Chromosomal diversification of reef fishes from genus <Emphasis Type="Italic">Centropyge</Emphasis>(Perciformes,Pomacanthidae)

The genus Centropyge is remarkable for species richness, composing a highly specialized fish group amongst members from family Pomacanthidae. However, cytogenetical reports are nearly absent in these animals. New data are provided from karyotypical studies carried out on Centropyge aurantonotus from the Brazilian coast of the Atlantic Ocean and C. ferrugatus from the Philippines Sea of the Indo-Pacific Ocean. Both species present 2n=48 but karyotypes are differentiated by fundamental number. C. aurantonotus has a great number of biarmed chromosomes (4 m + 14 sm+16 st+4 a), while C. ferrugatus presents only acrocentric chromosomes. Single nucleolar organizer regions (NORs) are located at interstitial position of an acrocentric pair in C. ferrugatus and on short arms of a subtelocentric pair in C. aurantonotus, as confirmed by fluorescent in situ hybridization (FISH) with 18S rDNA probes. Heterochromatin is distributed over NOR and centromeric regions in both species, but additional GC-rich heterochromatic blocks on short arms of up to eight chromosomal pairs can be detected in C. aurantonotus. 5S rDNA segments were located interstitially on two chromosomal pairs in C. ferrugatus and on nine pairs in C. aurantonotus, mostly equivalent to heterochromatic blocks on short arms of biarmed chromosomes. C. ferrugatus can be considered a species in which basal chromosomal features proposed for modern Teleosteans were conserved. The derived karyotype pattern of C. aurantonotus seems to be determined by pericentric inversions and heterochromatin addition which probably determined the notorious dispersion of 5S rRNA (pseudo)genes. It is demonstrated that, even within a group generally characterized by cytogenetical homogeneity as the family Pomacanthidae, diversified karyotypes can be found.     

Description of the digestive tract and feeding habits of the king angelfish and the Cortes angelfish

Morphologically, the digestive tracts of the king angelfish Holacunthus passer and the Cortes angelfish Pomacanthus zonipectus are similar, yet the king angelfish intestine is almost 30% longer than that of the Cortes angelfish. Both pomacanthids have a small mouth with villiform teeth, a short oesophagus, a well-defined stomach, and a terminal sac at the end of the digestive tract. The terminal sac, the acid pH in the stomach, and the long intestine may facilitate efficient use of seaweed nutrients. Stomach contents were analysed to determine diets and interspecific overlap. Seventy-one species were found in the stomachs of the king angelfish and 53 in the stomachs of the Cortes angelfish. Because of the wide range of species in their diets, both angelfish must be regarded as omnivorous. The most frequent foods were seaweed and sponges, but for the king angelfish, crustaceans were also important. A cluster analysis was done to determine whether the diets of these fish were similar by sex, size, or season. No similarities were found. Dietary overlap is high in relation to other pomacanthids.     

Transfer ofCentropyge multispinis (Teleostei; Pomacanthidae) from subgenusXiphypops to subgenusCentropyge

The angelfish,Centropyge multispinis, hitherto assigned to the subgenusXiphypops Jordan, 1922 is transferred to the subgenusCentropyge Kaup, 1860, on the basis of anatomical characters. Comparison of adult specimens ofC. (C.) multispinis with 5 other species,C. (C.) nox, C. (C.) eibli, C. (X.) shepardi, C. (X.) flavicauda, andC. (X.) acanthops, confirmed its subgeneric status.     

Habitat selection and territorial defense behaviors in juvenile cortez angelfish,Pomacanthus zonipectus (gill)

Scuba diving observations in the Gulf of California (Mexico) on juvenile Cortez angelfishes, Pomacanthus zonipectus (Gill), indicate that these fish select and defend territories centered about a rock crevice. By day, they make brief feeding excursions, venturing even over open sandy areas near the rocks. They are substrate feeders, and will remove ectoparasites from other fishes, even attempting to clean human divers. At night they remain in their rock crevices. Laboratory experiments, conducted to quantify habitat-selection and territorial-defense behaviors in juvenile P. zonipectus, revealed that they spend 75% of their time during the day near rocks and 25% over sand in a divided experimental tank. The frequency of attacks on a mirror image increased as the mirror was moved closer to the rock crevice which was the territorial focus.     

