Physical characteristics

Bathynellacea range in length between 0.02 in (0.5 mm) and 0.14 in (3.5 mm). As an adaptation to their subterranean existence, they do not have eyes and lack body pigment. The body is divided into head, thorax, and abdomen. The head carries the antennae with chemo- and mechanosensory structures as well as the mouthparts. The mandibles, used for biting, are symmetrical in structure. The thorax has seven pairs of biramous walking legs. The eighth pair is reduced in both sexes and in the male is...

Habitat

Terrestrial in rainforests, especially in leaf litter. BEHAVIOR Though poorly understood, the organism's foraging is thought to involve an excellent ability to respond to movement as detected by its 10 eyespots, as well as the detection of carbon dioxide given off by nearby hosts. Mechanoreceptors on the skin of these leeches allow them to pursue movements on land similar to footsteps. They move quite rapidly over surfaces in an inchworm fashion.

Sea slugs

Phylum Mollusca Class Gastropoda Subclass Opisthobranchia Number of families 110 Marine snails found in oceans throughout the world the diversity encompasses species that range in habit from pelagic to burrowing, in color from transparent to vividly colored, and in structure from those with protective shells to soft-bodied forms with flowing movements Photo This small nudibranch (Glossodoris stel-latus) is laying eggs. The swirl pattern of egg laying is a common one the color of the eggs is...

Significance to humans

Many kinds of bivalves, especially clams, cockles, mussels, oysters, and scallops, have served as important food sources for fish, vertebrates, other invertebrates, and humans. Aboriginal populations of many cultures have left evidence of eating bivalves in their kitchen middens (mounds or deposits of refuse from meals). Recent practices rely both on harvesting wild populations and on aquaculture in either open or closed aquatic systems. Members of the marine Pteriidae and freshwater Unionoidea...

Chitons

Phylum Mollusca Class Polyplacophora Number of families 10 Mollusks with a flattened, ovoid shape, broad ventral foot, and eight (sometimes seven) dorsal shell plates that overlap one another and allow the animal to bend and mold itself onto a rock to avoid wave dislodgement Photo The lined chiton (Tonicella lineata) is a slow moving mollusk with a shell composed of multiple plates. (Photo by David Hall Photo Researchers, Inc. Reproduced by permission.) The earliest fossil chitons occur in the...

Behavior

The large number and sheer diversity of protostomes necessitates a restriction on the kinds of behaviors (and species) that can be discussed in this chapter. The behaviors highlighted here are based in part on their importance to the survival of an individual organism. Protostomes are some of the most morphologically complex, ecologically diverse, and behaviorally versatile organisms in the animal kingdom. They consist of more than one million species divided into approximately 20 phyla. Major...

Feeding Ecology And Diet

It is a filter-feeding worm, dining on suspended organic material. Sea water is pumped through the tube by winglike notopo-dia, which secrete mucus that is drawn back, forming a bag. Blake, James A., B. Hilbig, and P. H. Scott. The Annelida Part 2 Polychaeta Phyllodocida (Syllidae and Scale-bearing families), Amphinomida and Eunicida. Taxonomic Atlas of the Benthic Fauna of the Santa Maria Basin and the Western Santa Barbara Channel series, Vol. 5. Santa Barbara, CA Santa Barbara Museum of...

Leeches

Leech Biology

Photo Newborn brood of aquatic leaf leeches. (Photo by Animals Animals K. Atkinson, OSF. Reproduced by permission.) Leeches are completely soft-bodied animals and could not be expected to leave a marked fossil record. Although there are two putative fossils from Bavarian deposits dating from the Upper Jurassic period (about 145 million years ago), Epi-trachys rugosus (Ehlers, 1869) and Palaeohirudo eichstaettensis (Kozur, 1970), neither has both the definitive caudal sucker and the ring-shaped...

Evolution and systematics

Pentastomida once was classified as a minor phylum, a fact reflected in most modern textbooks of parasitology. The classification is being changed, however. The evolutionary history of tongue worms is unique among parasites. The fossil record apparently extends to the late Cambrian period (500 million years ago mya ), exceeding that of the next oldest parasites, certain copepods, by some 370 million years. Tiny fossil tongue worms have been etched from ancient fine-grained, deep-water limestone...

Protostomes order list

Annelida Phylum Polychaeta Class Haplotaxida Order Lumbriculida Moniligastrida Opisthopora Arhynchobdellae Order Rhynchobdellida Aspidosiphoniformes Order Golfingiaformes Phascolosomatiformes Sipunculiformes Bonellioinea Order Echiuroinea Heteromyota Xenopneusta Arthropoda Phylum Crustacea Subphylum Remipedia Class Anostraca Order Notostraca Conchostraca Cladocera Malacostraca Class Phyllocarida Subclass Maxillopoda Class Thecostraca Subclass Acrothoracica Order Ascothoracica Rhizocephala...

