Indian Journal of Marine Sciences Vol. 31(3), September 2002, pp. 201-206

Occurrence of a new species of colonial ascidian – kaverium sp. nov. and four new records of Eudistoma to Indian coastal waters

V. K. Meenakshi Department of Zoology, A.P.C. Mahalaxmi College for Women, Tuticorin 628 002, Tamil Nadu, India [ E-mail: [email protected] ] Received 14 August 2001, revised 10 June 2002

Five species of colonial ascidians of the genus Eudistoma are reported of which Eudistoma kaverium sp. nov. is new to science and the other four ⎯ Eudistoma constrictum Kott, 1990; Eudistoma laysani (Sluiter, 1900); Eudistoma ovatum (Herdman, 1886); Eudistoma toealensis Millar, 1975 are new records to Indian waters.

[ Key words: colonial ascidians, Eudistoma kaverium, new records ]

So far only two species of the genus Eudistoma – long arising from a common basal test. The basal test Eudistoma viride Tokioka1, 1955 by Renganathan2, mass and about half of the base of the cylindrical 1984 and Eudistoma lakshmiani Renganathan3, 1986 lobes are intensely coated with sand and have sand have been reported from Indian waters. The present internally. The surface test of the head of the colony is study reports the occurrence of a new species – always free of sand. The free upper ends of the lobes Eudistoma kaverium sp. nov. and four more species – are usually circular to oval with 2 mm to 1 cm diame- Eudistoma constrictum Kott4, 1990; Eudistoma ter. The number of lobes in a colony range from laysani (Sluiter5, 1900); Eudistoma ovatum (Herd- 16-51. Occasionally the lobes show short branches. man6, 1886); Eudistoma toealensis Millar7, 1975 for Living colonies are translucent whitish (colour of cau- the first time from Indian waters. liflower) with light flesh coloured zooids. In preserva- Eudistoma kaverium sp. nov. tive the test becomes transparent and flesh coloured. Class: Faecal pellets are completely absent from the test. Order: Enterogona Suborder: Family: Genus: Eudistoma Species: Eudistoma kaverium sp. nov.

Habit and habitat ⎯ Many colonies, found at- tached to the upper surface of dead corals and mollus- can shells were collected from the littoral zone of Mandapam (lat. 9º16’N and long. 79º 8′E), south east coast of India (western Bay of Bengal).

Holotype ⎯ (VOCM AS51) deposited in the as- cidian collections of the Museum of the Research De- partment of Zoology, V.O. Chidambaram College, Tuticorin, Tamil Nadu, India.

Paratype ⎯ (AS.8) deposited in the national collec- tions of the Zoological Survey of India, Southern Re- gional Station, 100, Santhome High Road, Chennai 600 028, India.

External appearance ⎯ (Figs 1 and 2A,B) The colony consists of upright, cylindrical lobes 1-1.5 cm Fig. 1 ⎯ Colony of Eudistoma kaverium sp. nov 202 Indian J. Mar. Sci., Vol. 31, No. 3, September 2002

