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.
The Integumentary Mucous Secretions of the Ophiuroid Ophiocomina Nigra
The general histology of the integument of the ophiuroid Ophiocomina nigra is outlined. Two types of integumentary mucous glands are described in detail for the first time. The first is a multicellular gland, the basal end of which is located deep within the calcareous layer of the integument. The source of the secretion is a variable number of nuclei embedded in a common cytoplasmic mass filled with fine basiphil granules. These cells contributed their secretion to a duct which pursues a tortuous course through the integument. The ducts frequently branch and anastomose so that any one exit pore may extrude mucin derived from a number of separate, polynuclear sources. The structure so formed is, thus, a massive, multicellular gland. Histochemical studies demonstrate that the mucin is a highly sulphated acid mucopolysaccharide. The second type of mucus-secreting unit is a unicellular gland usually located superficially in the calcareous layer or sometimes restricted to the epidermis and distributed universally over the body. The secretion product of these cells is shown histochemically to be a simple acid mucopolysaccharide. The mucin secreted by the tube-foot glands is demonstrated also to be a highly sulphated acid mucopolysaccharide. The function of these secretions has been investigated to some extent. The massive glands secrete only under conditions of alarm and it is suggested that this mucus serves as a defence against predation. The unicellular glands secrete in a periodic fashion correlated with the act of feeding. This secretion is probably utilized in a suspension-feeding mechanism.
An Internet-based Real-time Heavy Rainfall Display System
A new storm warning system, which can be accessed through the Internet and by cellular phones is described. At the time of a heavy rainfall for disaster prevention, it is important that every resident understand how heavy is that rainfall. A real-time heavy rainfall display system designed for all of Japan provides such information (http://www.disaster-i.net/rain/). In that system values for 1-hour precipitation, 24-hour accumulated precipitation, etc. are displayed at every observatory. Advantages are that not only the latest observations but differences from the historical highest records can be seen. Almost all information is displayed by characters so that users have easy access to the system even when the communication network is crowded. Access date for the six months after the system opened shows that the average daily number of accesses of the top page was 306, and the largest number 3078. The maximum number for daily access to all the pages was about 21,500. This is about 2% of the number obtained on the same day for a similar system operated by the Ministry of Land, Infrastructure and Transport (http://www.river.go.jp/).