Schorno Sarah, Gillis Todd E, Fudge Douglas S
Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
J Exp Biol. 2018 Apr 6;221(Pt 7):jeb172254. doi: 10.1242/jeb.172254.
Hagfishes are known for their unique defensive slime, which they use to ward off gill-breathing predators. Although much is known about the slime cells (gland thread cells and gland mucous cells), little is known about how long slime gland refilling takes, or how slime composition changes with refilling or repeated stimulation of the same gland. Slime glands can be individually electrostimulated to release slime, and this technique was used to measure slime gland refilling times for Atlantic and Pacific hagfish. The amount of exudate produced, the composition of the exudate and the morphometrics of slime cells were analyzed during refilling, and as a function of stimulation number when full glands were stimulated in rapid succession. Complete refilling of slime glands for both species took 3-4 weeks, with Pacific hagfish achieving faster absolute rates of exudate recovery than Atlantic hagfish. We found significant changes in the composition of the exudate and in the morphometrics of slime cells from Pacific hagfish during refilling. Over successive stimulations of full Pacific hagfish glands, multiple boluses of exudate were released, with exudate composition, but not thread cell morphometrics, changing significantly. Finally, histological examination of slime glands revealed slime cells retained in glands after exhaustion. Discrepancies in the volume of cells released suggest that mechanisms other than contraction of the gland musculature alone may be involved in exudate ejection. Our results provide a first look at the process and timing of slime gland refilling in hagfishes, and raise new questions about how refilling is achieved at the cellular level.
盲鳗以其独特的防御性黏液而闻名，它们用这种黏液抵御用鳃呼吸的捕食者。尽管人们对黏液细胞（腺丝细胞和腺黏液细胞）了解很多，但对于黏液腺重新充满需要多长时间，或者黏液成分如何随着重新充满或对同一腺体的反复刺激而变化，却知之甚少。可以对黏液腺进行单独电刺激以释放黏液，这项技术被用于测量大西洋盲鳗和太平洋盲鳗的黏液腺重新充满时间。在重新充满过程中，以及在对充满的腺体进行连续快速刺激时，分析了所产生的渗出物的量、渗出物的成分以及黏液细胞的形态学指标。两种盲鳗的黏液腺完全重新充满都需要3至4周，太平洋盲鳗渗出物恢复的绝对速率比大西洋盲鳗更快。我们发现太平洋盲鳗在重新充满过程中渗出物的成分和黏液细胞的形态学指标有显著变化。在对充满的太平洋盲鳗腺体进行连续刺激时，会释放出多团渗出物，渗出物成分发生了显著变化，但丝细胞形态学指标没有变化。最后，对黏液腺的组织学检查显示，在耗尽后腺体中仍保留着黏液细胞。释放的细胞体积存在差异，这表明渗出物喷射可能涉及除腺体肌肉组织收缩之外的其他机制。我们的研究结果首次揭示了盲鳗黏液腺重新充满的过程和时间，并就如何在细胞水平上实现重新充满提出了新问题。
