Koehleraster abnormalis (de Loriol, 1883 )

Arachchige, Gayashan M., Jayakody, Sevvandi, Mooi, Rich & Kroh, Andreas, 2019, Taxonomy and distribution of irregular echinoids (Echinoidea: Irregularia) from Sri Lanka, Zootaxa 4541 (1), pp. 1-100 : 16-19

Koehleraster abnormalis (de Loriol, 1883)

Figures 7 , 10–12

1883 Echinoneus abnormalis de Loriol : p. 41; pl. 5:fig. 2.

1948a Echinoneus abnormalis de Loriol. —Mortensen: p. 80–81; pl. 12: figs. 20, 22.

Material studied. Two denuded tests: WUSL/EI/8 from Hiriketiya and WUSL/EI/9 from Baththalangunduwa 1, Sri Lanka.

Description. Shape and size —Test small to medium-sized, ovoid, 20.4 and 21.8 mm TL, TW 76 and 77% TL, height 47% TL.

Apical system —Tetrabasal; four gonopores, situated slightly anterior of centre of aboral surface, approximately 45% TL from anterior margin of test.

Ambulacra —Non-petaloid; interporiferous zone not elevated; pore-zone depressed and narrow; pores on oral surface smaller and closer together than those on aboral surface.

Tuberculation —Test surface densely covered by small, perforate, non-crenulate primary tubercles; ring of

imperforate and non-crenulate miliary tubercles more or less evenly distributed among primary tubercles; primary tubercles on aboral surface smaller than those on oral surface.

Peristome —Smaller than periproct, length approximately 15% and 16% TL; width 17% and 21% TL; irregularly oval to triangular in shape, pointed towards interambulacrum 2 and 4, moderately sunken, situated slightly anterior to centre of oral surface, c. 47% TL from anterior margin of test to anterior edge of peristome.

Periproct —Larger than peristome, length 25% and 29% TL; width 15% and 17% TL; teardrop-shaped, slightly pointed toward peristome, longitudinally elongate; located orally in interambulacrum 5, close to peristome, 13% TL from posterior margin of test to posterior edge of periproct.

Geographic range. Indo-West Pacific, from Mauritius (de Loriol 1883), East Indies ( Mortensen 1948a) to Coral Sea ( Miskelly 2002), South Pacific Islands ( Clark 1925a; Mortensen 1948a) and Hawaiian Islands ( Clark 1917).

Bathymetric range. Littoral to 85 m ( Mortensen 1948a).

Observed occurrence in Sri Lanka. Dead specimens were found among biogenic sands at Hiriketiya Bay Beach on the southern coast of Sri Lanka and in a coarse sand patch in a sea grass bed at 9 m in Baththalangunduwa on the north-western coast of Sri Lanka ( Fig. 12 ). This species was first recorded from Sri Lanka by Fernando (2006).

Remarks. Collected materials indicate that two genera of echinoneids occur in Sri Lankan waters. At Hiriketiya Bay Beach, dead specimens of E. cyclostomus and K. abnormalis occur together. As no live specimens of both species were collected together in their original habitat, it is inconclusive whether these two species cooccur in the same habitat. Mortensen (1948a: 81) suggests that the two species do not co-occur at the same localities.

Figures

FIGURE 7. SEM images comparing aboral tuberculation on Echinoneus cyclostomus and Koehleraster abnormalis: A, glassy tubercles, miliary tubercles, and primary tubercles of E. cyclostomus; B, primary tubercles and miliary tubercles of K. abnormalis; C, imperforate and non-crenulate primary tubercle of E. cyclostomus; D, perforate and non-crenulate primary tubercle K. abnormalis; A and C, E. cyclostomus (WUSL/EI/6): B and D, K. abnormalis (WUSL/EI/8).

FIGURE 10. Koehleraster abnormalis (WUSL/EI/8): A, aboral view; B, oral view; C, lateral view, right side.

FIGURE 11. SEM images showing details on test surface of Koehleraster abnormalis (WUSL/EI/8): A, apical system; B, periproct; C, orientation of pores on aboral surface; D, orientation of pores on oral surface.

FIGURE 12. Distribution map of Koehleraster abnormalis recorded in this study.