Polychaete worm

“ Most marine anglers are acquainted with that well-known and common bait the Lug-worm, Arenicola marina, amongst other Polychaet lures, which form part of the group of "marine worms, whose bodies are usually elongated and cylindrical; they either lead a free life swimming in the open sea or crawling along the bottom, or they pass their life in burrows or definite tubes of various kinds." Amongst other peculiarities, some species are polymorphic. ”

“ It is also observable, that they lose their colour if fed with aliments that are not of the same colour with themselves.
The polypes feed on the greater part of those insects that are to be found in fresh water. They may be nourished with worms, the larvæ of gnats, &c. they will also eat larger animals if they are cut into small pieces, as snails, large aquatic insects, small fish, butcher’s meat, &c. Sometimes two polypes seize the same worm, and each begins to swallow its own end, continuing so to do till their mouths meet, Plate XXIV. A. Fig. ”

“ The intestine is bent upon itself. In Ophelia limacina Rthk. the gills commence in the eighth segment, and the longitudinal ridge does not extend in front of this segment. The worm is about 11⁄2 inches long, and occurs between tide-marks. Travisia forbesi Jnstn., North Sea. Polyophthalmus pictus [390] Duj. is very abundant at some parts of the coast. There are two bundles of chaetae on each side of every segment; each bundle contains three chaetae, of which only one projects to any distance. Paired eye-like spots exist on the sides of twelve segments. The worm is about an inch in length. ”

“ There can be little doubt that many {301}Polychaetes are very "plastic," and can adapt themselves to changed conditions of life with considerable ease; for Nereis diversicolor, Arenicola marina, and others live equally well in water of very different densities, and with a different food supply. The great variety in the "habitats," and presumably therefore in their food supply, etc., exhibited by many Polychaetes, as well as the great variation observable in some species of Polynoina, and the close affinity of the species and genera of this sub-family, lead us to the same conclusion. ”

“ This kind of chaeta is found in all earthworms, and in not a few aquatic genera such as the Lumbriculidae. In some of the latter and in the Tubificidae and Naids there is the same form of chaeta, which is cleft at the free end, and possibly enables the worm to grasp the leaves of aquatic plants, and otherwise facilitates progression in a laxer medium than the stiff soil frequented by the earthworms. Even earthworms, at any rate the genus Pontoscolex, have chaetae of this kind; some of the aquatic Oligochaeta have elongated and hair-like bristles, such as that of Tubifex.
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Fig. ”

“ The amphinomid polychaete Hermodice carunculata (Annelida, Amphinomidae) is a cosmopolitan and ecologically important omnivore inhabiting coral reefs and other habitats throughout the Atlantic Ocean, including the Gulf of Mexico and the Caribbean Sea, as well as the Mediterranean and Red seas [1] . It is known to prey on a diverse suite of reef organisms such as zoanthids [2] , [3] , scleractinian corals [4] - [5] , milleporid hydrocorals [6] , [7] , anemones [8] and gorgonians [6] . ”

“ It is the giant of a family of white, red, yellow, green, purple, and violet worms whose habitat ranges from sea bottoms to jungle treetops. The worms shoot poison-tipped harpoons out of their brains. Most can shrink at will to less than a third of their ordinary length. They always shrink when they die. Some can break up into hundreds of fragments, each of which will grow into a complete new worm. ”

“ They perform a few actions instinctively, that is, all the individuals, including the young, perform such actions in nearly the same fashion. This is shown by the manner in which the species of Perichæta eject their castings, so as to construct towers; also by the manner in which the burrows of the common earth-worm are smoothly lined with fine earth and often with little stones, and the mouths of their burrows with leaves. One of their strongest instincts is the plugging up the mouths of their burrows with various objects; and very young worms act in this manner. ”

