Lowland streaked tenrec

The lowland streaked tenrec (Hemicentetes semispinosus) is a small tenrec found in Madagascar.

Lowland streaked tenrec[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Afrosoricida
Suborder: Tenrecomorpha
Family: Tenrecidae
Genus: Hemicentetes
Species:
H. semispinosus
Binomial name
Hemicentetes semispinosus
G. Cuvier, 1798
Lowland streaked tenrec range

Distribution and habitat

The species is found in tropical lowland rain forest, in the northern and eastern parts of Madagascar. They can be found on land, splashing in shallow waters or digging underground.

Description

Physical appearance

The lowland streaked tenrec (Hemicentetes semispinosus) belongs to the family Tenrecidae in the order Afrosoricida, and more specifically to the subfamily of the spiny tenrecs Tenrecinae.[3] The average body size for H. semispinosus is a length of 140 mm (5.5 in) however adults have been recorded to grow up to a maximum of 172 mm (6.8 in). Body weight for adults of this species can range from 125–280 g (4.4–9.9 oz).[4] This species has a black spiny pelage with yellow or chestnut-brown stripes that run the length of the body.[4][3] There is a median yellow stripe that runs down the rostrum along with one dorsal and two lateral stripes that mark the length of the body and may serve as a warning to predators. Quills are present in this species being longer and more numerous on the head and nuchal area. However, the ventral region contains few to no quills but have the ability to detach in predation defense.[4]

Unique Aspects

H. semispinosus possesses sensory hairs that are scattered on the dorsum that are similar to vibrissae.[4] The streaked tenrec has an evolutionary adaptation for its semifossorial habits with a well developed lateral and long heads of M. triceps brachii and enlarged M. teres major that function as an extensor of the elbow joint and as an adductor of the upper arm for digging. This species also has elongated hands and second, third, and fourth digit adaptation that acts as the main fossorial adaptation.[3] The middle of the skull of this species is long and low, the alveolar processes of the maxilla, premaxilla and mandible are reduced and the palate narrow. The teeth are small, spaced, and placed farther forward on the skull. The temporal muscles, sagittal, and nuchal crests are weaker compared to other tenrec species.[5]

Population Threats

These tenrecs, H. semispinosus, are threatened primarily by the loss of their natural habitat due to continuous deforestation, as it is with many other animals in the Madagascar region. This species is also being hunted for food. [6]

Behavior

Diet

The lowland streaked tenrec is active both during the day and at night. Its diet is made up primarily of earthworms, but they will sometimes prey on other invertebrates as well. They may be seen stamping their feet on the ground with their fore-paws, an adaptation which is believed to increase earthworm activity for easier foraging.[7] Most tenrecs possess a long snout for poking around in the ground to find their food. They are also capable of eating fruit.

Reproduction

Breeding takes place during October to December and possibly at other times, depending upon local food supply and temperature. The gestation period lasts 58 days, and the female gives birth to usually between 5 and 8 young. The young are weaned at 18 to 25 days.

Shelter

The streaked tenrec lives in long, shallow burrows which are usually occupied by family groups.

Spines as tools

H. semispinosus has hard keratinous quills located in the mid-dorsal region that act as a sounding device and is thought to be used for communication between mother and young and/or a warning signal to predators.[4][8] Movement of these quills causes the tips to rub together and create a high frequency sound.[4] These quills are located in a small area of the mid-dorsal region in a group of seven to sixteen arranged in three rows.[4][8] Five quills run laterally on each side and is flanked by five to six quills being light brown in color. The arrangement and number of quills does not alter during growth and neither does the length. The circumference of the quills however, does change from juvenile to adult.[8]

When an individual is aggravated a defense response is produced by erecting its quills laterally and forward and produces sound when the quills vibrate.[4][3] H. semispinosus has a highly developed sense of smell and this response along with foot stamping is also produced when the odor of a predator is detected.[4][9] This display additionally occurs when males fight for females and when unfamiliar males come across one another. Female encounters however, have tactile contact and then increase the distance between each other.[4] It uses its quills to communicate in two different ways, by raising them in agitation or by rubbing them together in a method known as stridulation – best known as the type noise produced by crickets and cicadas. The sound produced is too high to be perceived by human ears. [9]

