Turritella declivis Adams & Reeve, in Reeve, 1849 (Mollusca: Gastropoda) – a South African not an Australian species, and a characteristic component of the Agulhas Bank benthos David G. Herbert* KwaZulu-Natal Museum, Private Bag 9070, Pietermaritzburg, 3200 South Africa, and School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, 3206 South Africa Received 7 August 2013. Accepted 14 October 2013
The name Turritella declivis, as described by Adams and Reeve in the ‘The Zoology of the Voyage of HMS Samarang’ (Adams & Reeve 1848–1850), is currently used for two distinct species of turritellid gastropod, one inhabiting the Agulhas Bank off South Africa and the other occurring off the Australian coast. Examination of the type material clearly shows that the name is referable to the southern African species. The Australian species must henceforth be known as Turritella captiva Hedley, 1987, a name previously regarded as a junior synonym of T. declivis. The original type locality ‘China Seas’ is erroneous, as was often the case with material collected during the voyage of the Samarang. It is emended to be the Agulhas Bank, over much of which T. declivis is common and may, in places, be hugely abundant, forming Turritella-dominated benthic communities. Such communities have been recorded in other parts of the world and are frequently associated with seasonal upwelling events, but have not previously been documented off South Africa. Key words: Turritella declivis, taxonomy, distribution, South Africa.
he description of Turritella declivis given by Adams & Reeve (1850) (see below for correct authorship citation) in their report on the Mollusca of the voyage of HMS Samarang, has been cited as the original reference for two distinct turritellid species, one from Australia (now often referred to Gazameda) and one from South Africa (still referred to Turritella). This is clearly an untenable nomenclatural situation. The purpose of this short communication is to resolve this anomaly and clarify whether the name is correctly applied to the South African or Australian species. I show that the name should be used only for the South African species and at the same time, take the opportunity to provide additional information on its distribution and habitat, based upon a substantial amount of additional material now present in the
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KwaZulu-Natal Museum (NMSA). It is a poorly known species scientifically, but a familiar one in the demersal trawl fishery where it is known as the ‘bokhoring’. On parts of the Agulhas Bank it may comprise a significant component of the invertebrate benthos, occurring patchily at very high population densities. Current synonymy and chresonomy Original context Turritella declivis: Adams & Reeve, in Reeve 1849, pl. 10, fig. 52; Adams & Reeve 1850: 48, pl. 12, fig. 10; Tryon 1886: 200, pl. 62, fig. 70; Yen 1942: 203, pl. 15, fig. 62; Vos 2013. Type loc.: ‘China Seas: Belcher ’ – erroneous and here emended to be the Agulhas Bank. Turritella (Haustator) declivis: Kobelt 1897: 24, pl. 6, fig. 3. South African context Turritella declivis: Sowerby 1897: 17; 1903: 230; Martens 1904: 44, pl. 4, fig. 10; Smith, 1906: 46; Thiele 1925: 112, 355, 357, 358, 361; Tomlin 1925: 313, fig. 2; Barnard 1963: 167, fig. 33c; Kensley 1973: 74, fig. 243; Richards 1981: 41, pl. 13, fig. 107; Abbott & Dance 1982: 60; Steyn & Lussi 2005: 16; Marais 2011: 68. Turritella excavata: Sowerby 1870: 252, pl. 21, fig. 3. Type loc.: Agulhas Bank. Turritella (Torcula) excavata: Martens 1904: 44. Australian context Turritella captiva: Hedley 1907: 500, pl. 17, fig. 26; 1910: 357. Type loc.: Mast Head Reef, Capricorn Group, Queensland. Gazameda declivis: Garrard 1972; 311, pl. 28, fig. 12, pl. 30, fig. 5; Wilson 1993: 139, pl. 14, fig. 12; Atlas of Living Australia 2013; Australian Faunal Directory 2013; OBIS 2013.
