Taxonomical use of scale ornamentation: Challenges by intraspecific and intra-individual variations in four adult specimens of Polypterus bichir

Many actinopterygian fish groups, including fossil and extant polypteriforms and lepisosteiforms, fossil halecomorphs, and some basal teleosts, have stout bony scales covered by layers of ganoin-an enamel layer ornamented with minute tubercles. Ganoid scales preserve well as disarticulated remains and notably constitute most of the fossil record for polypteriform in both South America and Africa. Based on two variables (tubercle size and distance between tubercles), some authors reported that the ganoin tubercle ornamentation in these scales is constant within a species and differs between species and allows distinguishing species or at least groups of species. However, despite its promising potential for assessing polypteriform paleodiversity, this tool has remained unused, probably because the variables are not well defined, and intraspecific variation does not seem to have been considered. To address this gap, we aimed to test the intraspecific and intra-individual variation in the ornamentation of ganoid scales in the type species Polypterus bichir. We propose three different parameters to describe the tubercle ornamentation: the distance between contiguous tubercles centers, their density, and their relative spatial organization. With these parameters, we investigate the variation in ganoin ornamentation among four specimens and across different regions of the body. Our results show that the distribution of the tubercles is highly variable within a same species, regardless of the body region, and sometimes even between different sectors of a same scale. Moreover, the variation observed in P. bichir overlaps with the distribution described in the literature for several extant and fossil species. Thus far, the ornamentation of ganoid scales is not a reliable diagnostical feature for polypterids.

Living Taxa and Their Importance in Understanding the Extinct Diversity: A Look at Polypterid Pinnules

Pinnules are the peculiar, impaired spines that carry each of the numerous finlets that constitute the dorsal fins of polypterid fishes (Cladistia and Polypteriformes). Previous studies, including a recent detailed paper on the comparative analysis of the morphology of pinnules in most of the extant species (genera Polypterus and Erpetoichthys), suggest that they display unique characteristics that allow for species identification. Since most of the polypterid fossil records are composed of scales that lack specific characteristics and isolated pinnules, this work aims to test their taxonomic relevance before comparing the fossil pinnule morphologies across the fossil records in order to evaluate polypterid paleodiversity. Therefore, we describe the intra-individual and intra-specific morphological variations of the pinnules in the extant species Polypterus bichir. Furthermore, we compared it with the various morphologies described in the Polypteridae family. We report intra-individual variability related to the anteroposterior axis of the dorsal fin. We also report morphological differences in the pinnules among specimens that overlap those anticipated among different species, concluding that the pinnule morphology cannot support taxonomic purposes in polypterid fishes in their current state.

-Morphological variations in the dorsal fin finlets of extant polypterids raise questions about their taxonomical validity

Fossil polypterids are mainly represented by disarticulated material, most of them pinnules. However, there is no study that proves the taxonomical validity of these structures. Here we describe the pinnules of four species of extant polypterids and report for the first time intraindividual variations in the pinnules according to their position in the dorsal fin. Nevertheless, when comparing two different specimens of one species there is little or no interindividual variation, suggesting that pinnule morphology may have taxonomical validity. As the fossil polypterid record is based mainly on the articular head of the pinnules, we suggest caution when describing new taxa, especially if different fragments corresponding to specific positions in the dorsal fin occur in the same locality.

Brain myosin-V is a two-headed unconventional myosin with motor activity

Chicken myosin-V is a member of a recently recognized class of myosins distinct from both the myosins-I and the myosins-II. We report here the purification, electron microscopic visualization, and motor properties of a protein of this class. Myosin-V molecules consist of two heads attached to an approximately 30 nm stalk that ends in a globular region of unknown function. Myosin-V binds to and decorates F-actin, has actin-activated magnesium-ATPase activity, and is a barbed-end-directed motor capable of moving actin filaments at rates of up to 400 nm/s. Myosin-V does not form filaments. Each myosin-V heavy chain is associated with approximately four calmodulin light chains as well as two less abundant proteins of 23 and 17 kd.