O T

Institute of Ornithology, Heligoland R Ornithological Station T Dr. Peter Roben Academic Councillor, Zoological Institute, Heidelberg University Heidelberg, Germany Dr. Anton E. M. De Roo Royal Museum of Central Africa Tervuren, South Africa Dr. Hubert Saint Girons Research Director, Center for National Scientific Research Brunoy (Essonne), France Dr. Luitfried Von Salvini-Plawen First Zoological Institute, University of Vienna Vienna, Austria Dr. Kurt Sanft Oberstudienrat, Diesterweg-Gymnasium...

Peanut worms

Photo Peanut worm (Phascolosoma sp.) with partially extended introvert. (Photo by L. Newman & A. Flowers. Reproduced by permission.) No unambiguous fossil Sipuncula are currently known. Ot-toia prolifica from the Burgess Shale has been proposed as a fossil sipunculan, but might also be an aschelminth or Pria-pulida. The paleozoic Hyolitha has a mix of attributes of sipunculans and mollusks, suggesting a close phylogenetic relationship with both. Fossilized burrows possibly created by...

Lungbearing snails and slugs

Land Snails Reproduction

Number of families Approximately 120 Mainly terrestrial but also freshwater and marine slugs and snails, almost all having an enclosed lung Photo A garden snail Helix aspersa issuing defensive foam. Photo by Holt Studios, Int. Photo Researchers, Inc. Reproduced by permission. The earliest fossil pulmonate land snails date back over 300 million years to the Carboniferous period of North America and Europe, although there is some controversy as to whether these belong to primitive pulmonate...

Hydrothermal vent and cold seep worms

Hydrothermal Vent Vestimentiferans

Phylum Vestimentifera Number of families 8 Segmented worms that have an unusual anatomy and rely on symbiotic bacteria for nutrition. They are nearly always found in deep waters, some as members of hydrothermal vent communities and others found in association with reducing sediments such as cold seeps Photo This photo of Riftia pachyptila comes from a depth of 8,200 ft 2,500 m at 9 50 N. on the East Pacific Rise, and was shot on a dive in the submersible Alvin. Photo by Craig M. Young, Oregon...

Aplacophorans

Photo A caudofoveatan species unknown seen in the Antarctic. Photo by S. Piraino University of Lecce . Reproduced by permission. The class Aplacophora contains two subclasses Neome-niomorpha also called Solenogastres and Chaetodermo-morpha also called Caudofoveata . Most neomenioids creep by means of a narrow foot with a ventral groove that begins as a pedal pit toward the front of the animal. They have a sensory vestibule above the mouth a single midgut organ combining stomach and digestive...

Ovotestis Posterior hermaphrodite duct

Illustration by Christina St. Clair short periods of time as well. Benthic sea slugs are slow-moving organisms. They live relatively sedentary lives, and some species spend their entire life on one prey organism such as a sponge or coral reef. Almost all dispersal to new areas occurs during the veliger larval stage veligers will settle out of the water column only when suitable substrate is present. Some larvae have crossed entire ocean basins because of lack of suitable...

Earthworms

Photo A giant earthworm Haplotaxida burrows back into the moist leaf litter in the subtropical rainforest floor. Photo by Wayne Lawler Photo Researchers, Inc. Reproduced by permission. Earthworms belong to a well-defined clade, the Clitellata, which includes leeches, branchiobdellids, many aquatic and small terrestrial worms with a single cell-layered clitellum, and the earthworms, most of which have a multi-layered clitellum. However, earthworms as a group lack a defining characteristic unique...

Beard worms

Reproduction Biology

Phylum Annelida Class Pogonophora Number of families 13 Tube-living marine worms nourished by internal chemoautotrophic bacteria. Photo Ridgeia piscesae at Middle Valley hydrothermal site in the northeast Pacific Ocean, photographed through the porthole of Alvin, the Navy-owned deep submergence vehicle. The tubes are 0.20-0.39 in 5-10 mm in diameter. Photo by E. C. Southward. Reproduced by permission. The name Pogonophora comes from the Greek pogon, meaning beard, and phora, meaning bearing,...

Tantulocarida

Millipedes Have Two Penises

Phylum Arthropoda Subphylum Crustacea Class Maxillopoda Subclass Tantulocarida Number of families 4 Tiny parasitic crustaceans that spend most of their lives attached to the external body surface of their hosts, a wide range of other marine crustaceans Photo The tantulus larva and globular adult female of Microdajus langi, a tantulocaridan parasite, attached to its host, a tanaidacean crustacean. Photo by G. A. Boxshall. Reproduced by permission. Photo The tantulus larva and globular adult...

Clam sand and tubeworms

Chaetopterus Variopedatus

Phylum Annelida Class Polychaeta Number of families 86 Segmented worms with numerous bristles and one pair of parapodia per segment Photo Bristle or fire worms Chloeia sp. primarily come out at night and are scavangers. Photo Tony Wu www.silent-symphony.com. Reproduced by permission. Phylum Annelida Class Polychaeta Number of families 86 Segmented worms with numerous bristles and one pair of parapodia per segment Photo Bristle or fire worms Chloeia sp. primarily come out at night and are...

