Notes on Stomatopod’s visual ability: 3

Summary of the structure of Stomatopod’s eye

1

The compound eye of a Stomatopod is a hemispherical structure connected to an eye stalk.

The compound eye consists of many ommatidia.

Each ommatidia is mainly consists of

• a cornea (facet) on the surface,

• a crystalline cone underneath the cornea,

• distal pigment cells surrounding the crystalline cones,

• retinular cells (photoreceptor cells) underneath the crystalline cone.

(Assume that the distal - proximal axis of an ommatidia is vertical, as is illustrated in Notes on Stomatopod’s visual ability: 2 .)

6 rows of special ommatidia divides the hemispherical compound eye into two parts, namely dorsal and ventral hemispheres (DH & VH).

These 6 rows of special ommatidia has larger cornea (facet), and are termed as mid-band ommatidia, designated as MO[1-6].

The cell membranes of retinular cells extend and form rhabdomeres, and the rhabdomeres form a bundle structure termed rhabdom. The rhabdom functions as a light guide.

The retinular cells are simply described as “rhabdom” in some documents.

2

There are 8 retinular cells in an ommatidia, whose shape and location are different to each other, designated as R[1-8].

DH & VH retinular cells are divided into two layers (based on the shape of the cross section imaging), namely distal end layer and proximal end layer. All the 8 retinular cells in an ommatidia are present at each layer (tier) .

The distal end layer mainly consists of a single R[8] cell. The proximal end layer consists of R[1-7] cells, which form a flower-like ring structure, with the rhabdomeres at the center of the ring.

The retinular cells of MO[1-4] are three layered, with a distal end layer similar to that of DH & VH ommatidia, but the proximal end layer are divided into two sub-layers.

All the R[1-7] cells are present in the two sub-layers at the proximal end. In MO[1,3,4], the R[1,4,5] cells are above the R[2,3,6,7], while in MO[2], the R[2,3,6,7] cells are above the R[1,4,5] cells.

All the R[1-8] cells construct the retinula with both small distal projections (microvilli) in the rhabdom, and the axons connected to the optic nerve centers.

The retinula of all the ommatidia consist retina.

Notes on connectivity of optic neuropils

Lamina ganglionaris (lamina) and medulla externa (ME), medulla interna(MI), medulla terminalis(NT) in the eye rod are optic neuropils in Stomatopods.(Marshall et al., 2007)

All optic neuropils have subdivisions reflecting subdivisions of the retina - DH, midband, VH.(Marshall et al., 2007)

The axons of the photorecepters project to the lamina, forming synapses with lamina monopolar cells LMCs.(This conclusion is from a paper introducing butterfly, and thus may be inaccurate for mantis shrimps.) (Matsushita et al., 2022)

On the way from basement membrane to the lamina, axons form fasicles, in which the arrangement of the axons twists 180°. The collection of axons and LMCs consists of a structure termed as the cartridge.(Marshall et al., 2007)

In the image of the section at the level of the lamina, the lamina cartridge of MO[5,6] are ovoid in shape, the MO[1-4] rectangular, and DH/VH hexagonal.(Marshall et al., 2007)

References

Marshall, J., Cronin, T. W., & Kleinlogel, S. (2007). Stomatopod eye structure and function: a review. Arthropod Struct Dev, 36(4), 420-448. https://doi.org/10.1016/j.asd.2007.01.006

Matsushita, A., Stewart, F., Ilić, M., Chen, P.-J., Wakita, D., Miyazaki, N., Murata, K., Kinoshita, M., Belušič, G., & Arikawa, K. (2022). Connectome of the lamina reveals the circuit for early color processing in the visual pathway of a butterfly. Current Biology, 32(10), 2291-2299.e2293. https://doi.org/10.1016/j.cub.2022.03.066 (Current Biology)