Menachem Goren

Biogeography, diversity and conservation of the inland water fish communities in Israel

Abstract The inland fish fauna of Israel comprises 32 indigenous species belonging to eight families, and 14–16 introduced species. The native fishes of Israel are of different biogeographical origins: Africa, Central Asia, Levant, the Mediterranean and the Red Sea. The fishes inhabit three separate water systems which have been divided in this work into 12 subunits, which differ from each other in their ecological features. Twelve of the species are endemic to their catchments. Three of the species, all from the upper Jordan Valley, are extinct. The richest ichthyofauna is in the Jordan River Valley with 26 species, 19 of which are found in Lake Kinneret. The distribution patterns of the indigenous species have been updated and the fish assemblages in the different systems are characterized. The human impact on fish biodiversity in Israel is documented here for the first time, including changes in fish distribution patterns.

Effects of size and morphotype on dominance hierarchies and resource competition in the freshwater prawn Macrobrachium rosenbergii

Abstract Sexually mature males of the freshwater prawn, Macrobrachium rosenbergii, appear in three distinct morphotypes which coexist within populations. Two of the morphotypes, the Blue-clawed and the Orange-clawed, overlap in size but differ in claw to body length ratio. The effects of size and morphotype on dominance rank were studied in groups composed of these two morphotypes, each represented by prawns in three size categories. Blue-clawed males dominated Orange-clawed males irrespective of size. The effect of size was more pronounced within morphotypes. The effect of morphotype can be interpreted as an advantage for Blue-clawed males because of their larger claws. The alpha position, occupied by the largest Blue-clawed male, was evident from the first daily observation. A linear rank order was evident only in the following 2 days. The consequences of dominance were reflected in competition for resources, where the alpha male clearly had priority of access to food and shelter.

Localization of the Vitellin and Its Possible Precursors in Various Organs of Parapenaeus longirostris (Crustacea, Decapoda, Penaeidae)

Summary Histological studies and immunofluorescence revealed two phases of cytoplasmic development during oogenesis of Parapenaeus longirostris. The first phase includes synthesis of a substance which accumulates later in the peripheral cortical granules. During the second phase, yolk globules appear in the cytoplasm. Immunodiffusion, Immunoelectrophoresis and immunofluorescence demonstrated materials immunologically similar to vitellin in the yolk globules of developed oocytes but not in oocytes in the first phase of development. This material appears also in the subepidermal adipose tissue and in the hemolymph, indicating the extraovarian origin of vitellin.

Allorecognition Elements on a Urochordate Histocompatibility Locus Indicate Unprecedented Extensive Polymorphism

Tissue contacts between different colonies of the cosmopolitan urochordate Botryllus schlosseri resulted either in fusion between allogenic blood vessels or in the formation of rejections, characterized by necrotic areas. This colony specificity is manifested by a single, highly polymorphic mendelian locus, with codominantly expressed alleles, called the tunicate fusibility/histocompatibility (Fu/HC) haplotype. Two colonies sharing even one allele at the Fu/HC locus may fuse; rejecting colonies share no alleles. Previous studies have revealed up to 100 alleles on the Fu/HC locus in different natural populations. We studied Fu/HC polymorphism in three populations (> 1000 colonies) along the Mediterranean coast of Israel, 12–36 km apart. By using the protocol of colony allorecognition assays (CAAS) on 444 tests within localities, 58–306 alleles per locality were calculated. We also estimate a total of 479–560 Fu/HC alleles in the three Israeli populations. An additional 103 interpopulation CAAs resulted in zero fusion, an outcome which contradicts previous findings showing 4.4–12.0% fusions between more remote B. schlosseri populations such as those from Israel versus Monterey, California, and California versus Japan assays. We propose that the recorded unprecedented Fu/HC polymorphism is maintained through overdominant selection, which is promoted by the gregarious settlement of Fu/HC-compatible larvae and by the subsequent threat of germ cell parasitism following colony fusion.

Habitat condition and fish assemblage structure in a coastal mediterranean stream (Yarqon, Israel) receiving domestic effluent

The Yarqon stream is the largest urban stream in Israel. In the past 40 y it was severely impacted by human action. Fish kills occur along the polluted sections of the stream almost regularly following winter floods and when poor-quality effluent is discharged into the stream. These events attest to the serious ecological state of the Yarqon stream. We studied the interaction between habitat conditions and fish assemblage structure for four consecutive years. Comparison of certain water quality variables among selected sites along the upper and central stream sections of the Yarqon indicated that the two stream sections differ significantly in electric conductivity and organic load (BOD) but not in temperature and dissolved oxygen. The average species richness and fish abundance in the upper, relatively undisturbed section is significantly higher than in the downstream, upper reach of the central section where domestic effluents enter the stream. In contrast, fish biomass is usually higher in the central stream section. Organic load was the only factor among the four water quality variables measured that significantly correlates with variables of the fish assemblage. A curve fit analysis between organic load and fish species richness and abundance suggests a threshold at ca. 10 mg I-1 BOD, above which most fish species totally avoid polluted habitats. Separate Multi Dimensional Scaling (MDS) analyses of water quality variables and fish assemblages clearly separated between the sites in the upper and the central stream sections. When the result of the fish MDS analysis was graphically superimposed on the result of the water quality MDS analysis, we found a close overlap between the two, suggesting a strong association between water quality and the fish assemblage structure in the Yarqon stream.

