Exam 2 Fish Reproduction answer with definitions

What are Diverse Reproductive Habits in Fishes

**Change sex** when you reach a **certain body size**

• **Lure a female** into your lair **by humming**

• Hold new hatchlings in your mouth for safety (**mouth brooding**)

• **Eat your smaller, fraternal twin** while still in the uterus

• **Give birth to live young like mammals**

• **Parasitize your mate** who is many times larger than you are, hang on, **and just produce sperm**

• **Swim upstream to mate** in the same place you were born, and then **die of exhaustion.**

How do you explain how fishes could possibly exhibit so many strategies?

1. Basic Premise: **Natural Selection has favored those strategies** (that are heritable) **that insure successful production of young** of a species (and that avoid hybridization)........

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2. **Different strategies may be expressed**:
\-- at each stage in the process of reproduction
\-- in different ecological contexts

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3. **Costs and Benefits of a strategy** .......Benefits must outweigh costs

What is the Pre-requisite of Reproducton: Reproductive Physiology

Role of endocrine systems, stimulus production, sensory systems, “gonadal index” (male/female)

Reproduction

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Spawning Strategies – Where? When? How often?

– Migrations to spawning site – synchronized with seasonal gonadal maturation (oceanic, anadromy, catadromy)


– Triggers for spawning – environmental vs. biotic stimuli

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– Broadcast spawning vs. demersal spawning (incl. site selection, nest building, mouthbrooding, etc.)


– Semelparous vs. iteroparous spawning

Refer to the **regions in the water where fish and other aquatic animals release their eggs.**

Spawning sites

**Billions of gametes** (the combination of sperm and egg) a**re spewed** into the surrounding environment of the ocean.

broadcast spawning

**Externally fertilised eggs that are not free floating** and are **guarded after fertIlisation**

Demersal spawning

single reproductive episode before death

Semelparous

* Generally, in anadromous taxa are • Pacific salmon (pink, chinook, chum, coho) • Lampreys • American eels (Anguilla)


* Annual fishes – spawn and die at 1 year \` old (some killifishes) are

Semelparous

Repeated reproduction throughout lifetime

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most fishes

Iteroparous

Reproduction

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Mating Systems (e.g., sexual selection) – With whom?

– Promiscuous or polyandrous/polygynous or monogamous


– Alternative Strategies - Sneaker male behavior (e.g., midshipman)


– Post-Fertilization - Parental care – 22% of teleost families
• 11% care by male parent only
• 7% care by female parent only
• 4% biparental care

Refers to a social group that includes **one reproductively active female, several adult males,** and their offspring.

polyandrous

Anemonefishes are

polyandrous

refers to a social group that includes **one adult male, several adult females,** and their offspring

polygynous

– Sculpins, sea basses, damselfishes, wrasses, parrotfishes, surgeonfishes, trunkfishes, triggerfishes are

polygynous

no mate choice, e.g., broadcast spawners

Promiscuity

\- most common strategy among marine fishes are

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– Herrings, sea basses, damselfishes, wrasses, surgeonfishes are

Promiscuous

one mate for extended period or for life

Monogamy

Butterflyfishes, some pipefishes, damselfishes, hamlets, blennies, jawfishes are

Monogamous

– Requires temporal coordination, cues (solar, lunar)


– Most bony fishes

External Fertilization (ovipary only)

– Requires coordinated behavior, physiology

– **Requires an intromittent organ** (e.g., claspers); pelvic and anal fin specializations.

Internal Fertilization

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– (oviparous, ovoviviparous, or viviparous)

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Ovipary: eggs laid outside the body

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Ovoviviparous: producing living young from eggs that hatch within the body

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Viviparous: live birth

All Chondrichthyes, coelocanths, and a few groups of teleosts (e.g., some cyprinodontiforms \[guppies\]; embiotocids \[surf perches\]) perform

Internal Fertilization

Reproductive Strategies with External Fertilization

Ovipary

Reproductive Strategies with External Fertilization

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Ovipary – egg-layers

Indirect Development = Hatch followed by larval phase E.g., most bony fishes

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The advantage for the larva stage is dispersal, but the downside is that larvae are easy prey.

Reproductive Strategies with External Fertilization

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Ovipary – egg-layers

Direct Development = Longer embryonic phase (more extensive development) then hatches as juveniles = (no larval stage) E.g., Chondrichthyes, some bony fishes

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The advantage for the larva stage is dispersal, but the downside is that larvae are easy prey.

