The maggot is the larva of the fly and the zoea is the larva of the crab. A photo of the Zoea of Homarus gammarus. Photo by Hans Hillewaert under Creative Commons license. Many crustacean larvae were not immediately recognized as larvae when they were discovered and described as new genera and species. The names of these genera have been generalized to cover specific larval stages in large groups of crustaceans such as Zoea and Nauplius. Other terms describe forms that occur only in certain groups, such as the hermit crab glaucothoa or the slipper lobster and crayfish phyllosome. The genus Zoea was first described in 1802 by Louis Augustin Guillaume Bosc for an animal that is now known to be the larva of a crab. [1] The Zoea stage (plural: Zoeas or Zoeae), which occurs only in Malacostraca limbs,[5] is characterized by the use of mammary appendages for swimming and a large dorsal spine. [5] These modified zoeae are pelagic for periods of 3 to 4 weeks to 9 months in small reefs or large soil types.

and some thoracic limbs, the Zoea uses its thoracic limbs to swim, and the postlarval stages use the abdominal appendages. Most decapods skip the nauplius stage and hatch as zoeae, which can be heavily decorated with spines. The Zoea crab eventually turns into a megalope, resembling a small crab. More completely, the life cycle of a crustacean begins with an egg, which is normally fertilized but can instead be produced by parthenogenesis. This egg hatches in prelarva or pre-zoea. Through a series of moults, the young then pass through different zoea stages, followed by a megalope or post-larva. This is followed by metamorphosis into an immature form, which largely resembles the adult, and after a new molt, the adult form is finally reached. Some crustaceans continue to moult into adulthood, while for others, gonad development signals final moulting. Lipopolysaccharide and β-1,3-glucan binding proteins (LGBP) contain two polysaccharide recognition motifs for polysaccharide binding and one β-glucan recognition motif, sensor bacteria, and β-1,3-glucan (from yeast and fungi) (Nam et al., 2016). An LGBP (SpLGBP) has been cloned and characterized in silt crab, which is detected only in the late embryonic stages and its transcription levels are increased until it hatches as Zoea I larva, indicating the protective role of SpLGBP at Zoea I stage (Ma et al., 2019). In addition, evidence suggests that SpLGBP plays an important role in the innate immune system in the early stages of development of mud crabs.

The SpLGBP of the mud crab is the first to be purified and characterized (Ma et al., 2019). It contains several conserved domains, including two nitrogen-bound glycosylation sites, two integrin-binding units, a C-kinase phosphorylation site, a bacterial glucanase motif, and a β-1,3 bond of a polysaccharide recognition motif. Because conserved domains exist in the mud crab sequence, SpLGBP could recognize invasive pathogens as PRR, just as other crustaceans recognize LGBP. Real-time quantitative RT-PCR analysis showed that SpLGBP transcription increased in haemocytes and hepatopancreas within hours of challenge with LPS or V. parahaemolyticus. Recombinant SpLGBP could bind to LPS and peptidoglycan (PGN) and clump together with gram-positive and gram-negative bacteria in a Ca2+-dependent manner. The above results showed that SpLGBP played an important role as an PRR in pathogenic infections. SpLGBP responses have been shown to be associated with binding to bacterial cell membrane components, promoting bacterial agglutination, stimulating downstream innate immune pathways, and activating immune components that protect mud crab from invading pathogens (Ma et al., 2019).

The number of species represented in marine zooplankton is greatly enriched by the pronounced dispersal stages of many marine animals that spend their adult lives in the coastal or benthic zone. To varying degrees, these larvae are (the Amphiblastulae of sponges, the jellyfish and ephyres of the cnidarians coelenterates, the tilidia of the Nemerteans, the trochospheres of the polychaetes, the cypris larvae of the Cirripedes, the phyllosomes and zoeae of the Eucaridus malacostraca, the veligères of the lamellibranch molluscs, the various Auriculariae, Bipinnariae and plutei of echinoderms and the appendicular larvae of Ascidiana; (see Table II) share the tiny size ranges characteristic of species, membranous clarity and low swimming movements that are planktonic throughout their lives. Smaller examples (<20 μm) of these heterotrophic protists include nanoflagellates (some are closely related to photoautotrophic phytoflagellates, which are classified here as phytoplankton) and choanoflagellates. The fraction of microzooplankton (in the range of 20 to 200 μm) includes foraminifera and radiolars of rhizopod as well as a number of ciliates and suctorian ciliophores. More visible (0.2–20 mm) in marine zooplankton are comb jellyfish and gooseberries, "arrowworm" chaetognath (e.g. Sagitta), some specialized turbellarians (e.g. Convoluta, Microstomum) and polychaetes (e.g. Tomopteris), some opisthobranch gastropods (e.g. Clione, Limacina) and larvae (e.g. Oikopleura) and salps (e.g. Doliolum). The larvae of many groups of mantis shrimp are barely known.

In the superfamily Lysiosquilloidea, larvae hatch as antizoan larvae with five pairs of mammary appendages and develop into Erichthus larvae, where pleopods appear. In Squilloidea, a Pseudozoea larva develops into an Alima larva, while in Gonodactyloidea, a Pseudozoea larva develops into Erichthus. [9] Ontogenetic changes in N. The salt tolerance of pellets is closely related to their reproductive cycle. Zoea I hatches in brackish estuaries where juveniles and adults live before being exported to marine areas (Charmantier et al. 2002). Thus, Zoea I larvae can be considered euryaline, as can juveniles and adults (Bromberg 1992; Miranda, 1994; Novo et al., 2005). In contrast, the larvae of zoeal stages II to IV are stenohaline and develop in coastal areas where salinity is generally higher and more constant. Once megalopa is reached, larvae become euryhaline and re-enter the brackish adult environment, settling in semi-terrestrial habitats near adult burrows (Charmantier et al. 2002). It is interesting to note that the appearance of phenotypic plasticity has been demonstrated in the development of osmoregulatory capacity in N. granulata.

Previous exposure of eggs and larvae to reduced salinity (20‰) increased the ability of hyper-osmoregulation to cope with low salt levels (5-10‰) at all zoeal stages (Charmantier et al., 2002). This plasticity could have an important adaptive value for the species.