The zooids open by separate branchial and atrial vascular appendage projects from the posterior end of apertures on the upper surface placed near to each zooid. A maximum of 6 to 7 embryos are present in other in an oval transparent area of test. Each zooid is the atrial cavity of which one or two of them are tailed contained in a compartment in the test which is of the larvae. The larval trunk measures 0.5 to 0.7 mm long. same diameter without any constriction. The con- The tail is wound halfway round. Lateral and median tracted zooids are always found occupying the middle ampullae are present (Fig. 2E). or basal part of the compartment and they are never Remarks ⎯ The characters used to distinguish the severed. Zooids are arranged at right angles to the different species of this genus are the shape, colour of surface test and can be seen extending vertically the colony, cloacal system, test inclusions, number of through the transparent compartments. stigmata in each row, nature of alimentary canal and Internal structure ⎯ (Fig. 2C,D) Zooids are robust, larva. well-expanded zooids measure 9-10 mm. But usually So far only two species of the genus Eudistoma – the contracted zooids are only 3-4 mm long. Zooids Eudistoma viride and Eudistoma lakshmiani have are pinkish brown in preservative. Siphons are rela- been reported from Indian waters. The present species tively short. Thirteen longitudinal muscles are present lacks the characteristic black spots on either side of in the thorax which extends as 4 bundles into the ab- the oral siphon observed in Eudistoma viride and the domen. Twenty six circular muscles are present which larval characters of Eudistoma lakshmiani like the are closely placed in the anterior and middle part of four pairs of lateral ampullae subdivided into two the thorax and loosely placed in the posterior thoracic prominences in the distal end and a single median region. The number of stigmata varies from 12-16 and ampulla along the ventromedian line of the trunk. it is very difficult to count in contracted zooids. The In the absence of colonial systems the present spe- oesophageal neck is long and thin. The stomach is at cies resembles Eudistoma constrictum, Eudistoma the posterior end of the gut loop and the posterior microlarvum Kott, 1990; Eudistoma globosum Kott8, stomach is indistinct. Gonads are in the gut loop and the testis follicles in grape-like clusters spill over the sides. The vas deferens is prominent. A delicate long

Fig. 2 ⎯ Eudistoma kaverium sp. nov. (A) colony, {L-lobe], (B) Fig. 3 ⎯ Eudistoma constrictum (A) relaxed zooid showing gut upper surface of a lobe showing zooid openings, (C) contracted loop, [BA ⎯ branchial aperture; AA ⎯ atrial aperture; zooid drawn from the surface (D) contracted zooid with an em- S ⎯ stigmata; A ⎯ anus; E ⎯ endostyle; R ⎯ rectum; bryo, {AC ⎯ atrial cavity; E ⎯ embryo; BA ⎯ branchial aperture; O ⎯ oesophagus; F ⎯ faecal pellet; ST ⎯ stomach], (B) gut loop S ⎯ stigmata; O ⎯ Oesophagus; ST ⎯ stomach; T ⎯ testis folli- with gonads [I ⎯ intestine; T ⎯ testis follicles; PS ⎯ posterior cles], (E) larva. stomach; V ⎯ vascular process], (C) larva.

Meenakshi : Occurrence of species of Eudistoma 203

1957; Eudistoma elongatum (Herdman, 1886); Eudis- oid-bearing heads of the colony of Eudistoma elonga- toma laysani. It differs from Eudistoma constrictum tum. in the form and colour of the colony, in the absence of Whitish blue iridescence with no embedded sand sand from the surface test of the head of lobes, the and small zooids characteristic of Eudistoma laysani zooids contained in compartments of the test which is have not been observed in the present species. not constricted. The multilobed colony with the translucent whitish The specimen can be easily distinguished from test, long zooids contained in compartments of the Eudistoma microlarvum where the colonies are flat test, absence of sand from the surface test of head are investing sheets or cushions and not lobed like the characteristics of the species. In view of these special present species. The present species differs from the features the present species is identified as a new spe- colonies of Eudistoma globosum in the colour, shape cies and named Eudistoma kaverium sp. nov. of the lobes of the colony, absence of faecal pellets in the test, more than 15 stigmata per row, though they New records for India show similarities in the shape of the colony and the Eudistoma constrictum Kott, 1990 arrangement of zooids. Eudistoma constrictum Kott, 1990, p. 203 This species of Eudistoma can never be confused Habit and habitat ⎯ Many colonies were collected with the club-shaped to long cylindrical rope-like zo- from the intertidal rocky shore of Mandapam, Tamil Nadu, south east coast of India.

Distribution ⎯ Australia, India External appearance ⎯ Colonies irregular cush- ions extending to about 6-7 cm and up to 1 cm high. Zooids open separately in a sand free area. Sand and faecal pellets are present in the test which gradually becomes less towards the base. In some parts of the colony sand was completely absent. The zooid is con- tained in a compartment in the test which is not con- stricted in the upper part of the oesophageal neck.

