Volume 15

Squamation of Tetragonurus cuvieri Risso, 1810 (Stromateoidei, Tetragonuridae)

The pelagic perciform fish Tetragonurus cuvieri and the other two species of the Tetragonuridae (“squaretails”) display a striking structure of the integument and especially the squamation is of particular interest. The spinoid scales present a rhomboidal external surface and are arranged in oblique lines, thus superficially resembling a ganoid squamation. For teleost fishes this is unusual and the scales have frequently been referred to in the literature. But the structure of its integument, especially the squamation, has never been described in detail. Here we describe and distinguish three different types of scales in T. cuvieri. Type I scales are the main trunk scales and are mainly characterized by the first two spines of the middle ridges, which are always elongate and flattened. Furthermore, the anterior part of the scale forms a kind of lip which lies in grooves of the skin and constitutes the skeletal bottom of an antrum or pocket underneath the preceding scale. Type II scales cover the caudal fin peduncle, are folded and bear higher spines on the external surface. Type III scales are found between the rays of the caudal fin as well as pectoral and pelvic fins. They are very small and their flanks are turned upwards without spine rows in the middle area of the scale. We suggest that the squamation of these fishes might be connected with the specific prey, several tissues of jellyfish they ingest. Trunk scales form an antrum probably filled with mucus that may decontaminate the cnides of this prey.

Twenty years “sperm drinking” by female catfishes – and still nothing new? An essay about the different perception of amateurs and professionals

In 1995 KHODA et al. published a study, in which they described a “unique reproductive behaviour and a new mode of egg insemination” (p. 1) of the armoured catfish Corydoras aeneus. From their observations and experiments the authors claimed to have demonstrated that the females swallow the sperm of males during spawning (“sperm drinking”) and that after the passage through the gut these sperm inseminate and fertilize the eggs in the fin pocket formed by the female pelvic fins. Since then sperm drinking seems to be a commonly accepted fact in the primary and secondary scientific literature and was never seriously questioned herein. However, the way ejaculated sperm take to inseminate and fertilize egg was vigourously discussed already at the beginning and middle of the 20th century in the so-called “gray” literature by German and later North American aquarists on the basis of numerous observations, hypotheses and even experiments. For example, SCHUBERT (1907) suggested the oral uptake of sperm by the female and LIEBIG (1912) considered the possibility of „sperm drinking“ and the intestinal passage of sperm, but also other fertilization scenarios were taken into consideration. Especially the aquaristic literature from USA favoured the view that eggs are inseminated and fertilized during egg deposition. Later KNAACK (1955 ff.), who intensively studied the reproductive behaviour of several Corydoras spp., confirmed not only the earliest, but largely forgotten observations made by CARBONNIER (1881), but also plausibly rejected the intestinal passage of sperm performing similar experiments as KHODA et al. We give a brief overview of the lively debate on this subject in the first half of the last century, acknowledge the experiments performed by KNAACK as well as by KHODA et al., and discuss some problems that arise from these studies. Generally, our essay tells about an interesting episode of aquaristics and illustrates how much useful information and ideas are hidden in the so-called “gray” literature.

The phytal fauna of the SW Baltic Sea and its importance as reservoir for fish prey

The phytal fauna of the SW Baltic was investigated at three localities of the German coast: Flensburg fjord (Kiel Bight), Dahmeshöved (Lübeck Bight) and Salzhaff (NW Mecklenburg). The samples comprised five algae species (Fucus vesiculosus, Ceramium sp., Enteromorpha sp., Ectocarpus sp., Chorda sp.), two spermatophytes (Zostera marina, Zannichellia palustris) and animal aufwuchs by Mytilus edulis. Additionally, succession experiments were performed in the Mytilus and Ceramium belts of Dahmeshöved. The investigations were focused on the organisms living between the substrate and their possible exploitation by fish. Therefore, the question arose what substrate is best suited to be colonized by “invertebrates”. At all three localities highest biomass was found in the Ectocarpus belt in late spring, in Ceramium, Enteromorpha and Mytilus belts in summer. The Zostera belts presented highest values in spring, whereas Fucus and Zannichellia belts attained relatively low values. Production of fish prey animals was highest in Enteromorpha belts followed by Ceramium and Mytilus belts. F. vesiculosus attained low values in Flensburg fjord but clearly higher values in Salzhaff. The index of settlement which expresses the utilization of the substrate by fish prey organisms was highest in Enteromorpha belts, followed by Ceramium, Fucus and Zostera belts from Salzhaff. At the end of succession areas biomass of Mytilus and Ceramium belts was lower than in the control areas but taxa numbers were higher. In these experiments the Mytilus belt attained slightly higher biomass values than the Ceramium belt. The Enteromorpha and Ceramium belts proved to be especially suited reservoirs for fi sh prey organisms.

