Crustaceans Honor

Nature Study

Requirements

  1. Cite at least 4 characteristics of a crustacean.

    Answer: 1) Exoskeleton of chitin/carbonate. 2) Cephalothorax and abdomen. 3) Two pairs of antennae. 4) Jointed appendages. 5) Gills. 6) Mostly aquatic. 7) Molting (ecdysis). They belong to the phylum Arthropoda, class Crustacea. Each characteristic defines this unique group in real existing zoology. — Crustaceans are aquatic arthropods. Exoskeleton: protects and maintains shape; replaced during molts as the animal grows. Cephalothorax: head + thorax fused. 2 pairs of antennae: distinguishes them from insects (1 pair) and arachnids (0). Appendages: legs, chelipeds (claws), pleopods (swimming). Internal gills in a branchial chamber. Aquatic: marine (crab, lobster), freshwater (freshwater shrimp). Terrestrial: pillbug (Armadillidiidae) — the only fully adapted one. Ecdysis: shedding of the carapace with an increase in size. Economic and ecological importance.

  2. What is an exoskeleton?

    Answer: The exoskeleton is the external skeleton of arthropods (insects, arachnids, crustaceans), formed by chitin (a polysaccharide) and in some cases reinforced by calcium carbonate (in crustaceans). It protects internal organs, supports the body, prevents dehydration, and provides a surface for muscle attachment. It is periodically replaced through ecdysis (molting) as the animal grows. — External skeleton characteristic of arthropods. Composition: cuticle with 3 layers (impermeable epicuticle, hard exocuticle, flexible endocuticle). Chitin: nitrogenous polysaccharide. Calcification: crabs and lobsters have calcium carbonate for extra rigidity. Advantages: protection, support, muscle attachment, prevents water loss. Disadvantages: limits growth (requires molting), heavy at large sizes. Ecdysis is a vulnerable time: the animal is soft for hours. The old exoskeleton (exuvia) is frequently found.

  3. To which Phylum does this group belong?

    Answer: Crustaceans belong to the phylum Arthropoda, class Crustacea. Arthropoda is the most diverse phylum in the animal kingdom, including insects, arachnids, myriapods, and crustaceans. Characteristics: segmented body, chitin exoskeleton, jointed legs. Crustaceans are predominantly aquatic, with ~67,000 species described globally. — The phylum Arthropoda is the most diverse (more than 80% of known animals). Subphyla: Hexapoda (insects), Chelicerata (arachnids), Myriapoda (centipedes), Crustacea (crustaceans). Crustaceans: class Crustacea with subclasses such as Malacostraca (shrimp, crabs), Maxillopoda (barnacles, copepods), Branchiopoda (Artemia). 67,000+ cataloged species. Marine and freshwater life; some terrestrial. Economic importance: commercial fishing. Carl Linnaeus classified them in 1758.

  4. How is the body of these animals divided?

    Answer: The body is divided into two main parts: the cephalothorax (head + thorax fused, protected by the carapace) and the abdomen (the rear part, with pleopods in shrimp and a tail in lobsters). Jointed appendages emerge from the segments: antennae, mandibles, walking legs, and swimming pleopods. The tagmatic anatomy typical of the group. — Typical tagmatic anatomy. Cephalothorax: head + thorax fused under a single carapace, contains vital organs (brain, stomach, gills). Appendages: 2 pairs of antennae, mandibles, maxillae, pereiopods (walking legs, 5 pairs in decapods). Abdomen: 6 segments, pleopods (swimming), telson (last segment) with uropods forming the tail. Variations: crabs have a reduced abdomen folded under the cephalothorax. Tagmosis evolved independently several times, providing functional efficiency to crustaceans.

  5. In which book of the Bible, chapter, and verse do we find information telling us not to eat crustaceans?

    Answer: Leviticus 11:9-12 and Deuteronomy 14:9-10. Leviticus 11:10 teaches: 'But all that have not fins and scales in the seas, and in the rivers, of all that move in the waters, and of any living thing which is in the waters, they shall be an abomination unto you'. Crustaceans (shrimp, crab, lobster) have neither fins nor scales, being classified as unclean for food in the Mosaic law. — Mosaic law on clean and unclean foods. Lev 11:9-12: fish with fins + scales = clean; without both = unclean. Crustaceans are unclean: no fins, no scales. Adventists follow these dietary laws as healthful principles (not ceremonial). Reasons: filter-feeding animals accumulate toxins; high in cholesterol; frequent allergies. Other unclean sea creatures: octopuses, squid, sea urchins, mussels. Despite Acts 10 (Peter's vision), Adventists interpret it as an expansion of the gospel, not a dietary revocation.

  6. How can we tell a swimming crab from a true crab? In which environments do we find these animals?

    Answer: Swimming crab: the last pair of legs is paddle-shaped (flattened) for active swimming. True crab: pointed legs for walking. Swimming crabs live in marine waters and estuaries (Callinectes sapidus); true crabs live in mangroves, rocky shores, brackish water, and fresh water. Both are decapods with distinct adaptations: swimming crabs are swimmers, true crabs are walkers. — Morphological and ecological distinction. Swimming crab: flattened, paddle-shaped swimming legs; agile in the water. True crab: clawed legs for walking; slow in the water, agile on land. Swimming-crab habitat: beaches, flooded mangroves, estuaries — always close to salt/brackish water. True-crab habitat: mangroves (uçá crab), rocky shores (aratu crab), burrows. Crabs can stay out of the water for hours (modified respiration). Swimming crabs need to re-moisten their gills. Fishing: the blue crab is economically important. Distinct recipes: stuffed crab shell, crab stew.

