Red sea urchins (Echinus esculentus) and water flow influence epiphytic macroalgae density

In Volume 2 of the ‘ Philosophical Transactions ’ of the Royal Society, published in 1667, travellers to the East Indies are asked to enquire (p. 419) “ whether those shell-fishes, that are in these parts plump and in season at the full moon, and lean and out of season at the new, are found to have contrary constitutions in the East Indies ? ” This belief that the size of certain marine invertebrates, chiefly molluscs and echinoderms, varies with the phases of the moon is found in the literature of classical Greece and Rome and of the middle ages, and is held to-day in the fish markets around the Mediterranean and in the Red Sea. At Suez sea-urchins and crabs are said to be “ full ” at full moon and “ empty ” at new moon, at Alexandria the same thing is said of mussels and of sea-urchins, the Tarentines believe that oysters are fattest at full moon (34), while at Nice, Naples, Alexandria, and in Greece (17, p. 17, footnote) urchins are said to be fullest at full moon. The part of the sea-urchin which is eaten is the gonad, while in the crab it is the muscles, so that these tissues are supposed to vary in bulk with the phases of the moon. Now my own investigations, of which preliminary reports have already been published (8, 9) and a full account is to be given in this paper, have shown that while the supposition is untrue of mussels ( Mytilus sp .) and sea-urchins ( Strongylocentrotus lividus ) in the Mediterranean and of mussels ( Mytilus variabilis ) and crabs ( Neptunus pelagicus ) in the Red Sea, it is based on fact as concerns the sea-urchins found at Suez ( Centrechinus [ Diadema ] setosus ). In the last-mentioned form the gonads undergo a cycle of growth and development corresponding with each lunation throughout the breeding season. Just before full moon ovaries and testes are at their greatest bulk, filled with spermatozoa or eggs which are spawned into the sea at the time of full moon. The shrunken gonads then gradually fill again with ripening sexual products to be shed at the next full moon. It is remarkable, then, that a belief which was such common knowledge among the ancient inhabitants of Mediterranean countries that it was referred to by their poets and orators and one which is held to-day in the Mediterranean ports is indeed untrue of this region, while at Suez it is based on fact. It is possible that the Greeks originally obtained the belief from the ancient Egyptians, who would have it from the Red Sea (what really occurs there in sea-urchins being supposed to apply to all “ shell-fish ”), and that the same belief has survived around the Mediterranean until to-day. Or perhaps the belief had an independent origin in Greece, founded, not on fact, but on the supposed influence of the moon-deities on growth in general.

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Effects of handling and short-term captivity: a multi-behaviour approach using red sea urchins, Mesocentrotus franciscanus

PeerJ ◽

10.7717/peerj.6556 ◽

2019 ◽

Vol 7 ◽

pp. e6556 ◽

Cited By ~ 4

Author(s):

Aneesh P.H. Bose ◽

Daniel Zayonc ◽

Nikolaos Avrantinis ◽

Natasha Ficzycz ◽

Jonathan Fischer-Rush ◽

...

Keyword(s):

Red Sea ◽

Sea Urchins ◽

Abundant Species ◽

Ecosystem Functions ◽

Short Term ◽

Induced Stress ◽

Aggregation Behaviour ◽

Fitness Consequences ◽

Term Monitoring

Understanding the effects of captivity-induced stress on wild-caught animals after their release back into the wild is critical for the long-term success of relocation and reintroduction programs. To date, most of the research on captivity stress has focused on vertebrates, with far less attention paid to invertebrates. Here, we examine the effect of short-term captivity (i.e., up to four days) on self-righting, aggregation, and predator-escape behaviours in wild-caught red sea urchins, Mesocentrotus franciscanus, after their release back into the wild. Aggregation behaviour, which has been linked to feeding in sea urchins, was not affected by handling or captivity. In contrast, the sea urchins that had been handled and released immediately, as well as those that were handled and held captive, took longer to right themselves and were poorer at fleeing from predators than wild, unhandled sea urchins. These results indicate that handling rather than captivity impaired these behaviours in the short term. The duration of captivity did not influence the sea urchin behaviours examined. Longer-term monitoring is needed to establish what the fitness consequences of these short-term behavioural changes might be. Our study nevertheless highlights the importance of considering a suite of responses when examining the effects of capture and captivity. Our findings, which are based on a locally abundant species, can inform translocation efforts aimed at bolstering populations of ecologically similar but depleted invertebrate species to retain or restore important ecosystem functions.

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Harlequin Ducks (Histrionicus histrionicus) Scavenge Sea Urchin Fragments from Foraging Sea Otters (Enhydra lutris)

The Canadian Field-Naturalist ◽

10.22621/cfn.v130i2.1832 ◽

2016 ◽

Vol 130 (2) ◽

pp. 91 ◽

Cited By ~ 2

Author(s):

Erin Rechsteiner ◽

Angeleen Olson

Keyword(s):

Red Sea ◽

Sea Urchins ◽

Keystone Species ◽

Sea Otter ◽

Enhydra Lutris ◽

Sea Otters ◽

Important Prey ◽

Histrionicus Histrionicus ◽

Harlequin Ducks

Foraging animals may risk association with potential predators to obtain otherwise inaccessible prey. We observed this strategy in wintering Harlequin Ducks (Histrionicus histrionicus) scavenging fragments of Red Sea Urchins (Mesocentrotus franciscanus) from foraging Sea Otters (Enhydra lutris) that were re-occupying an area from which they had been ecologically absent since about 1850. Harlequin Ducks, like other sea ducks, have not previously been reported scavenging from other birds or mammals. In British columbia, Red Sea Urchins have reached large sizes and densities since the removal of Sea Otter predators by the marine fur trade in the 18th and 19th centuries. Observations of Sea Otters and Harlequin Ducks were made in 4 areas, spanning a time gradient of Sea Otter occupation from 1 to 5 years. During 3 months of observations (December 2013 – February 2014), Harlequin Ducks were associated with foraging Sea Otters only at sites that were recently occupied by Sea Otters (≤ 2 months), where the proportion of urchins in Sea Otter diets was highest and where the ducks acquired urchin fragments from foraging Sea Otters. We suggest that Sea Otters re-occupying their historic range and consuming predominantly large Red Sea Urchins provide a temporarily available prey subsidy for Harlequin Ducks. Our observations document a novel effect of Sea Otters providing important prey supplementation to a marine bird when foraging in urchin-rich habitats, contributing to the overall role of Sea Otters as a keystone species.

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