Visual pathways in the brain of the jumping spider Marpissa muscosa

• Published in: Journal of comparative neurology (1911) 2020-07, Vol.528 (11), p.1883-1902
• Main Authors: Steinhoff, Philip O. M., Uhl, Gabriele, Harzsch, Steffen, Sombke, Andy
• Format: Article
• Language: English
• Subjects: Axons; brain; Eye; jumping spider; Marpissa muscosa; Neural networks; Neuropil; principal eyes; RRID AB_1541510; RRID AB_2315147; RRID AB_2338680; RRID AB_2534074; RRID AB_2637882; RRID AB_477585; RRID AB_528479; secondary eyes; Spiders; Visual discrimination; visual neuropils; visual pathway; Visual pathways
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.24861

Some animals have evolved task differentiation among their eyes. A particular example is spiders, where most species have eight eyes, of which two (the principal eyes) are used for object discrimination, whereas the other three pairs (secondary eyes) detect movement. In the ctenid spider Cupiennius salei, these two eye types correspond to two visual pathways in the brain. Each eye is associated with its own first‐ and second‐order visual neuropil. The second‐order neuropils of the principal eyes are connected to the arcuate body, whereas the second‐order neuropils of the secondary eyes are linked to the mushroom body. We explored the principal‐ and secondary eye visual pathways of the jumping spider Marpissa muscosa, in which size and visual fields of the two eye types are considerably different. We found that the connectivity of the principal eye pathway is the same as in C. salei, while there are differences in the secondary eye pathways. In M. muscosa, all secondary eyes are connected to their own first‐order visual neuropils. The first‐order visual neuropils of the anterior lateral and posterior lateral eyes are connected with a second‐order visual neuropil each and an additional shared one (L2). In the posterior median eyes, the axons of their first‐order visual neuropils project directly to the arcuate body, suggesting that the posterior median eyes do not detect movement. The L2 might function as an upstream integration center enabling faster movement decisions. Most spider species possess eight eyes, of which two (the principal eyes) are used for object discrimination, whereas the other three pairs (secondary eyes) detect movement. Jumping spiders are particularly renowned for their visual abilities and we studied the neural substrate for visual processing in the jumping spider Marpissa muscosa. We show that the principal eye pathway involves two subsequent visual neuropils and the arcuate body. Among the secondary eyes, the anterior lateral and the posterior lateral eyes are connected to two subsequent visual neuropils (AL1, PL1, and AL2/PL2) and the mushroom body (MBp). They also share an additional second‐order visual neuropil (L2), which might serve as integration center. The small posterior median eye is connected via a single visual neuropil (PM1) with the arcuate body and might thus not detect movement. Additional data on the visual pathways in the ctenid spider Cupiennius salei are provided and differences to M. muscosa are discussed.