  7. Cite an example of a terrestrial crustacean.

    Answer: Common pill bug (Armadillidium vulgare), also called roly-poly. It is a terrestrial isopod that curls into a ball when threatened. It lives in humid environments under rocks, logs, and decomposing leaves. It feeds on plant matter and detritus, being an important decomposer. The only crustacean fully adapted to life on land. — The common pill bug is the terrestrial crustacean par excellence. Family Armadillidiidae, order Isopoda. Size: 1-2 cm. It feeds on decomposing organic matter (saprophagous). Important in the cycling of soil nutrients. Defense: curling into a ball (rolling, similar to mammalian armadillos — evolutionary convergence). Other terrestrial isopods: Porcellio scaber. Common in gardens, under pots, in compost. Harmless. They still depend on moisture because they breathe through modified gills (pseudotracheae).

  8. How can we tell male and female swimming crabs (or true crabs) apart? Why is this important?

    Answer: Males: narrow, triangular abdomen folded under the carapace. Females: wide, rounded, half-moon-shaped abdomen to shelter eggs. When carrying eggs, they hold the egg mass under the abdomen. Important for conservation: fishing for egg-bearing females is prohibited in Brazil by IBAMA, ensuring the natural reproduction of populations. — Differentiation by abdominal dimorphism. Males: narrow, triangular abdomen (reflects a different reproductive function). Females: wide, rounded abdomen to accommodate eggs under protection. Females with visible eggs (in cluster form) are called 'egg-bearing' or 'berried'. Importance of conservation: Federal Law and IBAMA prohibit the capture of egg-bearing females and during the closed season (generally November-March). Heavy fines. Sustainable fishing: undersized males are released; egg-bearing females are always returned. Principle: preserve reproduction = preserve future fishing.

  9. What is the importance of microcrustaceans to the environment?

    Answer: Microcrustaceans (copepods, daphnia, fairy shrimp) form the base of the aquatic food chain. They filter water and plankton, feeding fish, whales, and larvae. Bioindicators of water quality. They recycle nutrients. Without them, aquatic ecosystems would collapse for lack of a link between phytoplankton and larger fish. — Microcrustaceans = critical ecological link. Copepods (Calanoida): the most abundant of the plankton, the food base of blue whales (which eat 4 tons/day). Daphnia (Cladocera): 'water fleas' in lakes. Fairy shrimp (Anostraca) in temporary pools. Antarctic krill: feeds whales. Importance: 1) food chain (phytoplankton → microcrustaceans → fish); 2) nutrient cycling; 3) bioindication (sensitive species die in polluted water). Copepods are estimated to form the largest animal biomass on the planet.

  10. Carry out 2 of the following items, presenting an illustrated report:
    • Dissect a shrimp and identify its main parts.
    • In a practical lesson, observe, live or preserved, various types of crustaceans. Sketch at least 2 of them.
    • Be able to tell the difference between a land crab and a swimming crab, and know how to distinguish between male and female.

    Answer: Option 1: dissect a shrimp and identify the antennae, cephalothorax, pleopods, telson, and gills with an illustrated report. Option 2: a practical class with various live or preserved crustaceans, diagramming 2 of them. Option 3: a field outing identifying true crabs vs swimming crabs and their sexes with photos. Present a report with photos, drawings, and technical captions to the Honor instructor. — Hands-on activities. Dissection: fresh shrimp from the market, scalpel, magnifying glass, dish. Identify: rostrum, antennae, stalked eyes, cephalothorax (with internal gills), abdomen, swimming pleopods, telson, uropods. Practical lesson: visits to public aquariums (São Paulo Aquarium, Ubatuba), biology colleges, fish markets. Sketching: draw in pencil, identify parts. Field work: beaches and mangroves — observe behavior, sexing in situ. The illustrated report integrates theory and practice.

  11. Be able to identify, in person or through images, the following animals:
    • Barnacles
    • Hermit crab
    • Garden woodlouse (pillbug)
    • Lobster
    • Shrimp
    • Land crab
    • Swimming crab

    Answer: Barnacles: conical, on rocks and hulls. Hermit crab: uses a snail shell as its home. Pillbug: terrestrial, rolls into a ball. Lobster: large, long antennae, strong tail. Shrimp: small, transparent, elongated abdomen. Crab (caranguejo): walker, pointed legs. Swimming crab (siri): paddle-shaped legs for swimming. Each species has distinct morphology. — Visual catalog. Barnacles (Cirripedia): sessile, with calcareous plates. Hermit crab (Anomura): soft abdomen protected by an empty shell. Pillbug (Isopoda): the only adapted terrestrial one. Lobster (Decapoda): high commercial value, long antennae that detect movement. Shrimp: laterally compressed body, swimming efficiency. Crab (Brachyura): reduced abdomen. Swimming crab (siri): agile swimmer. Identification by photos requires attention to body shape, leg type, and habitat. Guide: 'Crustáceos do Brasil' (Melo).