Higher Invertebrates

1. Chapter 9 Higher Invertebrates

2. Phylum Mollusca • One of the most successful groups of animals in the ocean • Have soft bodies, usually covered by a calcium carbonate shell • Wide range of sizes, lifestyles and relationships to humans (i.e., some are food, others cause commercial damage)

3. Molluscan Body • 2 major parts: • head-foot: region containing the head with its mouth and sensory organs and the foot, which is the animal’s organ of locomotion • visceral mass: dorsal body region containing the other organ systems, including: • circulatory (heart and vessels) • digestive (stomach, digestive glands, intestine and anus) • respiratory (gill) • excretory reproductive systems

5. Molluscan Body • Mantle • protective tissue covering soft parts, extends from the visceral mass and hangs down on each side of the body, secretes the shell • mantle cavity: space between the mantle and the body • Radula • a ribbon of tissue containing teeth (found in all except bivalves) used for scraping, piercing, tearing or cutting pieces of food

6. Chitin Molluscs • Class Polyplacophora - Chitons • Have flattened bodies often covered by 8 shell plates • Attach tightly to rocks, usually in intertidal zone • Most scrape algae and other organisms off the rocks with radulae for food

8. Gastropod Molluscs • Class Gastropoda • May have no shell (nudibranchs), or a univalve (one-piece) shell • as the animal grows, whorls of the shell increase in size around a central axis

9. Feeding and nutrition for gastropods • exhibit wide variety of feeding styles • herbivores – using their radula, most feed on fine algae; some on large algae like kelps • carnivores – usually locate prey using its chemical trail; have evolved various behaviors for capturing/subduing prey • scavengers and deposit feeders • filter feeders

10. Bivalve Molluscs • Class Bivalvia • Have shells divided into 2 jointed halves (valves) • Includes: • clams • oysters • mussels • scallops

11. Bivalve anatomy • no head or radula • laterally compressed bodies • shell halves attached dorsally at a hinge by ligaments • mantle often forms inhalant and exhalant openings to facilitate filter feeding

13. Bivalve adaptations to different habitats • soft-bottom burrowers (infauna) • siphons: structures formed when the mantle is fused around inhalant and exhalant openings, which project above the surface of sediments • siphons facilitate filter feeding while remaining buried in sand

14. Cephalopod Molluscs • Class Cephalopoda • Squid • Octopus • nautilus • Named after the foot, which is modified into a head-like structure • Ring of tentacles projects from the anterior edge of the head, for use in prey capture, defense, reproduction and sometimes locomotion • Except for nautiloids, they lack shells or have small internal shells

15. Nautiloid cephalopods • produce large, coiled shells composed of chambers separated by septa (partitions) • gas-filled chambers aid with buoyancy • siphuncle: cord of tissue connecting the nautiloid to uninhabited chambers (it inhabits the last chamber) which removes seawater from each chamber as it forms • head has 60-90 tentacles coated with a sticky substance function in sensation or bringing food to the mouth

17. nautiloids (continued) • move using jet propulsion • usually dwell on the bottom during the day and migrate to the surface at night • eat hermit crabs and scavenge for other food on the bottom

18. squids have: • large cylindrical bodies with a pair of fins derived from mantle tissue • 10 appendages (8 arms + 2 tentacles) arranged in 5 pairs around the head and embellished with cup-shaped suckers which are attached by a short stalk and surrounded by toothed structures • the pen (a degenerate shell; an internal strip of hard protein) helps support the mantle

21. Octopus • octopods have 8 arms (no tentacles) with suckers without stalks or teeth, and sac-like bodies without fins • coleoids cloud water with a dark fluid called sepia containing melanin (a brown-black pigment) when disturbed • swim by jet propulsion by forcing water through a ventrally-located siphon or by fin undulation (in squids) • octopods – better adapted to crawling over bottom • have the most advanced, complex nervous system among invertebrates

22. Color and shape in cephalopods • arm/body movements and color changes are used in communication • chromatophores: special skin cells containing pigment granules which are concentrated or dispersed to change color • cephalopods can produce general body color changes or stripes and other patterns

23. Feeding and nutrition • carnivores – prey is located with highly developed eyes and captured by tentacles or arms • a pair of powerful, beak-like jaws in the oral cavity is used to bite or tear tissues; octopods use radula to drill holes in shells • diet depends on and varies with habitat • squids are pelagic: fish, crustaceans, squid • cuttlefish find invertebrates on the bottom • octopods forage or lie in wait near the entrances to their dens

24. Fun octopus links • https://www.youtube.com/watch?v=PmDTtkZlMwM • https://www.youtube.com/watch?v=IvvjcQIJnLg • https://www.youtube.com/watch?v=5MHJbxWO6OM

