Species Of Chthamalus Research Articles

Brewed in the African pot: the phylogeography of the toothed barnacle Chthamalus dentatus (Chthamaloidea: Chthamalidae)

ABSTRACT The toothed barnacle Chthamalus dentatus has a wide distribution in the intertidal zone along the coasts of Africa, ostensibly occurring from Madagascar and Mozambique in the West Indian Ocean to Senegal in the Eastern Atlantic Ocean. We studied the differences in the mitochondrial COI gene of 287 individuals from 15 different locations and found that this taxon, which morphologically is considered a single species, actually compromises three genetically distinct clades – the South African, the Namibian, and the Cameroonian. The genetic differences between these units are similar or larger than those found between different species of Chthamalus. We suggest that the nominal species C. dentatus is a cluster of three cryptic species. These cryptic species are separated by a series of upwelling systems that are likely to act as barriers to the distribution of propagules of C. dentatus. Based on molecular and morphological data, we indicate that C. dentatus is probably a close relative of the Caribbean and Central American species of Chthamalus.

Molecular analysis reveals a cryptic species ofChthamalus(Crustacea: Cirripedia) in the Cape Verde Islands

AbstractThe intertidal barnacle Chthamalus stellatus has a broad distribution, occurring in the Mediterranean, the east Atlantic shores and east Atlantic Macaronesian Islands (Madeira, the Canaries and the Azores). Traditionally, based on morphological characters, Chthamalus of the Cape Verde Islands were also regarded as C. stellatus. However, using a mitochondrial gene and two nuclear genes, we found that although Chthamalus from Cape Verde is morphologically similar to C. stellatus, there are genetic differences between the two that are larger than those found between different species of Chthamalus. We thus claim that these genetic differences justify the assignment of the Cape Verde populations as an evolutionarily significant unit and a sister clade to C. stellatus. We also show that the connection between taxonomic units that are close to each other lies not only in the resemblance between DNA sequences. We have found that numerous point mutations characterizing the Cape Verde Chthamalus are present as infrequent alleles in C. stellatus, indicating that two close taxonomic units can also share polymorphisms present in their common ancestor.

The influence of the rock mineralogy on population density of Chthamalus (Crustacea: Cirripedia) in the Ligurian Sea (NW Mediterranean Sea)

Settlement, recruitment and survival of sessile marine species are driven by many biotic and abiotic factors. Among them, substrate mineral composition is generally a neglected topic, despite it proved to be a relevant contributing variable in driving the structure of benthic communities. Thanks to their ecology, Chthamalus species are a good proxy to test the role of substrate in affecting settlement and final population density on exposed rocky shores. Differences in the number of individuals were analysed in eight localities along the Eastern Ligurian Riviera (north-western Mediterranean Sea), from Portovenere to Manara Cape. In this sector of the Ligurian littoral, the coast is constituted by different rocks characterised by variable concentrations of calcite, silicates and quartz. This situation constitutes an ideal setting to evaluate the influence of mineral composition of the rocks in structuring the epilithic macrobiota communities in energetic splash zones and under similar physical pressures. Rocks rich in calcites turned out to be more suitable for Chthamalus species than substrates containing high amounts of silicates, and of quartz in particular. Additionally, also the grain size of the main mineral component of the rocks, determining in turn the surface roughness seemed to influence barnacle densities, with a significant preference for finer-grained substrates.

Systematics and biogeography of Tropical Eastern Pacific Chthamalus with descriptions of two new species (Cirripedia, Thoracica)

