ABSTRACT
Introduction The hagshes are an ancient group of elongate, benthic craniates that inhabit mostly deep-sea habitats throughout the world’s oceans with an antitropical distribution. Hagshes are scavengers, but they are also known to take live prey such as soft-bodied benthic invertebrates (Martini, 1998). Recently, it was shown that hagshes are capable of preying on burrow-dwelling teleosts (Zintzen et al., 2011), although it is not known how common this behavior is. Hagshes possess several adaptations that make them supremely good scavengers. They have a low metabolic rate, which allows them to survive periods of low food availability and starvation (Lesser et al., 1997; Tamburri and Barry, 1999), and they also have an ability to nd and take advantage of falling carrion faster than
Introduction .................................................................................................... 321 Slime function ................................................................................................. 322 The slime glands............................................................................................. 323 Slime gland morphology .............................................................................. 323 Gland mucous cells ........................................................................................ 326 Gland thread cells .......................................................................................... 326 Slime thread synthesis within GTCs ........................................................... 327 Gland interstitial cells .................................................................................... 330 Slime composition, release, and setup ........................................................ 331 Mucous vesicle deployment ......................................................................... 332 Thread skein deployment ............................................................................. 333 Slime mechanics ............................................................................................. 333 Evolution of sliming in hagshes ................................................................ 334 Conclusions and remaining questions ........................................................ 335 References ....................................................................................................... 336
most other benthic scavengers, due to their exceptionally well-developed sense of smell and sensitivity to cues from dead organisms (Tamburri and Barry, 1999) and their moderately good swimming abilities (Lim, 2013). Once a hagsh arrives at a carrion fall, several adaptations allow it to take full advantage of the available food, including a knot-tying behavior that provides the leverage needed to tear off chunks of esh with their modest jaws and keratinous teeth (Clark and Summers, 2007). Although hagshes typically enjoy being some of the rst animals to arrive at deep-sea carrion falls, other scavengers and predators inevitably show up. To fend off both competitors and predators, hagshes possess a unique adaptationthe ability to release large amounts of brous slime from numerous epidermal slime glands (Ferry, 1941; Newby, 1946; Downing et al., 1981a, b; Fernholm, 1981; Fudge et al., 2005). Most aquatic animals, including hagshes, produce some form of epidermal mucous as a barrier defense against microbial pathogens and parasites (Subramanian et al., 2009), but hagsh slime differs from epidermal mucous in its manner of production, its mode of release, and its function. In this chapter, we will describe what is known about the composition, cellular origins, and functions of the slime, as well as its mechanisms of deployment. We will conclude with some thoughts on the evolution of the slime, as well as some new questions that are inspiring further research in this area.
