19 



Early authors supposed the long tongue to be folded in an s-shape within the closed mouth 

 (Moller 1932). Next, the tongue was disproved to be inserted witliin a dermal pouch as in 

 woodpeckers or Phohdota. In fact, the tongue, when not m use, shortens to an extent that 

 it fits into the mouth cavity. Later on, anatomical studies revealed an extremely complex 

 morphology of the tongue musculature. 



Hie M. genioglossus is broadened into an extrinsic tongue muscle, the M. stemohyoideus 

 is integrated mto the tongue as a retractive muscle ("hi fimctional terms, it could be called 

 Stemoglossus" Wille 1954; "tumiel insertion" in Griffiths 1983) and considerably leng- 

 thened - its origin at the sternum being shifted back from the manubriimi to the base of 

 the xiphoid process. Simultaneously, the insertion of the M. stylohyoideus at the tongue is 

 shifted from ventral to lateral, thus enabling to support the M. stemohyoideus when 

 retracting the tongue. 



hi Glossophaga, the tongue is passed through by one comparatively enormous central 

 artery (Lonchophyllinae: two arteries) and two lateral large veins (Griffiths 1978). The 

 latter are covered by muscle bundles which contract and press the stenmied flow of blood 

 up to the tongue tip thus eloiigatmg and stiffening the tongue additionaUy (vasoliydrauhc 

 tongue). All the time the entire tongue remains entirely flexible and can be bent in all 

 directions. Furthermore, it reacts with a reflex on contact with sugar, thereby moving into 

 nectar droplets without need of visual control. 



Thus, the nectar supply is exploited within very short time. It is, anyway, still unknown 

 how the rapid in- and efflux of the blood necessary for the high frequent hcking 

 movements - 12 movements per second (v. Helversen & v. Helversen 1975) is achieved. 

 Dorsally and laterally the tongue is covered with papiUae, wliile its imderside is 

 completely smooth. A detailed description of various papiUae was given by Griffiths 

 (1982). Essentially, effective nectar intake is acliieved by means of the hair papillae 

 (PapiUae fihfomies) of the tongue situated at the anterior tliird and laterally (bmsh-hke 

 tongue). Aided by specialized lateral (Lonchophyhmae) or median (Glossophaginae) 

 grooves, these structures retain considerable amounts of fluid wliich is set free by 

 compression of the tongue at the palate during retraction. Nevertheless, the detailed 

 process and the coordination of tongue motoricity and swallowing are not yet sufficiently 

 known. 



Esophagus 



All chiropterans have a quite narrow esophagus, as they usuaUy chew up their food 

 thoroughly before swaUowiiig. This is the same m nectar feeders which take in fluid food 

 or very smah particles. Compared to insect-eating chiropterans, the esophagus epithehum 

 is much thirmer in nectar feeding bats (Dobat & Peikert 1985) and not keratinized as in 

 pure insect-eaters. 



Stomach 



The stomach of blossom bats is designed to take large quantities of fluid within a ratlier 

 short time. According to Howell (1979), Leptonycteris will absorb 4g - corresponding to 

 22% of its body weight - within just 20 minutes. Interestingly, the muscle layer of the 

 stomach is very thin. In macroscopical respect there is a conspicously oversized blind sack 

 and an enlarged pylorus area, botli features contributmg to the necessary volume capacity. 

 Furthermore, the low proportion of pepsinogen producing cells within the fimdus glands 

 of the mucosa (Rouk & Glass 1970, Forman 1971) correlates with the diet being 

 comparatively poor in proteins. 