Fig. 5 ⎯ Eudistoma ovatum (A) upper surface of the colony show- ing openings of zooids, (B) embedded sand on the surface test and Fig. 4⎯ Eudistoma laysani (A) zooid showing gut loop, (B) gut the apertures of the zooids in a sand free area, (C) gut loop with loop with gonads, (C) larva gonads, (D) larva.

204 Indian J. Mar. Sci., Vol. 31, No. 3, September 2002

Internal structure (Fig. 3A,B) ⎯ Zooids pinkish sand throughout the test, absence of circular systems brown when alive but on preservation the colour was and the presence of a narrow constriction between the completely lost. Longitudinal and circular muscles are thorax and abdomen. well developed. Longitudinal muscles extend into the The specimen studied has been deposited in the abdomen as bands. Short siphons, very fine branchial National Collections, Zoological Survey of India, tentacles are present at the base of the branchial si- Chennai (Reg. No.AS.11). phon. About 12-15 stigmata could be counted in each row. The dorsal end of the anterior row curves for- Eudistoma laysani (Sluiter, 1900) Distoma laysani Sluiter 1900, p.9. ward. A short oval posterior stomach present, 2 9 embryos were present in the peribranchial cavity. laysani: Sluiter 1909, p.4. Larval trunk measures 5-6 mm. Lateral and median Eudistoma laysani: Millar 1975, p.221. ampullae alternate with the adhesive organs. Tail is Distoma parva Sluiter 1900, p.6. wound three quarters (Fig. 3C). Eudistoma parvum: Kott 1957, p.77. Polycitor (Eudistoma) olivaceum: Tokioka10 1942 p.497. Remarks ⎯ This species is being reported for the first time in India. The present species resembles Eud- Eudistoma laysani: Kott 1990, p.214. istoma constrictum. The differences noted are consid- Habit and habitat ⎯ Many colonies were collected ered as geographical variations. It can be easily dis- from the intertidal rocky areas of Valinokkam, Ervadi tinguished by the smooth sand free surface test, with and Mandapam, Tamil Nadu, south east coast of India. Distribution – Australia, Palau Islands, Indonesia, Philippines, Hawaii, India

External appearance ⎯ Colonies are lobed with a basal mass of common test. The lobes have a cylin- drical stalk which slightly expands into a flat or rounded head. The lobes are about 3 mm in diameter and 1cm high. The head is covered by delicate trans- parent test. Crowded faecal pellets make the stalks opaque. The stalk is covered by epibionts but devoid of sand. Zooids open separately and there are no sys- tems. About 40-50 zooids are found in a lobe. Living colonies are with bluish white iridescence, but in pre- servative they are more or less colourless.

Internal structure (Fig. 4A,B) ⎯ Well expanded zooids are narrow, very long, with a long narrow oe- sophageal neck. The thorax is about 1 mm. Branchial and atrial apertures have six triangular lobes and the siphons have circular muscles. Fine longitudinal mus- cles are present in the thorax which extend into the abdomen. Circular muscles are present only in the thorax. The atrial siphon originates opposite to the first row of stigmata. A pre-stigmatal area is well de- fined. The branchial sac has three rows of stigmata with 17-20 stigmata in I row and 13-14 in the II and III rows. The smooth stomach is at the posterior end of the abdomen and an oval posterior stomach is pre- sent. Gonads are in the gut loop and 2-3 embryos were present in the atrial cavity. Larvae are small with a trunk 0.5 mm to 0.6 mm and the tail wound halfway around it. An otolith and an ocellus are present. Four

single median ampullae alternate with stalked adhe- Fig. 6 ⎯ Eudistoma toealensis (A) colony, (B) whole zooid, (C) gut loop with gonads (D) larva. sive organs (Fig. 4C).

Meenakshi : Occurrence of species of Eudistoma 205

Remarks – This species is being reported for the Remarks ⎯ This species is being reported for the first time in Indian waters. Though some differences first time in India. The thin coat of sand with interrup- like decrease in the number of zooids and stigmata tion at places of apertures, small zooids, rounded were observed in the present specimens, they are con- lobes of apertures, 15-16 stigmata in a row are charac- sidered within the variation limits. The distinctive teristic of the species. features of the species are lobed colonies, whitish blue The specimen studied has been deposited in the iridescence on the terminal part of the lobes, no em- National Collections, Zoological Survey of India, bedded sand, small zooids and small larvae. Chennai (Reg. No. AS10).

