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<I>Patiriella Vivipara</I> (Echinodermata: Asteroidea

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<I>Patiriella Vivipara</I> (Echinodermata: Asteroidea AUSTRALIAN MUSEUM SCIENTIFIC PUBLICATIONS Prestedge, G. K., 1998. The distribution and biology of Patiriella vivipara (Echinodermata: Asteroidea: Asterinidae) a sea star endemic to southeast Tasmania. Records of the Australian Museum 50(2): 161–170. [7 October 1998]. doi:10.3853/j.0067-1975.50.1998.1277 ISSN 0067-1975 Published by the Australian Museum, Sydney naturenature cultureculture discover discover AustralianAustralian Museum Museum science science is is freely freely accessible accessible online online at at www.australianmuseum.net.au/publications/www.australianmuseum.net.au/publications/ 66 CollegeCollege Street,Street, SydneySydney NSWNSW 2010,2010, AustraliaAustralia Records of the Australian Museum (1998) Vol. 50: 161-170. ISSN 0067-1975 The Distribution and Biology of Patiriella vivipara (Echinodermata: Asteroidea: Asterinidae) a Sea Star Endemic to Southeast Tasmania GEOFFREY K. PRESTEDGE 16 Geeves Crescent, Midway Point Tasmania 7171, Australia ABSTRACT. The asterinid sea star Patiriella vivipara is endemic to southeast Tasmania and has a highly restricted distribution, being only known from four locations. It has an unusual pattern of viviparous reproduction, giving birth to juveniles. In this study the birth rate, growth rate, size and age at commencement of reproduction of P vivipara was examined in aquaria for a period of six years. The population of P vivipara at Pittwater was also monitored through monthly examination of a permanent 1m2 quadrat in which the number of adults and juveniles were counted and recorded. These counts were made over an eight-year period. Patiriella vivipara gives birth to juveniles through the year with a period of enhanced reproduction from November to January. Records of water salinity and temperature were taken at Pittwater, as were air temperatures and exposure times during low tide. PRESTEDGE, GEOFFREY K., 1998. The distribution and biology of Patiriella vivipara (Echinodermata: Asteroidea: Asterinidae) a sea star endemic to southeast Tasmania. Records of the Australian Museum 50(2): 161-170. Patiriella vivipara (DartnallI969) (Asterinidae) is a small aboral surface. It is not known whether self, cross 5 armed asterinid sea star that incubates its young in the fertilisation or both takes place. An unusual feature of P gonads (Dartnall 1969; Byrne 1991, 1996). When first vivipara and P parvivipara is that intragonadal cannibalism described (Dartnall, 1969) it was the only known species supports post-metamorphic growth to an advanced size of sea star to exhibit viviparity. Three other viviparous (Byrne, 1996). asteroids were subsequently found and these are also Patiriella vivipara is endemic to southeast Tasmania, asterinids. They are Asterina pseudoexigua pacifica, and has a highly restricted distribution. In the original (Hayashi, 1977) from Japan, Patiriella parvivipara, survey (Dartnall, 1968) this species was recorded from only (Keough & Dartnall, 1978) from South Australia and P three localities, Pittwater, Roches Beach and Eagle Hawk pseudoexigua from Queensland, (Byrne, pers. comm.). Neck. In 1990 another colony was found on the southern Patiriella vivipara is a simultaneous hermaphrodite and shore of Fortescue Bay (Fig. 1). Patiriella vivipara is a most of the gonads are ovotestes, thereby creating the uniform orange/yellow orally and aborally, has a maximum potential for self fertilisation (Byrne, 1996). The juveniles radius (R) of 15 mm and the average adult size is emerge through the gonopores which are located on the approximately 10.00 mm R. 162 Records of the Australian Museum (1998) Vol. 50 The popUlation of Patiriella vivipara at Pittwater was examined on the shore and in aquaria. From 1976 to 1982 specimens were maintained in glass aquaria to determine growth rate, size at first reproduction, birth rate and potential for reproduction in isolation. The sea stars fed on an algal film that formed on the walls of the aquaria. For the growth rate study, five juvenile P. vivipara (radii 1.25-2.25 mm), were followed for up to six years. They were placed in aquaria in isolation and periodically removed to measure their radius (R) from the centre of the disc to the end of the arm. These sea stars were also used to determine the potential for reproduction in isolation, and the aquaria were monitored for the appearance of new juveniles. The size at which these P. vivipara produced their first young was recorded. For the reproductive output study, six adults (R = 9.0 mm) were placed in each of two aquaria and the number of juvenile births recorded. The population of Patiriella vivipara at Pittwater was censused at approximately monthly intervals from 1976- 1983. Each month the number of individuals in a fixed 1 m2 quadrat was counted and their radii measured. The quadrat was sited at the base