25. Ecological Roles of Molluscs • Food for humans and other animals • snail shells are a calcium source for some marine birds • sperm whales consume masses of squid • Some snails are intermediate hosts to parasites • A few bivalves have commensal relationships (attaching to other animals)

26. Now we will talk about Annelids (segmented worms)

27. Annelids: The Segmented Worms • Annelids—worms whose bodies are divided internally and externally into segments • segments increase mobility by enhancing leverage • hydrostatic skeleton – compartment contained fluid providing support to worm body • setae—small bristles used for locomotion, digging, anchorage and protection • Types of marine annelids • polychaetes • echiurans • Pogonophorans – tube worms

29. Polychaetes • Polychaetes (class Polychaeta) are the most common marine annelids

30. Polychaetes • Feeding and digestion • some errant species have mouth equipped with jaws and teeth and are active predators; tube dwellers may partially or completely leave the tube to feed • many sedentary species are filter or suspension feeders • digestive tract is usually a straight tube from the mouth to the posterior anus • food enters the mouth, nutrients are absorbed in the intestine, and wastes are excreted through the anus

31. Pogonophoran Annelids – deepsea worms near hydrothermal vents

32. Now we will talk about Nematodes

33. Nematodes • Class Nematoda (Roundworms) • Round, slender, elongated bodies, tapering at both ends • Critical role as scavengers • Some are parasitic • Mast are hermaphroditic, some have separate sexes

34. Ecological Role of Marine Worms • Nutrient cycling • through burrowing in sediment, release nutrients buried in the ocean bottom back to the surface for use by producers • Predator-prey relationships • Important links in food chains – consume organic matter unavailable to larger consumers, and then become food for largaer consumers themselves

35. Ecological Role of Marine Worms • nematodes are the most abundant members of meiofauna • echiurans may be significant in the diet of some fishes • polychaetes are a major food source for invertebrates and vertebrates • Symbiotic relationships • tubes and burrows of non-carnivorous polychaetes provide protected and ventilated retreat for many commensals, e.g., scale worms, bivalves, small crabs

36. Now we will talk about the Arthropods • Arthropods include insects and crustaceans • Most numerous animals on Earth • Very successful

37. Arthropods: Animals with Jointed Appendages • Phylum Arthropoda = 75% of identified species (include insects) • Have exoskeleton—a hard, protective exterior skeleton composed of protein and chitin • Molting—shedding and replacement of exoskeleton to permit animal’s growth • Body is divided into segments • Usually, each segment has a pair of jointed appendages, for locomotion, mouthparts, sensation, ornamentation

38. Arthropods: Animals with Jointed Appendages • Have highly developed nervous systems • sophisticated sense organs • capacity for learning • 2 major groups of marine arthropods: • chelicerates – have a pair chelicerae (oral appendages) and lack mouthparts for chewing food • crustaceans – have appendages called mandibles that can be used to chew food

39. Arthropod Chelicerates • Primitive group include spiders, ticks, scorpions, horseshoe crabs and sea spiders • 6 pairs of appendages; 1 pair are chelicerae for feeding • Horseshoe crabs • 3 body regions • cephalothorax – largest region with the most obvious appendages • abdomen – contains the gills • telson – a long spike used for steering and defense • body is covered by a carapace—a hard outer covering

41. Arthropod Chelicerates • Horseshoe crabs (continued) • locomotion by walking or swimming by flexing the abdomen • mostly nocturnal scavengers • smaller males attach to females to mate, and eggs are laid in a depression on the beach; larvae return to the sea to grow

42. Arthropod Chelicerates • Sea spiders • have small, thin bodies with 4 or more pairs of walking legs • feed on juices from cnidarians and other soft-bodied invertebrates, using a long sucking proboscis

43. Arthropod Crustaceans • Crustaceans—marine mandibulates • Crustacean anatomy • 3 main body regions: • head • thorax • abdomen • appendages: • 2 pairs of sensory antennae • mandibles and maxillae used for feeding • walking legs, swimmerets (swimming legs), legs modified for reproduction, chelipeds (legs modified for defense)

46. Arthropod Crustaceans • gas exchange • small crustaceans exchange gases through their body surface • larger crustaceans have gills • Molting • Crucial part of the life cycle • Frequency of molting decreases with age • Controlled by specific hormones produced in a gland in the head, initiated by environmental conditions, e.g., temperature, photoperiod

47. Decapod Crustaceans • Order Decapoda • Crustacean animals with 5 pairs of walking legs: • crabs • lobsters • true shrimp • 1st pair of walking legs are chelipeds—pincers used for capturing prey and for defense • Wide range in size