Life Cycles. Fry: begin feeding (fry can undergo several more developmental stages, which vary by species, as they mature into juveniles.

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Howard Holt
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1 Life Cycles Fish life cycle - general Eggs + sperm fertilized eggs after temperature-dependent development hatch into - Larvae: live off a yolk sac, this stage is often referred to a sac fry. When the yolk sac is fully absorbed the young fish become fry * Alevins: Unique to salmon begin feeding even though the yolk sac has not been fully absorbed Fry: begin feeding (fry can undergo several more developmental stages, which vary by species, as they mature into juveniles. * Early juveniles are often called fingerlings Juveniles: The time fish spend developing from fry into reproductively mature adults - Adults: When fish are able to reproduce, they are considered adults Spawning: female fish release eggs into the water and male fish fertilize eggs by releasing milt (sperm).

2 Trout Life Cycle

3 Anadromous and Catadromous Life Cycles anadromous fish grow to adults mostly in the ocean but return to freshwater to breed in fresh water. Most salmon are anadromous.

4 catadromous fish grow to adults mostly in fresh water but return to the ocean to breed.

5 Mollusk life cycle general Eggs + sperm fertilized eggs after temperature-dependent development hatch into Trochophore larvae: microscopic (~ 0.2 mm) free-living larvae swim in the water column, living off yolk, beginning of shell development, when the yolk is fully utilized (typically 24 hrs) the larvae metamorphosis into Veliger larvae: this larvae has a distinctive velium organ, resembling two ciliated flaps, aiding in swimming and the collection of particulate algal cells from the water column At this stage, bivalve species have already developed a hinged bivalve shell. Because of the distinctive shape of the shell, culturists often call this stage, a D-stage veliger larvae. * abalone veliger larvae are unusual in that they do not feed during the veliger stage. Pediveliger larvae: After several weeks, veliger larvae develop an eyespot causing the larvae to become negatively phototatic. Using a foot which also develops at this stage, pediveliger larvae seek out appropriate clean benthic substrate as a metamorphic site. Settling down and losing their velium, they attach to the substrate and metamorphose into Spat: molluscan post larval stage. Begins filtration feeding as a settled benthic organism After a month or more post larval spat become fully formed * in the case of abalone, scraping the algal film from surfaces Juveniles: as the spat grow they are referred to as juveniles and continue feeding until the grow into adults Adults: when they are able to reproduce. Spawning: female mollusks typically release eggs into the water column stimulating males of the species to release milt (sperm) allowing fertilization in the water column.

6 Oyster Life Cycle

7 Crustacean life cycle general * Molting: Crustaceans are members of the phylum Arthropoda (which also includes insects and spiders). Characteristic of the group is an external skeleton, called an exoskeleton. The exoskeleton completely covers the outside of the body and the muscles inside adhere to it. The crustacean exoskeleton being heavily calcified are particularly hard. Because the exoskeleton is hard and rigid, a crustacean cannot grow unless it sheds its old exoskeleton and secretes a new one. This process is called molting. Arthropod growth is limited to molting, so growth happens in steps rather than continuously. The stage between moltings is referred to as intermolt. The extent of an individual's growth between molts and the length of time between molts are related to the temperature as well as to the amount of food an individual gets. The molting process can either be a simple growth phenomenon where there is no change in the external morphology except for size or metamorphic where there is a change in the morphology after molting such as is seen during the larval process. Eggs + sperm In shrimp, the eggs are broadcasted the water column where the fertilized eggs after temperature-dependent development hatch as * Most decapods, such as crawfish and lobsters, carry the eggs attached extermally under the tail until hatching. Nauplii: The main features of a nauplius larva are a simple, unsegmented body, three pairs of appendages (antennules, antennae, and mandibles), and a single, simple, naupliar eye. The free-living larvae swim in the water column, living off yolk until they molt into Zoea: The zoea stage larvae have will developed thoracic appendages used for swimming and filtering algal cells from the water column. After feeding and growing for several days the zoea have a metamorphic molt into Mysis: The mysis stage of crustaceans such as shrimp has developed a full range of appendages allowing for the capture of zooplankton while swimming. Again after feeding and growing for several days the mysis have a metamorphic molt into * Although there are some species differences in the time spent at various stages, the overall length of the larval period of shrimp is approximately eleven day. * The larval stages of crawfish take place in the egg and thus they hatch out have an appearance similar to the adult.

8 Post larvae: Typically referred to as PL s by shrimp culturists, post larvae have the morphology of adult shrimp although they are only a little over one millimeter in length. Culturist often keep track of how old a group of shrimp are for the first several months by designating the days since they metamorphosed into post larvae by a subscript. A PL25 group turned post larvae twenty-five days ago. At about twenty-five days after turning post-larvae the gills have become branched and the post larvae are considered Juvenile shrimp Juvenile shrimp are grown for another three to five months (four and six months of age since hatching) depending on species at which time they have grown to typical market size of twenty five grams. * Crawfish take about six months to grow to twenty five grams depending on temperature. Shrimp life cycle

Chapter 7. Marine Animals Without a Backbone

Chapter 7. Marine Animals Without a Backbone Chapter 7 Marine Animals Without a Backbone Molluscs Characteristics of Phylum: More than 200,000 species Name means "soft body" Basic body plan head, muscular foot and visceral mass in most species Mantle-