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On the Breeding Habits of Echinus miliaris, with a Note on the Feeding Habits of Patella Uulgata

Published online by Cambridge University Press:  11 May 2009

J. H. Orton
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Extract

While on shore-collecting expeditions in this district it was frequently observed that Echinus miliaris has the habit of associating together in pairs, and sometimes in groups of more than two. The association of these pairs and groups is sometimes so intimate that it is not possible to interpose even the blade of a penknife between the interlocking spines of the urchins. In all cases observed except one, such pairs were placed side by side, but in one particular case the apical region of one individual was almost certainly placed adjacent to the apical portion of the other. In all the collecting expeditions—made at various times of the year between April and August—on which groups were collected, the total number of urchins of all sizes obtained amounts to about 710. Among this number were obtained 84 groups, which amount in all to 189 specimens. In the earlier part of the investigation a group was taken as such if the members were merely fairly close together, but afterwards only those specimens were recorded which were actually touching one another in the manner described above. Out of the total of 84 groups only 27 were actually recorded definitely as touching one another, although some of the other groups may have been touching. Of these 27 closely associated forms all the individuals were ripe except 3 small specimens belonging to two pairs which were recorded as having an immature gonad. The remainder consisted of 19 pairs, 2 pairs, 1 pair, and 3 groups respectively.

Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 10 , Issue 2 , June 1914 , pp. 254 - 257
Copyright
Copyright © Marine Biological Association of the United Kingdom 1914

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References

* In a few cases as many as from 13 to 21 individuals have been found close together under one stone.

† In the search for groups of these urchins I am much indebted to the laboratory fisherman, William Searle, for the zeal and care with which he helped in the collecting.

‡ In this group the O+ associated with the male was almost certainly spent, although it was difficult to make certain whether on the other hand it might be immature. Hence it is not grouped with the definite pairs of male and female.

* Echinocardium cordatum when living in deep water inhabits fine sand, from which it can only be captured by means of a dredge, and in a 3-foot dredge a short haul may sometimes yield as many as 15 individuals. This species occurs in great numbers in the Salcombe estuary within a very small area, but this aggregation is probably due more to the presence of only a small area of suitable ground than to a desire of the individuals to associate. Nevertheless in this locality these heart-urchins associate closely in groups of twos, threes, and sometimes in larger numbers. The sexes of the members of such groups have not, however, been observed.

† I am indebted to Mrs. Orton for the drawing for this figure, which has been copied from a sketch made in my collecting book.

‡ Tennent, D. H., Journ. Exp. Zool., Vol. IX, No. 4, p. 659, 1910.Google Scholar

* O. Hertwig, Zeit. für Wiss. Zool. Jen., Vol. XXIV, p. 282, 1890.

† Ainsworth Davis, J. R. and Fleure, H. J., Patella L.M.B.C. Memoir, Vol. X, London, 1903.Google Scholar