Membrane current of retinal rods of Caudiverbera caudiverbera (Amphibia: Leptodactylidae): Dark noise, spectral and absolute light sensitivity

Abstract

We investigated the photocurrents from isolated rods of the South American anuran, Caudiverbera caudiverbera. Rod outer segments were on average 66.4 +/- 11.2 microm (mean +/- S.D., n = 104) in length and 6.6 +/- 0.9 microm (mean +/- S.D.) in diameter: 40 +/- 22 photoisomerizations (mean +/- S.D., range 10-99, n = 16) were required for eliciting a half-saturating photocurrent response. The time-to-peak was 911 +/- 217 ms (mean +/- S.D., n = 14, 20 degrees C) in the linear range of the response and the integration time of the current response was 1744 +/- 451 ms (mean +/- S.D., n = 14). The time-to-peak appears to be slower and the integration time shorter in Caudiverbera than in Ambystoma tigrinum, Rana pipiens or Xenopus laevis rods under similar experimental conditions. The a-band of rod spectral sensitivity has a lambda(max) at 520 +/- 2.1 nm (mean +/- S.D., range 516-525 nm, n = 24) and the bandwidth fits a porphyropsin visual pigment. The single-event response amplitude ranges from 0.31-0.51 pA, depending on the calculation method. The intrinsic dark current (variance at dark minus variance under bright light) was 0.045 +/- 0.040 pA2 (mean +/- S.D., n = 24). Our results support the presence of a dark-noise component below 1 Hz, with kinetics similar to the single-photon evoked response and a rate of 0.006 events s(-1) (n = 9).

A Cambrian origin for vertebrate rods

“…Error bars for lamprey are SEM. Letters next to the data points correspond to the following references: a ( Palacios et al, 1998 ), b ( Ala-Laurila et al, 2007 ), c ( Baylor et al, 1984 ), d ( Baylor et al, 1979a , 1979b ), e ( Baylor et al, 1980 ), f ( Nakatani et al, 1991 ), g ( Robinson et al, 1993 ), h ( Field and Rieke, 2002b ), i ( Field and Rieke, 2002a ), j ( Okawa et al, 2010 ), k ( Mendez et al, 2001 ), l ( Burns et al, 2002 ), m ( Azevedo and Rieke, 2011 ), n ( Krispel et al, 2006 ), o ( Luo and Yau, 2005 ), p ( Makino et al, 2004 ), q ( Wen et al, 2009 ), r ( Gross and Burns, 2010 ), s ( Palma et al, 2001 ), t ( Donner et al, 1990 ), u ( Vogalis et al, 2011 ), v ( Nikonov et al, 2006 ), w ( Rieke and Baylor, 2000 ). DOI: http://dx.doi.org/10.7554/eLife.07166.009 …”

Visual sensitivity to a conspicuous male cue varies by reproductive state inPhysalaemus pustulosusfemales

“…When the vocal sac of male túngara frogs is inflated it has higher reflectance, and therefore is likely to be more conspicuous, against the dark background than any other body region measured (Fig.·2). This increase in reflected light is predominantly in the middle wavelength region (450-550·nm), which corresponds to the visual sensitivity of most anuran rods (reported max values, 498-529·nm) (Liebman and Entine, 1968;Hárosi, 1975;Donner et al, 1990;Fyhrquist et al, 1998;Palma et al, 2001), and consequently the increase in reflected light is likely to be detectable by conspecifics.…”

Decision letter: A Cambrian origin for vertebrate rods

“…Error bars for lamprey are SEM. Letters next to the data points correspond to the following references: a (Palacios et al, 1998), b (Ala-Laurila et al, 2007, c (Baylor et al, 1984), d (Baylor et al, 1979a(Baylor et al, , 1979b, e (Baylor et al, 1980), f (Nakatani et al, 1991), g (Robinson et al, 1993), h (Field and Rieke, 2002b), i (Field and Rieke, 2002a), j (Okawa et al, 2010), k (Mendez et al, 2001), l (Burns et al, 2002), m (Azevedo and Rieke, 2011), n (Krispel et al, 2006), o (Luo and Yau, 2005), p (Makino et al, 2004), q (Wen et al, 2009), r (Gross and Burns, 2010), s (Palma et al, 2001), t (Donner et al, 1990), u (Vogalis et al, 2011), v (Nikonov et al, 2006), w (Rieke and Baylor, 2000). DOI: 10.7554/eLife.07166.009 the fractional single photon response a % and the SNR are potentially subject to overestimation due to the fact that their denominators (the circulating current in darkness for a % and the biological dark noise for the SNR) appear smaller if the outer segment is damaged or is not fully within the recording pipette (see however the evidence above that these conditions were respected in our experiments), this issue does not exist when estimating the absolute amplitude a.…”