Echinolampas ovata (Leske, 1778)

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 : 24-26

Echinolampas ovata (Leske, 1778)

Figures 14B, D , 15B , 17 , 18

1778 Echinanthus ouatus Leske : p. 127; pl. 20: c, d.

1948a Echinolampas ovata (Leske) .—Mortensen: p. 275–281; pl. 4: figs. 1–8.

Material studied. Five denuded tests: WUSL/EI/3, EI/112, and EI/114, from Negombo 1, WUSL/EI/113, from Baththalangunduwa 1, WUSL/EI/4, from Silavathurai, Sri Lanka.

Description. Size and shape —Test moderately large, 44.7–57.0 mm TL; elongated outline, TW 85–92% TL; strongly inflated, TH 60–71% TL, with widest point coinciding with tip of posterior petals; posterior margin pointed.

Apical system —Monobasal, with four gonopores; situated anterior of centre, 29–34% TL from anterior margin of test.

Ambulacra —Petals with unequal poriferous zones, anterior poriferous zones usually four pore pairs longer than posterior ones in posterior paired petals; length difference in anterior paired petals often not as pronounced and showing more variation (in the studied specimens, posterior poriferous zones between 3 to 6 pore pairs longer than anterior ones); poriferous zone IIIa 2 to 3 pore pairs longer than zone IIIb; outer and inner pores of pore pairs equal in size and rounded in shape; poriferous zones of paired petals converge toward distal ends; posterior paired petals, anterior paired petals, and petal III extending up to 56%, 66%, and 61% of corresponding test radius, respectively; at their widest point, petals bear 7 to 9 tubercles across the interporiferous zone; phyllodes typically consisting of inner series with up to 4 pores per column, outer series with up to 9 pores; medial double row of up to 13 sphaeridial pits; buccal pores large and slightly elongated.

Interambulacra —Bourrelets relatively well-developed, indenting peristome; distinct naked zone in oral interambulacrum 5 almost extending from periproct to peristome; reduced naked zone in oral ambulacrum III; likewise, adoral tuberculation of lateral interambulacra sparse.

Peristome —Small; slightly elongated transversely; length 7–9% and width approximately 11% TL; sunken, with steep walls formed by distinct bourrelets; located anterior of centre, c. 32% TL away from anterior margin of test.

Periproct —Inframarginal; slightly larger than peristome, length 12–14% and width 11–13% TL.

Geographic range. Indian Ocean, from the Red Sea (Agassiz & Desor 1887), Mauritius ( Mortensen 1948a), Sri Lanka ( Clark 1917), Bay of Bengal ( Koehler 1922), and Northern Australia ( Clark 1925a) to East Indies ( Agassiz 1872).

Bathymetric range. 9–75 m ( Mortensen 1948a).

Observed occurrence in Sri Lanka. This species typically occurs in sandy patches between patch reefs along the western, north-western, and northern coasts of Sri Lanka at depths of 6–28 m ( Fig. 18 ). First reported from Sri Lanka by de Loriol (1875).

Remarks. Elongation of test was observed to vary considerably in the studied material, which is in line with the observations by Mortensen (1948a: 276–277). The present material shows marked variations in size of the apical system and gonopore diameter.

Figures

FIGURE 14. Comparison of pore-pairs (A and B) and peristome (C and D) between Echinolampas alexandri (A and C, WUSL/EI/1) and Echinolampas ovata (B and D, WUSL/EI/3).

FIGURE 15. Comparison of interambulacrum 5 between Echinolampas alexandri (A, WUSL/EI/1) and Echinolampas ovata (B, WUSL/EI/3).

FIGURE 17. Echinolampas ovata (WUSL/EI/3): A, aboral view; B, oral view; C, lateral view.

FIGURE 18. Distribution map of Echinolampas ovata recorded in this study.