“ While the animal is contracted by seizing its prey, the arms are observed to swell like the muscles of the human body when in action. Though no appearance of eyes can be observed in the polype, they certainly have some knowledge of the approach of their prey, and shew the greatest attention to it as soon as it comes near them. It seizes a worm the moment it is touched by one of the arms, and in conveying it to the mouth, it frequently twists the arm into a spiral line like a corkscrew, by which means the insect is brought to the mouth in a much shorter time than otherwise it would be ”

“ The Bermudian genus Onychochaeta offers a very strange peculiarity in that the chaetae on the hinder segments of the body are enormously larger than those in front, and end in strong hooks; it seems likely that their function is to maintain a tight hold of the ground while the worm is leaning out of its burrow, as every one has seen the common earthworms of this country do. ”

“ The worms of this family are nearly always of small size, sometimes minute; they never exceed an inch or so in length, and that is a rare occurrence. They are equally at home in water and in soil, some species being common to the two media; a few are marine or littoral in habit, while others are parasitic in vegetable tissues. Like most earthworms, and unlike the majority of aquatic worms, the chaetae are without a bifid termination; the body-wall, too, is comparatively thick. The perivisceral fluid is often (as in certain Naids) loaded with elliptical or rounded corpuscles. ”

“ Polyzoa are very abundant in the Cainozoic beds of Australia, New Zealand, and elsewhere (Fig. 25) . In the Mesozoic series, on the other hand, they are not so well represented; but in Europe and North America they play an important part in forming the Cretaceous and some Jurassic strata by the abundance of their remains.
WORMS (VERMES) .—The hard, calcareous tubes of Sea-worms, the Polychaeta (“many bristles”) are often found in fossiliferous deposits, and sometimes form large masses, due to their gregarious habits of life ”

“ In systematic zoology, however, the use of a division Vermes has been abandoned, as it is now recognized that many of the animals that even a zoologist would describe as worms belong to different divisions of the animal kingdom. The so-called flatworms (Platyelmia, q.v.) , including the Planarians (q.v.) . Flukes (see Trematodes) , Cestodes (see Tapeworm) and the curious Mesozoa (q.v.) , are no doubt related. The marine Nemertine worms (see Nemertina) are isolated. ”

“ Hence it is necessary to keep a sharp watch for dead specimens, which should, of course, be removed at once. The presence of a putrefying worm may often be detected by the appearance of a whitish fungoid growth round the mouth of what appears to be an empty tube; and if, through neglect, the water of the aquarium has been allowed to become contaminated by the products of decomposition, it will often happen that some of the living worms will come entirely out from their tubes, as if to seek a more sanitary situation. ”

“ They are divisible into the Haplodrili (q.v.) or Archiannelida, the Polychaeta containing the marine worms, the Oligochaeta or terrestrial and fresh-water annelids (see EARTHWORM) , the Hirudinea or leeches (see Leech) , and a small group of parasitic worms, the Myzostomida (q.v.) .
The distinctive characters of the class Chaetopoda as a whole are partly embodied in the name. They possess (save for certain Archiannelida, most Hirudinea, and other very rare exceptions) setae or chaetae implanted in epidermal pits. ”

“ Regeneration of lost Parts.—The process of budding and fission of the worm into two parts is merely an extension of that resulting in the formation of new segments when the worm is injured. In most of the Nereidiform Polychaetes the number of segments forming the body continues to increase throughout life by the formation of new segments between the anal segment and the one in front of it; that is to say, there is normally a process of budding taking place at this point. Now in many of the longer worms it may be noticed that the segments of the hinder end suddenly become smaller than the rest ”

“ The first female which presents itself allows us to answer this question. It is not a parasitical worm, at least under this form, because each female contains only one or two eggs. Parasites have so few chances of arriving at their destination, that two young ones would not be sufficient. They must have hundreds or thousands, and then the chances are against them. This worm is evidently a Rhabditis, but is it that which lives in the earth, or an allied species? ”

