chapter 28

Diversity of Invertebrates II Lecture 28

General Information

• Location: Namaqumaqua, Viti Levu, Fiji
• Date: 24 July 2019
• Focus: Indo-Pacific Christmas Tree Worm (Spirobranchus corniculatus)

Biblical Reference

• Reference from Gospel of Matthew: "Again, the kingdom of heaven is like a merchant looking for fine pearls. When he found one of great value, he went away and sold everything he had and bought it." – Matthew 13:45-46 NIV

Ribbon Worms (Phylum Nemertea)

General Characteristics

• Exhibit bilateral symmetry.
• Bodies are elongated and lack segmentation.
• No true head; possesses a complete gut.
• Example: unidentified ribbon worm (Paranemertes sp.), observed in Mendocino Headlands, California, on 8 October 2023.

Proboscis

• Definition: A simple or barbed structure at the anterior end of ribbon worms.
• Function: Used for injecting toxins to attack prey.

Structure of Ribbon Worms

• Key Components:
  • Eyes
  • Proboscis
  • Prey

Habitat and Diet

• Most ribbon worms are marine and benthic (living on the seafloor).
• They are primarily carnivorous but some may be symbiotic, living within other organisms.
• Example: unidentified ribbon worm (Paranemertes sp.), observed in Mendocino Headlands, California, on 3 October 2021.

Examples of Ribbon Worms

• Six-lined Ribbon Worm (Tubulanus sexlineatus), Mendocino Headlands, California, 15 May 2021.
• Ruber Ribbon Worm (Tubulanus ruber), Spring Ranch Preserve, California, 16 May 2021.

Segmented Worms (Phylum Annelida)

General Characteristics

• Highly variable in size and shape.
• Body is segmented.
• Example: unidentified polychaete observed in Albion, California, on 5 July 2024.

Polychaetes (Class Polychaeta)

• Definition: Characterized as "Many setae."
• Habitat: Nearly all species are marine.
• Some species are known to build reefs.
• Example: reef-building Sand-builder Worm (Sabellaria vulgaris), Port Mahon, Delaware, 4 June 2021.

Setae

• Definition: Bristles usually present on each body segment.
• Example: unidentified scaleworm (family Polynoidae), observed in San Francisco Bay, California, on 17 October 2016.

Parapodia

• Definition: Paddle-like appendages usually present on each segment.
• Example: unidentified scaleworm (family Polynoidae), observed in San Francisco Bay, California, on 17 October 2016.

Lifestyle of Polychaetes

• Variety of lifestyles including:
  • Crawling on the surface
  • Burrowing into sediments
  • Building tubes
• Example: Yellow Fanworm (Notaulax occidentalis), West End, Roatán, Honduras, 31 August 2017.

Examples of Polychaetes

• Bicanaliculate Worm (Platynereis bicanaliculata), Mendocino Headlands, California, 3 October 2021.
• Pacific Lugworm (Abarenicola pacifica), Albion, California, 29 June 2021.
• Pacific Feather Duster (Sabellastarte spectabilis), Kosrae, Micronesia, 19 June 2013.
• Caribbean Christmas Tree Worm (Spirobranchus giganteus), West End, Roatán, Honduras, 27 August 2012.
• Example: unidentified spiral tube worms (subfamily Spirorbinae) observed in Spring Ranch Nature Preserve, California, on 2 October 2021.

Segmented Worms (Class Clitellata)

Earthworms (Subclass Oligochaeta)

• Definition: Characterized by "Few setae" and absence of parapodia.
• Habitat: Mostly terrestrial and freshwater, with few marine species.
• Example: unidentified earthworm (family Lumbricidae) observed in Rosa de Saron, Amazonas, Brazil, January 2017.

Clitellum

• Definition: A section of swollen segments with reproductive structures.
• Example: unidentified earthworm (family Lumbricidae) observed in Angwin, California, 30 December 2023.

Leeches (Subclass Hirudinea)

• Characteristics: Setae and parapodia are absent; flattened and tapered at the front.
• Total segments: 34 segments.
• Example: unidentified jawless leech (family Piscicolidae) observed in San Francisco Bay, California, 4 November 2015.

Features of Leeches

• Suckers are located at the front and back of the body, surrounding the mouth.
• Clitellum is present.
• Habitat: Most leeches are freshwater or terrestrial with a parasitic lifestyle.
• Example: Brown Leech (Haemadipsa zeylanica) observed in Kottawa Conservation Forest, Sri Lanka, 14 July 2025.

Medical Use

• Anticoagulants, primarily hirudin, inhibit clotting and aid in enhancing blood flow for reattached skin and digits post-surgery.
• Example: attack by Brown Leech observed in Kottawa Conservation Forest, Sri Lanka, 14 July 2025.

Mollusks (Phylum Mollusca)

General Characteristics

• Exhibit bilateral symmetry.
• No segmentation in body structure.
• Soft body covered by a mantle that often secretes a limestone shell.
• Example: King Helmet Snail (Cassis tuberosa), St. Thomas, US Virgin Islands, 29 March 2003.

Body Structure

• Typically possess an anterior head and a muscular ventral foot.
• Example: African Giant Snail (Lissachatina fulica), Kosrae, Micronesia, 21 June 2013.

Radula

• Definition: A feeding structure with longitudinal rows of chitinous teeth, present in most groups of mollusks.

Venom and Feeding

• Radula is employed to inject a highly toxic venom in cone snails (family Conidae).
• Example: Geography Cone (Conus geographus).

Habitat and Diet

• Mollusks can be marine, freshwater, or terrestrial and occupy various ecological roles including filter feeders, herbivores, carnivores, scavengers, and parasites.
• Example: Garden Snail (Cornu aspersum), Lands End, San Francisco, California, 20 April 2025.