Purification and partial characterization of vitellin from the ovaries of Parapenaeus longirostris (Crustacea, Decapoda, Penaeidae)

1. 1. The vitellin of Parapenaeus longirostris was isolated from ripe ovaries by gel filtration on Sepharose 6B followed by ion exchange chromatography DEAE-Sepharose. 2. 2. The vitellin was identified by comparative PAGE of homogenates prepared from undeveloped and from ripe ovaries as determined by histological sections. The purified vitellin showed one glycoprotein band in disc electrophoresis and one precipitation line in immunoelectrophoresis and immunodiffusion. 3. 3. SDS-PAGE of the purified substance showed two types of subunits weighing 45,000 and 66,000 daltons. 4. 4. Antiserum prepared against the purified vitellin of P. longirostris reacted with homogenates obtained from ripe ovaries of Penaeus semisulcatus.

Comparative evaluation of the larvivorous fish Gambusia affinis and Aphanius dispar as mosquito control agents

Under laboratory conditions Aphanius was more successful than Gambusia in preying upon the 3rd, 4th and pupal stages of mosquitoes. The reverse was found for the first two instars. However. Aphanius consumed more 2nd instar larvae under the cover of vegetation when larger fish were able to penetrate shallow water and feed on the mosquito larvae.The two species showed a similar prey-size selection except for Aphanius of the medium size (31–35 mm) which ate larger larvae than Gambusia of the same size range.When provided access to the surface, neither fish species showed any adverse effect at oxygen levels as low as 0.5 mg l-1 (6% saturation). When denied access to the surface, both species behaved ‘normally’ at oxygen levels as low as 1.3 mg l-1 (15% saturation).This study suggests that Gambusia affinis and Aphanius dispar can complement each other as mosquito control agents in different habitat conditions. We suggest that in mosquito infested situation which are characterized by high organic matter and low oxygen levels biological control could best be achieved by introduction of a range of sizes of both fish species. Repeated introductions of the fish, in large enough numbers, may be required for ad-hoc alleviation of a mosquito problem. Best results are thus to be expected in relatively small water bodies such as oxidation ponds.

The Agonistic Behaviour of the Three Male Morphotypes of the Freshwater Prawn Macrobrachium Rosenbergii (Crustacea, Palaemonidae)

The agonistic behaviour of the freshwater prawn, Macrobrachium rosenbergii, was studied in the laboratory. One hour long contests were conducted between prawns matched to size in each of the three sexually mature male morphotypes of this species; Small Males, Orange Clawed males and Blue Clawed males. An agonistic ethogram was established, consisting of 18 different acts. These acts were classified into indicators of dominance or subordinance following the application of cluster analysis. Prawns contests consisted usually of 3 phases: pre-escalated fighting phase, escalated fighting phase and post-escalated fighting phase. Contest phases differed both in the frequency of several acts and in the distribution of acts between the eventual winner and loser. In addition, the relative orientation and elevation of the opponents changed across phases. The inter and intra-individual sequences of acts of the winner and loser during the escalated fight were studied. Despite the similarity found in the behaviour of the two opponents during the escalated fighting, the eventual winner could be predicted by the relative number and duration of nips or by the relative number of times in which Complete and Incomplete-Lifting (two major displays of fight) were performed simultaneously with the snapping of the claws. Differences found among morphotypes pointed out a tendency of shifting from interactions with physical contact towards ritualized interactions without physical contact. This was correlated with the morphotypic developmental pathway and the concomitant increase of claw size.

Morphotype Related Dominance Hierarchies in Males of Macrobrachium Rosenbergii (Crustacea, Palaemonidae)

Agonistic interactions in groups of Macrobrachium rosenbergii males were investigated in the laboratory. Each of the ten replicate groups consisted of the three distinct male morphotypes of this species: two Blue Clawed (BC) males and two Orange Clawed (OC) males matched to size, and two, much smaller, Small Males (SM). Male prawns formed a linear dominance hierarchy in which BC males were dominant over OC males which, in turn, were dominant over SM. Stabilization of the hierarchy over a period of three days was evident from reduction in the number of agonistic interactions and their intensity with time. The three male morphotypes differed in the extent to which they were involved in agonistic interactions and the nature of these interactions.

Characteristics of the introduced fish fauna of Israel.

Fishes have been introduced worldwide with deleterious effects on various native ecosystems. To gain insight into this phenomenon in Israel, we studied the introduced ichthyofauna. There are 27 species of introduced fishes in the freshwater habitats of Israel, a large number for a nation this size. Ten of these species reproduce in the wild. Most of these fishes were introduced for aquaculture; some are constantly restocked. The proportion of restocked versus established species in Israel is high compared to other regions. New fish introductions continue in recent decades, unlike the global trend. In Israel these species are found in the Jordan Basin, Lake Kinneret (Sea of Galilee), and the coastal plain rivers. A few species are widespread, and most are found in Lake Kinneret. Harmful effects of introduced fishes have been suspected and in several cases demonstrated. We encourage further caution when new introductions are contemplated; in some regions eradication should be attempted.