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Comparative observations The type material of Turritella declivis Adams & Reeve, in Reeve, 1849 is lodged at the Natural History Museum, London (NHMUK) and comprises two lots, one shell (Fig. 1A,B) from the collection of Mrs J. Lombe-Taylor (NHMUK 1874.12.11.165) and two shells (one illustrated, Fig. 1C,D) from the collection of Hugh Cuming (NHMUK 1982185). They are identified as syntypes and the locality is given as ‘China Seas’. This is consistent with the known disbursement of much of the molluscan material from HMS Samarang (Tomlin 1925; Dance 1986). The specimen from the Lombe-Taylor collection was illustrated by Yen (1942) and identified as the ‘holotype’, presumably because it was at that time the only type specimen known, the Cuming specimens not yet having come to light in the NHMUK collection. All three specimens are now considered syntypes, with the Lombe-Taylor specimen most closely resembling the original figure. All three specimens clearly belong to the same species. Comparative examination of the syntypes clearly shows that they represent the South African species. The adult whorls are relatively flat-sided, though slightly inflated above the suture and shallowly concave near mid-whorl. They lack any prominent spiral cords and are sculptured only by close-set spiral lirae and collabral growth-lines. The colour pattern, albeit now somewhat faded, comprises a broad brown mid-whorl band. These are features typical of southern African material. The original description mentions a necklace of brown subsutural spots, but these are no longer evident in the type material. They are, however, present in fresher juvenile specimens (Fig. 1H) from the Agulhas Bank. In contrast, according to Garrard (1972) in the Australian species ‘from the thirteenth whorl onwards a heavy cingulum develops at top of each whorl, followed by a concave space with two lirae, the lower decidedly stronger; this is followed by two heavy cords at base of each whorl with a fine thread between’. The colour pattern also differs in comprising red-brown blotches ‘irregular in outline and extending vertically down the whorls’. These features are evident in the figures provided by Garrard (1972) and Wilson (1993), but they are clearly not present in the syntypes of Turritella declivis, nor were they mentioned in the original description. It is therefore puzzling why this name was ever applied to Australian material, though it may stem from the fact that the necklace of brown
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subsutural spots on the juvenile shell also occurs in the Australian species. Resolution of the nomenclatural anomaly mentioned above is thus clear – the name Turritella declivis is applicable only to the South African species. For the Australian species there is already another available name, Turritella captiva Hedley, 1907, which recent authors have considered a junior synonym of the Australian T. declivis (Garrard 1972; Wilson 1993; Australian Faunal Directory 2013; OBIS 2013). The original locality given for T. declivis, namely ‘China Seas’ is not consistent with its occurrence in South Africa, but this locality, like ‘Eastern Seas’ is known to have been used liberally and with little care by the HMS Samarang captain, Sir Edward Belcher (Tomlin 1925). It was frequently erroneous (Petit 2007). The ship is known to have done some dredge hauls on the Agulhas Bank en route to southeast Asia and there are other examples of South African molluscs described from the HMS Samarang with similarly erroneous locality data, e.g. Marginella diadochus Adams & Reeve, 1848 and Pleurotoma impages Adams & Reeve, 1848 (Petit 2007) and Margartia bicarinata Adams & Reeve, 1850 (Herbert 1987). I thus emend the type locality to be the Agulhas Bank. Although this species was first collected during the voyage of HMS Samarang, publication of the description in the zoology of this voyage (Adams & Reeve 1850) was delayed and as a result preempted by Reeve’s monograph of the genus Turritella in the Conchologica Iconica, published in 1849. In this work Reeve cited ‘Adams and Reeve, Moll. Voy. Samarang’ and authorship of the species must therefore be cited as Adams & Reeve, in Reeve, 1849 (Petit 2007). Variability Turritella declivis is a morphologically variable species, both in terms of shape and coloration. The common, typical form (Fig. 1A,B) is more or less flat-sided, with only a slight swelling of the whorls above the suture and a shallow to almost imperceptible mid-whorl concavity. At the opposite extreme is the morph named Turritella excavata by Sowerby (1870), which is markedly more tumescent above the suture and has a distinct mid-whorl concavity (Fig. 1I,J). However, between these extremes, there are many intermediates which grade imperceptibly into one another (Fig. 1C–F). The swollen basal part of the whorl should not be interpreted as a spiral cord, as occurs in the Austra-
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Fig. 1. Turritella declivis Adams & Reeve, in Reeve, 1949; A, B, figured syntype (NHMUK 1874.12.11.165, Lombe-Taylor), length 47.3 mm; C, D, one of two additional syntypes (NHMUK 1982185, Cuming), length 53.9 mm; E, well-pigmented individual (NMSA V1366, off Storms River, 116 m), length 63.7 mm; F, specimen with intermediate mid-whorl concavity (NMSA S8613, mid-entrance False Bay, 54 m), length 57.4 mm; G, live-taken specimen with heavily eroded shell and narrow brown band (NMSA V4525, off Tsitsikamma, 120 m), length 59.0 mm; H, juvenile specimen with brown subsutural spots (NMSA B8382, off Nahoon, East London, 85 m), length 22.0 mm; I, J, specimen with deep mid-whorl concavity, holotype of Turritella excavata Sowerby, 1870 (NHMUK 1874.12.11.167, Lombe-Taylor), length 60.1 mm. All figures reproduced to the same scale, except H.