Cleaning Activity of Juvenile Angelfish, Pomacanthus paru, on the Reefs of the Abrolhos Archipelago, Western South Atlantic

Studies on fish cleaning symbiosis in the tropical western Atlantic concentrate on specialized cleaner gobies and wrasses. On the reefs of the Abrolhos Archipelago, off the eastern Brazilian coast, juvenile french angelfish, Pomacanthus paru, clean a rich and varied community of fish clients. We recorded 31 reef fish species, including large predators such as groupers, jacks, and morays, being serviced by the french angelfish on cleaning stations situated mostly on seagrass flats. The angelfish performs a characteristic fluttering swimming at the station and, during cleaning events, touches the body of the clients with its pelvic fins. Frequency of encounters between the cleaner and its clients do not reflect the local abundance of client species; most of these move from the reefs to the sand flats to be cleaned. We found no correlation between client size and duration of cleaning events. The conspicuous black and yellow pattern, the fluttering swimming, the tenure of cleaning stations, the physical contact with the client, and the varied community of clients, qualify the juveniles of P. paru as specialized cleaners comparable to the gobies of the genus Elacatinus.     

Colour morph of a probable queen angelfish Holacanthus ciliaris from Dry Tortugas, Florida

An unusual colour morph of a probable Holacanthus ciliaris was observed in Dry Tortugas, Florida, which can possibly be explained by recessive homozygosity, however, further testing is necessary. This variation of H. ciliaris has previously only been described at St Paul's Rocks, Mid-Atlantic Ridge.     

Development of polymorphic microsatellite loci for conservation genetic studies of the coral reef fish Centropyge bicolor

A total of 23 novel polymorphic microsatellite marker loci were developed for the angelfish Centropyge bicolor through 454 sequencing, and further tested on two spatially separated populations (90 individuals each) from Kimbe Bay in Papua New Guinea. The mean ± s.e . number of alleles per locus was 14·65 ± 1·05, and mean ± s.e . observed (H_O) and expected (H_E) heterozygosity frequencies were 0·676 ± 0·021 and 0·749 ± 0·018, respectively. The markers reported here constitute the first specific set for this genus and will be useful for future conservation genetic studies in the Indo‐Pacific region.     

A comparative analysis of the feeding apparatus in pomacanthids, with special emphasis of oesophageal papillae in Genicanthus personatus

Of the pomacanthids examined in the present study (22 species; seven genera), only Genicanthus (eight species) had unique oesophageal papillae. The papillae of the masked angelfish, Genicanthus personatus are arranged in a radial fashion, finger-like or polypoid in shape, very abundant, fill the lumen, and vary considerably in length (0·38–2.40 mm) and width (0·12–1·18 mm). The surface pores (2.8–45.2 μm in diameter) of each papilla are part of the gastric or mucus-secreting oesophageal glands as determined by histological examination. Preliminary stomach content analyses revealed that G personatus consumes a variety of animal and plant material, including algae, copepods, diatoms, and eggs, but dominated in volume by plant material. The oesophageal papillae may constitute a morphological specialization of the digestive tract at the genus level. This may enable Genicanthus spp. to utilize and process a food source not readily available to other pomacanthid species. Additional studies are necessary to determine other ecological, behavioural, social, and morphological variables that separate this large and diverse group of fishes ecologically.     

Density-dependent protogynous sex change in territorial-haremic fishes: models and evidence

Several hypotheses of the proximate control of protogynous (female-to-male)sex change propose that social group composition triggers sexchange, but they do not address how proximate cues are alteredby population density. I present three mutually exclusive encounter-ratethreshold hypotheses that assume that population density determinesrates of contact between social group members and that ratesof contact are cues for sex change. Different densities arepredicted to induce sex change, depending on the encountersassumed to be important in the sex change process (e.g., encounterswith smaller and larger individuals). Tests of the models usea pomacanthid angelfish(Centropyge potten) to show that continuedpresence of a smaller (female) conspecific is needed for sexchange, and that continued presence of a larger (male) conspecificcan either inhibit sex change or prevent its behavioral stimulation.Using constant social group composition, sex change is preventedat higher density but not at a lower density. The absolute encounter-ratethreshold hypothesis, which predicts sex change under intermediate-densityconditions, is the most probable model of the social controlof sex change in C.potteri