Bulletin Zoölogisch Museum UNIVERSITEIT VAN AMSTERDAM Vol. 12 No. 4 1989 Pneumoderma heronensis nov. sp.: A new Pteropod (Opisthobranchia; Gymnosomata) from Australian waters L.J. Newman & S. van der Spoel Abstract In April 1987, seven specimens of a new species of the gymnosomatous pteropod, Pneumodermaheronensis were collect- , ed from surface waters between Heron and Wistari Reefs, southern Great Barrier Reef, Australia (23° 27’S 151° 55’E). Addi- tional specimens were identified from CSIRO plankton collections from the Northwest Shelf, Western Australia (19° 25’S 119° 30’E). This new species is describedand illustrated from living specimens. Uniquely, P. heronensis possess 12 lateral buccal arm suckers, arranged alternately in two rows. Morphological comparisons are made with closely related species; P. mediterraneum (Van Beneden, 1838), P. atlanticum atlanticum (Oken, 1815) forma eurycotylum (Meisenheimer, 1905) and P. degraafíi Spoel & Pafort-van Iersel, 1982. INTRODUCTION cíes are distinguished by the number of lateral buccal Pneumodermatidae are rare within Australian waters, arm suckers, the number of lateral radula teeth, and only three species have been previously reported. the arrangement of the gills. Pneumoderma mediterraneum (Van Beneden, 1836) is known from the Great Barrier Reef and Ara- fura Sea (Russel & Coleman, 1935; Spoel, 1976). METHODS Pneumodermopsis paucidens (Boas, 1886) and P. All specimens were collected situ while SCUBA div- spoeli Newman and Greenwood, 1988 occur within ing or by dipnet from surface waters of Heron Island. Great Barrier Reef waters (Newman & Greenwood, Animals were immediately relaxed with Ms222 and 1988).The family Pneumodermatidae is distinguished four specimens everted their buccal apparatus within from all other gymnosomatous pteropods by the pre- 20 minutes. Radulae were dissected out, soaked in sence of acetabuliferous (sucker bearing) lateral buc- 10% KOH for 24 hours, sonically cleaned and pre- cal arms. In the genus, Pneumoderma the median pared for light microscopy and scanning electron mi- buccal arm is reduced or lacking, and both lateral and croscopy. Hooksacs were stained with acid fuchsin posterior gills are fringed (Van der Spoel, 1976). Spe- and mounted for light microscopy. 82 Each hooksac is armed with numerous Pneumoderma heronensis nov. sp. proboscis. (approximately 100) fine hooks. The hooks are ar- Material examined ranged in four longitudinal rows along the inner mar- from in size towards the proximal end; Holotype: Collected while SCUBA diving surface wa- gin, decreasing ters off the north side of Heron Reef on April 19,1987. The even smaller hooks are distributed over the entire animal was sexually mature and measured 12.5 mm in surface of the hooksac (fig. 1C). The radula formula is length when relaxed (Australian Museum C# 156728). Paratypes: Six paratypes were collected by dipnet from 6-0-6, with 23- 25 rows (fig. 2A & B). surface waters off the northeast side of Wistari Reef (23° 27'S 151° 55'E) on 20,1987. Relaxed body lengths April REMARKS All ranged from; 10.9 to 15.9 mm. specimens are pre- heronensis resembles P. me- served in buffered 5% formalin and lodged at the Australi- Pneumoderma closely Australia C# 156729 - and an Museum, Sydney 156732, diterraneum which has been previously reported from the Institute for Taxonomie Zoology, University of Amster- the Great Barrier Reef (Russel & Coleman, 1935). dam ITZ, ZMA. Moll. 389010. The major difference between these species is in the buccal there 7 Type Locality number of lateral arm suckers, being North side of Heron Reef, southern Great Barrier suckers per arm in P. mediterraneum and 12 in P. Reef, off Gladstone, Queensland, Australia (23° 27'S heronensis. The arrangement of these suckers also between alternate in two 151° 55'E); bottom dept approximately 20 m. differs species as they rows but in in Twenty-three specimens were identified from CSI- in P. heronensis, are arranged a single row Russel noted RO plankton samples, collected on October 27,1983 P. mediterraneum. & Coleman (1935) from the Northwest Shelf, of Western Australia (19° that the lateral arm in their one specimen was only 25'S 119° 30'E). Lengths of these contracted speci- partially extended. Without dissection, these authors from 5.85 not have all the suckers and mens (stored in 70% ethanol) ranged to may observed present it P. mediterraneum. 