Ca(2+)-dependent phosphorylation of the tail domain of myosin-V, a calmodulin-binding myosin in vertebrate brain

1. Myosin-V from vertebrate brain is a novel molecular motor with a myosin-like head domain, a calmodulin-binding neck region and a unique tail domain of unknown function. Previous studies showed brain myosin-V to be a phosphoprotein substrate for Ca2+/calmodulin-dependent protein kinase associated with actomyosin. In the present study we describe the preparation of a specific actin-cytoskeletal fraction which is enriched in brain myosin-V. 2. We show that Ca2+/calmodulin-dependent protein kinase activity is also associated with this preparation and phosphorylates brain myosin-V. 3. Calpain, a Ca(2+)-dependent protease, generates a M(r) 80,000 fragment from the COOH terminal region of brain myosin-V containing most or all of the phosphorylation sites. 4. These results suggest that the unique tail domain of this novel myosin is subject to Ca2+ control via phosphorylation by kinase activity associated with the actin cytoskeleton.

Biochemical and immunological characterization of p190-calmodulin complex from vertebrate brain: a novel calmodulin-binding myosin

We have recently identified a novel 190-kD calmodulin-binding protein (p190) associated with the actin-based cytoskeleton from mammalian brain (Larson, R. E., D. E. Pitta, and J. A. Ferro. 1988. Braz. J. Med. Biol. Res. 21:213-217; Larson, R. E., F. S. Espindola, and E. M. Espreafico. 1990. J. Neurochem. 54:1288-1294). These studies indicated that p190 is a phosphoprotein substrate for calmodulin-dependent kinase II and has calcium- and calmodulin-stimulated MgATPase activity. We now have biochemical and immunological evidence that this protein is a novel calmodulin-binding myosin whose properties include (a) Ca2+ dependent action activation of its Mg-ATPase activity, which seems to be mediated by Ca2+ binding directly to calmodulin(s) associated with p190 (maximal activation by actin requires the presence of Ca2+ and is further augmented by addition of exogenous calmodulin); (b) ATP-sensitive cross-linking of skeletal muscle F-actin, as demonstrated by the low-speed actin sedimentation assay; and (c) cross-reactivity with mAbs specific for epitopes in the head of brush border myosin I. We also show that p190 has properties distinct from conventional brain myosin II and brush border myosin I, including (a) separation of p190 from brain myosin II by gel filtration on a Sephacryl S-500 column; (b) lack by p190 of K(+)-stimulated EDTA ATPase activity characteristic of most myosins; (c) lack of immunological cross-reactivity of polyclonal antibodies which recognize p190 and brain myosin II, respectively; (d) lack of immunological recognition of p190 by mAbs against an epitope in the tail region of brush border myosin I; and (e) distinctive proteolytic susceptibility to calpain. A survey of rat tissues by immunoblotting indicated that p190 is expressed predominantly in the adult forebrain and cerebellum, and could be detected in embryos 11 d post coitus. Immunocytochemical studies showed p190 to be present in the perikarya and dendritic extensions of Purkinje cells of the cerebellum.

Epidemiology of dermal leishmaniasis in the Rio Doce Valley, State of Minas Gerais, Brazil

Dermal leishmaniasis is prevalent in the predominantly settled agricultural areas in the Rio Doce Valley in the eastern part of the State of Minas Gerais, Brazil. The disease has been recorded almost equally in both sexes. Cases have been confirmed in all age groups but youths aged ten to 14 years form the population segment at greatest risk to infection. Cases of single cutaneous lesions, multiple cutaneous lesions and muco-cutaneous lesions have been recorded in the area. Isolates of parasites include representatives of the Leishmania mexicana and L. braziliensis complexes and at least one parasite that does not fit into either category. Infections have not been detected in small mammals (mainly rodents) but about 3% of dogs are infected. The phlebotomine fauna includes no species (or close relatives of species) previously incriminated as vectors of mexicana and braziliensis infections in Brazil. In the complex and confusing epidemiological situation in the Rio Doce Valley it seems unwise to apply traditional specific names to Leishmania of the area.