9 public questions tagged with this topic.
Crustaceans, like prawns, excrete wastes through antennal (or green) glands.
Ref: NCERT Class 11 Biology Chapter 16: Excretory Products and their Elimination Urine Formation - Glomerular Filtration
Green glands (also called antennal glands) perform excretory functions in crustaceans like prawns.
Ref: NCERT Class 11 Biology Chapter 16: Excretory Products and their Elimination Nephron Structure - Glomerulus and Bowmans Capsule
Green glands (also called antennal glands) in crustaceans help regulate salt and water balance.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Arthropoda
Crustaceans, such as crabs and prawns, have green glands for excretion.
Ref: NCERT Class 11 Biology Chapter 4: Animal Kingdom Phylum Arthropoda
Malacostraca represents dominant and most diverse crustacean class incorporating familiar decapods like brachyuran crabs, lobsters, shrimps and prawns plus peracarids such as amphipods and isopods and euphausiaceans krill. Body plan consists of 8 thoracic segments forming thorax covered partially or fully by carapace, 6 abdominal segments plus telson, pleopods and gills. Branchiopoda includes fairy shrimp and cladocerans, Ostracoda bean-like bivalved forms, Copepoda tiny copepods dominating zooplankton. Malacostracan ecological success attributes to carapace protection, efficient gill respiration and versatile appendage specialization supporting benthic, pelagic and terrestrial niches.
Ref: Campbell Biology, 12th ed., Chapter 33: Malacostraca; NCBI Bookshelf, Crustacea Classification
Crustaceans as ancestral mandibulate arthropods characteristically bear two pairs of antennae, first antennae called antennules often biramous with aesthetascs for chemoreception and second antennae frequently longer with exopod scale for swimming and mechanoreception. This dual antennal configuration doubles sensory input and enhances equilibrium via statocysts at base. Insects, myriapods and chelicerates have one pair or lack antennae entirely due to evolutionary reduction, cephalization and tagmosis. Presence of two pairs distinguishes Crustacea taxonomically from Atelocerata or Hexapoda and Chelicerata, reflected in head appendage formula used in classification keys and phylogeny.
Ref: Brusca & Brusca, Invertebrates, 3rd ed., Crustacea Antennae; NCERT Class 11, Chapter 4, Arthropoda
Nauplius is diagnostic first free larval stage of Crustacea exhibiting unsegmented ovoid body, single median naupliar eye, and three pairs of appendages: first antennae antennules for swimming, second antennae and mandibles. It swims using second antennae, feeds on yolk or microplankton depending on lecithotrophic or planktotrophic mode, then molts through successive stages adding trunk segments, thoracic appendages, compound eyes developing into metanauplius, protozoea, zoea and mysis in decapod sequence. Veliger characterizes molluscs, trochophore annelids and molluscs, pilidium nemerteans. Nauplius therefore marks crustacean development and dispersal.
Ref: Campbell Biology, 12th ed., Chapter 33: Crustacean Larvae Nauplius; Hickman et al., Chapter 20
Crustacean excretory organs are antennal or green glands situated within cephalothorax at base of second antennae, named for greenish pigmentation. Each comprises end sac where hemolymph filters across coelomosac forming primary urine, labyrinth for selective reabsorption and secretion adjusting salt balance in marine versus freshwater habitats, and bladder storing excreta before discharge via nephropore on antenna. Ammonia excretion diffuses also across gills. Arachnids use coxal glands and Malpighian tubules, insects Malpighian tubules, myriapods Malpighian tubules. Antennal gland structure parallels vertebrate nephron functional analogy but anatomically distinct as crustacean diagnostic.
Ref: Hickman et al., Chapter 20: Crustacean Antennal Glands; Brusca & Brusca, Chapter 20, Excretion
Aquatic arthropods predominantly respire using gills, diverse filamentous or lamellate outgrowths with large surface area and thin diffusion barrier. Crustacean gills classified as phyllobranchiate or trichobranchiate, located in branchial chambers ventilated by bailer appendage scaphognathite. Horseshoe crabs possess book gills, leaf-like lamellae attached to opisthosomal appendages. Book lungs and internal tracheal tubes are terrestrial adaptations reducing evaporative loss, forming air-filled invaginations with hemolymph counterflow. Cutaneous skin diffusion insufficient for larger active arthropods. Hence gill retention reflects secondary aquatic lifestyle and requirement for efficient oxygen extraction from water.
Ref: Brusca & Brusca, Invertebrates, 3rd ed., Arthropod Respiration Gills; Campbell Biology, 12th ed., Chap 42
