John Blake (1947–2016) was a leader in fluid mechanics, his two principal areas of expertise being biological fluid mechanics on microscopic scales and bubble dynamics. He produced leading research and mentored others in both Australia, his home country, and the UK, his adopted home. This article reviews John Blake’s contributions in biological fluid mechanics, as well as gives the author’s personal viewpoint as one of the many graduate students and researchers who benefitted from his supervision, guidance and inspiration. The key topics from biological mechanics discussed are: “squirmer” models of protozoa, the method of images in Stokes flow and the “blakelet” solution, discrete cilia modelling via slender body theory, physiological flows in respiration and reproduction, blinking stokeslets in microorganism feeding, human sperm motility and embryonic nodal cilia.

The majority of research on Histomonas meleagridis was performed in the first half of the last century, especially those on morphological aspects. In the present study identical monoxenic settings for cultures of the same H. meleagridis clonal strain in its virulent low passage and attenuated high passage form enabled a comparative analysis of parasite characteristics. For the first time, it could be shown that long-term in vitro cultivation led to a severe shift in cell morphology, with the occurrence of a very distinct phenotype expressing a flagellated and highly amoebic cell morphology. Furthermore, the attenuated parasites showed better growth rates and a higher tenacity when confronted with adverse conditions. During these experiments up to 100% of the parasites, both virulent and attenuated, assumed a completely rounded morphology elucidated by electron microscopy. The findings indicate that such previously reported cyst-like stages are a defence strategy of H. meleagridis, independent of the passage level in vitro and pathogenicity in vivo. In conclusion, long-term in vitro passaging of H. meleagridis led not only to an attenuation of the parasite, as previously demonstrated, but also to a shift in the parasite's phenotype regarding morphology, growth behaviour and a higher level of tenacity.

Asterosap, a sperm-activating peptide (SAP) from the starfish egg jelly coat, is diffusible and controls a cGMP-signalling pathway in starfish sperm in the same manner as resact, a potent chemoattracting SAP in sea urchins. This fact suggests that asterosap may serve as a chemoattractant like resact at concentrations with appropriate gradients. Since asterosap is one of three egg jelly components, which in concert induce the acrosome reaction, it is still worthwhile to evaluate how asterosap modulates sperm motility prior to this reaction. We analysed the flagellar movement of sperm of the starfish Aphelasterias japonica in artificial seawater (ASW) containing the asterosap isoform P15 at 1 μmol l−1. We found that sperm swim straighter with more symmetrical flagellar movement in P15 than in ASW, but without any significant difference in the flagellar beat frequency and the swimming velocity. The flagellar movement is, however, dramatically different between sperm firmly attached to the solid surface by the head in P15 and those attached in ASW: in P15 the flagellum bends to a greater extent, with higher curvature and with higher shear angle up to a right angle to the flagellar wave axis, and beats at an increased frequency. The vigorous flagellar movement of sperm, which can be activated when sperm are placed in high-load circumstances just as entering into a jelly layer, may increase propulsive forces and hydrodynamic resistances, allowing sperm to undergo the acrosome reaction as effectively as possible.