Eudistoma ovatum (Herdman, 1886) Eudistoma toealensis Millar, 1975 Psammaplidium ovatum Herdman, 1886, p.246. Eudistoma toealensis Millar, 1975, p.222. Polycitor arenaceus Sluiter, 1909, p.13. Polycitor scaber Sluiter, 1909, p.25. Habit and habitat ⎯ Many colonies were collected Eudistoma ovatum: Hastings11, 1931, p.82. from the upper surface of rocks exposed during low Eudistoma pyriforme: Tokioka12, 1967, p.110. tide at Valinokkam. Eudistoma ovatum: Kott, 1990, p.222. Distribution ⎯ Kei Islands, Toeal, India External appearance (Fig. 6A) – Colonies are very Habit and habitat ⎯ Many colonies were collected small to massive occupying 5 to 8 cm. The colony has from the undersurface of calcrete rocks in the inter- a basal mass of test completely encrusted with sand, tidal rocky coasts of Mandapam. shell pieces, hydroids, worm tubes, sponges etc. Many Distribution – Australia, Gulf of Carpentaria, Indo- cylindrical lobes arise with a diameter of 3 mm to nesia, Palau and Gilbert Islands, India 5 mm and 1 cm to 1.5 cm length. The lobes are usu- External appearance (Fig. 5A,B) – Colonies firm ally branched and in a colony of 5 cm diameter there encrusting sheets extending over large areas up to are about 120 lobes. Many lobes are dichotomous at 8-10 cm with a thickness of 0.5 to 1 cm. The upper their tips. The stalk and head are not demarcated. surface of the colony is slightly convex towards the Colonies are transparent with flesh coloured zooids. middle and thin towards the edges and form irregular The test is soft, gelatinous and has crowded faecal surfaces. Sand is evenly distributed throughout the pellets but no embedded sand. Sand is present at the test, slightly less in the thoracic than the abdominal base of the stalk; the remaining part of the stalk and region. Faecal pellets not crowded and the test is the upper surface of the head is free of sand. Zooids transparent. Zooids are creamy white to light pink. are crowded, opening all round the surface. Atrial and Circular systems are quite clear as the surface of the branchial apertures open close together. Colonial sys- colony is devoid of sand in the region of the apertures. tems not well formed. Sand present in the remaining part of the surface test Internal structure (Fig. 6B,C) ⎯ Zooids 3 mm to gives a mosaic pattern. Zooids are evenly placed in a 5 mm long when contracted. The branchial siphon is system of 3 mm diameter, short, atrial slightly longer indicating rudimentary

Internal structure (Fig. 5C) ⎯ Zooids are small, the system. Longitudinal and circular muscles form a contracted thorax is quite narrow and about 1mm meshwork in the thorax. Longitudinal muscles con- long. The atrial siphon is long and muscular. The tinue into the abdomen. 12-15 stigmata could be branchial siphon has well developed branchial tenta- counted in each row. Zooids are with a long oeso- cles. Lobes of apertures are rounded. Longitudinal phageal neck, small smooth stomach and a small pos- and transverse muscles are present. The longitudinal terior stomach at the posterior end of the descending muscles extend into the abdomen. Fifteen to sixteen limb of the gut loop. Gonads are in the gut loop. Most stigmata in a row. Gonads and stomach are in the pos- of the zooids were breeding with a maximum of 4 terior end of the abdomen. In contracted zooids the larvae in the atrial cavity. Larval trunk measures 0.6 digestive system is variously wrinkled. Only one em- to 0.7 mm. Ampullae alternate with the adhesive pa- bryo in the atrial cavity. Larvae small, trunk only pillae. Ocellus and otolith are present (Fig. 6D). 0.5 mm long. The tail is wound round three quarters Remarks ⎯ This species is being reported for the around the trunk. Three slender stalked adhesive or- first time from Indian waters. In almost all the fea- gans in the median line anteriorly. Median ampullae tures it resembles the description of Eudistoma have parietal branch (Fig. 5D). toealensis. The characteristic shape of the colony,