Das Standardwerk „HOLLY, MEINKEN & RACHOW: Die Aquarienfische in Wort und Bild” und seine Bedeutung für die Ichthyologie

[The standard reference „HOLLY, MEINKEN & RACHOW: Die Aquarienfische in Wort und Bild” and ist signifi cance for ichthyology]

Das Standardwerk „HOLLY, MEINKEN & RACHOW: Die Aquarienfische in Wort und Bild“ erschien von 1934 bis 1967 mit 1328 Tafeln in 130 Lieferungen. Die einzelnen bearbeiteten Arten werden mit ihrem Autor, der Lieferung, der heutigen korrekten Bezeichnung der Art und dem Erscheinungsdatum in Tabellen aufgeführt. Von 1934 bis 1938 wurde das Buch (Loseblattsammlung) im Verlag von Julius E.G. Wegner, Winnenden, verlegt und von 1938 bis 1967 erschien es im Alfred Kernen Verlag, Stuttgart. Das Buch ist eines der bedeutendsten deutschsprachigen Werke der Aquarienliteratur, das auch wertvolle ichthyologische Informationen enthält. Die Entstehungsgeschichte dieses Werkes wird dargestellt. Die Biographie und der Anteil der Autoren HOLLY (6.6.1901 bis ?), MEINKEN (1896-1976) und RACHOW (1884-1960) am Gesamtwerk werden ebenso wie seine ichthyologische Bedeutung beschrieben.

[The core literature „HOLLY, MEINKEN & RACHOW: Die Aquarienfische in Wort und Bild“ was edited from 1934 to 1967 with 1328 plates in 130 supplies. The different species were listed with the author, the supply, the correct scientific name and the date of edition in tables. The book (loose leaf book) was edited in the publishing house Julius E.G. Wegner, Winnenden, from 1934 to 1938, and from 1938 to 1967 in the publishing house Alfred Kernen, Stuttgart. The book is one of the most important publications on aquariumfishes in German language, which contains valuable ichthyological information. The history of the origin of this book is documented. The biography and the part of the authors HOLLY (6.6.1901 to ?), MEINKEN (1896-1976) and RACHOW (1884-1960) and the ichthyological importance of this book are described]

Description of a new Heros species (Teleostei, Cichlidae) from the Rio Orinoco drainage and notes on Heros severus Heckel, 1840

Heros liberifer sp. n. is described from the drainage of the upper and middle Rio Orinoco in Venezuela. The new species is distinguished from all other Heros species by its unique colouration pattern of several horizontal series of tiny bright red dots on the lower half of the body sides and by its unusual brood care. Heros liberifer sp. n. can be distinguished from the syntopic Heros severus Heckel, 1840 by a distinct caudal spot, narrower lips, a bright red iris and the 4th vertical bar, which is not shortened, but extends from the anal fin base to the base of the dorsal fin. In addition, comments are made on the colouration of live specimens of Heros severus, its distribution and ecology.

Predatory attack on spawn of damselfish by parrotfish in the Caribbean

Im Korallenriff der Insel Margarita (Karibik, Venezuela) wurden wiederholt Fälle von Laichräuberei durch Prinzess-Papageifische (Scarus taeniopterus, Scaridae) beobachtet. Opfer waren die Laichnester des Sergeanten Abudefduf saxatilis (Pomacentridae). Diese befinden sich auf schwarzem, vulkanischem Untergrund, den die Männchen des Riffbarsches von allem Aufwuchs befreien. So entstehen besonders auffällige Areale von etwa 15 cm im Durchmesser, auf dem die angelockten Weibchen laichen und die Männchen das Gelege bewachen. Herumstreunende junge S. taeniopterus, die diese Nester entdecken, stürzen sich auf den Laich und locken durch dieses Verhalten weitere Artgenossen an. Auf Grund solcher Massenansammlung stehen die Laichräuber senkrecht am Laichplatz; das Sergeant-Männchen wird vertrieben. Es handelt sich hier offenbar um Lernvorgänge, denn Auslösereiz für S. taeniopterus ist offensichtlich der schwarze Laichplatz von A. saxatilis.

Fishes of a stranded Sargassum meadow at Punta Cana, Dominican Republic

Das Stranden einer größeren Sargassum-Matte an der Küste von Punta Cana, Dominikanische Republik, ermöglichte einen Blick auf die damit assoziierte Fischgemeinschaft. Auch wenn typisch Sargassum-assoziierte Arten, wie Histrio histrio, gefunden wurden, weicht doch die Zusammensetzung der Fischgemeinschaft deutlich von anderen Untersuchungen im Atlantik, inklusive dem Karibischen Meer, ab. Lobotes surinamensis und Kyphosus sextatrix, die sonst untergeordnete Bedeutung haben, waren in sehr großen Anzahlen vorhanden, Stephanolepis hispidus konnte nicht nachgewiesen werden, obwohl diese Art meist den Großteil der Individuen in Sargassum-Matten stellt. Möglicherweise weist die ungewöhnliche Zusammensetzung auf einen längeren Transport des Algenteppichs hin.