Lytocarpia delicatula ( Busk, 1852 )

Chakraborty, Oishinee & Raghunathan, C., 2020, Notes on seven Aglaopheniids (Cnidaria: Hydrozoa: Aglaopheniidae) from Andaman and Nicobar Islands with three new records to India, Zootaxa 4790 (2), pp. 291-317 : 300

Lytocarpia delicatula ( Busk, 1852)

( Fig. 2d , 4 a–f)

Plumularia delicatula Busk, 1852: 396 .

Aglaophenia delicatula Bale, 1884: 167 ; Borradaile, 1905: 843; Billard, 1913: 106; Jaderholm, 1920: 8; Jarvis, 1922: 350; Pennycuik, 1959: 185; Watson, 2000: 57.

Thecocarpus delicatulus Millard & Bouillon, 1973: 94 ; Millard, 1975: 455.

Lytocarpia delicatula Schuchert, 2003: 235–237 ; Di Camillo et al., 2011: 528; Schuchert, 2015: 360.

Material examined. Stn. 2: 10.ix. 2017, 8 m; Stn. 25: 14.v. 2018, 18 m; Stn. 29: 21.iii. 2018, 13 m; Stn. 31: 19.iii. 2018, 20 m; Stn. 33: 06.x. 2016, 18 m; Stn. 35: 23.iii. 2018, 13 m; Stn. 38: 22.ix. 2016, 15 m.

Description. Colonies with pinnately arranged hydrocladia and no second order of branching ( Fig. 4e ). Hydrocaulus monosiphonic with a prosegment and two basal hinge joints ( Fig. 4f ). Entire hydrocaulus, above the hinge joint, divided by oblique nodes. Each node bearing a hydrocladium and a hydrocladial apophysis. Hydrocladial apophysis with one mamelon and three nematotheace; one inferior anterior and one on either side of the apophysis. Hydrocladia segmented by transverse nodes and the entire segment covered by the hydrotheca. Hydrothecae completely adnate on the adcauline side. Hydrothecal margin bearing 5 teeth with one prominent abcauline tooth. Intrathecal shelf present extending from adcauline to abcauline wall of the lower part of the hydrotheca ( Fig. 2d ). Lateral nematothecae directed upwards and reaching beyond the hydrothecal margin. Median inferior nematotheca adnate for half its length. Free half gutter shaped, reaching beyond the hydrothecal margin. Reproductive structures were absent.

Colour. Brown hydrocaulus, white hydrocladia ( Fig. 4a ).

Remarks. This species is a new report to Indian waters and only sterile specimens of the species were encountered in the Andaman Islands with a bathymetric range of 8– 20m.

Associated fauna. The bivalve Pterelectroma physoides (Lamarck, 1819) was found attached to the colony. Also, egg masses of nudibranch were observed at the base of the colonies ( Fig. 4d ).

Substrate. The species was observed to be overgrowing entire surfaces of rocks and boulders ( Fig. 4c ) and on polychaete tubes ( Fig. 4b ).

Distribution. Type locality; Torres Strait.

India; Andaman and Nicobar Islands (Present study).

Elsewhere; Northern Australia, Great Barrier Reef, Australia, Indonesia ( Di Camillo et al., 2011), Seychelles, Maldive Islands, Mozambique (Di Camillo et al. 2012) and Okinawa Islands, Japan ( Schuchert, 2015).

Figures

FIGURE 2. Illustrations of hydrothecae. a, Aglaophenia cupressina Lamouroux, 1816. b, Gymnangium hians (Busk, 1852). c, Lytocarpia brevirostris (Busk, 1852). d, Lytocarpia delicatula (Busk, 1852). e, Macrorhynchia philippina Kirchenpeuer, 1872. f, Macrorhynchia phoenicea (Busk, 1852). g, Monoserius pennarius (Linnaeus, 1758). Scale bar, a, b, g= 200µm, c, d, e, f, h, i=100µm.

FIGURE 4. Lytocarpia delicatula. a, In-situ photo of colony at Rifleman Island. b, Colonies growing on polychaete tubes at Guitar Island. c, Colonies overgrowing entire substrate surfaces at Rifleman Island. d, Nudibranch egg masses attached at the base of the colonies. e, Colony showing alternately arranged hydrocladia. f, Hinge joint at the basal portion of the hydrocaulus. Scale bar, e, f= 2mm.