• Invertebrates
  • Studies on Amphipoda: Proceedings of the 6th International

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    Contraction of the dorsoventral muscles lowers the roof of the seg- ment. Among other defining characteristics (Box 22A) is a uniquely echinoderm feature known as the water vascular system, a complex sys- tem of channels and reservoirs that is derived from the coelom and serves a vari- ety of functions. Some joints are constructed to allow movement in more than one plane, much like a ball-and-socket joint.
  • Invertebrates
  • Plant Parasitic Nematodes in Subtropical and Tropical

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    Common examples include the earthworms, insects, and spiders. Communities pass laws relating to the humane treatment of vertebrates, and they build zoos for their display. Various au- thors have reported that carbohydrases, proteases, cellulase, and chitinase are produced from the midgut epithelium. A synopsis of the genus Trachusa with notes on the nesting habits of T. perdita (Hymenoptera: Megachilidae). Vosmaer (1877) was responsible for removing the sponges and Hatschek (1889) for removing the ctenophores as separate groups.
  • Invertebrates
  • Animals Without Backbones: 2

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    Burrowers in marine sediments. (e.g., Orbinia, Scoloplos) ORDER OWENIIDA FAMILY OWENIIDAE: Small, tube-dwelling poly- chaetes with prostomium often lobed or folded. (e.g., Owenia) ORDER PHYLLODOCIDA FAMILY ALCIOPIDAE: Body homonomous, but form varies from short and broad to long and slen- der; body transparent except for pigment spot in some genera; with pair of huge complex eyes on prostomium; planktonic predators. (e.g., Alciopa, Al- ciopina, Torrea, Vanadis) FAMILY APHRODITIDAE: Body broad, oval or ob- long, with less than 60 segments; with flattened, solelike ventral surface, and rounded dorsum covered with scales (elytra) overlaid by a thick felt- or hairlike layer, giving some the common name of “sea mouse”; slow-moving; epibenthic or burrowers; most are omnivorous. (e.g., Aphrodita, Pontogeneia) FAMILY GLYCERIDAE: Long, cylindrical, tapered, homonomous body; enormous pharynx armed with four hooked jaws used in prey capture; large pha- ryngeal proboscis also used in burrowing; most are infaunal burrowers in soft substrata. (e.g., Glycera, Glycerella, Hemipodus) FAMILY NEPHTYIDAE: Often large, or long and slender, with well developed parapodia; burrowing in marine sands and muds; reversible, jawed pharynx used in prey capture and burrowing. (e.g., Aglaophamus, Micronephtyes, Nephtys) FAMILY NEREIDAE: Moderate to large polychaetes tending to homonomy; mostly errant predators with well developed parapodia; one pair of large, curved pharyngeal jaws.
  • Invertebrates
  • Biogeography and Numerical Taxonomy of the Oegopsid Squid,

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    In fact, except for the eyes, the functions of various leech sense organs are not well understood at all, and most of the information is based on behavioral responses to dif- ferent stimuli. The earliest records of any lophophorate are of various ectoprocts reported in the sixteenth centu- ry. They are also used in biogeographic analyses, wherein taxa are replaced by their appropriate areas of endemism, and the “homo- logues” are thus sister groups shared by geographic areas.
  • Invertebrates
  • Süßwasserfauna von Mitteleuropa, Bd. 7/2-2 Chelicerata:

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    The nervous system is a plexus of basiepithelial neurons serving sensory and motor systems (Fig 7-6). Dayton, Scripps Institution of Oceanography The most primitive centralized nervous system may have been similar to that seen today in some free-living flatworms, with pairs of longitudinal cords attached to one another by a series of transverse connectives (Figure 3.32B). The digestive tract was relatively simple and straight (Figure 15.33B), extending from the mouth on the ventral side of the cephalon to the anus on the pygidium.
  • Invertebrates
  • Invertebrate Structure and Function

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    Typically have planula larvae (ciliated, motile, gastrula larvae) BOX 8A Characteristics of the Phylum Cnidaria Figure 8.2 Tissue layer homologies in cnidarians. (A) A hydrozoan polyp. (B) An anthozoan polyp. (C) A hydro- zoan medusa, shown upside down for similar orientation. Included are some of the author’s thoughts on recapitulation.] Jefferies, R. Most of these groups have biting mouthparts, but some (such as certain flies) have sucking mouthparts.
  • Invertebrates
  • Lecture Notes on Invertebrate Zoology

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    But once you study the life cycles and food chain, you’ll have a better understanding of nature’s handiworks. Most phylactolaemates display ei- ther lophopodid or plumatellid colony forms. Evolution of a regulatory gene family: HOM/Hox genes. All phyla of animals are invertebrates with the exception that only two of the three subphyla in Phylum Chordata are invertebrates: Urochordata and Cephalochordata. So, three hypotheses have been offered to explain the “shell problem” in molluscan evolution: (1) The multi- plate shell may have been ancestral, the single-shell de- 62 CHAPTER TWENTY UNCORRECTED PAGE PROOFS Figure 20.54 The molluscan cross: (A) Gastropoda (Lymnaea). (B) Polyplacophora (Stenoplax). (C) Sipuncula (Golfingia). (D) Aplacophora (Epimenia).
  • Invertebrates
  • Rotifera IX: Proceedings of the IXth International Rotifer

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    Once a larva becomes competent, it generally begins to respond to certain environmental cues that induce set- tling behavior. Although trypanosomes can change the direc- tion of flagellar beat in response to chemical or physical stimuli, usually the beat begins at the tip of the flagel- lum and proceeds toward the kinetosome. The males, however, are only a few millimeters long, very reduced in complex- ity, and often retain remnants of larval ciliation.
  • Invertebrates
  • Prolegs, Legs and Wings of Insects: [Entomonograph, Vol. 5]

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    Most of them, from Marine Biology to Biomechanics, and especially Invertebrate Zoology, delve into the evolution and ecology of invertebrates. Not surprisingly, due to their great age,* the genetic differences among prokaryotes are much greater than those seen among eukaryotes, even though these differences do not typi- cally reveal themselves in gross anatomy. Most 258 CHAPTER EIGHT Figure 8.40 Scyphozoan scyphistoma (and one strobi- la) (A), and strobila (B) of Aurelia (Semaeostomae, Scyphozoa). (C) A “typical” 8-armed ephyra. (D) A 12- armed ephyra. (A) (B) (C) (D) Figure 8.39 The hollow planula larva of the hydroid Gonothyraea (longitudinal section).
  • Invertebrates
  • Leeches (Ooey-Gooey Animals)

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    This scenario assumes that the first cnidarians were exclusively polypoid, and that the medusa phase arose later. Popular hypotheses are that mucous secretions by the nudibranch limit the discharge, or that a form of accli- mation occurs (like that suspected to occur between anemone fishes and their host anemones), or perhaps that only immature nematocysts survive, to later under- go maturation in the dorsal cerata. In both hexapods and crustaceans, longitudinal connectives of the CNS originate in the segmental neu- rons, whereas in myriapods they derive from neurons in the cerebral ganglia that send their axons posteriorly to set up long parallel connectives.