The marine gastropod Conomurex luhuanus (Strombidae) has high-resolution spatial vision and eyes with complex retinas

Abstract

All species within the conch snail family Strombidae possess large camera-type eyes that are surprisingly well-developed compared to those found in most other gastropods. Although these eyes are known to be structurally complex, very little research on their visual function has been conducted. Here, we use isoluminant expanding visual stimuli to measure the spatial resolution and contrast sensitivity of a strombid, Conomurex luhuanus. Using these stimuli, we show that this species responds to objects as small as 1.06° in its visual field. We also show that C. luhuanus responds to Michelson contrasts of 0.07, a low contrast sensitivity between object and background. The defensive withdrawal response elicited by visual stimuli of such small angular size and low contrast suggests that conch snails may use spatial vision for the early detection of potential predators. We support these findings with morphological estimations of spatial resolution of 1.04°. These anatomical data therefore agree with the behavioural measures and highlight the benefits of integrating behavioural and morphological approaches in animal vision studies. Using contemporary imaging techniques (serial block-face scanning electron microscopy (SBF-SEM), in conjunction with transmission electron microscopy (TEM)), we find that C. luhuanus have more complex retinas, in terms of cell type diversity, than expected based on previous studies of the group using TEM alone. We find the C. luhuanus retina is comprised of six cell types, including a newly identified ganglion cell and accessory photoreceptor, rather than the previously described four cell types.

Evolution of Large Eyes in Stromboidea (Gastropoda): Impact of Photic Environment and Life History Traits

“…6) (Seyer 1994; Blumer 1996; Land and Nilsson 2012). High visual acuity in strombids is supported by both behavioural and anatomical studies of strombid Conomurex luhuanus (Seyer et al 1994; Irwin et al 2022); however, no behavioural experiments have yet investigated differences in visual capabilities between the large- and small-eyed groups. Nevertheless, the spatial resolution of C. luhuanus , approximately 1°, is almost four times finer than that of the littorinid Littorina littorea (Seyer et al 1992, 1994; Irwin et al 2022).…”

“…Nevertheless, the spatial resolution of C. luhuanus, approximately 1°, is almost four times finer than that of the littorinid Littorina littorea (Seyer et al 1992(Seyer et al , 1994Irwin et al 2022).…”

“…6) (Seyer 1994;Blumer 1996;Land and Nilsson 2012). High visual acuity in strombids is supported by both behavioural and anatomical studies of strombid Conomurex luhuanus (Seyer et al 1994;Irwin et al 2022); however, no behavioural experiments have yet investigated differences in visual capabilities between the large-and small-eyed groups.…”

“…In strombids, withdrawal into the shell can be initiated in behavioural studies by rapidly expanding visual stimuli that mimic fast-approaching potential predators (Irwin et al 2022).…”

A new genetically tractable non-vertebrate system to study complete camera-type eye regeneration

“…The outer segment of the photoreceptors is an area where the visual pigments, molecules that activate a signaling cascade when hit by photons, are hosted on the membranes 19,20 . Camera-type eyes can also be found in invertebrate organisms such as mollusks and specifically cephalopods as well as some gastropods, such as the tiger conch, Conomurex luhuanus [3][4][5]21 .With the goal of finding an organism with camera-type eyes and high regenerative potential, we sought to determine if the apple snail P. canaliculata had camera-type eyes suitable for study (Figure 1A). The P. canaliculata eye bulb is located on top of a short eye stalk and the cornea is a circular transparent epithelium on its apical part (Figure 1B).…”