre-patent period (time to first reproduction), female size, egg size, or fecundity of these nematodes. However, female size was positively related to egg size, fecundity, and pre-patent period. Host compatibility may thus not be the primary determinant of specificity in these parasitic nematodes if there are few apparent trade-offs with reproduction, but rather, the encounter opportunities for new host species at the micro-evolutionary level, and other processes at the macro-evolutionary level (i.e. phylogeny). Because host specificity is recognized as a key factor determining the spread of parasitic diseases understanding factors limiting host use are essential to predict future changes in parasite range and occurrence.

SUMMARYHost-parasite interactions generally involve communities of parasites. Within these communities, species will co-exist and/or interact with one another in a manner either benefiting the species involved or to the detriment of one or more of the species. At the level of helminth infracommunities, evidence for intra- and inter-specific competition includes numerical responses, i.e. those regulating helminth intensity of infection, and functional responses, i.e. where the presence of competitors modifies the realised niche of infrapopulations. The objectives of this study are to assess the numerical and functional responses of helminths in infracommunities from 3 rajid skates using general linear models. Despite a lack of numerical responses, functional responses to intra- and inter-specific interactions were observed. A positive correlation between the number of individuals in an infrapopulation and its niche breadth (functional response) was observed for the tapewormsPseudanthobothriumspp. andEcheneibothriumspp., in all their respective hosts, and for the nematodePseudanisakissp. in the little skate. Evidence for inter-specific competition includes niche shifts inPseudanthobothrium purtoni(exlittle skate) andPseudanisakissp. (exthorny skate) in the presence ofPseudanisakissp. and the tapewormGrillotiasp., respectively. These results are consistent with other studies in providing evidence for competition between helminths of skates.

On two occasions in November and December 2009, whilst being captured and handled for banding in Tasman Bay, New Zealand, two variable oystercatchers (Haematopus unicolor Forster, 1844) voided a number of cestode strobilae from their cloaca. Their morphology indicates that they belong to the family Hymenolepididae, confirmed by BLASTn searches of large and small subunits of ribosomal DNA partial sequences (18S and 28S, respectively). However, they cannot currently be assigned to any species reported for any oystercatcher species from New Zealand nor from oystercatchers worldwide. We present a checklist of all cestode parasites reported in the literature for Haematopus species, along with their sources and synonyms. While the taxonomy of New Zealand oystercatchers is currently uncertain, more detailed knowledge of the parasite fauna of this bird group may help to elucidate the historical biogeography of the oystercatchers. The means of collection of these tapeworms is unusual and does not appear to have been reported in the literature previously.

Monthly variation in parasite populations and communities, from the blenniid fish Scartichthys viridis, were assessed during two consecutive years in order to examine monthly and seasonal temporal patterns. A total of 969 S. viridis was collected from September 2006 to August 2008 in central Chile. Sample size and fish total length (TL) varied among months. The S. viridis parasite community included 17 parasite taxa, of which five species were present throughout the year: a leech (Piscicolidae gen. sp.), two copepods (Lepeophtheirus zbigniewi and Colobomatus sp.), a monogenean (Microcotyle sp.) and a trematode (Lecithasteridae gen. sp.). The parasite prevalence, abundance and biovolume varied among months. More precisely, the leech and the copepod Colobomatus sp. were the most prevalent and abundant parasites, reaching their maxima between November and January (austral spring-summer). The parasite communities also showed seasonal patterns; prevalence, abundance and species richness of parasites were higher between October and January (spring-summer) than between March and May (autumn-winter). The population and community descriptors of parasites were significantly correlated with fish TL. Consequently, the variation in parasite populations and communities was associated with fish growth throughout the year. Postlarval settlement of S. viridis, in the intertidal rocky pools, occurs in autumn, with fish reaching larger body size in summer.

SUMMARYParasites have evolved a myriad of attachment structures closely adapted to their hosts and sites of attachment. Here, using members of the genusAcanthobothriumvan Beneden, 1850 (Cestoda: Tetraphyllidea: Onchobothriidae), we (i) examined the influence of host body size and phylogeny, in addition to morphological features of these tapeworms, on the size of 3 structures used in attachment (bothridia, accessory suckers and hooks) by means of general linear models and phylogenetic-independent contrasts methods, and (ii) quantified the scaling exponents of relationships between size of attachment structures and tapeworm body size. Our results indicate that there exists a positive relationship, albeit not directly proportional, between size of attachment structures andAcanthobothriumspp. body size, and hook size and size of bothridia and accessory suckers. These results suggest that the resource investment in whole-body growth is greater than that in attachment structures, and that a greater investment in development of bothridia and accessory suckers is required to maintain an equivalent functional efficacy to hooks. In addition, host body size also influences, though less markedly, the size of attachment structures inAcanthobothriumspp. independently of parasite size itself.Acanthobothriumspecies have evolved a generalized mode of attachment that is successful in maintaining their position on various intestinal mucosal topographies across a variety of hosts exploiting different food resources.