Sound

The streaked tenrec is the only mammal known to use stridulation for generating sound, a method more commonly associated with insects and snakes.[10][11] Due to its rarity, there are not sufficient information regarding the functional-morphological mechanism of the streaked tenrec. The sounding quills are different from the spines and hair and are found in the mid-dorsal region of the streaked tenrec. The arrangement and length are similar throughout the streaked tenrec's life span, making up three rows in its midline area and adjacent areas bilaterally.[12] Cutaneous muscles underneath the quills were confirmed and are known as quill vibrator disc; they are around 16.8 mm long and 8.55 mm in width for an adult. These cutaneous muscles were the apparatus that contribute the vibration of the quills and production of sound for communication. [13]

Physiology

The streaked tenrec has the ability to enter torpor seasonally however, it is dependent on altitude, age, fat stores, and temperature. Torpor for this species generally occurs during June and July and during winter. However, H. semispinosus is a facultative hibernator and will come out of torpor during winter and forage. When foraging the soil and leaf litter is prodded with the tip of the nose until prey is detected.[4] Elongated hands and digit adaptation (digits 2, 3, and 4) are the tenrecs main digging apparatus allowing it to unearth and pull its prey form the earth.[3]

The skull has an elongated rostrum with a slender jaw with small spaced dentition placed more forward in the mouth.[4][5] This species has zalambdodont molars with a dental formula of I 3/3, C 1/1, P 3/3, M 3/3 having a total of 40 teeth.[4] The sagittal crest and nuchal are less prominent in this species and the zygomatic processes are long and slender resulting in less projection from the sides of the skull.[4][5] The occipital region in this species along with the visceral skeleton are commonly very conservative.[9]


It is also very closely related to the Highland Streaked Tenrec.

References
  1. Bronner, G.N.; Jenkins, P.D. (2005). "Order Afrosoricida". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 77. ISBN 978-0-8018-8221-0. OCLC 62265494.
  2. Stephenson, P.J.; Soarimalala, V.; Goodman, S. (2016). "Hemicentetes semispinosus". IUCN Red List of Threatened Species. IUCN. 2016: e.T40593A97189434. doi:10.2305/IUCN.UK.2016-1.RLTS.T40593A97189434.en. Retrieved 14 December 2019.
  3. Endo, H., Oishi, M., Yonezawa, T., Rakotondraparany, F., & Hasegawa, M. (2007). The semifossorial function of the forelimb in the common rice tenrec (Oryzorictes hova) and the streaked tenrec (Hemicentetes hemispinosus). Anatomia, histologia, embryologia, 36(6), 413-418.
  4. Marshall, C., & Eisenberg, J. (1996). Hemicentetes semispinosus. Mammalian Species, (541), 1-4. doi:10.2307/3504327
  5. Butler, P. (1941). A Comparison of the Skulls and Teeth of the Two Species of Hemicentetes. Journal of Mammalogy, 22(1), 65-81. doi:10.2307/1374685
  6. Olson, Link E. “Tenrecs.” Current Biology, Current Biology, 2013, www.cell.com/current-biology/pdf/S0960-9822(12)01324-3.pdf.
  7. "Hemicentetes semispinosus (streaked tenrec)". Animal Diversity Web. Retrieved 2017-06-18.
  8. Endo, H., Koyabu, D., Kimura, J., Rakotondraparany, F., Matsui, A., Yonezawa, T., ... & Hasegawa, M. (2010). A quill vibrating mechanism for a sounding apparatus in the streaked tenrec (Hemicentetes semispinosus). Zoological science, 27, 427-432.
  9. Schunke, A. C., & Zeller, U. (2010). Chondrocranium and dermal bones of the lowland streaked tenrec Hemicentetes semispinosus (Afrosoricida, Tenrecidae) and their comparison with Potamogale and other insectivoran-grade placental mammals. Vertebrate Zoology, 60(1), 37-72.
  10. "World's loudest animal is recorded for the time". Archived from the original on 2011-07-05. Retrieved 2011-07-09.
  11. Bizarre mammals filmed calling using their quills and spiders
  12. name="Endo et al 2010">Endo, H., Koyabu, D., Kimura, J., Rakotondraparany, F., Matsui, A., Yonezawa, T., ... & Hasegawa, M. (2010). A quill vibrating mechanism for a sounding apparatus in the streaked tenrec (Hemicentetes semispinosus). Zoological science, 27, 427-432.
  13. Hideki Endo, ["A Quill Vibrating Mechanism for a Sounding Apparatus in the Streaked Tenrec (Hemicentetes semispinosus)"], "Zoological Science", 2010
  • Simon and Schuster's Guide to Mammals
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