Ten species of epifaunal sea urchin were identified at Preslies Bay, Transkei, establishing new southern geographical distributions for seven of the species. Local distributions intertidally, subtidally, and within the Mtakatye estuary were documented. Estimates of abundance on the intertidal rocky shore indicated vertical separation between certain species

Hodgson, A.N.

Marshall, D.J.

Pretorius, R.A.

English

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204 Short Communication New southern geographical records of intertidal sea urchins (Echinodermata: Echinoidea), with notes on abundance D.J. Marshall * and A.N. Hodgson Department of Zoology and EntomolQgy, Rhodes University, Grahamstown, 6140 Republic of South Africa R.A. Pretorius Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, 6140 Received 15 May 1991; accepted 12 August 1991 Ten species of epifaunal sea urchin were identified at Preslies Bay, Transkei, establishing new southern geographi-cal distributions for seven of the species. Local distributions intertidally, subtidally, and within the Mtakatye estuary were documented. Estimates of abundance on the intertidal rocky shore indicated vertical separation between certain species. nen spesies van epifauniese seekastaiings is by Preslies-baai, Transkei, ge"identifiseer, wat 'n nuwe suidelike geogra-fiese verspreicling vir sewe van die spesies daarstel. Die be-staan van plaaslike bevolkings is vasgestel in die tussengety-en ondergetysones, sowel as in die Mtakatye riviermonding. Skattings van die hoeveelheid daarvan op die rotsagtige tussengetystrook dui op 'n vertikale skeicling tussen sekere spesies. • To whom correspondence should be addressed Members of the class Echinoidea are common inhabitants of intertidal and subtidal rocky substrata. Within Southern Africa the taxonomy and geographical distribution of rock-dwelling echinoids is documented and summarized by Day (1974), and more extensively by Clark & Courtman-Stock (1976). Whereas only one intertidal species, Parechinus anguJosus, is found along the southern and western coast-lines, the east coast is particularly rich in sea urchin species (Clark & Courtman-Stock 1976). With the exception of P. angulosus, the ecology of the sea urchins inhabiting the east coast has apparently not been investigated (Fricke 1979, 1980; Greenwood 1980; Greenwood & Bennett 1981; Bux-ton & Field 1983; Sweijd 1990). In this paper we present results which extend the southern distribution of seven species of sea urchin and document their local distributions and abundance at Preslies Bay, Transkei. To investigate the richness of sea urchins, a survey was, undertaken intertidally and subtidally along a rocky shore at Preslies Bay, and subtidally in the mouth of the nearby Mtakatye estuary, Transkei (31°53'S /29°15'E; 32°S par-allel). Representatives of each species present, were collec-ted and are to be housed in the East London Museum. After species richness had been established, species abundance on an intertidal rocky platform was estimated by stratified sampling along a transect (using a 1 x 6 m area). Eight S.-Afr. Tydskr. Dierk. 1991,26(4) samples were taken in the low-shore (cochlear and lower balanoid zones; Branch & Branch 1983, pp. 26), as well as in the upper-shore (upper balanoid and Uttorina zones). These regions were distinguishable by the presence of Gelidium pristoides in the low-shore region. Both the open rock and rock pools were examined. Ten species representing seven families of epifaunal sea urchin were found at Preslies Bay (fable 1). Fa- seven of the species this represents an extension of their recorded southern distribution. All species, excepting Eucidaris metuJaria, of which only one specimen was found, were common. The most remarkable new records are those of E. metuJaria, Echinothrix calamaris, Echinostrephus molaris and DilUJema setosurn (presumably mistaken by Day (1974) for the more common Diadema savigny,), all of which have not previously been reported south of the 2~ parallel (Mtunzini). Other than P. anguiosus, these species are regarded as being Tropical Indo-West Pacific in their distri-bution, and only three additional epifaunal species, Asuo-pyga radiata, Temnopleurus toreumalicus and Toxopneustes pi/eo Ius occur at Inhaca, Mozambique (26°00'S; 650 Ian N; Clark & Courtman-Stock 1976). Subsequent intertidal sur-veys at Morgan Bay (32°42'S; 78 Ian S) and East London (33°OO'S; 108 km S), revealed that only Tripneustes gratilla, P. angulosus and Echinometra maJhaei were present at Morgan Bay (conflnning their distributions as reported by Day (1974», with only P. anguJosus being abundant. P. angulosus is the only species which occurs south of East London (33°OO'S), extending its southern distribution to Cape Agulhas (34OW'S; Clark & Courtman-Table 1 List of species of sea urchin inhabiting rock substrata identified at Preslies Bay, Transkei (31° 53'S 129°15'E). PreviOUS southernmost distributions according to Day (1974) and Clark & Courtman-Stock (1976) are also given. Species showing a new southern record are marked with an asterisk. Dash indicates no record. 1° Ref. represents the co-ordinates for one degree reference squares. That within which Preslies Bay is located, is thus 32°S 129°E C&C-S (1976) Day (1974) Family: Species I" Rd. Place Place Cidaridae: Eucidaris ~tuJaria" 26"S!33"E Inhaca Diadematidae: DiaMma salligllyi" 31"S/l9"E Port Edward DiaMma setosum" 26"S!33"E Inhaca Durban EchillOthriJe calamaris" 29"S/31 "E MwnDni Stomechinidae: StomoPfUllIStu lIarwlaris" 31"S/l9"E Port Edward Port St Johns Temopleuridae: SalmIJcis bicolor" 29"S/31 "E MtunDni Durban Toxopneustidae: TripllellStes gratilla 32"SI29"E Coffee Bay EastLondm Echinidae: ParechillllS a1l8w1osllS 34"SI23"E Cape Agulhas Cape Agulhas Echinometridae: EchillO~tra molhaei 30"S13O"E Amanzimtoti Morgm Bay EchillOstrephus molaris" 29"S/31 "E MwnDni Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2010). S. Afr. J. Zoo1. 