ALBERT

Notes: Genetic differences within species of tilapias were investigated. These differences are, for instance, expressed in the molecular composition of the erythrocyte membrane.Specimens of Oreochromis aureus (Steindachner 1864) and O. niloticus (Linné 1766) were immunized with alloantigenic erythrocytes. Results ofagglutination assays with the obtained antisera indicated the occurrence of a minimum offive and seven isoantigens in the investigated groups of O. aureus and O. niloticus, respectively. Comparative tests did not reveal an identity of any of the O.aureus and O. niloticus isoantiens.Apart from these ceflular blood group structures, the existence of soluble blood group substances in the plasma of the two investigated species was indicated by WESTERN blot tests.

Notes: Gonad development and somatic growth were studied in the hybrid between Barbus longiceps and Capoeta damascina (Pisces: Cyprinidae) from Lake Kinneret (Lake Tiberias), during the years 1987–1990. Reproductive eriods of both parental species were considerably overlapping. Among 39 hybrid specimens sampled, 5 were found to be males with arrested spermatogenesis, 31 were females with abnormal gonads and 3 were structural hermaphrodites with arrested gametogenesis. In all hbrids gonad development was impaired. No ripe eggs or spermatozoa were ever observed in histological sections of the hybrid gonads. However, during the breeding season the hybrids possessed secondary sex characteristics, similar to those present in the parental species. Hybril somatic growth was intermediate between that of the parental species. The hybrid dressing rate was also intermediate between that of the parental species.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungGonadenentwicklung und somatisches Wachstum eines intergenerischen Hybriden karpfenartiger Fische aus dem See Genezareth, IsraelDie Gonadenentwicklung und das Wachstum wurden am Hybriden zwischen Barbus longiceps und Capoeta damascini (Pisces: Cyprinidae) aus dem See Genezareth (See Tiberias) in den Jahren 1987 bis 1990 untersucht. Die Vermehrungsperiode beider Elternarten überlappen erheblich. Fünf der 39 untersuchten Hybriden waren Männchen mit stagnierender Spermatogenese; 31 Weihchen hatten abnormale Gonaden und 3 Tiere waren strukurell als Hermahroditen mit gehemmter Gametogenese einzustufen. Die Entwicklung war in allen Hybriden-Gonaden gehemmt. In keinem Fall wurden reife Eier oder Spermatozoen in den histologischen Schnitten der Hybridengonaden gefunden. Trotzdem besaßen die Hybriden während der Laichzeit sekundäre Geschlechtsmerkmale, ähnlich denen der Elternarten. Das somatische Wachstum der Hybriden war im Vergleich zu den Elternarten intermediär Die Schlachtausbeute der Hybriden lag ebenfalls zwischen derjenigen der Elternarten.

Notes: The yearly gonadal cycle of two Kinneret teleosts, Barbus longiceps and Capoeta damascina and of their hybrid, was assessed by measuring the gonadosomatic index (GSI) in both sexes, as well as the spermatozoan index (SPI) in the males. SPI was established through a computerized analysis system, using light microscopy images of histological preparations of the testes. Barbus longiceps specimens had highest GSI in March, 6.31 for males and 1.40 for females. Capoela damascina had highest GS1 in January, 6.63 for males and 6.88 for females. In the male-like hybrids, the highest GSI was 5.57 in February, and in female-like hybrids 1.83 in March; no gametes were ever formed in hybrid gonads. The highest SPI appeared in B. longiceps in April, while in C. damascina the highest SPI was found in March. In both species, the highest SPI was attained several weeks after the highest GSI was observed. It is suggested that the peak of the breeding season of both species is actually represented by the highest SPI. In males, the decreasing GSI, which corresponds to the highest SPI, represents the loss of gonad weight, which is due to the elimination of the spermatid residual bodies, prior to spermiation. In the females the decreasing GSI is the result of ovulation, and characterizes the peak of spawning activity.

Notes: General muscle proteins and parvalbumins of Tilapia dageti (Thys van den Audenaerde), T. guineensis (Bleeker) and T. zillii (Gervais) (Pisces, Cichlidae) which occur sympatrically in Ghana were subjected to various electrophoretic and immunological assays, and erythrocytes of the species underwent agglutination tests. These investigations aimed to identify species-specific markers, as discrimination of the three closely related species based on morphology has been difficult. A positive agglutination reaction of T. zillii erythrocytes with the soy bean lectin distinguished this species from the other two. Allozyme screening of general muscle proteins revealed loci at which the three species were monomorphic and fixed for different alleles. Polyacrylamide gel electrophoresis and isoelec-trofocussing of parvalbumins revealed species-specific protein profiles for the three tilapias. Immunoelectrophoresis and Western blot tests of parvalbumins with an antiserum to T. guineensis parvalbumins also produced species-specific band patterns. The results offer alternative options for the unambiguous identification of the investigated species as well as of closely related organisms in general. This is a prerequisite for the study, conservation or breeding of any species.

