Non-invasive MRI Studies of Ventilatory and Cardiovascular Performance in Edible Crabs Cancer pagurus During Warming Under Elevated CO2 Levels

The thermal tolerance of marine decapod crustacea is defined through their capacities for oxygen uptake and distribution. High ambient CO2 levels were previously shown to reduce hemolymph oxygen levels at enhanced cardiac performance during warming. This study investigated the impacts of warming under two CO2 levels on ventilation and hemolymph circulation in edible crabs Cancer pagurus. It also highlights changes in the ventilatory and cardiac pauses displayed by Decapoda under routine metabolism. Animals were exposed to step-wise, sub-critical warming (12–20°C over 5 days) under control (470 μatm) and high (1,350 μatm) water PCO2. Flow-through respirometry was combined with magnetic resonance imaging and infra-red photoplethysmography to allow for simultaneous, non-invasive measurements of metabolic rates (M˙O2), ventilation and cardiovascular performance. Crabs spent significantly more time in a low M˙O2 state (metabolic pause), when experiencing high CO2 conditions above 16°C, compared to normocapnic warming. Heart rates leveled off beyond 18°C at any CO2 level. Cardiac output continued to increase with high-CO2-warming, due to elevated cardiac stroke volumes. Consequently, temperature-dependent branchial hemolymph flow remained unaffected by CO2. Instead, a suppressing effect of CO2 on ventilation was found beyond 16°C. These results indicate constrained oxygen uptake at stable cardiovascular performance in a decapod crustacean.Cancer pagurus: urn:lsid:zoobank.org:act:B750F89A-84B5-448B-8D80-EBD724A1C9D4

Detecting Cryptic Female Choice in Decapod Crustaceans

Decapod Crustacea (shrimps, lobsters, and crabs) employ a range of different reproductive mechanisms that affect paternity, but does it include cryptic female choice (CFC)? This chapter focuses on events surrounding the fertilization of an egg by a sperm and the opportunities where cryptic fertilization bias might occur. It presents a new model of decapod fertilization, defined in terms of space and time to fertilization. Females have several ways to store sperm and influence fertilization outcomes, which should be affected by (1) their growth pattern (indeterminate or determinate), (2) the link between molting and mating (soft-shell or hard-shell mating), (3) fertilization latency, and (4) how sperm are protected (no protection or storage is separate from the oviduct, or storage in a seminal receptacle is linked to the oviduct). Paternity data available for 26 decapods show that in 85% of species, females carry broods with multiple paternity and 15% have broods with single paternity. Therefore many (if not most) females mate with several males and so they certainly could make a choice. However, whether this pattern is due to CFC or merely reflects mating history is a matter of debate. At present, there are no unequivocal data that demonstrate CFC: outcomes caused by male mate guarding and sperm competition cannot be distinguished from female choice. The challenge is to understand what females might be choosing and how to detect that choice. Detecting CFC in field data is difficult, if not impossible, because both single and multiple paternities could be favored.

Presence of Cyrtograpsus angulatus Dana, 1851 (Decapoda, Brachyura) on the Chilean northern Patagonian coast

The marine fauna of decapod Crustacea, in all its diversity, can be negatively affected as a result of environmental changes, both on a local or a global scale. The present study aims to report the existence ofCyrtograpsus angulatusDana, 1851, on the northern Patagonian coast, while concurrently describing some other decapod species associated with the various habitats.C. angulatuswas originally described from the Chilean coast north of 36°43′S, and the present study revealed its presence down to 44°S. In the estuaries investigated,C. angulatusis the exclusive decapod species, whereas in coastal zones it can coexist with other species of marine decapods. Nevertheless, according to the null model of the co-occurrence of species, the species associations tested did not show any structured pattern. Some ecological and biogeographical patterns in relation to this species and its biocoenoses are discussed.

The contribution of Henry Charles Williamson (1871–1949) to Scottish and Canadian fisheries research

The Scottish zoologist Henry Charles Williamson was one of a group of young men who initiated fisheries science in the late Victorian age, schooled under Professor William Carmichael McIntosh at St Andrews University. Initially working for the Fishery Board of Scotland, Williamson contributed original studies on fish anatomy, morphology, systematics and life cycles; decapod Crustacea life-history stages; fish diseases and parasites. He was at the forefront of attempts to transport herring ova to Australia and New Zealand to introduce this European food fish to antipodean waters. That involved him researching how to retard development of ova using low temperatures and developing glass settlement-plate techniques for their transportation. He left Scotland in 1925 to spend five years in the Canadian Pacific, studying salmon migration by tagging and latterly becoming responsible for pilchard and herring work there too. Returning to his home town of Dundee in retirement, he lived a quiet life, giving talks to local groups, supporting his church's administration and contributing articles to the fishermen's press. Sadly he died before he could complete the two volumes on fishes that he was in the course of writing.

Diet and feeding strategy of the forkbeard Phycis phycis (Pisces: Phycidae) from the Portuguese continental coast

The diet and feeding behaviour of the forkbeard Phycis phycis was studied based on 246 stomachs collected between May 2011 and April 2012 from a commercial fleet operating off the central west coast of Portugal. A total of 44 prey items were identified in the stomachs which were merged into major groups to avoid problems with low expected frequencies. The following taxonomic categories were considered: non-decapod Crustacea, Caridea, Anomura, Munida spp., Processa spp., Brachyura, Pisces, Trisopterus luscus. In order to investigate possible diet differences between fish size classes, a cluster analysis was performed using the mean abundance of each prey group by forkbeard 5 cm length class, and three length groups (LG) were obtained: <22.5, 27.5–37.5 and >42.5 cm. Seasonally, Caridea was the main prey group during winter and autumn while Pisces was predominant during the rest of the year. Caridea was the most important prey group for LG1 and LG2 while in LG3 Pisces was the principal one. The forkbeard feeding behaviour may be characterized as presenting a shift pattern from a more generalist diet (small Crustacea, mainly Caridea) in the young adults to a more specialist strategy (teleosts) in the adults.