IL SISTEMA NERVOSO Nei gruppi primitivi la catena

  • Slides: 14
Download presentation
IL SISTEMA NERVOSO Nei gruppi “primitivi” la catena nervosa ventrale conserva talvolta ancora l'aspetto

IL SISTEMA NERVOSO Nei gruppi “primitivi” la catena nervosa ventrale conserva talvolta ancora l'aspetto definito 'a scala di corda': le parti destra e sinistra sono ben distinte e lontane fra loro e i 2 gangli di ciascun segmento sono uniti da commessure trasversali doppie. Negli altri gruppi le 2 parti della catena ventrale tendono a ravvicinarsi sulla linea mediana e inoltre i gangli tendono ad abbandonare la disposizione metamerica, raggruppandosi insieme.

Ganglio sopraesofageo o cervello, composed of 3 ganglia fused together in an anterioposterior direction:

Ganglio sopraesofageo o cervello, composed of 3 ganglia fused together in an anterioposterior direction: protocerebrum, deutocerebrum, and tritocerebrum. Ganglio subesofageo Ganglio toracico Gangli addominali

Ghiandole endocrine I Crostacei posseggono molte ghiandole a secrezione interna, i cui prodotti agiscono

Ghiandole endocrine I Crostacei posseggono molte ghiandole a secrezione interna, i cui prodotti agiscono sul fenomeno della muta, sull'adattamento cromatico del tegumento, sulla gametogenesi, sul differenziamento sessuale e sulla riproduzione. Tali ghiandole sono: la ghiandola della muta, detta anche organo Y, la ghiandola del seno (particolarmente studiata nei Decapodi), l'organo X, la ghiandola androgenica propria degli Anfipodi, degli Isopodi, dei Leptostraci e dei Decapodi reptanti e natanti. La principale ghiandola neuroendocrina dei crostacei è il complesso formato dall’ Organo X e dalla ghiandola del seno. Organo X e ghiandola del seno sono localizzati nel peduncolo ottico.

Le ghiandole endocrine più importanti sono: l’Organo Y e la ghiandola androgenica. • I

Le ghiandole endocrine più importanti sono: l’Organo Y e la ghiandola androgenica. • I crostacei non producono ormone giovanile come gli insetti, ma il suo precursore, il metil farnesoato (MF), prodotto dagli organi mandibolari (MO), omologhi dei corpora allata degli insetti, sito di produzione dell’ormone giovanile. • Le ghiandole androgeniche si trovano accollate ai deferenti. Si è visto che il loro trapianto in femmine provoca la comparsa di caratteristiche maschili: gli ovari divengono testicoli, si formano i deferenti e compaiono le apofisi genitali tipiche del maschio. Queste ghiandole controllano e regolano il differenziamento sessuale nei maschi genetici; nelle femmine gli ovari controllano il differenziamento degli ovidutti e il manifestarsi dei caratteri sessuali esterni.

Crustacean reproduction is dependent upon a highly integrated neuroendocrine system Mandibular organ

Crustacean reproduction is dependent upon a highly integrated neuroendocrine system Mandibular organ

Regulates glucose level, reproduction, growth Crustacean hyperglicemic hormone Growth and gonad stimulation Ecdisone Methyl

Regulates glucose level, reproduction, growth Crustacean hyperglicemic hormone Growth and gonad stimulation Ecdisone Methyl farnesoate Mandibular organ Gonad stimulation Molt inhibiting hormone Gonad stimulating factor

The control of reproduction is a complex interplay between Y-organ inhibition and stimulation of

The control of reproduction is a complex interplay between Y-organ inhibition and stimulation of gonad growth. MIH Mandibular Organ MOIH Methyl Farnesoate Thoracic Ganglia 5 -HT Gonad Stimulating Hormone (GSH) GIH

Presence of vertebrate –like steroids in crustaceans has been proposed by several authors. hemolymph

Presence of vertebrate –like steroids in crustaceans has been proposed by several authors. hemolymph hepatopancreas gonads

Role of neuropeptides in reproduction The hormonal control of reproduction has been studied in

Role of neuropeptides in reproduction The hormonal control of reproduction has been studied in many crustacean species, including crayfish, shrimp, crab, lobsters, etc. A number of hormones from neuroendocrine organs play an essential role in controlling gonad maturation. Gonad maturation in crustaceans appears to be regulated by two antagonistic neuropeptides: 1. GIH (also called vitellogenesis inhibiting hormone, VIH, in females) synthesized and secreted from the X-organ–sinus gland (XO–SG) complex of the eyestalk, 2. gonad stimulating hormone (GSH), thought to be produced by the brain and thoracic ganglion.

Role of VIH in female crustacean reproduction The removal of the eyestalk during sexual

Role of VIH in female crustacean reproduction The removal of the eyestalk during sexual inactivity led to rapid increase in ovarian size and precocious egg deposition, apparently because of the removal of GIH. Eyestalk removal in non-breeding adult males induces precocious spermatogenesis, and hypertrophy in the androgenic gland. The eyestalk extract possesses both gonad inhibitory and gonad stimulatory effects on both sexes.

Effects of environmental factors on hormone levels and reproduction Crustacean reproduction is controlled by

Effects of environmental factors on hormone levels and reproduction Crustacean reproduction is controlled by several hormones, which aid in evaluating environmental conditions to determine the best time to reproduce. Neuroendocrine coordination of the appropriate environmental factor is essential to ensure that annual reproductive and molting events take place in the appropriate temporal sequence. Temperature, salinity and photoperiod manipulations, have been employed in different shrimp species. Reproduction was stimulated by photoperiod. Stability of water temperature and optimal temperature along with salinity are essential to maintaining reproductive captivity in marine crustaceans.

Information about the environmental and endogenous factors that control crustacean molt and reproduction is

Information about the environmental and endogenous factors that control crustacean molt and reproduction is required to enhance profitable aquaculture programs. Photoperiod has been reported to be a strong inducer of reproduction in several crustacean species.