1991, 26(4) 15 10 • GI 'u GI 0. • -0 ... 5 GI .0 E ~ c 0 I • I 1 I 2 I I 3 4 I 5 distance (100 kml I 6 p • I 7 m • e • I 8 Figure 1 Species richness of epifaunal rock-dwelling sea urchin occurring at Inhaca, Mozambique (i; from Clark & Courtman-Stock 1976), and at, three sites of various distances south of Inhaca: Preslies Bay, Transkei (P), Morgan Bay (m) and East London (e). Stock 1976), and thence up the West Coast. The present study shows that there is a marked decline in species richness over a small distance south of Preslies Bay (108 kID S; Figure 1). The change from a tropical to a temperate echinoid fauna therefore appears to occur within a short defmable region. It would be interesting to determine whether similar transitions exist for tropical representatives of other littoral fauna and flora. Four species were recorded in the estuary and subtidally, alike (Table 2). However, the absence of records of other species in these regions may be due to the possible incom-pleteness in sampling. Two species, E. calamaris and Salmacis bicolor, were found in the Mtakatye estuary only (Table 2). Intertidally, species diversity was greatest in the upper-shore zone with six species being recorded from pools (Table 2). E. matMei was the most abundant urchin having Table 2 Lower and upper intertidal, subtidal (S) and estuarine (E) distributions and abundance of epifaunal sea urchin at Preslies Bay (N, total number of individuals counted within 8 x 6 m2 ; n, number of samples in which the species was present). P indicates an observation of more than one individual; N/O indicates species was not observed L/intertidal VI intertidal Species N (fI) N (fI) S E Diadema savigflyi N/O 34 (7) P P Diadema setoslU1l N/O 5 (4) N/O P EehillOlhrix ealamaris N/O N/O N/O P Stomopfleustes vario/aris 105 (8) 40 (7) P N/O Sa/macis bie%r N/o N/O N/O P Tripneustes gratilla N/O 4 (3) P N/O Parenchillus angll/osus 107 (8) N/O N/O N/O Eehillometra malhaei N/O 166 (8) P N/O Eehillostrepluu molaTis N/O 27 (6) N/O N/O 205 a density of 166 individuals per 48 m2 (3,46 ± 1,55 (8) m·2; i ± SD (n». There was variability in abundance and species composition between pools in the upper-shore. Where D . savignyi was abundant, there was a low count for Stomo-pneustes variolaris, and D. setosum and T. gratilla were observed in 50% or less of sampled pools . Only two species, P. angulosus and S. variolaris were found on the low-shore, where they occurred in equal num-bers (Table 2). P. angulosus, however, was notably more common at the extreme low-water level. Although S. vario-laris showed the widest vertical distribution, their abun-dance declined upshore. It is interesting to note that P . angulosus was absent from the upper-shore at Preslies Bay, as this species was commonly found in upper-shore pools at Morgan Bay. The distributions of these urchins could be influenced by a number of factors, and studies on inter-specific competi-tion and resource partitioning could prove rewarding. Toler-ance of physical conditions is also of importance in deter-mining their distribution. Firm adhesion to the substratum by P. angulosus in comparison to the upper-shore urchins, Diadema and P. gratilla (pers.obs. D.J.M), will allow it to withstand more vigorous forces of wave-wash. The long, slender spines of Diadema, whilst affording protection against predators, will offer resistance to wave-wash. The distribution of the boring urchin, E. molaris, must depend on rock substratum. Acknowledgements We thank Peter and Sandy Wynn for providing accommoda-tion near Preslies Bay. References BRANCH, G.M & BRANCH, M.L. 1983. The living shores of· Southern Africa. Struik, Cape Town. BUXTON, C.D. & FIELD, J.G. 1983. Feeding, defaecation and absorption efficiency in the sea-urchin, ParechinllS ang.uosllS (Leske). S. Afr. J. Zool. 18: 11-14. CLARK, A.M. & COURTMAN-STOCK,J. 1976. The echinoderms of Southern Africa. British Museum (Natural History), London. DAY, J.H. 1974. A guide to marine life on southern African shores. A.A. Balkema, Cape Town. FRICKE, A.H. 1979. The effect of kelp grazing by the common local sea urchin Parechinus ang.uosllS (Leske). S. Afr. J. Zool. 14: 143-148. FRICKE, A.H. 1980. Aspects of the population structure of Parechinus ang.uosllS (Leske) around the Cape Peninsula. S. Afr. J. Zool. 15: 177-185. GREENWOOD, PJ. 1980. Growth, respiration and tentative energy budgets for two populations of the sea urchin Parechinus ang.uosllS (Leske). Estum. cstl. shelf Sci. 10: 347-367. GREENWOOD, PJ. & BENNE'IT, T. 1981. Some effects of temperature-salinity combinations on the early development of the sea urchin Parechi,,1IS a"g.uosllS (Leske). J. Exp. Mar. Bioi. &01. 51: 119-131. SWEUD, N.A. 1990. The digestive mechanisms of an intertidal grazer, the sea urchin Parechinus ang.uosllS (Leske). M.Sc. thesis, Rhodes University, South Africa. Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2010). 

New southern geographical records of intertidal sea urchins (Echinodermata: Echinoidea), with notes on abundance

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New southern geographical records of intertidal sea urchins (Echinodermata: Echinoidea), with notes on abundance

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