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Fig. 2. Distribution of Turritella declivis. p = NMSA and SAMC material; r = literature records (Martens 1904; Thiele 1925; Barnard 1963).
lian species, although the surface as a whole bears fine close-set spiral lirae. With regard to coloration, the ground colour is cream-white and the most common form bears a broad, dark maroon-brown band at mid-whorl, but this is conspicuously thinner in some specimens (Fig. 1G) and may even be almost completely lacking. At some localities, the surface of the shell is badly corroded or etched (Fig. 1G), presumably due to the nature of the substratum. The largest specimen available measures 96 mm in length, but it has a broken apex and may have exceeded 100 mm if undamaged. Distribution and habitat Turritella declivis is primarily an Agulhas Bank species, ranging from off the Kei River westward to Cape Point and False Bay (Fig. 2), at depths of 40–220 m [live-collected specimens 50–120 m] (see online supplement for locality records). Barnard (1963) recorded additional material from the Atlantic coast of the Western Cape and a further sample has been obtained from the Northern Cape (off Hondeklip Bay – DAFF demersal research survey, cruise 279). However, the extent to which the species occurs off the Atlantic Cape requires further study. No specimens were found in over 50 dredge samples undertaken at depths of 50–200 m between Table Bay and St Helena Bay during the course of the Natal Museum Dredging Programme (1981–1997). A record from Angola (Valdivia Station 81, Große Fisch-Bucht [Baía dos Tigres], Thiele, 1925) was based on material
in a mislabelled sample from the Agulhas Bank (Kilburn 1996). The species may be common to abundant on a variety of substrata, ranging from thick mud to coarse sand, shell gravel and pebbles. On sand and gravel substrata it frequently co-occurs with the bivalves Atrina squamifera (Sowerby, 1835), Nuculana belcheri (Hinds, 1843) and Pitar medipictus Lamprell & Kilburn, 1999, and the scaphopod Schizodentalium plurifissuratum Sowerby, 1894. Judging from dredge hauls, it must in some places constitute a major component, if not the greater bulk of the benthic biomass. A single dredge haul may produce many thousands of T. declivis shells, both dead and alive, and little else (pers. obs.). Such high population densities have been found at localities primarily on the western portion of the Agulhas Bank, between Quoin Point (34.78°S, 19.64°E) and Cape St Blaize (34.19°S, 22.16°E). Nonetheless, even in this area, abundance is patchy and, given the rather limited evidence available, it is not obviously related to the nature of the substratum. Similar Turritella-dominated benthic communities have been found to occur in other parts of the world (Allman 1988 and references therein), but have not to date been documented off southern Africa. In Ghana densities of 5000–10000 individuals/m2 were recorded for T. annulata (Buchanan 1958). Allman (1988) observed that areas of high turritellid abundance frequently also exhibited seasonal upwelling, yet at the same time he noted