Tetraphyllidean cestodes are cosmopolitan, remarkably host specific, and form the most speciose and diverse group of helminths infecting elasmobranchs (sharks, skates and rays). They show substantial interspecific variation in a variety of morphological traits, including body size. Tetraphyllideans represent therefore, an ideal group in which to examine the relationship between parasite body size and abundance. The individual and combined effects of host size, environmental temperature, host habitat, host environment, host physiology, and host type (all likely correlates of parasite body size) on parasite length were assessed using general linear model analyses using data from 515 tetraphyllidean cestode species (182 species were included in analyses). The relationships between tetraphyllidean cestode length and intensity and abundance of infection were assessed using simple linear regression analyses. Due to the contrasting morphologies between shark and batoid hosts, and contrasting physiologies between sharks of the Lamnidae family and other sharks, analyses were repeated in different subsets based on host morphology and physiologies (“sharks” vs. batoids) to determine the influence of these variables on adult tetraphyllidean tapeworm body size. Results presented herein indicate that host body size, environmental temperature and host habitat are relatively important variables in models explaining interspecific variations in tetraphyllidean tapeworm length. In addition, a negative relationship between tetraphyllidean body size and intensity of infection was apparent. These results suggest that space constraints and ambient temperature, via their effects on metabolism and growth, determine adult tetraphyllidean cestode size. Consequently, a trade-off between size and numbers is possibly imposed by external forces influencing host size, hence limiting physical space or other resources available to the parasites.

SUMMARYA parasitological survey in the Bay of Fundy, Canada, resulted in the recovery of mature specimens from 5 species of phyllobothriid tapeworms (Cestoda: Tetraphyllidea) from 4 rajid skates: Echeneibothrium canadensis and E. dubium abyssorum specimens from Amblyraja radiata; E. vernetae and Pseudanthobothrium n.sp. from Leucoraja erinacea and L. ocellata; and P. hanseni from A. radiata and Malacoraja senta. Partial sequence data of a variable region (D2) from the large subunit ribosomal DNA (LSU) were used here to determine the host distribution of immature specimens for 4 of these 5 species (E. d. abyssorum was not included in the analyses). Immature specimens from both Pseudanthobothrium spp. were identified in the same hosts as recorded previously for mature specimens, thus suggesting that there are mechanisms that prevent the attachment of the parasite in an ‘unsuitable’ host species. Immature E. canadensis specimens were recovered exclusively from A. radiata, whereas immature E. vernetae specimens were recovered from L. erinacea and A. radiata, despite the latter host species not harbouring mature E. vernetae specimens. Their presence in the latter host species may be explained by host restriction or resistance, which allows the attachment of the parasites in the ‘wrong’ host species, but not establishment or development.

During a parasitological survey of Leucoraja erinacea, L. ocellata, Malacoraja senta and Amblyraja radiata from Passamaquoddy Bay and waters surrounding the West Isles of the Bay of Fundy, NB, Canada, seven species of cestodes were recovered. Examination of these skates revealed the presence of two distinct species of Pseudanthobothrium Baer, 1956: one was retrieved from M. senta and A. radiata, identified as P. hanseni Baer, 1956 and redescribed herein; the other was retrieved from L. erinacea and L. ocellata and differs from previously described species. The new species is described herein as P. purtoni n. sp. on the basis of the degree of apolysis, the maximum width of the strobila, the length of the cirrus-sac and the number of testes. Additionally, the distinctiveness of both species of Pseudanthobothrium is supported by the characterisation of a 643 base-pair nuclear marker, which includes most of the D2 variable region of the large subunit ribosomal DNA (LSU). The recovery of two different tetraphyllidean species, each from two different host species, challenges the oioxeny (strict host-specificity) of echeneibothriine cestodes and can be explained, at least in part, by the similarities in diet and substrate preference within each host pair.