Lophogastrids

Phylum Arthropoda Subphylum Crustacea Class Malacostraca Order Lophogastrida Number of families 2 Small shrimplike marine crustaceans with elongate carapaces covering, but not fused to, all thoracic somites segments stalked eyes and strongly developed swimming legs on the first five abdominal somites Illustration Giant red mysid Gnathophausia ingens . Illustration by John Megahan

Millipedes

Allergic Reaction From Millipede Photos

Photo A millipede Sigmoria aberrans displaying warning colors. Photo by Gilbert S. Grant Photo Researchers, Inc. Reproduced by permission. The class Diplopoda contains about 10,000 described species in 15 orders and 148 families. Scientists believe that as many as 70,000 additional species have yet to be identified. The millipedes were once classified as a subclass of the class Myriapoda, which also contained the centipedes now assigned to class Chilopoda . Since then, all four major myria-pod...

Reproductive Biology

Reproduction Biology

CONSERVATION STATUS Not listed by the IUCN. SIGNIFICANCE TO HUMANS None known. Barnes, Robert D. Invertebrate Zoology. 4th ed. Philadelphia Saunders College Publishing, 1980. Beesley, Pamela L., Graham J. B. Ross, and Alice Wells. Mollusca The Southern Synthesis, Part A. Canberra Australian Biological Resources Study, 1998. Geise, Arthur C., and John S. Pearse. Reproduction of Marine Invertebrates. Vol. V, Mollusks Pelecypods and Lesser Classes. London Academic Press, 1975. Purchon, R. D. The...

Symbiosis

Examples Parasitism

Without symbiosis, living organisms would be quite different from what they are today. This is true not only because symbiotic relationships were fundamental to the separation of eukaryotes organisms whose cells have true nuclei from prokaryotes cellular organisms lacking a true nucleus , but also because they represent a unique biological process without which many organisms could not exist. All herbivorous mammals and insects, for example, would starve without their cellulose-digesting...

Startle Displays And Flash Coloration

When stimulated by an aggressor, some protostomes quickly modify their posture to make them appear larger and at the same time to quickly present a flash of color. The various postures and displays are characterized by their position, such as frontal displays and lateral displays. The colors associated with these displays are often effective forms of defense because aggressors learn to associate certain colors with results that may have occurred through prior interaction with the intended prey....

Reproduction development and life history

Hydrostatic Skeleton Earthworms

All animals must reproduce, passing copies of their genes into separate new bodies in future generations. These genetic copies may be genetically identical, produced by asexual processes, or genetically distinct, produced by sexual processes. In sexual processes, which are by far the more common among animals, the initial result of reproduction is a single cell, known as a zygote, containing the new and unique set of genes. Yet, by definition animals are multicellular, and generally consist of...

Isopoda

Families Terrestrial Isopoda Oniscidea

Phylum Arthropoda Subphylum Crustacea Class Malacostraca Order Isopoda Number of families Approximately 120 Small, generally gray, usually flat, marine, freshwater, or terrestrial animals with numerous legs some species are parasitic Photo Pill woodlouse Armadillidium vulgare rolled up in defensive mode. Photo by Nigel Cattlin Holt Studios Int'l Photo Researchers, Inc. Reproduced by permission. With approximately 10,000 known species in 10 suborders, the order Isopoda falls under the class...

Predatory Feeders

Arguably the most sophisticated protostome feeders are those that obtain food by hunting, which requires the animal to locate, pursue, and handle prey. Most invertebrates locate prey by chemoreception others use vision, tactile, or vibration, or some combination thereof. Predators can be classified as stalkers, lurkers, sessile opportunists, or grazers. Planarians Platyhelminthes are an excellent example of animals that obtain food through hunting. The vast majority of planarians are...

Thecostraca

Anatomy Goose Barnacle

Phylum Arthropoda Subphylum Crustacea Class Maxillopoda Subclass Thecostraca Number of families 48 Highly modified, mainly free-living sessile and parasitic crustaceans, usually enclosed within a calcareous carapace or forming a chitinous saclike body Photo Species of the genus Synagoga, found on the species Antipathella wollastoni at a depth of 131 ft 40 m in waters off of the Azores. Photo by Peter Wirtz. Reproduced by permission. The calcareous carapaced forms of thecostracans have provided...

What is a protostome

Meaning Protostome

The term Protostomia from the Greek proto, meaning first, and stoma, meaning mouth was coined by the biologist Karl Grobben in 1908. It distinguishes a group of invertebrate animals based upon the fate of the blastopore the first opening of the early digestive tract during embryonic development. Animals in which the blastopore becomes the mouth are called protostomes those in which the mouth develops after the anus are called deuterostomes from the Greek deutero, meaning second, and stoma,...

Echiurans

Bonellia Male Female

Photo A spoon worm Bonellia in Western Australia, with its forked tongue fully extended. Photo by L. Newman amp A. Flowers. Reproduced by permission. As the echiurans' body has no large hard parts, fossils of these animals are rare. There are two fossils for this group a fossil from Illinois, United States, dated from the Late Carboniferous and another fossil from Namibia, dated from the Late Cambrian. A free-swimming trochophore larva is present in echiurans, sipunculans, mollusks, and...