. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MICROTUBULES IN SPERM OF MACROSTOMUM The motile spermatozoon of Macrostomum contains cortical singlet micro- tubules and there are no free or incorporated axonemes (Fig. 1). Negative staining reveals that, typically, the subunits of the cortical singlets are helically arranged, and sometimes undergo a transition to the protofibrillar configuration; this latter configuration was found to terminate in at least 12 protofibrils for a number of singlet microtubules. •&1 MATERIALS AND METHODS Specimens of Macrostomum sp. were
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MICROTUBULES IN SPERM OF MACROSTOMUM The motile spermatozoon of Macrostomum contains cortical singlet micro- tubules and there are no free or incorporated axonemes (Fig. 1). Negative staining reveals that, typically, the subunits of the cortical singlets are helically arranged, and sometimes undergo a transition to the protofibrillar configuration; this latter configuration was found to terminate in at least 12 protofibrils for a number of singlet microtubules. •&1 MATERIALS AND METHODS Specimens of Macrostomum sp. were collected from still water below the dam of University Lake near Chapel Hill, North Carolina. Whole animals were placed in a Columbia watchglass containing 1% aqueous phosphotungstic acid (PTA), pH The animals were teased with steel needles, and drops of the PTA, containing spermatozoa freed from the animal, were transferred to Formvar- CORTICAL SINGLET MICROTUBULES. FIGURE 1. Diagram of the arrangement of cortical singlet microtubules in the nuclear region of a spermatozoon of Macrostomum. No axonemes are present. carbon-coated 200-mesh copper grids. After approximately 6 minutes, the fluid was drained from the grids which were then allowed to dry; preparations were examined with the Zeiss 9A electron microscope. RESULTS In sectioned spermatozoa of Macrostoimtm, there are ca. 60-80 cortical singlet microtubules; 30-40 were present in material negatively stained with PTA (the remainder presumably having been digested away or lost spatially from the total complement during the process of negative staining). Three arrangements of the subunits in these PTA-treated microtubules were found. (1) In a few regions, the subunits were in the intact helical configuration (Fig. 2), comparable to that described for cortical singlet microtubules in spermatozoa of other flatworms. (2) There were large areas in which the lateral spacing of the subunits was increased, but the circumferen
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
