Colonization of Pacific islands by parasites of low dispersal ability: phylogeography of two monogenean species parasitizing butterflyfishes in the South Pacific Ocean

Aim To investigate the phylogeographical patterns of two poorly dispersing but widely distributed monogenean species, Haliotrema aurigae and Euryhaliotrematoides grandis, gill parasites of coral reef fishes from the family Chaetodontidae. Location South Pacific Ocean (SPO). Methods Sequence data from the mitochondrial cytochrome oxidase subunit I (COI) gene were obtained from samples from five localities of the SPO (Heron Island, Lizard Island, Moorea, Palau and Wallis) for the two parasite species. Phylogenetic and genetic diversity analyses were used to reconstruct phylogeographical patterns, and dates of cladogenetic events were estimated. Results Overall, 50 individuals of 17 Haliotrema aurigae and 33 of Euryhaliotrematoides grandis were sequenced from five localities of the SPO for COI mtDNA (798 bp). Our results revealed a deep phylogeographical structure in the species Euryhaliotrematoides grandis. The molecular divergence between individuals from Moorea and individuals from the remaining localities (7.7%) may be related to Pleistocene sea‐level fluctuations. In contrast, Haliotrema aurigae shows no phylogeographical patterns with the presence of most of the mitochondrial haplotypes in every locality sampled. Main conclusions Our study shows contrasting phylogeographical patterns of the two monogenean parasite species studied, despite many shared characteristics. Both parasites are found on the same host family, share the same geographical range and ecology, and are phylogenetically close. We propose two hypotheses that may help explain the diparity: the hypotheses involve differences in the evolutionary age of the parasite species and their dispersal capabilities. Additionally, the lack of phylogeographical structure in Haliotrema aurigae contrasts with its apparently restricted dispersion, which is likely to occur during the egg stage of the life cycle, inducing a passive dispersal mechanism in butterflyfish monogeneans.     

Biogeography of the chaetodontidae: an analysis of allopatry among closely related species

Synopsis A recent survey of chaetodontid osteology has produced a hypothesis of relationships among 22 osteologically distinct genera and subgenera. Fourteen supra-specific taxa have distributions that are Indo-Pacific or larger. Most sister taxa inferred by osteology are broadly sympatric. The basal dichotomy within the large genusChaetodon contrasts monophyletic groups centered in the Atlantic and Indo-Pacific with little overlap. Divergence of Atlantic and Indo-Pacific distributions is correlated with the closing of the Tethys seaway 18–13 million years ago. Distributional data of Burgess (1978) and Allen (1980) are reevaluated in the context of putative species pairs and complexes. Species in nearly two thirds of these complexes (18 of 31) are distributed allopatrically. Eight complexes are examined in more detail. Five of these eight contain at least one peripherically isolated species. Distributions of species in four complexes indicate that previously wide-spread species were cleaved more symmetrically. Sympatric distributions within two species pairs indicate that the more narrowly distributed species in each pair arose through central isolation within a broadly distributed ancestor. The area of central isolation corresponds to the classical center of origin. A new hypothesis of vicariance followed by dispersal may partially explain the diversity gradient so prominently featured in dispersal-oriented tropical marine biogeography.     

