Ehud Spanier

Lessepsian migration: a continuous biogeographical process

Abstract The opening of the Suez Canal unintentionally initiated an important event — the joining of two biogeographical provinces. For over 120 years, Red Sea species, migrating through the canal, have been colonizing the Mediterranean. The recent proliferation of a Red Sea jellyfish along the Levant coast highlights the profound changes in the indigenous biota.

Shelter preferences in the Mediterranean slipper lobster: effects of physical properties

Abstract The physical properties of shelter and biotic factors associated with shelter selection were studied in the Mediterranean slipper lobster Scyllarides latus (Latreille) in both the field and laboratory. In laboratory experiments, lobster significantly preferred a shaded cover or an opaque shelter to a transparent shelter of the same dimensions. No preference was exhibited by lobsters between a shaded transparent shelter and an opaque shelter. Lobsters also demonstrated a significant preference for shelters with more than one opening and for those that were in a horizontal as opposed to vertical position. They also tended to shelter together with other conspecifics. S. latus preference for horizontal dens with a small entrance, close to the substratum and with multi-openings were observed in natural and artificial reefs. Tendencies for cohabitation, shelter sharing with moray cels, and bringing clams to the shelter after night foraging, were also etected among field lobsters. No correlations between the various sheltering behaviors and sex or size of lobsters were found. It is suggested that these characteristics are anti-predator adaptations of S. latus which lack any morphology for active defense.

Some physical properties of shelter that influence den preference in spiny lobsters

Abstract Several properties of shelter were analyzed for their importance in den selection by the California spiny lobster Panulirus interruptus (Randall). Field surveys indicated that dens of spiny lobsters usually had more than one entrance and that entrances were much smaller than the inner diameter of a den. Dens always had top cover and a back wall, but they did not always have side walls. In laboratory experiments lobsters completely avoided transparent artificial shelters in favor of opaque ones of the same size and shape. No preference was exhibited by lobsters for opaque shelter when transparent shelter was shaded. Den preference was found to depend more on presence of shaded cover than on den walls. Single, isolated shelter having front and rear entrances was preferred to shelter having only one entrance, though this preference was lacking when a second shelter was attached laterally. A function of lobster antennae in defensive behavior is suggested based on their positioning as observed in laboratory trials. Antennae were held posteriorly, possibly to guard the abdomen and telson, when residency was established in shelter having openings both at front and back ends. Antennae were directed anteriorly, outside the shelter, when residency was established in shelter having only one entrance. Shade, shelter, antennae posturing, and conspecific attraction are discussed relative to their probable roles in predatory defense in this species.

In situ biofiltration: a means to limit the dispersal of effluents from marine finfish cage aquaculture

Net pen fish farms generally enrich the surrounding waters and the underlying sediments with nutrients and organic matter, and these loadings can cause a variety of environmental problems, such as algal blooms and sediment anoxia. In this study we test the potential of biofiltration by artificial reefs for reducing the negative environmental impacts surrounding fish farms in the Gulf of Aqaba, Red Sea. Two triangular-shaped artificial reefs (reef volume 8.2 m3) constructed from porous durable polyethylene were deployed at 20 m; one below a commercial fish farm and the other 500 m west of this farm in order to monitor the colonization of these reefs by the local fauna and to determine whether the reef community can remove fish farm effluents from the water. Both reefs became rapidly colonized by a wide variety of organisms with potential for the removal of compounds released from the farms. Within the first year of this study fish abundances and the number of species reached 518–1185 individuals per reef and 25–42 species per reef. Moreover, numerous benthic algae; small sessile invertebrates (bryozoa, tunicates, bivalves, polychaetes, sponges, anemones) and large motile macrofauna (crustaceans, sea urchins, gastropods) settled on the reef surfaces. Depletion of chlorophyll a was measured in the water traversing the artificial reefs in order to assess the biofiltration capacity of the associated fauna. Chlorophyll a was significantly reduced to a level 15–35% lower than ambient concentrations. This reduction was greatest at intermediate current speeds (3–10 cm s−1), but was not influenced by current direction. The reef structures served as a successful base for colonization by natural fauna and flora, thereby boosting the local benthic biodiversity, and also served as effective biofilters of phytoplankton.