**Planktonic/pelagic eggs** (small eggs, high fecundity = r-selection)

– broadcast spawning with external fertilization

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• **most marine fishes**

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• planktonic / pelagic larvae – embryonic and larval development in the water column

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Fecundity: “the ability to produce an abundance of offspring or new growth; fertility“

Ovipary

**Demersal eggs** (large eggs, low fecundity = K-selection) – intentional
placement of eggs after internal or external fertilization


• in vegetation
• in substrate
• nest (nesters, parental care)
• **mouth brooders** \[cichlids\] – **rare among marine fishes**
• **pouch brooder**s \[seahorses, pipefish\] - **rare among marine fishes**

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Fecundity: “the ability to produce an abundance of offspring or new growth; fertility“

Ovipary

Examples of Demersal Eggs with Parental Care

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Amia and Protopterus are x

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Teleosts

* Sculpins, Blennies, Gobies

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* Sticklebacks – x in vegetation

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* Centrarchids – x in sand mud

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* Cichlids – x in vegetation, in sand

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* Damselfishes – x on rocks

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* Betta – bubble x

Nest Builders

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x means nest

–lay eggs then put them somewhere

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Mouthbrooding (Arapaima, many cichlids)

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Intestinal brooding

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Brood pouches - male seahorses and pipefishes (Sygnathidae)

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Deposit brooding - bitterling (cyprinid) deposit eggs in FW mussel

Brooders

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deposit eggs are put in freshwater mussels because they provide protection and oxygen, which is critical for developing.

1\. **Lay eggs and pick them up in mouth**

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2\. Egg spots are egg mimics, near male vent where sperm is released

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3\. **Female broods eggs as they are fertilized** and then hatched

Mouth Brooding in Cichlid Fishes

Reproductive Strategies Requiring Internal Fertilization

Ovovivipary

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Vivipary

**large eggs** (K-selected), **limited by capacity of female reproductive tract**


– **Retention in oviduct** (=uterus, in sharks) **or** retention in **ovary**


– Large eggs --> **large emerging young**

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– “gestation period” - 1-2 d in tropical teleosts, 1-2 years in sharks (!)

Ovovivipary

– **Large eggs** (K- selected) - **limited by capacity of female reproductive tract**


– **Largest eggs, large young** (carcharhinids, hammerheads)


– **Defined by presence of pseudo-placentation**; **exchange of gases or nutrients between embryo and
mother** – e.g., cyprinodontids (Heterandria, Jenynsia); Anableps (4 eyed fish), carcharhinids,
hammerheads; nutrition (e.g., Sebastes); uterine secretions (Torpedo rays), large fins (surf perches)

Vivipary

Taxonomic Distribution of Reproductive Strategies

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- fertilization???, oviparous, Direct development (no larvae???)

Hagfishes

Taxonomic Distribution of Reproductive Strategies

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\-external fertilizers (FW), oviparous \[no care\], larvae (ammocoetes larva -filter feeder)

Lampreys

Taxonomic Distribution of Reproductive Strategies

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– ALL internal fertilizers, but either oviparous, ovoviviparous, or viviparous

Chondrichthyes

Taxonomic Distribution of Reproductive Strategies

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\- ALL external fertilizers (broadcast or demersal), oviparous (some w/parental care), some with direct development (no distinct larval stage)

Non-teleost Bony Fishes

Taxonomic Distribution of Reproductive Strategies

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Lots of diversity

Teleosts

Sex Change include

Simultaneous and Sequential hermaphroditism

Sequential hermaphroditism

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Why switch from female to male

This is called Protogynous

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Advantages of being a large male (competition)

* defending territory (and food
resources)?
* getting more females to mate with them? – ...and thus, passing their genes to the next generation.

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• Angelfishes, wrasses, parrotfishes, gobies

Sequential hermaphroditism

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Why switch from male to female

This is called protandrous

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Advantages of being a large female (fecundity)

• Anemonefishes, some moray eels

**Several males and one female**
in a group - polyandry


• **Largest male mates w/female**


• **If female dies, the largest male
turns into female**....

Protandry in Anemonefishes(clownfish)

Reproductive Ecology is and ask

Behavior + Ecology →Costs and Benefits

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**When to Mate** – seasonality, time of day

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**Where to Mate** – need safe habitat, exploit current patterns, avoid of predators, exploit two habitats. (marine vs. FW, via migration)

At the end of the Larval Phase, we ask

**how to find a “settlement site” where you can “transform” to the juvenile stage** and **be “recruited” to the population.**

fertilization through hatching (4-5 mm)

Embryo

hatch through transformation

Larva

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– **Pelagic Larvae**, other specialized stages (e.g., **salmon, eels)**

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– Organogenesis, sensory development, swim bladder, shift from endogenous to exogenous feeding, flexion, skeletal ossification, loss of any specialized larval characters

larval to juvenile transformation

Metamorphosis

* final adult meristics (# fin rays)
* scales form
* guanine, pigmentation
* thickened skin Settlement = change in behavior - go to juvenile habitat Recruitment = join population • Juvenile = growth phase • Adult = sexual maturity (gonadal

change in behavior - go to juvenile habitat

Settlement

join population

Recruitment

sexual maturity (gonadal)

Adult