ASSIGNMENT TITLE

3-spined stickleback fish

Subject Ethology

Submitted by Aftab Badshah

Roll no 11

Bs Zoology Sem 5TH

Submitted to Mam Brekhna

Deptt: Zoology UCSS

Dated Friday, 24 Oct 2014

3 - S P I N E D S T I C K L E B A C K F I S H

O V E R V I E W

Scientific Classification

Kingdom Animalia Phylum Chordata Class Actinopterygii

Order Gasterosteiformes Family Gasterosteidae

Genus Gasterosteus Species G.aculeatus

Why called as 3-spined stickleback

it bears 10-14 dorsal fins in front of which are the three spines that give the fish its name

Why favored for studies of animal behavior????????

It shows great morphological variation throughout its range, ideal for questions about

evolution and population genetics

Most populations live in seawater but breed in fresh or brackish water and very tolerant of

changes in salinity, a subject of interest to physiologists.

It displays elaborate breeding behavior like defending a territory, building a nest, taking care

of the eggs and fry etc and it can be social living in shoals outside the breeding season

making it a popular subject of enquiry in fish ethology and behavioral ecology.

Its antipredator adaptations, host-parasite interactions, sensory physiology, reproductive

physiology, and endocrinology have also been much studied

Characteristics

Size usually 5 cm (2 in) long (but may reach, exceptionally, twice that length)

Body laterally compressed and scales are absent

Tail The base of the tail is slender

Fins

o The caudal fin has 12 rays

o The dorsal fin has 10-14 rays;

o The anal fin has eight to 11 rays and is preceded by a short spine

o The pelvic fins consist of just a spine and one ray

o The pectoral fins are large, with 10 rays

Coloration

o drab olive or silvery green dorsal side

o In males during the breeding season, the eyes become blue and the lower head, throat,

and anterior belly turn bright red

o The throat and belly of breeding females can turn slightly pink

Habitat

Found only in the Northern Hemisphere,

usually inhabits coastal waters or freshwater bodies

can live in either fresh, brackish, or salt water

prefers slow-flowing water with areas of emerging vegetation.

It can be found in ditches, ponds, lakes, backwaters, quiet rivers, sheltered bays, marshes, and

harbours.

Diet

a bottom-feeder, basically on benthic prey, normally the chironomid larvae being the most abundant

prey; however, this fish species can also consume terrestrial prey on the surface. [8] It can cannibalize

eggs and fry.[9]

Life history

Many populations take two years to mature ,others 3 years, but some in extreme latitudes take

even 1 year

Mostly experience only one breeding season before dying

Reproduction

Breeding season

o From late April until July, males and females move from deeper waters to shallow areas.

Building of nests

o Each male defends a territory where he builds a nest on the bottom.

o Starts by digging a small pit.Then fills it with plant material (often filamentous algae),

sand, and various debris which he glues together with spiggin, a proteinaceous substance

secreted from the

o He then creates a tunnel through the more or less spherical nest by swimming vigorously

through it.

o Nest building typically takes 5–6 hours. though it may also be spread out over several

days.

Territorial Courtship

o After nest building , the male courts gravid females that pass by with a zigzag dance.

o approaches a female by swimming very short distances left and right, and then swims

back to the nest in the same way.

o If the female follows, the male often pokes his head inside the nest, and may swim

through the tunnel.

o The female then swims through the tunnel as well, where she deposits 40−300 eggs.

Mating behavior

o The male follows to fertilize the eggs. The female is then chased away by the male.

o For the duration of the eggs' development, the male will chase away other males and non-

gravid females.

o He may, however, court other gravid females (more than one batch of eggs can be

deposited in the same nest).

Parental behavior

o The male takes care of the developing eggs by fanning them.

o He lines himself up with the entrance of the nest tunnel and swims on the spot.

o The movement of his pectoral fins creates a current of water through the nest, bringing

fresh (well-oxygenated) water to the eggs progressively during day and night

o Fanning levels tend to increase until the eggs are about to hatch, which takes 7–8 days at

18−20 °C.

o Fanning levels also increase when the water is poorly oxygenated

o Towards the end of the egg development phase, the male often makes holes in the roof

and near the rim of the nest, presumably to improve ventilation of the nest during fanning

at a time when the eggs are more metabolically active.