Gastropods (Class Gastropoda)

• Definition: Known as "Stomach foot," which includes snails, conchs, cowries, abalones, limpets, sea hares, nudibranchs, slugs, etc.
• Example: Queen Conch (Aliger gigas), West End, Roatán, Honduras, 9 September 2015.

Shell Characteristics

• Shells often spiral, but are absent in sea hares, nudibranchs, and slugs.
• Example: Mourning Dorid (Jorunna funebris), Kosrae, Micronesia, 17 June 2014.

Diet Variety

• Feeding strategies include herbivorous, carnivorous, scavenging, and parasitic behavior.
• Example: Eastern Oyster Drill (Urosalpinx cinerea), observed in Don Edwards San Francisco Bay National Wildlife Refuge, California, 15 January 2022.

Notable Species of Mollusks

• Fingered Limpet (Lottia digitalis), observed in Salmon Creek, California, 10 November 2015.
• Red Abalone (Haliotis rufescens), observed in Spring Ranch Nature Preserve, California, 13 September 2020.
• California Sea Hare (Aplysia californica), observed in Salmon Creek, California, 11 November 2015.
• Opalescent Nudibranch (Hermissenda opalescens), Mendocino Headlands, California, 1 July 2021.
• Button's Banana Slug (Ariolimax buttoni), in the wild, Kosrae, Micronesia, 18 June 2013.
• Illustrated species include Queen Conch (Aliger gigas) from Buccoo Reef, Tobago, 27 March 2012, and Ivory Cone (Conus eburneus), Nome, Fiji, 25 July 2019.
• Tiger Cowry (Cypraea tigris), observed in Kosrae, Micronesia, 18 June 2013.

Chitons (Class Polyplacophora)

• Characteristics: Flattened bodies covered dorsally by 8 overlapping shell plates, exclusively marine and common on rocky shores.
• Diet: Most are herbivorous, though a few are carnivorous.
• Examples: Regular Chiton (Tripoplax regularis), observed in Mendocino Headlands, California, 1 July 2021; Mossy Chiton (Mopalia muscosa), observed in Salmon Creek, California, 13 April 2015; Flame Lined Chiton (Tonicella lokii), Point Arena, California, 13 October 2019; Gumboot Chiton (Cryptochiton stelleri), observed in Mendocino Headlands, California, 27 April 2024.

Bivalves (Class Bivalvia)

• Definition: Characterized by "Two valves" including clams, mussels, oysters, scallops, etc.
• Morphology: Bodies are laterally compressed with dorsally hinged valves and poorly developed heads.
• Feeding Strategy: Most are filter feeders.
• Examples: Noah’s Giant Clam (Tridacna noae), observed in Mana Island, Fiji, 20 July 2019; Nutall's Cockle (Clinocardium nuttallii), observed in Seward, Alaska, 19 July 2016; various species like Eastern Oyster (Crassostrea virginica), Atlantic Ribbed Mussel (Geukensia demissa), and California Mussel (Mytilus californianus) observed across different locations and dates.

Tusk shells (Class Scaphopoda)

• Definition: Shells shaped like tusks, open at both ends, burrowing into soft sediments.
• Diet: Carnivorous.
• Example: Unidentified tusk shell observed in Galle, Sri Lanka, 14 July 2025.

Cephalopods (Class Cephalopoda)

• Definition: Known as "Head foot."
• Notable extinct group: Ammonoids, abundant but extinct at the end of the Cretaceous period.
• Example specimen: unidentified ammonite at PUC Geology Museum, Angwin, California, 7 April 2015.

Major Groups Within Cephalopods

• Includes Nautiloids, squids, cuttlefishes, and octopuses.
• Body Structure: Most species lack a shell; cuttlefish possess an internal shell known as a cuttlebone, while nautiloids have a snail-like shell.

Unique Characteristics

• Body is elongated along the dorsoventral axis with highly developed lens eyes.
• Mouth features a horny, parrot-like beak with a pair of venom glands (modified salivary glands).
• Example: unidentified squid observed in Monterey Bay Aquarium, California, 26 October 1993.

Human Health Risks

• Several human deaths have occurred from bites of blue-ringed octopuses (genus Hapalochlaena)).
• Example: various unidentified blue-ringed octopuses observed.

Locomotion

• Cephalopods use jet propulsion for locomotion, with octopuses crawling using their arms or fins on their mantle (in the case of cuttlefishes).
• Example species includes Brazilian Reef Octopus (Octopus insularis) and various squid and octopus species observed in locations such as Roatán and Mendocino Headlands.

Roundworms (Phylum Nematoda)

General Characteristics

• Bilateral symmetry with elongated cylindrical bodies that are tapered at both ends.
• Usually very small, exhibit a peculiar thrashing motion.
• Example: Caenorhabditis elegans.

Habitat and Distribution

• Abundant and widespread across marine, freshwater, and terrestrial environments.
• Feeding Types: Herbivores, carnivores, and parasites.

Human Diseases Associated with Roundworms

• Intestinal diseases can arise from ingesting eggs through contact with human feces.
  • Notable species include:
  • Intestinal Roundworm (Ascaris lumbricoides).
  • Pork Worm (Trichinella spiralis) causing trichinosis from undercooked meats.
  • Hookworm species that penetrate through the skin (usually through the feet), including Ancylostoma duodenale and Necator americanus).

Closing Notes

Reminder for Students

• Prepare for a quiz covering lectures 27-28 (Chapter 33).

This study guide encompasses an extensive range of details from a lecture on invertebrate diversity, focusing on different classes and examples of invertebrates such as ribbon worms, segmented worms, mollusks, and roundworms.