Notes: Stomach contents were examined from 136 Amazonian wingfin anchovy, Pterengraulis atherinoides (Engraulidae), caught from intertidal mangrove creeks at diurnal neap tides between June and September 1997 (early dry season) near Bragança (northern Brazil). The study found that P. atherinoides are specialized predators of juvenile Natantia and Teleostei (mean: 67 and 28% by dry weight, respectively). On average, 5.2 g ha−1 day−1 of Natantia and 2.6 g ha−1 day−1 of Teleostei (wet weight) were eaten by P. atherinoides. Diet changed with fish size as well as by month. While smaller sizes still fed on several food items (e.g. the copepod Pseudiaptomus marshii, the brachyuran crab Pachygrapsus gracilis, amphipods), fish 〉13 cm standard length (SL) fed exclusively on Natantia and Teleostei. Copepods were especially abundant in July and August, dominating the diet of fish 〈9 cm SL in numbers (92%). Our results suggest a positive relationship between predator size and prey size, both in penaeid and piscine prey. However, the largest predator size class apparently selected fewer but larger Teleostei prey. More than 64% of Natantia were juvenile penaeid shrimps of commercial importance (Fenneropenaeus subtilis, F. schmitti, Xiphopenaeus kroyeri). Comparison with ichthyoplankton samples taken simultaneously showed that Sciaenidae and Mugilidae were positively selected while Gobiidae and Engraulidae were negatively selected. The presence of pranzia larvae in the stomachs of fish 〈10 cm SL, from July onward, suggests that these sizes fulfil a mutually beneficial ‘cleaning’ function on other fish. Block net sampling at neap tides showed that P. atherinoides were present in intertidal mangrove creeks throughout the submergence period, suggesting temporal optimization of the foraging time in the eulittoral.

Notes: In past studies erformed to differentiate among commercially important species of the Tilapia group, erythrocytes o the different species were successfully investigated in agglutination tests with lectins and Tilapia antisera. The present publication reports on WESTERN blot analyses of humoral plasma proteins from Oreocbromis aureus (Steindachner 1864), O. niloticus (Linne 1766) and Sarotherodon galilaeus (Artedi 1757). For lectin blots, in addition to comlete plasma samples, N-acetyl glucosamine tearing plasma glycoproteins were investigated after their affinity-chromatographical isolation from the plasma using a WGA agarose column. For immunoblots, only complete plasma samples were used. After SDS treatment the samples were electrophoretically separated and transferred onto nitrocellulose membranes. The transferred proteins were then tested for their reactions with lectins and antisera. In all cases the employed indicator molecules showed species-specific differences, enabling a clear identification of the investigated species.In addition, molecular weights of all native SDS-treated plasma proteins of the 3 Tilapia species are listed in an appendix.〈section xml:id="abs1-2"〉〈title type="main"〉Zusammenfassung WESTERN Blot-Analyse von Plasmakomponenten der drei Tilapia-Arten Oreochromis aureus, O. niloticus und Sarotherodon galilaeusIn früheren Untersuchungen zur Unterscheidung wirtschaftlich wichtiger Arten der Gattung Tilapia wurden deren Erythrozyten in Agglutinationstests mit verschiedenen Lektinen und Tilapia-Antiseren erfolgreich eingesetzt. Die vorliegende Publikation zur gleichen Fragestellung beschreibt WESTERN-Blot-Analysen humoraler Plasma-Proteine der Arten Oreocbromis aureus (Steindachner 1864), O. niloticus (Linne 1766) und Sarotherodon galilaeus (Artedi 1757). Fur Lektin-Blots wurden neben Gesamtplasmaproben auch N-Acetyl-Glucosaminhaltige Glykoproteine eingesetzt, die affinitätschromatographisch mit Hilfe einer WGA-Agarose-Säude aus dem Plasma isoliert worden waren, während fur Immunoblots nur Proben von Gesamtplasma verwendet wurden. Nach SDS-Behandlung und elektrophoretischer Auftrennun wurden die Proben auf Nitrocellulose-Membranen übertragen. Die transferierten Proteine wurden jann auf ihre Reaktion mit Lektinen und Antiseren getestet. In allen Fällen zeigten die eingesetzten Indikatormoleküle artspezifische Unterschiede an, die eine klare Differenzierung zwischen den untersuchten Arten erlaubten. In einem Anhang sind zudem die Molekulargewichte sämtlicher nativer und SDS-behandelter Plasmaproteine der 3 Tilapia-Arten aufgelistet.