206 Indian J. Mar. Sci., Vol. 31, No. 3, September 2002

long finger like lobes with dichotomous branching, Acknowledgement small zooids, larger larval trunk and the absence of a The author expresses her deep sense of gratitude to whitish-blue iridescence distinguish the present spe- Dr. T.K. Renganathan, V.O.Chidambaram College, cies from the other Eudistoma species. Tuticorin for his kind help in confirming the identifi- cation and to the UGC, New Delhi for financial assis- The specimen studied has been deposited in the tance. National Collections, Zoological Survey of India, Chennai (Reg. No. AS9). References Key to the species of Eudistoma recorded from India 1 Tokioka T., Ascidians from the Palao Islands (II), Publs Seto mar. biol. Lab., 5(1955) 43-57. 1. Sand absent from surface test. Black spots on 2 Renganathan T.K., New record and redescription of a rare each side of the oral siphon …...…..…... E. viride colonial ascidian, Eudistoma viride Tokioka 1955 from the Indian waters, Geobios new Reports, 3(1984) 49-51. Sand present in surface test. No black spots on 3 Renganathan T.K., Eudistoma lakshmiani n.sp. ⎯ A new co- each side of the oral siphon ……...…...…….…..2 lonial ascidian from Tuticorin coast of India, Geobios new 2. Colony not lobed ………...……………………..3 Reports, 5(1986) 163-164. Colony lobed……………...………………..…...4 4 Kott P., The Australian Ascidiacea Part 2, Aplousobranchia (1), Mem. Qd. Mus., 29 (1990) 203-220. 3. Sand absent from surface test over anterior ends 5 Sluiter C.P., Tunicaten aus dem Stillen Ocean, Zool. Jb. of zooids. Zooids contained in a compartment in (Systematik), 13(1900) 6-9 the test ..…………………………. E. constrictum 6 Herdman W.A., Report on the Tunicata collected during the Sand present over anterior end of zooids. Zooids voyage of H.M.S.Challenger during the years 1873-76. Pt. not contained in compartment in the test 11, Ascidiae compositae, Zool. Chall. Exp., 14 (1886) 110-246. ……………………….…………...….. E. ovatum 7 Millar R.H., Ascidians from the Indo-west- Pacific region in 4. Lobes finger-like with a dichotomous tip ….. the Zoological Museum, Copenhagen (Tunicata, Ascidi- …...……...………………………… E. toealensis aceae), Steenstrupia, 3(1975) 221- 223. Lobes not finger like without a dichotomous 8 Kott P., Ascidians from Australia 11, Aplousobranchiata La- hille; Forbes and Hanley and Polyclinidae Ver- tip ……….……………………..….………...… 5 rill, Aust. J. mar. Freshw. Res., 8(1957) 72-77. 5. Zooids contained in a long compartment of test 9 Sluiter C.P., Die Tunicaten der Siboga Expedition Pt. 2. Die ………..………..…………… E. kaverium sp.nov merosomen Ascidien, Siboga Exped., 56(1909) 4-25. Zooids not contained in a long compartment of 10 Tokioka T., Ascidians found on the mangrove trees in test ……...……...…………..………………….. 6 Iwayama Bay, Palao, Palao trop. biol. Stn. Stud., 2(1942) 497-506. 6. Stalked colonies without sand embedded in stalk 11 Hastings A.B., Tunicata, Scient. Rep. Gt Barrier Reef Exped., …...…………………..……………….. E. laysani 4(1931) 82-83. Stalked colonies with sand embedded in stalk 12 Tokioka T., Pacific Tunicata of the United States National …………………………..………... E. lakshmiani Museum, Bull. U.S. natn. Mus., 251(1967) 110-112.