MASTERARBEIT Titel der Masterarbeit „Diversity, habitats & size-frequency distribution of the gastropod genus Conus at Dahab (Gulf of Aqaba, Northern Red Sea)“ verfasst von Sarah Zauner BSc angestrebter akademischer Grad Master of Science (MSc) Wien, 2015 Studienkennzahl lt. Studienblatt: A 066 833 Studienrichtung lt. Studienblatt: Master Ökologie Betreuerin / Betreuer: Univ.-Prof. Mag. Dr. Martin Zuschin O C TABLE F ONTENTS ABSTRACT .................................................................................................................................................................................... 2 ZUSAMMENFASSUNG ............................................................................................................................................................... 3 INTRODUCTION ......................................................................................................................................................................... 4 STUDY AREA ................................................................................................................................................................................ 5 LF F THE GU O AQABA................................................................................................................................................................................5 ABITAT TYPES MATERIALH & METHODS................................ ...................................................................................................................................................................................................................................................................................................................5 6 AMPLING STATIONS S ATA ................................................................................................................................................................................ 6 SAMPLING DESIGN.....................................................................................................................................................................................7 ANALYSIS RESULTSD ................................................................................................................................................................................................................................................................................................................................................................................8 9 PECIES COMPOSITION ABUNDANCE S Y D & .................................................................................................................................................. 9 ICROHABITAT UTILIZATION M B ................................................................................................................................................................ 11 SIZE-FREQUENC ISTRIBUTION.........................................................................................................................................................11 HERMIT CRA OCCUPATION DISCUSSION ...............................................................................................................................…………………………………………………………………………………………………………………...............................................12 13 PECIES DIVERSITY AND ABUNDANCE S Vermivorous species ..................................................................................................................................................................................................................................................................................................................... 13 PECIES DISTRIBUTION MICROHABITAT UTILIZATION S Molluscivorous and& piscivorous species ............................................................................................................................................................................................................................................... 14 F 14 Y D 15 PECIES COMPOSITION O HABITAT TYPES S B ........................................................................................................................................ 15 SIZE FREQUENC ISTRIBUTION..........................................................................................................................................................16 ERMIT CRA OCCUPATION CONCLUSIONH .............................................................................................................................................................................................................................................................................................................................................17 18 ACKNOWLEDGEMENTS .............................................................................. 19 ................................................................................... FIGURES & TABLES ............................................................................................................................................................... 20 SUPPLEMENTARY MATERIAL ...…………………………………………………………………………………………………… 36 ....... REFERENCES .………………………………………………………………………………………………………………………………….. 37 1 ABSTRACT Conus, one of t e Theuted venomous gastropodt tal genuse the of themos diverse marin genera,larly is widelye distribthe throughout coas on.marin environments al tropics and iseparticu diversed in Indo-Weslly Pacific regi al Previousoral ecologic ort theassessments t haver fdemonstrat Conus that topographicathe t complexon subtid , c reefsl reefsupp ehighes of numb o species with lowes , populati densitiese dalintertida flats the ar t intermediatee diversity. ander,high abundance oand extensiv subti sanded areasConus are leason divers habitat types Howev d no studyTherefore,has sI providefar particularly a first ecologicaladdress assessmentdistributi of the genuspatterns Conusin the alongNorthern a fringingRe Sea.reef coastline in the Southern Sinai (Dahab, analyzing sampling quadrats from a total of 73 line-transects in five ecologically distinctEgypt), habitats with water depths ranging from 0 to 15 m. Ecological information was obtained for a total of 258 individuals of 14 species (9 living and 12 dead). 175 livingThe and three 83 deadmost individualsabundant species were collected C. parvatus for identification, andC. taeniatus size measurement with calipers. C. tessulatus , predominantlyWalls, feeding 1979 accountedHwass in Bruguière,for 80 % of 1792 the total and living assemblage.Born, 1779Hard substrata were dominatedon bypolychaetes, C. parvatus whereas soft substrata supported a high abundance of C. tessulatus, suggesting that hard and soft substrata are generally dominated by different Conus species according to their feeding ecology and the availability of refuges. Results demonstrated that the distribution of Conus subtidal reefs around Dahab strongly overlapped with other habitat types from on are considered to be the most heterogeneous habitat where coralthe blocks region. alternatingSubtidal reefswith sand patches and rock of varying portions establishtype, numerous microhabitats which can be exploited by Conus. Contrastingly, the other habitats showed a more characteristic species composition, whereby subtidal and intertidal sand characterized by large, uniform areas of soft substratum with similar ecological properties were almost identical in species composition. Conus The average shell length of was 15 ± 9 mm inFurthermore, the living and except 17 for± 14 the mm intertidal, in the livingdead assemblageand dead assemblages with a general of the size individual range of 6habitats - 85 mm. showed high similarities and peaked between 9 and 15 mm of size, indicating that postmortem processes may not be influential for the distribution of Conus around Dahab. Living and dead specimens from subtidal sand and the reef flat averagely consisted of smaller individuals than those of other habitats suggesting that these topographically simpler habitat types do not provide adequate refuges for larger specimens. The most dominant and smallest shells C. parvatus, C. taeniatus and C. miliaris), were the ones most frequently occupied by hermit crabs,( preferentially on the reef flat where the abundance of empty Conus shells was high. Results indicate that hermit crab distribution is influenced by favorable environmental conditions and the availability of empty gastropod shells such as Conus as a resource and that this supply is well utilized due to their general rarity. 2 ZUSAMMENFASSUNGDie giftige Gastropoden-Gattung Conus, eine der diversesten marinen Gattungen, ist in den Küstenlebensräumen der Tropen weit verbreitetals und besonders artenreich im Indo-West Pazifik. Vorangegangene ökologische Erhebungen haben gezeigt, dass topographisch komplexe subtidale Korallenriffe die höchste Conus Diversität jedoch die geringste Populationsdichte aufweisen. Das intertidale Riffdach weist intermediate Diversität und hohe Abundanz auf und extensive subtidale Sandflächen sind jene Habitate mit der niedrigsten Diversität. Bis dato wurden jedoch in keiner Studie die Verteilungsmuster der Gattung Conus im nördlichen roten Meer untersucht, weshalb hier der erste ökologische Zensus dieser Art entlang einer Saumriffküste im Süd-Sinai gypten) erhoben wurde. Die Probennahme erfolgte mittels entlang von 73 Transekten(Ä in fünf unterschiedlichen Habitat Typen in Tiefenstufen Quadratenvon 0 bis 15 m. Ökologische Daten wurden für 258