Long-beaked echidna (genus Zaglossus)

Family Tachyglossidae

 The modern long-beaked echidnas belong to the genus Zaglossus, which includes three species. They are confined to altitudes between 600–4150 m in the New Guinea highlands, where they are found in a range of ecosystems from montane forests to alpine grasslands (Flannery and Groves, 1998; Opiang, 2009; Wilson and Reeder 2005).  Zaglossus bruijnii is from western New Guinea and possibly Western Australia; Zaglossus bartoni is from central and eastern New Guinea, and the poorly known Zaglossus attenboroughi is known only from the Cyclops Mountains along the north coast of New Guinea (Flannery and Groves, 1998).

In the wild, Zaglossus have a diet of earthworms and wood-boring grubs (Opiang 2009).  Z. bartoni is now known to construct large underground dens or burrows, most likely to avoid predation (Opiang, 2009).

Sensory glands and push-rod mechanoreceptors have been identified at the tip of the beak of the long-beaked echidna (Zaglossus bruijnii; Manger et al., 1997).  The presumably electrosensory gland includes a large dermal gland that produces a seromucous secretion and is connected to the epidermal surface by a duct.  The duct is about 450 µm in length and opens through a pore 100 µm wide.  The gland is innervated at the papillary region where the duct enters an epidermal peg.  

The push-rod mechanoreceptors are usually 250 µm long and 45 to 50 µm wide, a little larger than the same apparatus in the beak of the short-beaked echidna, but smaller than that in the platypus bill.  The push-rod of the long-beaked echidna is attached to the surrounding epidermis (as also seen in the short-beaked echidna), implying a more restricted vertical movement of the rod compared to the push-rod mechanoreceptors in the platypus bill.  Touch on the beak surface produces vertical displacement of the rod, which is detected and transmitted to the central nervous system.

The beak is used in a similar way to short-beaked echidnas, i.e. as a push probe searching moist leaf litter for prey.  In fact the beak of the long-beaked echidna is probably a more effective electrosensory apparatus than that of the short-beaked echidna. Spatial density of sensory glands is about 12/mm2 of skin, but might be higher at the beak tip.  The total population of sensory glands has been estimated at 3,000 (i.e. more than in Tachyglossus but fewer than in the platypus; Manger et al., 1997).

References

Flannery TF and Groves CP (1998) A revision of the genus Zaglossus (Monotremata, Tachyglossidae), with description of new species and subspecies. Mammalia 62, 367–396.

Manger PR, Collins R and Pettigrew JD (1997) Histological observations on presumed electroreceptors and mechanoreceptors in the beak skin of the long–beaked echidna. Zaglossus bruijnii. Proceedings of the Royal Society of London. Series B. Biological Sciences 264, 165–172.

Opiang MD (2009) Home ranges, movement and den use in long–beaked echidnas, Zaglossus bartoni, from Papua New Guinea. Journal of Mammalogy 90, 340–346.

Wilson DE and Reeder DM (Eds) (2005) Mammal Species of the World. A Taxonomic and Geographic Reference. 3 edn. Johns Hopkins University Press, Baltimore.