Secretion of a Highly Sulphated Acid Mucopolysaccharide by the Brittle-star, Ophiocomina nigra
THE secretion of a mucus from the tube-feet of ophiuroids is well known1, although the chemical nature of this substance has not been investigated. In a study of the feeding mechanisms of ophiuroids, I find that Ophiocomina nigra (Abildgaard), a common littoral species widespread in the north-east Atlantic and Mediterranean, in addition to the mucin of the tube-feet, secretes all over the body surface an abundant mucus used in conjunction with a detritus-feeding mechanism. Attempts to find the source of this secretion have revealed two types of mucus glands previously undescribed for the species.
Feeding mechanisms and the functional morphology of podia and spines in some New Zealand ophiuroids (Echinodermata)
The feeding methods of seven intertidal ophiuroids are described. In each method the podia are used as an integral part of the feeding mechanism, and varying use of the spines has been observed. Both podia and spines contain mucous glands and certain similarities are apparent in their secretions. Where mucus is used directly for food capture, and ingested with the food, it is acid, rich in wboxyl groups and at least partly sulphated. Further, the mucus in spinal glands is fibrillar while that of the podia is granular. Some integumentary glands are basiphilic and highly sulphated while other are acidophilic. The possible functions of these glands are discussed.
On the Nervous System of the Starfish Marthasterias glacialis (L.)
In the year 1815, Tiedemann observed on the oral surface of the disk of the starfish Astropecten aurantiacus (L) a circumoral band of tissue continuous, in the mid-line of each arm, with a radial band. To these bands he ascribed a vascular function. Johannes Muller (1850), however, indicated that the radial and circular bands were more properly to be regarded as nerve cords, an observation which Owsjannikow (1871), Greeff (1871, 1872, a , 1872, b ), Hoffmann (1872), and Teuscher (1876) subsequently confirmed. Lange (1876), while not accepting the findings of previous authors as to the nervous nature of the circumoral and radial cords, discovered two ridges of tissue above each of the “V’’-shaped radial cords, one lying to the right and the other to the left of the mid-line. These are constituted by thickenings of the coelomic epithelium which lines the radial perihaemal canals, and were considered by Lange to represent nervous tissue. This opinion has been substantiated by Ludwig (1878), Hamann (1883, 1885), and Cuenot (1891) among others; but these and all recent investigators agree that the radial and circumoral cords must also be regarded as constituting part of the asteroid nervous system. Cuenot (1891) therefore distinguishes between the part of the nervous system derived from the ectoderm, such as the circumoral and radial cords, and the part—presumably of mesodermal origin—situated in the coelomic epithelium.