Determinants of lungworm specificity in five cetacean species in the western Mediterranean

Background Current data about Pseudaliidae show contrasting patterns of host specificity between congeneric species. We investigated how both contact and compatibility between hosts and parasites contributed to the patterns of lungworm infection observed in a community of five species of cetaceans in the western Mediterranean. Methods The lungs of 119 striped dolphins Stenella coeruleoalba, 18 bottlenose dolphins Tursiops truncatus, 7 Risso’s dolphins Grampus griseus, 7 long-finned pilot whales Globicephala melas, and 6 common dolphins Delphinus delphis were analysed for lungworms. Parasites were identified by morphology and analysis of ITS2 sequences using both maximum likelihood and Bayesian inference methods. Body length was used as a proxy for lungworm species fitness in different hosts and compared with Kruskal-Wallis tests. Infection parameters were compared between cetacean species using Fisher’s exact tests and Kruskal-Wallis tests. Phylogenetic specificity was explored by collating the overall lungworm species prevalence values in hosts from previous surveys in various localities. To explore the relative importance of vertical and horizontal transmission, Spearman’s rank correlation was used to look for an association between host size and lungworm burden. A Mantel test was used to explore the association between lungworm species similarity and prey overlap using dietary data. Results Halocercus delphini had higher infection levels in striped dolphins and common dolphins; Stenurus ovatus had higher infection levels in bottlenose dolphins; and Stenurus globicephalae had higher infection levels in long-finned pilot whales. These results are congruent with findings on a global scale. Morphometric comparison showed that the larger nematodes were found in the same host species that had the highest parasite burden. Lungworms were found in neonatal striped dolphins and a Risso’s dolphin, and there was a weak but significant correlation between host size and parasite burden in striped dolphins and bottlenose dolphins. There was also a weak but significant association between prey overlap and lungworm species similarity. Conclusions Data indicate that phylogenetic specificity has an important role in governing host–parasite associations, as indicated by the higher infection levels and larger nematode size in certain hosts. However, diet can also influence infection patterns in these preferred hosts and contribute to less severe infections in other hosts.

Trophic ecology and morphology of Anolis bartschi (Squamata: Dactyloidae) in Viñales National Park, Cuba

Trophic ecology and morphology of Anolis bartschi (Squamata: Dactyloidae) in Parque Nacional Viñales, Cuba. Little is known about the trophic ecology of most anoles of Cuba. Morphology is directly related to ecological functions in lizards, such as feeding strategies, interspecifc competition or energetic demands linked to reproduction. Anolis bartschi is a regionally endemic species, restricted to karstic hills of western Cuba. Here, we offer new insights into the trophic ecology of this species, and its relation to head morphology. We captured 131 adults; males were larger than females in size and head width. Most of them had prey in their stomachs. Males consumed more prey than females, but the latter consumed larger prey. Prey overlap within sexes was detected in the dry season, but trophic segregation occurred in the rainy season. Hymenoptera was the most frequently consumed prey in both sexes. In addition, females ate Blattodea and Coleoptera, and males consumed more Diptera. We suggest that this lizard prefers sedentary rather than mobile prey. According to our dataset and feld observations, A. bartschi is a bimodal forager lizard, but research on temporal (daily and annual) variation in diet is recommended for a proper forage classifcation of this lizard.

Match-mismatch dynamics in the Norwegian-Barents Sea system

A key process affecting variation in the recruitment of fish into fisheries is the spatio-temporal overlap between prey and predator (match-mismatch hypothesis, MMH). The Northeast Arctic cod Gadus morhua and its dominant prey, the copepod Calanus finmarchicus, have long been studied in the Norwegian-Barents Sea system. However, the mechanistic explanation of how cod survival is affected by MMH dynamics remains unclear. Most MMH studies have focused on either the time synchrony or the spatial overlap between trophic levels. Here, we used G. morhua larvae and C. finmarchicus data collected in the Norwegian-Barents Sea via ichthyoplankton surveys from 1959-1992 to assess the effect of the predator-prey relationship on predator recruitment to the fisheries at age 3 (as a measure of survival) and to develop a metric of predator-prey overlap using spatio-temporal statistical models. We then compared the interannual variability of the predator-prey overlap with the predator’s abundance at recruitment to assess how MMH dynamics explain the survival of cod during its early life stages. We found that the amount of overlap between cod larvae (length: 11-15 mm) and their prey explained 29% of cod recruitment variability. Positive correlations between predator-prey overlap and subsequent recruitment were also found for predators of 6-10 and 16-20 mm, but not for 21+ mm. This improved predator-prey overlap metric is thus (1) useful to better understand how predator-prey dynamics at early life stages of fish impact the survival of later stages; and (2) a valuable tool for assessing the state of an ecosystem.

The importance of predator–prey overlap: predicting North Sea cod recovery with a multispecies assessment model

Kempf, A., Dingsør, G. E., Huse, G., Vinther, M., Floeter, J., and Temming, A. 2010. The importance of predator–prey overlap: predicting North Sea cod recovery with a multispecies assessment model. – ICES Journal of Marine Science, 67: 1989–1997. The overlap between predator and prey is known as a sensitive parameter in multispecies assessment models for fish, and its parameterization is notoriously difficult. Overlap indices were derived from trawl surveys and used to parametrize the North Sea stochastic multispecies model. The effect of time-invariant and year- and quarter-specific overlap estimates on the historical (1991–2007) and predicted trophic interactions, as well as the development of predator and prey stocks, was investigated. The focus was set on a general comparison between single-species and multispecies forecasts and the sensitivity of the predicted development of North Sea cod for the two types of overlap implementation. The spatial–temporal overlap between cod and its predators increased with increasing temperature, indicating that foodweb processes might reduce the recovery potential of cod during warm periods. Multispecies scenarios were highly influenced by assumptions on future spatial overlap, but they predicted a considerably lower recovery potential than single-species predictions did. In addition, a recovery of North Sea cod had strong negative effects on its prey stocks. The consequences of these findings for management are discussed.