Notes: Rapid and reliable identification of tilapiine taxa and strains is essential for selective breeding purposes and the conservation of natural genetic resources. There is evidence that antisera-mediated erythrocyte agglutination assays can fit these requirements. We evaluated the applicability of agglutination tests by studying the capacity of species characteristic antisera to recognize erythrocytes from individuals of 10 natural Ghanaian populations of Oreochromis niloticus and Sarotherodon melanotheron. The vast majority of the 218 tested individuals could be identified based on antisera-mediated erythrocyte recognition. Controls indicated the specificity of these reactions. Still, erythrocytes from 16% of all tested specimens did not respond to any antiserum (zero responders), indicating the possible existence of blood group properties in tilapias. We discuss the specificity of the antisera, the relevance of zero responses and the applicability of these tests in aquaculture and field studies.

Notes: The objective of this study was to develop a method of differentiation among commercially important species of the genus Tilapia.A variety of lectins was used in agglutination tests with native and enzyme-treated red blood cells of Tilapia aurea (Steindachner 1864), Tilapia nilotica (Linné 1766) and Tilapia galilaea (Artedi 1757). Species-identification was proved to be possible by positive or negative agglutination reactions of enzyme-treated erythrocytes and certain lectins which occurred only with blood cells of one of the three species.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungDer Einsatz von Lektinen in Erytbrozylen-Agglutinationstests zur Differenzierung zwischen Tilapia-ArtenZiel dieser Arbeit war es, eine Methode zur Unterscheidung wirtschaftlich wichtiger Arten der Gattung Tilapia zu entwickeln.Eine Auswahl von Lektinen wurde in Agglutinationstests mit nativen und enzymbehandelten Erythrozyten der Arten Tilapia aurea (Steindachner 1864), Tilapia nilotica (Linné 1766) und Tilapia galilaea (Artedi 1757) verwendet. Die Identifizierung der Arten erwies sich als möglich durch Einsatz von enzymbehandelten Erythrozyten und positive bzw. negative Agglutinationsreaktion mit einzelnen Lektinen, die jeweils nur bei einer der drei Arten auftrat.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméL'utilisation de lectins dans des tests d'agglutination de globules rouges pour la différenciation des espèces TilapiaLe but de ce travail était de développer une méthode de différenciation entre des espèces commercialement importantes du genre Tilapia. Une sélection de lectins fut utilisée dans des tests d'agglutination avec des globules rouges natifs et ceux traités d'enzymes des espèces Tilapia aurea (Steindachner 1864), Tilapia nilotica (LiNNé 1766) et Tilapia galilaea (Artedi 1757).L'identification des espèces différentes se démontra possible par l'utilisation de globules rouges traités d'enzymes et la réaction d'agglutination positive ou bien négative avec certains lectins qui se produisit chaque fois seulement avec une des trois espèces.

Notes: The present study considers the important role of bone resorption for bone growth in general, and aims to clarify if and how bone resorption contributes to the skeletal development of carp, Cyprinus carpio L., a teleost species with ‘normal’ osteocyte-containing (cellular) bone. To ensure the identification of osteoclasts and sites of bone resorption independently from the morphology of the bony cells, bones were studied by histological procedures, and by demonstration of the enzymes which serve as osteoclast markers, viz. tartrate resistant acid phosphatase (TRAP), ATPase and a vacuolar proton pump. Two types of bone-resorbing cells were observed in juvenile carp: (1) multinucleated giant cells displaying morphological and biochemical attributes which are known from mammalian osteoclasts; and (b) flat cells which lack a visible ruffled border and for which identification requires the performance of enzyme histochemical procedures. Bone resorption performed by osteoclasts mainly occurs at endosteal bone surfaces. To a lesser extent, bone resorption also takes place at periosteal bone surfaces, but without an apparent connection to bone growth. The latter observation, and the occurrence of bone remodelling, suggest that the endoskeleton of juvenile carp might be involved in mineral metabolism. Morphological differences and biochemical similarities to bone resorption in teleosts with acellular bone are discussed.