of the rockfill along the southern side of the eastern causeway and was marked by rocks on a gently sloping area of the rockfill. Several environmental parameters were measured at the area in Pittwater occupied by P. vivipara. These included air and sea temperature and water salinity. Water salinity Figure 1. Locality map for Patiriella vivipara in south-east and temperature were recorded on a monthly basis Tasmania. approximately 1.5 hrs before or after high tide, using a salinity/temperature meter. Patiriella vivipara can be emersed for several hours at low tide and so the air Viviparity in P. vivipara represents the most derived temperature was recorded from a thermometer set up at life history pattern in the Asteroidea, and provides my home. The length of time that the sea stars were important in sights into the evolution of development emersed during the low tide was recorded by noting the (Byrne, 1996; Byrne & Cerra, 1996). Patiriella is a time with a watch. specious genus in Australia (Dartnall, 1970) and their Day and night feeding activity of P. vivipara at Midway divergence was associated with developmental change Point in the Pittwater area was also examined. This (Byrne, 1995; Byrne & Cerra, 1996; Hart, et al., 1997). involved documentation of the position of the sea stars on Considering the highly restricted distribution of P. vivipara, top of or under rocks, and whether they had their stomachs its non-dispersive life history and its scientific importance, extruded. this study provides essential information for the conservation biology of this unique sea star. Results Methods Distribution and habitats In this study reproduction and growth of Patiriella vivipara The sites where Patiriella vivipara occurred are shown in was documented in aquarium and field observations Fig. 1. At each site P. vivipara was found only in the upper spanning a eight-year period from 1975 to 1983. The area of the intertidal zone. At Pittwater this sea star was population of P. vivipara on the shore was also monitored found among or under loose rock on a gently sloping at Pittwater (42°48'S 147°32'E), Eagle Hawk Neck sandstone shelf (Figs. 2a-c), and at a maximum depth of (43°01'S 147°55'E) and Roches Beach (42°54'S 147°30'E). 1.5 m at H.W.S. The shore in Upper Pittwater where the The length of shoreline at all sites occupied by this asteroid main concentration of P. vivipara occurred (Fig. 1) was estimated by noting the presence of the asteroids while consisted of approximately 50% sand or sandy mud and measuring the distance walked along the shore. During 50% sandstone shelf. Lower Pittwater was mostly sand or 1995 the popUlation on the southern shore of Fortescue sandy mud, except for a small area of sandstone on the Bay (42°08'S 147°57'E) was examined, and the length of southern end of Midway Point where P. vivipara could be shoreline occupied by P. vivipara was also measured. found (Figs. 2a-c). 1\vo causeways, approximately 1 km Emphasis was placed on the Pittwater site because this long, link Midway Point to the western and eastern shores has the largest known population of P. vivipara. of Pittwater respectively. Just below high water, P. vivipara Prestedge: endemic Tasmanian sea star 163 occurred in a narrow band on the sandstone and basalt rocks used to construct the causeways. Pittwater is a sheltered bay opening to the open sea by a narrow channel at the south-east corner. Pittwater had the largest population of P. vivipara, comprised of several thousand specimens. At this site P. vivipara inhabited approximately 5 km of the shoreline. At Roches Beach (Fig. 1) the population of P. vivipara was limited to a sandstone shelf approximately 100 m2 that protrudes out from the middle of a sandy beach. Although Roches Beach is a relatively sheltered site, the rock shelf can be subjected to considerable wave action at times, dependent upon the wind direction. There was a good cover of loose rocks where P. vivipara could shelter. Here P. vivipara only inhabited the inshore northern quarter of the rock shelf in an area roughly 35 m 2 • In 1983 the population was estimated to be comprised of approximately 400 animals. The Eagle Hawk Neck (Fig. 1) site differs from the other two locations in being a large platform of sedimentary rock on the open (eastern) coast where it is exposed to Tasman Sea conditions. A well known tourist attraction (The Tessellated Pavement), the site has an estimated population of 1500 P. vivipara sheltered amongst carpets of the small mussel Xenostrobus pulex. During calm sea conditions in the summer months specimens were occasionally found in the open in pools on the pavement. At Eagle Hawk Neck a second population of P. vivipara is located about half a kilometre to the north of The Tessellated Pavement. Here P. vivipara were found on the rock platform under rocks. Their numbers were difficult to estimate due to the size and placement of the rocks. The combined length of shoreline inhabited by P.
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