Swimming of the Mediterranean slipper lobster

Escape swimming observed in the Mediterranean slipper lobster Scyllarides latus (Latreille, 1803) in the field was studied under controlled laboratory conditions using a videosystem. Lobsters demonstrate a “burst-and-coast” type of swimming found also in some negatively buoyant fast-swimming fish. Large amplitude movements of the tail propel them quickly backwards, alternating periods of acceleration (top velocities of 2.5–3.6 body lengths · s−1) with powerless gliding (average velocities of 0.5–1 body lengths · s−1). Force · tail-beat−1) ranges between 125 000 and 305 000 dyn and correlates significantly with body length. However, no significant correlation was found between lobster length and acceleration which was found to range between 250 and 500 cm · s−2. It is suggested that the increased force, probably due to larger muscle and telson, is required in larger lobsters to move the larger mass rather than to increase speed and acceleration. This intermittent fast swimming is assumed to be used by lobsters to escape, especially through the back opening of their diurnal shelter in case a predator is successful in penetrating it. It is of short duration and is suggested as an emergency means in which the animal invests considerable energy resources to reduce its exposure time in an open area until it reaches an alternative shelter.

Ciguatoxin-like substances in edible fish on the eastern Mediterranean

Background. The consumption of edible fish (e.g., Siganus spp) was assumed to have caused ciguatera poisoning at an atypical site, the eastern Mediterranean. This pilot study assesses the presence of ciguatoxin-like substances in edible fish on the eastern Mediterranean coast of Israel. Methods. Samples of Siganus rivulatus from polluted seawater (Haifa Bay), Siganus rivulatus from relatively clean seawater (Dor), and fish from the freshwater Sea of Galilee not inhabited by toxic algae were analyzed during summertime. Ciguatoxin-like substances were tested by a membrane immunobead assay that yields a color reaction (positive, weakly positive, negative). Results. Significantly more large and small fish from Haifa Bay yielded positive color reactions compared to fish from Dor. Sea of Galilee fish gave no positive color reactions. Conclusions. Our results suggest the presence of ciguatoxin-like substances in edible fish of the eastern Mediterranean. Additional analyses are needed to determine whether these substances are ciguatoxins or related polyethers.

The Biology and Fisheries of the Slipper Lobster

INTRODUCTION Introduction to the Biology and Fisheries of Slipper Lobsters, K.L. Lavalli and E. Spanier BIOLOGY OF SLIPPER LOBSTERS Taxonomy and Evolution, W.R. Webber and J. Booth Genetics of Slipper Lobsters, A.M. Deiana, A. Libertini, A. Cau, R. Cannas, E. Coluccia, and S. Salvadori Early Life Histories of Slipper Lobsters, H. Sekiguchi, J.D. Booth and W.R. Webber Factors Important in Larval and Postlarval Molting, Growth, and Rearing, S. Mikami and A.V. Kuballa Feeding Morphology and Digestive System of Slipper Lobsters, D. Johnston Behavior and Sensory Biology of Slipper Lobsters, K.L. Lavalli, E. Spanier, and F. Grasso The Mineralization and Biomechanics of the Exoskeleton, F.R. Horne and S.F. Tarsitano Growth of Slipper Lobsters of the Genus Scyllarides, M. Bianchini and S. Ragonese Directions for Future Research in Slipper Lobster Biology, E. Spanier and K.L. Lavalli FISHERY BIOLOGY OF SLIPPER LOBSTERS Observations on the Ecology of Scyllarides aequinoctialis, S. nodifer, and Parribacus antarcticus and a Description of the Florida Scyllarid Lobster Fishery, W.C. Sharp, J.H. Hunt, & W. H. Teehan The Northwestern Hawaiian Islands Lobster Fishery: A Targeted Slipper Lobster Fishery, G. DiNardo and R. Moffitt The Biology of the Mediterranean Scyllarids, D. Pessani and M. Mura Biology and Fishery of the Galapagos Slipper Lobster, A. Hearn, V. Toral-Granda, C. Martinez, and G. Reck Biology and Fishery of Slipper Lobster, Thenus orientalis, in India, E.V. Radhakrishnan, M.K. Manisseri, and V.D. Deshmukh Biology and Fishery of the Bay Lobster, Thenus spp., C.M. Jones Fishery and Biology of Commercially Exploited Australian Fan Lobsters (Ibacus spp.), J.A. Haddy, J. Stewart, and K.J. Graham Slipper Lobster Fisheries-Present Status and Future Perspectives, E. Spanier and K.L. Lavalli List of Contributing Authors List of Reviewers for Chapters Index

