Spawning synchrony and aggregative behaviour of cold-water echinoderms during multi-species mass spawnings

Although many marine invertebrates reproduce by releasing gametes into the water, major spawning events have rarely been observed for cold-water invertebrates. We documented mass spawnings by the sea star Asterias vulgaris and the ophiuroid Ophiopholis aculeata on 6 July 1996 and 2 July 1998, and by these 2 species plus a second ophiuroid Ophiura robusta and the sea urchin Strongylocentrotus droebachiensis on 3 July 2003. In each year, the abrupt spawning events coincided with the first major intrusion of warm surface water into a region normally dominated by cold upwelling. The behaviours of the ophiuroids and sea stars favoured fertilization success. First, they spawned from elevated surfaces, with the central disc raised, to increase suspension and mixing of gametes. Second, many individuals pseudocopulated, which involved crawling over one another in the case of the sea star, and individuals holding their central discs together in the case of the 2 ophiuroids. Models of fertilization success need to incorporate such behaviours to better understand fertilization in the sea.published_or_final_versio

Gonad structure and gamete morphology of the eastern South Pacific chiton Acanthopleura echinata Barnes, 1824

Volume: 47Start Page: 141End Page: 15

Effects of the toxic dinoflagellate Alexandrium catenella on histopathogical and escape responses of the Northern scallop Argopecten purpuratus

International audienceJuvenile Northern scallops Argopecten purpuratus were exposed to cultures of the paralytic shellfish toxin (PST) producing dinoflagellate, Alexandrium catenella, or a non-toxic microalga as a control, T-iso. After 3 and 6 days of exposure to either A. catenella or T-iso, scallops were stimulated to elicit an escape response by exposing them to the predatory sea star Meyenaster gelatinosus. We monitored the escape response of the scallops in terms of reaction time after first contact with the sea star, number of claps (burst of rapid valve closures) until exhaustion, clapping time, clapping rate, the time scallops spent closed when exhausted, and recovery from the initial number of claps, clapping time and clapping rate. Additionally, histopathological and stress responses (through heat-shock protein [hsp70] induction), as well as accumulation of Paralytic Shellfish Poisoning (PSP) toxins, were monitored on scallops after 3 and 6 days of exposure to A. catenella. After 6 days of exposure, scallops exposed to A. catenella accumulated PSTs and reacted more rapidly with a higher clapping rate, however the duration of their escape response was shorter than controls, when exposed to M. gelatinosus. Additionally, scallops exposed to A. catenella showed histopathological features, especially after 6 days of exposure, including increased melanization of the tissues and myopathy, with high levels of degeneration of the muscle fibers. A six-day exposure to A. catenella also caused an increase in prevalence of rickettsiales-like organisms within scallop tissues. This study suggests that PST accumulation can affect the interaction between the Northern scallop and both pathogens and predators, potentially increasing their susceptibility to either of them

Midfoot plantar pressure significantly increases during late gestation

A rise in plantar pressure has been observed in pregnant women with foot pain. The current literature on plantar pressure in pregnancy is sparse. It has been postulated that changes in plantar pressure result from the physiological effects of pregnancy. In this study we aim to quantify the plantar pressure of women in late pregnancy. Methods Twenty-two pregnant women undergoing a caesarean section and twenty non-pregnant women were recruited from University Hospital Coventry and Warwickshire between May to June 2007. Plantar pressure measurements were performed using an in-shoe measurement system. The control group was compared with the pregnant group at 38 weeks gestation. A selection of the pregnant group had repeat measurements at 4 months post-partum. The pre and post-partum measurements were also compared. Results The pregnant group (PG) exerted a significantly higher mean midfoot pressure compared to the non-pregnant control group (CG) (PG=115.5kPa, CG=95.4kPa; p=0.001). Post-partum (PP), there was a significant reduction in the mean and maximum midfoot pressure (mean; PG=111.9kPa, PP=66.2kPa; p<0.001, maximum; PG=184.0kPa, PP=108.3kPa; p<0.001). Conclusions The physiological changes in late pregnancy result in an increase in midfoot plantar pressure. This increase resolves post-partum

Locomotion And Burrowing In Limbless Vertebrates

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62754/1/242414a0.pd