Bio 119: Endocrine System Of Fish

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endocrine axis

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formed by endocrine cells; series of reflexes that involves a stimulus and effector

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endocrine cell

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detects stimulus; integrating organ; effector organ (??)

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vertebrate pituitary gland/hypophysis

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master gland; activity is highly regulated by higher brain centers, esp. hypothalamus;

2 embryonic origins: neural and ectodermal

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infundibulum

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vertebrate neural origin of hypophysis; evagination of 3rd ventricle; neurohypophysis in adults

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Rathke's pouch

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vertebrate ectodermal origin of hypophysis; adenohypophysis in adults

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axon terminal

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distal part of neurohypophysis; formed by the long axons of the neurons at the hypothalamus

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fish pituitary

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absence of portal system and infundibulum; aso has 2 embryonic origins; also under strict regulation by hypothalamic neurons

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fish neurohypophysis

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neural origin; consists of the posterior pars nervosa; has intimate contact with posterior adenohypophysis

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pars nervosa

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posterior neurohypophysis

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fish adenohypophysis

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consists of the pars distalis and pars intermedia

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pars distalis

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anterior adenohypophysis

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pars intermedia

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posterior adenohypophysis/ meta adenohypophysis

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rostral pars distalis

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pro adenohypophysis

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proximal pars distalis

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meso adenohypophysis

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neuro-intermediate lobe

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made up of the pars intermedia and pars nervosa

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hypothalamo-hypophysiotropic hormones

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released in response to environmental cues

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differential staining

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histologically classifying pituitary cells as either acidophilic or basophilic

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adrenocorticotrophic hormone (ACTH)

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secreted by corticotrophs in the rostral pars distalis, basophilic

; acts on interrenal cells @ head kidney to initiate synthesis and release of corticosteroids

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corticosteroids

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sea-water adaptation in fish, particularly euryhaline fish

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melanophore stimulating hormone (MSH)

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secreted by pars intermedia; stimulates melanocytes at dermis that carry melanin granules to disperse/aggregate making fish pale/dark

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dark fish

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stressed fish

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lactotroph (PRL)

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secreted by rostral pars distalis, acidophilic follicles;

aggregate of lactotrophs would form follicles with cavity to inhibit Na+ pump activity of osmoregulating cells (freshwater adaptation for euryhaline)

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PRL in seahorses

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nourishes young inside marsupium

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Growth hormone (GH)

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also lactogenic; produced by somatotrophs at proximal pars distalis, acidophilic

does not directly act on target organs; mediated first by Insulin Growth Factors (IGF; somatomedin) = also reg. Na+ pump activity

responsible for growth

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Thyroid stimulating hormone (TSH)

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produced by tyrotroph at proximal pars distalis, acidophilic;

stimulates thyroid cell

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somatolactin (SL)

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produced in the pars intermedia; for osmoregulation during migration;

mobilizing stored nutrients (especially since FW bound maturing adults do not eat otw to natal stream)

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gonadotropin hormone (GTH)

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secreted by gonadotrophs at proximal pars distalis, basophilic;

consists of GTH1 and GTH2

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PPD hormones

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made up of A and B subunits

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A subunits

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subunits identical to each other

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B subunits

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subunits that provide specialty

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GTH1

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B subunit; similar to follicle stimulating hormone (FSH) so is a vitellogenic hormone

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GTH2

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B subunit; similar to LH, so increase during ovulation and follicle will rupture

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Neurophysical hormones

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secreted by pars nervosa in neurohypophysis; are vastocin-like hormones

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octopeptides

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products of neurophysical hormones, made up of 8 amino acids; stored in pars nervosa where axon terminals are found, awaiting stimulus

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depressor effects

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responsible for constricting blood vessels;

increase in blood pressure: osmoregulation due to more water released

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non-pituitary sites: thyroid tisse

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very diffused distribution; branchiogenic origin; produces thyroid hormone

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thyroid hormone

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precursor is amino acid, thyrosine-->forms T1-T4 with I and an enzyme

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T3 and T4

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biologically active; found in significant increase in SW migrating smolts and coincides with new moon;

important for growth due to permissive action

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non-pituitary sites: interrenal and chromaffin cells

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@ head kidney; homologous with medulla; responsible for synthesis of adrenaline and epinephrine

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non-pituitary sites: utimobranchial tissue

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branchiogenic origin; produces calcitonin for calcium regulation

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non-pituitary sites: stanns corpuscles

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@ anterior kidney; secretes stannocalcin, which is hypocalcemic or antagonizes calcitonin; for osmoregulation

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non-pituitary sites: caudal neurosecretion

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@tail end; neurohaemal structure and urotensins

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neurohaemal structure

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axon terminals; site for storage of neurosecretory products; well supplied by blood vessels; made up of Dahlgren cells

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urotensins

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hypoactive secretions = basodilation of blood vessels; contraction of smooth muscles of urinary bladder for osmoregulation

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non-pituitary sites: digestive tract

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secretes peptides; act on other cells that make up lining of digestive tract;

initially function as neurotransmitters in early vertebrates;

brain-gut axis?

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non-pituitary sites: pancreas

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glucagon, insulin, etc.

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glucagon

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secreted by pancreas; hyperglycemic

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insulin

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secreted by pancreas; hypoglycemic

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Pancreatic cells

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Brockmann bodies

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non-pituitary sites: epiphysis

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@ roof of diencephalon; light sensitive tissue; secretes melatonin (increases during nighttime)

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non-pituitary sites: gonads

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respond to GTH by secreting gonadal steroids which initiate growth and development of gametes

(somatic cells have the endocrine fxn)