WHAT ARE THE CHARACTERISTICS OF A GOOD ARTIFICIAL REEF FOR LOBSTERS

Artificial reefs have been used to concentrate fish. In order to characterize good artificial reefs for lobsters, information on the bahaviour and ecology of lobsters on natural substrates is needed. Habitat and microhabitat selection, predator-prey and intraspecific interactions, and related facets are reviewed for late juvenile and adult clawed, spiny, and slipper lobsters. These data, together with the results of several experiments with man-made habitats, indicate the behavioural-ecological processes associated with shelter selection. Horizontal shelters with opaque cover and multiple den openings were preferred by most species studied. These characteristics are considered anti-predator adaptations. Yet, a survey of artificial reefs established in the recent decade has revealed that lobsters were reported in only a small proportion of the projects. It is suggested that the majority of these reefs has not been designed and constructed to fit the behavioural-ecological preferences of the target lobster species for shelter.

THE UNDISCOVERED LOBSTER: A FIRST LOOK AT THE SOCIAL BEHAVIOUR OF THE MEDITERRANEAN SLIPPER LOBSTER, SCYLLARIDES LATUS (DECAPODA, SCYLLARIDAE)

To investigate the behaviour of Scyllarides latus we built a 3000 1 tank with one glass side for observations, setup with ambient, unfiltered, running seawater and a natural assemblage of organisms. Half of the bottom was covered with a substrate made up of large biogenic rocks resembling the rocky reefs where the lobsters are abundant, the other half was covered with bare sand. Eight lobsters, 3 males and 5 females, were tagged and placed in the tanks. Lobsters initially spent significantly more time on the rock substrate, however, after two months they ceased to show a preference. After five months we added two large and two small concrete shelters, placed against the glass for observation. Lobsters preferred to reside together in the large rock shelter. In aggressive displays, usually in competition for food, the slipper lobsters displayed some distinctive behaviour patterns all centered around dislodging the opponent from its grip on the substrate. A dominance matrix made from tallying these aggressive encounters revealed a fairly linear dominance hierarchy amongst lobsters in the tank with the largest female in the dominant position.

Nematocysts of Rhopilema nomadica (Scyphozoa: Rhizostomeae), an immigrant jellyfish in the eastern mediterranean

Rhopilema nomadica—a recently discovered scyphomedusa in the eastern Mediterranean—is considered a lessepsian migrant. Its nematocysts were extracted from the scapular and mouth‐arm tentacles and examined using light and electron microscopy techniques. The morphometric parameters of the nematocysts were measured before and after complete discharge. Three categories of nematocysts were identified: heterotrichous isorhiza haploneme, holotrichous isorhiza haploneme, and heterotrichous microbasic eurytele. The relative abundance of the nematocysts and their occurrence in tissues of the jellyfish were noted. A brief discussion concerning the classification of certain types of nematocysts is given. A comparison with the available data on other Rhopilema species revealed that the nematocyst categories of R. nomadica are more similar to those of the Atlantic R. verrilli than to those of the Western Pacific R. esculentum. A brief comparison of the injuries caused by these species is given.