Novelty and emergent patterns in sperm: Morphological diversity and evolution of spermatozoa and sperm conjugation in ground beetles (Coleoptera: Carabidae)

Abstract

The beetle family Carabidae, with about 40,000 species, exhibits enough diversity in sperm structure and behavior to be an excellent model system for studying patterns and processes of evolution. We explore their potential, documenting sperm form in 177 species of ground beetles using light microscopy and collecting data on one qualitative and seven quantitative phenotypic traits. Our sampling captures 61% of the tribal-level diversity of ground beetles. These data highlight the notable morphological diversity of sperm in ground beetles and suggest that sperm in the group have dynamic evolutionary histories with much morphological innovation and convergence. Sperm vary among species in total length (48-3,400 μm), head length (0.5-270 μm), and head width (0.2-6.3 μm). Most ground beetles make sperm with heads that are indistinct from the flagella at the gross morphological level. However, some or all Omophron, Trachypachus, and Dyschiriini make broad-headed sperm that show morphological differences between species. Most ground beetles package their sperm into groups of sperm, termed conjugates, and ground beetles show variation in conjugate form and in the number and arrangement of sperm in a conjugate. Most ground beetles make sperm conjugates by embedding their sperm in a hyaline rod or spermatostyle. The spermatostyle is remarkably variable among species and varies in length from 17 to 41,000 μm. Several unrelated groups of ground beetles make only singleton sperm, including Nebriinae, Cicindelinae, many Trechinae, and the tribe Paussini. In order to study patterns in sperm evolution, we combine these data with a low-resolution phylogeny of ground beetles. Results from modern comparative analyses suggest the following: (a) sperm differ from conjugates in some aspect of their underlying evolutionary process, (b) sperm have influenced conjugate evolution and vice versa, and (c) conjugation with a spermatostyle likely evolved early within the history of Carabidae and it has been lost independently at least three times.

Figure 14 from: Maddison DR (2020) Shards, sequences, and shorelines: two new species of Bembidion from North America (Coleoptera, Carabidae). ZooKeys 1007: 85-128. https://doi.org/10.3897/zookeys.1007.60012

“…nr. transversale in some other publications (Gómez and Maddison 2020;Kanda, et al 2015;Pflug, et al 2020).…”

Bayesian Pixel Density Estimation Modeling to Detect Human Sperm Sample Image Based on Sperm Head Shape

“…Because the position of the sperm head tended to be uncertain in an image, an uncertainty parameter with a random value was added (Gómez & Maddison, 2020). The set of random values formed subset D that represents the data found and the model parameter , so for each inference, the combined probability distribution of all the random sums of the two parameters was obtained.…”

Figure 1 from: Maddison DR (2020) Shards, sequences, and shorelines: two new species of Bembidion from North America (Coleoptera, Carabidae). ZooKeys 1007: 85-128. https://doi.org/10.3897/zookeys.1007.60012

“…Genome size (1C), as measured by flow cytometry, 2118 Mb in males and 2193 Mb in females (Pflug, et al 2020). Most specimens with singleton (non-conjugated) sperm (Gómez and Maddison 2020).…”