10.2 mm. hence mistakenly ascribed to Additionally, Tesch (1950) noted that there is an in- suckers with in Pneumo- crease in the number of age DESCRIPTION dermatidae. However, P. heronensis cannot be con- adults of the latter The extended body is barrel shaped, with brown and fused with P. mediterraneum, as suckers their black chromatophores over all surfaces exculding the species have fewer despite greater 20 wings. The median footlobe is long and pointed; the body size (length mm; Van der Spoel, 1976). lateral footlobes joint at the anterior margin. The The two formae of P. atlanticum have between 8 to each Forma wings are short, and broad distally. The lateral gill is 16 suckers on lateral buccal arm. eury- well developed and fringed. The posterior gill is cotylum (Meisenheimer, 1905) differs from P. heron- fringed, with four radiating crests that join medially. ensis in having a reduced number of lateral radula median radular rounded median foot- The visceral mass does not extend to the posterior teeth, a tooth, a end of the body (fig. 1A). All specimens had devel- lobe, and only the posterior gill is fringed. Forma pyg- differs in four later- oped ovotestes, as seen through the body wall. maeum (Tesch, 1903) possessing lateral and The everted buccal apparatus displays two lateral al radular teeth, a short gill, eight suckers, 3 Van der arms with 12 stalked suckers arranged alternately in being small in size (length mm; Spoel, two rows (fig. 1B). The suckers are flat, disc-shaped, 1976). heronensis differs from P. on short stalks and unequal in size. The largest suck- Pneumoderma degraaffi the of buccal suckers ers (up to 1 mm in diameter) are situated medially on in possessing twice number the buccal arm and the terminal four to live suckers (stalked), whereas in the latter, the suckers are at- the tached the buccal wall. The radula formula also dif- are extremely small. The proboscis can extend to to bears in P. heronensis there is double the same length as the body and, uniquely, two fers, whereby Pafort-van short 'tentacles' medially. The hooksacs are long, ap- number of lateral teeth (Van der Spoel & proximately one-half to two-thirds the length of the lersel, 1982). 83 Fig. 1 Pneumoderma heronensis nov. sp. A, holotype, whole animal; B, paratype, everted buccal apparatus, C, partially ev- erted hooksac, Northwest Shelf (bar= 1 mm). 84 A B Fig. 2 Scanning electron micrograph of the radula of Pneumoderma heronensis 20 KV: A, one complete side of the radula, bar= 0.1 mm; B, details of the lateral radular teeth, bar- 0.01 mm. 85 BIOLOGY University Women (Brisbane) and the Zoology De- Heron Island specimens were observed in situ, within partment, University of Queensland. The study was a plankton swarm ot predominantly ctenophores, lar- facilitate by assistance from: the Heron Island Re- vaceans, siphonophores and the euthecosomatous search Station; CSIRO - Division of Fisheries, Hobart; pteropod Diacavolinia longirostris forma longirostris the Electron Microscope Centre, University of (Blainville, 1821). The Northwest Shelf specimens Queensland. Special thanks goes to Dr. J.G. Green- in full of D. for- wood for his advice and were also found samples longirostris comments. carnivorous and ma longirostris. Gymnosomes are their selective feeding on euthecosomatous ptero- pods has been investigated by Lalli (1970 a & b). LITERATURE CITED BOAS, J.E.V. 1886. Spolia atlantica. Bidrag til Pteropo- Boas (1886) found specimens of Pneumodermawith dernes. sustematik til kundskaden Morfologi og smat Cavolinia tridentata in their guts. It is assumed that om deres geografiske udbredelse.- Vidensk. Selsk. P. heronensis were feeding on the abundant euthe- Skr. (6) (naturvidensk. mathemat. Avd. 4 (1): 1 - 231. LALLI, C.M. 1970a. Morphology of Crucibranchaea macro- cosome D. longirostris f. longirostris both at Heron chira (Meisenheimer), a gymnosomatous pteropod.- Island and off the Northwest Shelf. Proc. malac. Soc. London, ¿2(1): 1-14. LALLI, C.M. 1970b. Structure and function of the buccal These gymnosomes were observed, to be rapid apparatus of Clione limacina (Phipps), with a review of swimmers, frequently avoiding capture by a SCUBA the feeding in gymnosomatous pteropods.- J. Exp. diver or dipnet. Paratypes were only successfully mar. Biol. Ecol. 4(2): 101-118. NEWMAN, L.J. & J.G. GREENWOOD, 1988. A new captured by using a dipnet at the surface and follow- gym- nosome, Pneumodermopsis spoeli (Gastropod, Opis- ing individuals from a dinghy. thobranchia) from the Great Barrier Reef, Autralia.- Ve- liger, 21 (1/2): 75-79. RUSSEL, F.S. & J.S. COLEMAN, 1935. Mollusca.- Sc. Etymology Rep. Great Barrier Reef Exped., g: 236-253. The specific name heronensis is given in honour of SPOEL, van der S. 1976. Pseudothecosomata, Gymno- the Heron Island Research Station (a facility of the somata and Heteropoda (Gastropoda), 484pp. (Bohn, Scheltema, and Holkema. Utrecht). University of Queensland), Gladstone, Queensland, SPOEL, van der S. & T. PAFORT-Van IERSEL, 1982. Australia. Pneumoderma degraaffi n. sp., a pteropod new to science (Mollusca Opisthobranchia).- Bull. zool. Mus. Univ. Amsterdam, 2 (3): 17-20. TESCH, J.J. 1950. The Gymnosomata.- Dana Rep., 6 (36): ACKNOWLEDGEMENTS 1-55. Funding was provided by the Australian Federation of L.J. Newman, Zoology Department, University of Queensland, St. Lucia, Brisbane, Old., Australia. 4067. S. van der Spoel, Institute for Taxonomie Zoology, University of Amsterdam, P.O. Box 4766, 1009 AT Amsterdam, Received: 6 February 1989. Netherlands. Distributed: 3-XI-1989..