Distribution patterns of Chthamalus along the Tropical Eastern Pacific region have not yet been described, mostly due to unknown species ranges and the presence of cryptic species that has biased previous attempts to describe them. Prior to this paper, four formal and two informal species of Chthamalus have been recognized as occurring along the Pacific Americas coast: C. dalli Pilsbry; C. fissus Darwin; C. anisopoma Pilsbry; C. panamensis Pilsbry, Chthamalus sp. “cortezianus” and Chthamalus sp. “mexicanus”. The two informal species were already known to exist, based on previous studies using allozymes and gene sequencing, but their morphological characterizations were not determined, thus preventing their recognition and the ascertainment of their status under the International code of Zoological Nomenclature. The main goal of the present study was to discover the morphological differences that distinguish these two species, to determine their latitudinal range, to establish some relationship among the other species of Chthamalus, and to correlate these with the informal names previously used. Two new species of Chthamalus are described: C. hedgecocki sp. nov. occurring along the Mexican coast (Mexican province) and Chthamalus southwardorum sp. nov. occurring from the Gulf of California (Mexico) to the north of Peru, being a typical member of Panamanian s. l. Province. Both species belong to the Chthamalus fissus group of species as they have bidenticulate setae with basal guards on cirrus II and an absence of conical spines on the outer face of the exopod of cirrus I. The names Chthamalus sp. “cortezianus” is herein associated with C. hedgecocki and Chthamalus sp. “mexicanus” with C. southwardorum. An extensive sympatric distribution of Chthamalus species was noticed along the Eastern Pacific, and Chthamalus panamensis, previously known to be limited to the Panamanian coast, was found up to the Mexican coast in sympatry with C. hedgecocki. The COI genetic divergence between C. panamensis and C. hedgecocki varied between 2.8–4.3 using (GTR+G). We suggest that these species form a sibling pair based on to their morphological, ecological and genetic similarities and their evolution took place along the Eastern Pacific coast after the closure of the Isthmus of Panama. Chthamalus southwardorum is the best choice for a sibling pair with C. proteus, as they share morphological and ecological features; nevertheless they present a very high genetic divergence (24.3 to 25.1 GTR+G). Further studies are needed to clarify the evolutionary processes that led to the evolution of the Chthamalus fissus group of species along the Tropical Eastern Pacific coast and in the Caribbean.

A new barnacle species from Hong Kong: Chthamalus neglectus sp. nov. (Cirripedia: Thoracica: Chthamalidae)

A new barnacle, Chthamalus neglectus sp. nov. is described from Hong Kong. Light microscopy and scanning electron microscopy investigations of adult morphology show obvious differences from previously recorded Chthamalus species, and that this species belongs to the ‘C. challengeri group’ of Chthamalidae.

Larval Morphology of a Recently Recognized Barnacle, Chthamalus Neglectus (Cirripedia: Thoracica: Chthamalidae), from Hong Kong

Abstract A new barnacle species, Chthamalus neglectus Yan and Chan, 2004, was described from Hong Kong. It belongs to the “challengeri” group of Chthamalidae. The larvae of Chthamalus neglectus differ from C. challengeri, C. antennatus, C. montagui, and C. dalli (challengeri group) in the teeth of the labrum, shape of cephalic shield, setation formula, and cephalic shield sculpturing under both light and scanning electron microscopes. This further confirms it is a new Chthamalus species.

A KEY FOR THE IDENTIFICATION OF THE NAUPLII OF COMMON BARNACLES OF THE BRITISH ISLES, WITH EMPHASIS ON CHTHAMALUS

Abstract Chthamalus stellatus and C. montagui are warm-water barnacles common on rocky shores in southwest England, Ireland, and southern Europe. They are partly sympatric, with overlapping vertical and horizontal distributions. It has been suggested that the differing horizontal distribution of the adults may be related to differences in the distribution of the larval stages. To this end, we have examined plankton samples taken during the summer breeding period at Plymouth, from inshore to 15 miles offshore. The samples also contained large numbers of other cirriped nauplii, notably Elminius modestus, Balanus perforatus, B. crenatus, and Verruca stroemia, from which the chthamalids had to be distinguished. The chthamalids can be separated from the other nauplii by use of characters that include a unilobed or trilobed labrum, the length of posterior processes and the shape and size of the cephalic shield, but the two species of Chthamalus are more difficult to distinguish. Scanning electron microscopy (S....

Larval development of Chthamalus malayensis (Cirripedia: Thoracica) reared in the laboratory

Larvae of Chthamalus malayensis (Cirripedia: Thoracica) from Hong Kong were cultured in the laboratory. Larval development includes six naupliar stages and a non-feeding cypris stage. Larvae reached the cypris stage in 20 d at ∼21°C compared to 14 d at ∼28°C. Morphological features including the cephalic shield, frontal horns, labrum, abdominal process, antennules, antennae and mandibles in all nauplius and cypris stages were described and illustrated using a combination of light microscopy and scanning electron microscopy. Attempts were made to compare morphological differences between the nauplii and cyprid of C. malayensis with those of other Chthamalus species including C. stellatus, C. montagui, C. dentatus, C. fragilis, C. dalli, C. antennatus, C. fissus and C. challengeri. The present description of the nauplii of C. malayensis is not in agreement with the previous description of this species.