Eye camouflage and false eyespots: chaetodontid responses to predators

Synopsis The roles of eye camouflage and eyespots are examined within the genusChaetodon as are the various theories explaining the evolutionary significance of the brilliant colors. While eye camouflage is not common among reef fishes, 91% of the 90 species ofChaetodon, have eyemasks (82) or black heads (4). Eye camouflage occurs concomitantly with diurnal false eyespots in 45.5% (41 of 90) of the species. Diurnal false eyespots serve to misdirect attacks by predators and/or to advertise unpalatability. False eyespots are located on areas of the body which allow escape and survival following an attack. Data suggesting that predators learn about the undesirability of butterflyfishes are presented. Butterflyfishes are inactive at night, forage during the day and spawn at dusk. It is unlikely that nocturnal color changes are useful in conspecific interactions and are therefore believed to provide visual cues to potential predators. Nocturnal eyespots probably function to intimidate potential predators but could also remind them of unpalatability. The aggression release hypothesis (Lorenz 1962, 1966) to explain the brilliant coloration of chaetodontids is not supported because butterflyfish coloration changes and few species are territorial. The species recognition hypothesis (Zumpe 1965) is not supported by results of field experiments. The disruptive coloration hypothesis (Longley 1917) is rejected as a general explanation for poster coloration but does explain the prevalence of eyebars ofChaetodon spp. The aposematic hypothesis (Gosline 1965) is supported by morphology, behavior, a lack of predation and field observations. The possibility of Mullerian mimicry is suggested. It is concluded that the primary selective force behind chaetodontid coloration, particularly eyespots, has been predation and color patterns have evolved to minimize this threat.     

The reproduction of Chaetodon austriacus,C. fasciatus and C. paucifasciatus (Chaetodontidae,Perciformes) in the Jordan Gulf of Aqaba

Synopsis Aspects of the reproduction of three sympatric and endemic chaetodontids, Chaetodon austriacus, C. fasciatus and C. paucifasciatus, from the Jordan Gulf of Aqaba were investigated. Chaetodon fasciatus had a higher fecundity than the other species which, in turn, had similar fecundities. The major egg release of C. austriacus and C. paucifasciatus began in August, that of C. fasciatus in September. Based on the gonadosomatic index of both sexes, the spawning period of C. austriacus was from July through October, that of C. paucifasciatus from August through October and that of C. fasciatus from September through December. The maturity length of the three chaetodontids is given and reproductive isolation among the sympatric species is discussed.     

The eye muscles and their innervation inChaetodon trifasciatus (Pisces,Teleostei, Chaetodontidae)

Synopsis InChaetodon trifasciatus, the large eye has the form of a thick disk rather than that of a globe. A deep cutaneous groove surrounds the eyeball, probably allowing rapid eye movements. The form and innervation of the three pairs of extraocular muscles are described. Each muscle is made of two types of fascicles of fibres, thick and thin. There is neither an anterior nor posterior myodome. The skull attachment of the obliques and of the inferior rectus is made on the thin sagittal ethmoidal membranous septum while that of the other recti occurs on osseous pieces of the skull. The attachment on the eyeball is made on the cartilaginous sclera. The ratio of the lengths of the antagonist muscles, superior vs. inferior oblique, superior vs. inferior rectus and medial vs. lateral rectus, is about 1.43:1. The three oculomotor nerves (III: common oculomotor, IV: trochlear and VI: abducens) as well as the ciliary system are described. For the following reasons, an analogy between the lateral rectus ofChaetodon trifasciatus and the lateral rectus + retractor bulbi of other vertebrates is indicated: (1) the nucleus of nerve III (which innervates four muscles) has four sectors, while that of IV (which innervates only the superior oblique) is made of one sector; (2) nerve VI consists of two roots corresponding to two groups of nerve cells of its motor nucleus and (3) in other vertebrates, nerve VI innervates both the lateral rectus and the retractor bulbi.     

Correlations between chaetodontid fishes and coral communities of the Gulf of Aqaba (Red Sea)

Synopsis The relationships existing between the chaetodontid fishes and the surrounding coral communities were investigated in the Gulf of Aqaba. Quantitative data were analysed by a correspondence and a cluster analysis. The results demonstrated a similarity in the spatial distribution of both communities. Significant correlations were found between the density of chaetodontid fishes and the diversity of the coral community as well as the substratum coverage by the coral colonies. The density of exclusive coral browsers was also correlated to the abundance of branching colonies. Among the different genera of branching corals, correlations were significant only for the genusAcropora. These results suggested the existence of strong links between coral and chaetodontid fish assemblages.