Oponentno procesiranje v mrežnici dvorepega paše (Charaxes jasius, Lepidoptera: Nymphalidae)

Fon Mervič, Lucija (avtor), Belušič, Gregor (mentor)

Dvorepi paša, Charaxes jasius (Lepidoptera: Nymphalidae) je največji evropski metulj, ki ima zelo velike oči, zato je primeren za fiziološke raziskave vida. Njegovo mrežnico smo raziskali z anatomskimi, elektrofiziološkimi in optičnimi metodami. Izmerili smo spektralno in polarizacijsko občutljivost fotoreceptorjev, izdelali odlitek kornee in serijske svetlobno mikroskopske rezine mrežnice ter posneli odsev iz oči. Ugotovili smo, da vsako oko sestavlja ~14000 omatidijev, ki odsevajo zeleno ali rdečo svetlobo in vsebujejo po 9 fotoreceptorjev, urejenih na enak način, kot pri ostalih metuljih iz družine pisančkov. Distalna fotoreceptorja R1 in R2 sta občutljiva na UV (λmax = 340 - 350 nm), modro (B; λmax = 415 - 430 nm) ali zeleno (G; λmax = 535 nm) svetlobo; distalna fotoreceptorja R3 in R4 imata širokopasovno občutljivost, z vrhom v zelenem (G; λmax = 545 nm). Proksimalni receptorji R5-8 imajo širokopasovno občutljivost, z vrhom v zelenem (G; λmax = 545 nm) ali oranžnem (OR; λmax = 580 nm). Pri fotoreceptorjih R1 in R2 smo opazili negativne odzive na svetlobne dražljaje v dolgovalovnem delu spektra. S selektivno kromatično adaptacijo, z injekcijo toka in z meritvijo receptivnih polj smo dokazali, da negativni signali izvirajo iz fotoreceptorjev R3-9 znotraj istega omatidija, ki na R1 in R2 pošiljajo inhibitorne sinapse in z njimi tvorijo barvno oponentne pare. S selektivno adaptacijo smo posredno izmerili tudi spektralno občutljivost rdeče oponentne enote (R; λmax = 620 nm). Ta je najbrž R9, bazalni fotoreceptor, ki v dolžino meri vsega 8 - 18 μm. R1 in R2 prejemajo inhibitorne signale bodisi od R3 in R4, bodisi od R5-8, bodisi od R9, ter tako tvorijo oponentne pare UV+G-, UV+OR-, B+G-, B+OR- in G+R. Predpostavljamo, da R3-9 izražajo enak rodopsin (R540), ki pa ima v R5-9 vrh absorbance dolgovalovno premaknjen zaradi filtriranja z distalnimi rabdomerami in rdečimi filtrskimi pigmenti. Rdeči pigmenti so prisotni v omatidijih z rdečim odsevom, ki so zgoščeni v ekvatorialnem in ventralnem delu mrežnice. Dvorepi paša je prvi metulj iz družine pisančkov z opredeljenimi oponentnimi pari fotoreceptorjev, z zeleno občutljivim receptorjem na poziciji R1 in R2 ter z rdečim bazalnim receptorjem.

• Jezik: Slovenski jezik
• Ključne besede: Charaxes jasius, barvni vid, sestavljene oči, omatidij, fotoreceptor
• Vrsta gradiva: Magistrsko delo/naloga
• Organizacija: BF - Biotehniška fakulteta
• Leto izida: 2021
• PID: 20.500.12556/RUL-128640
• COBISS.SI-ID: 71936771
• Datum objave v RUL: 22.07.2021

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Opponent processing in the retina of the two-tailed pasha (Charaxes jasius, Lepidoptera: Nymphalidae)

Izvleček

The two-tailed pasha, Charaxes jasius (Lepidoptera: Nymphalidae) is the largest European butterfly. It has a pair of very large eyes that are suitable for physiological investigations of vision. Its retina was examined with anatomical, electrophysiological and optical methods. We measured the spectral and polarization sensitivity of the photoreceptors, moulded a replica of the cornea, produced serial light microscopic sections of the retina and recorded the eye shine. We have found that each compound eye is assembled of ~14000 ommatidia, which reflect green or red light and contain 9 photoreceptors, arranged similar as in other nymphalid butterflies. The distal photoreceptors R1 in R2 are sensitive to UV (λmax = 340 - 350 nm), blue (B; λmax = 415 - 430 nm) or green (G; λmax = 535 nm) light; the distal photoreceptors R3 and R4 have broadband sensitivity, peaking in the green (G; λmax = 545 nm). The proximal receptors R5-8 have broadband sensitivity, peaking in the green (G; λmax = 545 nm) or orange (OR; λmax = 580 nm). Photoreceptors R1 and R2 have negative-going responses to long-wavelength light. Using selective chromatic adaptation, current injection and receptive field measurements, we have proved that the negative signals originate from photoreceptors R3-9 within the same ommatidium, which project inhibitory synapses to R1 and R2 and together form colour-opponent pairs. We have indirectly measured the spectral sensitivity of the red opponent unit (R; λmax = 620 nm). Its identity is probably R9, the basal photoreceptor, which is only 8 - 18 μm long. Photoreceptors R3-9 are not postsynaptic to adjacent photoreceptors. R1 and R2 receive inhibitory input from either R3 and R4, or R5-8, or with R9, and thus form the opponent pairs UV+G-, UV+OR-, B+G, B+OR- and G+R-. We assume that R3-9 express the same rhodopsin (R540), which has in R5-9 its absorbance peak further long-wavelength shifted due to filtering with distal rhabdomeres and red screening pigments. The red pigments are contained within the ommatidia that reflect red eye shine, which are enriched in the equatorial and ventral retina. The two-tailed pasha is the first Nymphalid butterfly with described opponent pairs of photoreceptors, with a green-sensitive photoreceptor in location R1 or R2, and with a basal red receptor.

• Ključne besede: Charaxes jasius, color vision, compound eyes, ommatidium, photoreceptor