Wednesday, October 19, 2016

[Ichthyology • 2014] Siganus insomnis • A New Species of Rabbitfish (Perciformes: Siganidae) from southern India, Sri Lanka and the Maldives


Siganus insomnis 
Woodland & Anderson, 2014


Abstract

Siganus insomnis sp. nov. is described from the Maldives, Sri Lanka and southern India. It most closely resembles S. lineatus (Valenciennes) from the Western Pacific but differs in coloration, principally in that most if not all of the bronze bands on its mid and upper sides continue horizontally and unbroken through to the nape and opercular slit. By contrast, in S. lineatus, typically the anterior area below the spinous dorsal fin down to the mid-sides is irregularly marked with golden bronze spots, commas, or a maze of contorted lines. S. guttatus (Bloch) is the third member of this group of sibling species; its sides are covered with orange to bronze-gold spots. It is distributed throughout S.E. Asia, i.e., it occupies a geographic position between the areas inhabited by S. lineatus and S. insomnis. Thus the gene pools of S. lineatus and S. insomnis are quarantined from one another by distance and the intervening presence of S. guttatus in S.E. Asia. The geographical separation of the populations of S. lineatus and S. insomnis from one another is reinforced by the absence of suitable, coralline habitats for these species in the western half of the Bay of Bengal.

Keywords: Siganidae, rabbitfish, Siganus insomnis sp. nov., Siganus lineatus, Siganus guttatus, systematics, biology


FIGURE 5. Siganus insomnis, subadults, ca. 15–20 cm SL, Horubadhoo I. (= Royal I.), Baa Atoll, Maldives.

  Photo: Dieter Grage.  DOI: 10.11646/zootaxa.3811.1.8

Siganus insomnis Woodland & Anderson, 2014
Bronze-lined Rabbitfish. 

Local names: ori, (thammas at Addu Atoll), Maldives; oora (Tamil), leella (Sinhalese), Sri Lanka. These local names may also be used to refer to other species of Siganus.

Diagnosis. A deep-bodied species of Siganus which differs from all other siganids in that the whole of the sides of the body with the possible exception of the belly and a narrow strip adjacent to the base of the spinous dorsal fin (where a row of bronze spots may occur) are decorated with horizontal, parallel bronze bands extending the full length of the sides from nape and opercular slit back to and below the large yellow spot below the base of the soft dorsal fin. The majority of these lines on the sides are complete (i.e., uninterrupted) along their length.

FIGURE 6. Siganus insomnis, large adults, ca. 35 cm SL, Komandoo I., Lhavyani Atoll, Maldives. 
  Photo: Dieter Grage.  DOI: 10.11646/zootaxa.3811.1.8 

Etymology. We chose the specific epithet insomnis (Latin, sleep-less) to allude to the nocturnal activity of this fish. It is an adjective agreeing in gender with Siganus (masculine).


Woodland, David J. and R. C. Anderson. 2014. Description of A New Species of Rabbitfish (Perciformes: Siganidae) from southern India, Sri Lanka and the Maldives.
Zootaxa. 3811(1); 129–136.  DOI: 10.11646/zootaxa.3811.1.8

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