The evolution of red blood cell shape in a continental radiation of fishes

Abstract

The size and shape of Red Blood Cells (RBC) can provide key information on life history strategies in vertebrates. However, little is known about how RBC shape evolved in response to environmental factors and the role of phylogenetic relationship. Here, we analyzed RBC morphometrics in a continental radiation of fishes testing the hypothesis that phylogenetic relationship determines species occupation of morphospace. We collected blood samples of five specimens of 15 freshwater fish species from six orders and used basic stereological methods to measure cell and nucleus area, perimeter, and diameter, cell and nucleus volume, nucleus:cytoplasm ratio, and shape factor of 50 cells per specimen. Then, we conducted a phylogenetic Principal Components Analysis using a dated phylogeny and built a phylomorphospace. To test if the phylogenetic relationship predicted the phenotypic similarity of species, we calculated multivariate phylogenetic signal. We also estimated the evolution rate of RBC shape for each node and tip using ridge regression. Finally, we tested if the position in the water column influenced RBC shape using a phylogenetic GLS. RBC shape seems to have evolved in a non-stationary way because the distribution pattern of species in the phylomorphospace is independent of the phylogeny. Accordingly, the rate of evolution for shape was highly heterogeneous, with an increase in the genus Pygocentrus. Water column position does not influence RBC shape. In conclusion, RBC shape seem to have evolved in response to multiple selective pressures independent of life history characters.

The evolution of red blood cell shape in fishes

“…The shape of red blood cells (RBCs) of bony fish species studied varied from oval to ellipsoid, with a rounded nucleus (Figure 3). The mean cell area in bony fish was 76.64 µm 2 (see data in Martins et al., 2020), and it varied by an order of magnitude, from the largest cell of Synbranchus (174.96 µm 2 ) to the smallest in Leiopotherapon (33.16 µm 2 ). The same phenomenon happened to cell volume, with Synbranchus having 1,631.07 µm 3 one order of magnitude larger than Leiopotherapon 143.83 µm 3 .…”

“…Here, we used data for RBC shape from two major sources: (1) cell size database (http://www.genomesize.com/cellsize/fish.htm) maintained by T. Ryan Gregory and (2) data for specimens collected in the field by us. Specifically, we extracted four variables from the cell size database: cell largest and smallest diameter and nucleus largest and smallest diameter for 38 species from 21 orders of Teleostei and 12 species of four orders of Elasmobranchii (data available at Martins et al., 2020).…”

“…All measurements were made in Motic Images Plus 2.0 in a double‐blind fashion (see Figure S2). We calculated the mean of each variable for each species (data available at Martins et al., 2020), which were used as phenotypic traits in further analysis.…”

“…This analysis automatically finds nodes in which there was a rate shift. The R markdown dynamic document describing how analyses were conducted and associated data are available at Figshare (Martins et al., 2020).…”

Investigating bone resorption in Atlantic herring fish intermuscular bones with solid-state NMR

“…The largest pores 16 in adult IB are only 2.5 μm × 5 μm, far smaller than the nucleated red blood cells of the herring fish 61 (10.7 μm × 7.8 μm) and other fishes. 62 Thus it is impossible to have blood vessels like Haversian or Volkmann channels in herring IB. A recent study on bone resorption shows that osteoclasts rely heavily on increased aerobic glycolysis, 63 a mechanism noticed in active brain cells 64 and proliferating cancer cells.…”