Hatching of youngs

o Once the young hatch, the male attempts to keep them together for a few days, sucking up

any wanderers into his mouth and spitting them back into the nest.

o Afterwards, the young disperse and the nest is either abandoned by the male, or repaired

in preparation for another breeding cycle.

An exceptional case of parental behavior in sticklebacks

In Nova Scotia, a form of three-spined stickleback departs from the usual pattern of parental care.

Unlike other sticklebacks that nest on the substrate, Nova Scotian male sticklebacks build nests in

mats of filamentous algae. Surprisingly, almost immediately after fertilization, the males disperse the

eggs from the nest and resume soliciting females for eggs. Hence, there appears to have been a loss of

parental care in this population. Because these males have reduced dorsal pigmentation, resulting a

pearlescent white appearance, they have been dubbed "white sticklebacks". It is currently unknown

whether they are a distinct species, or simply a morph of the common Atlantic stickleback. [20][21]

Cooperative Behavior

Some evidence indicates the existence of cooperative behavior among three-spined sticklebacks,

mainly cooperative predator inspection. Predator inspection appears to allow acquisition of

information about the risk a potential predator presents, and may deter attack, with the cost being an

increased chance of being attacked if the predator proves to be hungry.

Tit-For-Tat Strategy

Sticklebacks are known to cooperate in a tit-for-tat (TFT) strategy when doing predator

inspection. The idea behind TFT is that an individual cooperates on the first move and then

does whatever its opponent does on the previous move. This allows for a combination of

collaborative (it starts by cooperating), retaliatory (punishes defection), and forgiving

(respond to cooperation of others, even if they had defected previously) behavioral responses.

When three-spined sticklebacks approaching a live predator were provided with either a

stimulated cooperating companion or a stimulated defecting one, the fish behaved according

to tit-for-tat strategy, supporting the hypothesis that cooperation can evolve among egoists.

Typically, sticklebacks operate in pairs. Individuals have partners with which they repeatedly

perform pairwise predator inspection visits. Two reciprocal pairs per trial occur significantly

more often than what was expected due to chance. These results provide further evidence for

a tit-for-tat cooperation strategy in sticklebacks.

Stickleback behavior is often cited as an archetypal example of cooperative behavior during

predator inspection. Fish from three sites differing in predation risk inspected a model

predator in pairs and reciprocated both cooperative moves and defections by the partner, but

not on every opportunity.

Sticklebacks that originated in the two sites containing piscivorous fish were more likely to

reciprocate following a cooperative move than following a defection. Individuals from

higher-risk sites were generally more cooperative. Individuals accompanied by a model

companion show reciprocal moves of cooperation and defection in response to the model's

movements about a third of the time. Both examples of stickleback behavior demonstrate the

elements of a strategy of cooperation that may resemble tit-for-tat.

Partner-Dependence

The tit-for-tat cooperation strategy has been shown to be evident in sticklebacks. In addition,

the size of a stickleback's partner fish may also be a factor in determining what a stickleback

will do when both fish are faced with a predator. Two sticklebacks simultaneously presented

to a rainbow trout, a predator much larger in size, will have differing risks of being attacked.

Usually, the larger of the two sticklebacks has a higher risk of being attacked.

Individual sticklebacks are more likely to move closer to a trout (or some other predator)

when a larger potential partner moves close to the trout than when a smaller partner

approaches the trout. Although both large and small partners behave similarly, a small

partner's behavior affects the strategy of the test fish more than that of the large partner.

Regardless of whether it is alone or with a partner that cooperates, a larger fish will approach

a predator more closely than does a smaller fish. If a partner defects, then a stickleback's

condition-factor (i.e. its ability to flee) determines how closely it approaches the predator

rather than the stickleback's size. [26] Both the strategy and reaction to different-sized partners

seem to be dependent on whether the partner cooperates or defects.