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that areas of major, year-round upwelling were not known to harbour high density turritellid populations. The Agulhas Bank, particularly its western half, though beyond the core of the Benguela upwelling system, is undoubtedly influenced by it and subject to local upwelling events (Lutjeharms & Walters 1985; Shannon 1989; Lutjeharms 2006). Allman (1988) postulated that being suspension/deposit feeders, turritellids would prosper on account of the increased phytoplankton production resulting from the nutrientrich upwelling. Why they should not occur at high density in areas of major upwelling is not clear, but it may be associated with the severity of benthic anoxic events in such areas, lower temperatures, acidified water, or a combination thereof. Hence an area such as the western Agulhas Bank which lies adjacent to a major upwelling system, but outside its core, might be more suited to high turritellid biomass. While information on the ecology of this species is currently very limited, the high density at which it may sometimes occur indicates that it is a species worthy of further study with regard to the ecology of the Agulhas Bank and its associated fisheries. I thank Liz Hoenson for information on the Turritella declivis material in the South African Museum (SAMC), and also Winston Ponder (Australian Museum, Sydney) and Shirley Slack-Smith (Western Australian Museum, Perth) for investigating the use of the name Turritella captiva Hedley, 1907 for the Australian species. Images of NHMUK syntypes were supplied by Harry Taylor, NHMUK Photographic Unit, facilitated by Andreia Salvador. The Sea Fisheries Research Institute (now Fisheries Division of the Department of Agriculture, Forestry and Fisheries) kindly provided ship time on board the RV Sardinops and RS Africana in the 1990s. REFERENCES ABBOTT, R.T. & DANCE, S.P. 1982. Compendium of Seashells. E.P. Dutton, New York. ADAMS, A. & REEVE, L. 1848–50. Mollusca. In: The zoology of the Voyage of HMS Samarang: Under the command of Captain Sir Edward Belcher, C.B., F.R.A.S., F.G.S. During the Years 1843–46, (ed.) A. Adams, pp. 1–24 (1848), 25–87 (1850). Reeve, Benham & Reeve, London. ALLMAN, W.D. 1988. Ecology of the Recent turritelline gastropods (Prosobranchia, Turritellidae): current knowledge and paleontological implications. Palaios 3: 259–284. ATLAS OF LIVING AUSTRALIA, 2013. Gazameda declivis (Adams and Reeve, 1848). Online at:http://bie.ala. org.au/species/urn:lsid:biodiversity.org.au:afd. taxon:7690715a-5459-4b8b-b520-08e1fc4b72e5 (accessed 9 July 2013).
AUSTRALIAN FAUNAL DIRECTORY, 2013. Gazameda declivis (Adams and Reeve, 1848). Online at: http://www.environment.gov.au/biodiversity/ abrs/online-resources/fauna/afd/taxa/Gazameda%20 declivis (accessed 9 July 2013). BARNARD, K.H. 1963. Contributions to the knowledge of South African marine Mollusca. Part III. Gastropoda: Prosobranchiata: Taenioglossa. Annals of the South African Museum 47(1): 1–199. BUCHANAN, J.B. 1958. The bottom fauna communities across the continental shelf off Accra, Ghana (Gold Coast). Proceedings of the Zoological Society of London 130: 1–56. DANCE, S.P. 1986. A History of Shell Collecting. E.J. Brill, W. Backhuys, Leiden. GARRARD, T.A. 1972. A revision of Australian Recent and Tertiary Turritellidae (Gastropoda: Mollusca). Journal of the Malacological Society of Australia 2(3): 267–338. HEDLEY, C. 1907. The Mollusca of Mast Head Reef, Capricorn group, Queensland. Part II. Proceedings of the Linnean Society of New South Wales 32: 476–513. HEDLEY, C. 1910. Catalogue of the marine Mollusca of Queensland. Report of the Australasian Association for the Advancement of Science 12: 343–371. HERBERT, D.G. 1987. Revision of the Solariellinae (Mollusca: Prosobranchia: Trochidae) in southern Africa. Annals of the Natal