“ The comparatively unresisting nature of the medium in which they live, water or fine mud, does not necessitate so strong a development of the layers of the body-wall as is essential to the earth-living forms, which have also thick septa in the anterior region, to protect the organs of reproduction as the strong muscular contractions of the body force the worm's way through the dense soil. With the weak structure of the integument are perhaps also correlated the simplicity of other organs of the body in the aquatic Oligochaeta. ”

“ The worms are tubicolous; "gland-shields" are present on the thoracic segments.
Sub-Order 2. Hermelliformia.—The peristomium (Fig. 135) is enormously developed, and forms a bilobed hood capable of closing over the mouth; the truncated free end of each lobe carries three semicircles of peculiar chaetae, which act as an efficient protection when the worm is withdrawn into its tube. ”

“ These Annelids, unlike their allies the marine Polychaeta, and even their allies on two other sides, the leeches and flatworms, have no complexly organised eyes or other sense organs. They have in fact no organs to which a definite sense can be attached on histological grounds. There is nothing comparable to an eye or to the auditory sacs of other low worms. There are only particular cells of the epidermis, often associated into small groups, and those again into larger associations of rows of such groups of cells. ”

“ The roundworms are slender, smooth, cylindrical worms pointed at both ends. They are all very long in proportion to their diameter, although their actual length may be short. Some species are of microscopic size; as the Trichina worm, which is about 1/20 in. long; while the guinea-worm, one of the worst parasites of man, may reach a length of six feet. Many of the roundworms are parasites living in the various organs of other animals. Some, however, lead an independent free life in water or in damp earth. ”

“ The worms are cylindrical, with many segments, but these segments are only indistinctly marked externally—by girdles of cilia in Protodrilus, or by faint grooves in Polygordius; but there are none of the characteristic Chaetopod bristles or chaetae. The small prostomium which overhangs the mouth is provided with a pair of ciliated pits, and carries a pair of tentacles, serving as sensory organs, which, in Protodrilus, are also respiratory. The anus is surrounded by glandular papillae in Polygordius, by means of which the animal can fix itself ”

“ When seen swimming in the water it presents the appearance of a long, many-ringed worm, which impels itself through and by the aid of its hundreds of flat, oar-like legs. Closer inspection reveals the startling fact that this seemingly single worm is really a multiple worm—six or more individuals being joined together, thus forming a living chain. This creature reproduces itself by fissigemation; that is, when the young worms arrive at a certain age they separate from the parent worm and begin life as individuals. ”

“ It is of an extremely predacious nature, and feeds on the various species of small worms, and other water animals, that happen to approach. When any animal of this kind passes near the polype, it suddenly catches it with its arms, and, dragging it to its mouth, swallows it by degrees, much in the same manner as a snake swallows a frog. ”

“ The worm, coming out of the mouth of the polype, forces it to enlarge itself considerably, especially if it comes out doubled up. When the polype is in this state, I take it gently out of the water, without disturbing anything, and place it on the edge of my hand, which is simply moistened, so that it [Pg 66] may not adhere too closely. I oblige it to contract more and more, and this also enlarges the stomach and mouth. ”

“ Polychaetes nearly all the Eunicidae secrete a parchment-like tube, and some Polynoids form mud tubes. Among the "sedentary worms" there are forms which merely burrow; while Myxicola readily leaves its gelatinous tube and swims freely; Pectinaria carries its house with it as it moves about, and Polycirrus, a Terebellid, does not form any tube at all.
Owing to their sedentary habits, quite a representative collection of genera may be made, especially at a spring tide, at any seaside place which is provided with a sandy shore, and with rocks and seaweed. ”

“ From this great and unnatural group, which has survived as "Vermes" even in some quite modern text-books, we can separate off those forms which show a plain segmentation or division of the body internally as well as externally into a series of more or less similar rings, as a Class Chaetopoda. This Class, consisting of the Orders mentioned on p. 241, includes the worms which form the subject of the present chapter—the Oligochaeta, as they were originally called by Grube, on account of the fewness of their chaetae as compared with the number possessed by the majority of the Polychaeta. ”