Museum 28(2): 283–382. KENSLEY, B. 1973. Sea-shells of Southern Africa. Gastropods. Maskew Miller, Cape Town. KILBURN, R.N. 1996. Notes on the benthic stations sampled by the deutsche Tiefsee-Expedition (1898– 1899) in southern African waters. South African Journal of Marine Science 17: 325–328. KOBELT, W. 1897. Die Gattung Turritella. In: Systematisches Conchylien Cabinet F.H.W. Martini & J.H. Chemnitz [2nd edn], 1(27): 1–81, pls 1–21. Bauer & Raspe, Nurnberg. LUTJEHARMS, J.R.E. 2006. The Agulhas Current. Springer, Berlin. LUTJEHARMS, J.R.E. & WALTERS, N.M. 1985. Ocean colour and thermal fronts south of Africa. In: South African Ocean Colour and Upwelling Experiment, (ed.) L.V. Shannon, pp. 227–237. Sea Fisheries Research Institute, Cape Town. MARAIS, A. 2011. Field Guide to South African Seashells: Cape Region. Centre for Molluscan Studies, Groenkloof, South Africa. MARTENS, E. VON. 1904 [1903]. Die beschalten Gastropoden der deutschen Tiefsee-Expedition 1898–1899. A. Systematisch-geographischer Teil. Wissenschaftliche Ergebnisse der deutschen Tiefsee-Expedition auf dem Dampfer ‘Valdivia’ 7(A): 1–146, pls 1–5. OBIS, 2013. Gazameda declivis (Adams & Reeve, 1848). In: Indo-Pacific Molluscan Database at http://clade.ansp. org/obis/search.php/15661 (accessed 9 July 2013). PETIT, R.E. 2007. Lovell Augustus Reeve (1814–1865): malacological author & publisher. Zootaxa 1648: 1–120. REEVE, L.A. 1849. Monograph of the genus Turritella. Conchologica Iconica 5, pls 1–11. Reeve, Benham & Reeve, London. RICHARDS, D. 1981. South African Shells – A Collector’s Guide. Struik, Cape Town.
Short communications SHANNON, L.V. 1989. The physical environment. In: Oceans of Life in Southern Africa, (eds) A.I.L. Payne & R.J.M. Crawford, pp. 12–27. Vlaeburg Publishers, Cape Town. SMITH, E.A. 1906. On South African marine Mollusca, with descriptions of new species. Annals of the Natal Museum 1(1): 19–71. SOWERBY, G.B. 1870. Descriptions of forty-eight new species of shells. Proceedings of the Zoological Society of London 1870: 249–259. SOWERBY, G.B. 1897. Appendix to the Marine Shells of South Africa. Sowerby, London. SOWERBY, G.B. 1903. Mollusca of South Africa. Marine Investigations in South Africa 2: 213–232. STEYN, D.G. & LUSSI, M. 2005. Offshore Shells of Southern Africa: a Pictorial Guide to more than 750 Gastropods. Published by the authors. THIELE, J. 1925. Gastropoda der Deutschen TiefseeExpedition, II. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer
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“Valdivia”, 1898–1899, 17(2): 35–382, Pls 13–46. [Dual pagination; also numbered 1–348, Pls 1–34.] Gustav Fischer, Jena. TOMLIN, J.R. le B. 1925. Reports on the marine Mollusca in the collections of the South African Museum. 1. Family Turritellidae. Annals of the South African Museum 20: 309–316. TRYON, G.W. 1886. Naticidae, Calyptraedeae, Turritellidae, Vermetidae, Cæcidae, Eulimidae, Turbonillidae, Pyramidellidae. Manual of Conchology. Ser. 1, Vol. VIII. G.W. Tryon, Philadelphia. Pp. 1–461, pls 1–79. VOS, C. 2013. Turritella declivis Adams & Reeve, 1850. In: World Register of Marine Species at http://www. marinespecies.org/aphia.php?p=taxdetails&id= 731296 (accessed 7 July 2013). WILSON, B. 1993. Australian Marine Shells, Prosobranch Gastropods. Vol. 1. Odyssey, Kallaroo, W. Australia. YEN, T-C. 1942. A review of Chinese gastropods in the British Museum. Proceedings of the Malacological Society of London 24: 170–289. Responsible Editor: D. Pillay