Distribution, abundance and recruitment of Chthamalus (Crustacea: Cirripedia) populations along the central coast of Portugal

The distribution, abundance and recruitment of Chthamalus species were studied for one year at two rocky shores on the central coast of Portugal. Chthamalus montagui is the most abundant intertidal barnacle on the Portuguese mainland. Higher abundance of C. montagui was found on the lower levels of the more sheltered shore, which is closer to the influence of the Tagus estuary. Chthamalus stellatus was also present, in very low densities, and always confined to the lower level of the barnacle zone. Chthamalus stellatus was more common at the shore farther away from the estuary, in which exposure to wave action is higher. The metamorphs of C. stellatus settled at the studied shores are considered to be immigrants from other populations, where the density of adults is sufficient for cross-fertilization to occur. Chthamalus spp. recruited almost continuously throughout the year, with a peak between July and September and a gap during February and March. Variations in phytoplanktonic assemblages and temperature may be the main factors controlling the reproductive season of Chthamalus spp. Recruitment was usually stronger on the lower shore levels but extended for a longer period higher on the shore. Seasonalvariations of C. montagui abundance were greater on the lower levels of the more exposed shore. This is probably due to faster growth and higher mortality of barnacle populations occupying the lower shore levels at the more exposed habitats.

Larval development of the intertidal barnacles Chthamalus stellatus and Chthamalus montagui

Two recently-distinguished species of Chthamalus (Cirripedia) are found on rocky shores in the north-eastern Atlantic: C. stellatus predominant on islands and headlands and C. montagui more abundant in bays. Larvae of the two species were produced in laboratory cultures to describe and compare the morphology and to allow identification in plankton samples. Nauplius larvae of C. stellatus are up to 30% larger than those of C. montagui. Differences in setation are minor. The two species are easily distinguishable from the size and shape of the cephalic shield. Chthamalus stellatus has a subcircular shield with longer body processes in later stages while C. montagui is more ovoid. The former develop more slowly in culture than the latter. Chthamalus stellatus larvae in a culture at 19 °C reached stage VI in 16 d compared to 11 d for larvae of C. montagui at the same temperature. The morphology and longer development time of C. stellatus larvae suggests adaptation to a more oceanic lifestyle and wider dispersal to reach more fragmented habitats than larvae of C. montagui.

Genetic structure of populations of two species of Chthamalus (Crustacea: Cirripedia) in the north-east Atlantic and Mediterranean

Protein electrophoresis on starch gels was used to investigate population genetic structure of the barnacles Chthamalus montagui Southward and C. stellatus (Poli) over their north-east Atlantic and Mediterranean ranges. In each species, a single locus exhibited marked differentiation of allele frequencies between Atlantic and Mediterranean localities; in C. stellatus, genetic differentiation between the two basins had not previously been noted. In both species, mean heterozygosity per locus appeared higher in the Mediterranean samples than in the Atlantic, and Mediterranean populations had more alleles at the loci studied. Possible explanations for the differentiation between the Atlantic and the Mediterranean populations are discussed.

Barnacle ecology: is competition important? The forgotten roles of disturbance and predation

The view that interspecific competition with balanoid barnacles has caused the evolutionary decline of chthamaloids (Stanley and Newman 1980), is challenged on 3 grounds. First, as a phyletic stock, chthamaloid size, as indicated by the mean adult basal diameter of extant taxa, has been decreasing, probably since the end of the Cretaceous. Small organisms will lose in interspecific competition to larger ones. However small body size reduces the susceptibility to predation and various forms of disturbance, and therefore allows chthamaloids to inhabit intertidal areas denied to balanoids. Second, although many species of Chthamalus occupy a high intertidal “refuge,” there is little evidence that competition is the primary ecological force maintaining them there. Predation is the most significant influence in tropical areas. In many temperate zone communities characterized by intense invertebrate predation or physical disturbance, chthamaloids achieve their maximum density lower in the intertidal than do balanoids or coronuloids. Last, the fossil evidence supporting a decline in chthamaloids is missing. The difficulty of seeking a single mechanism to explain global, multispecific phenomena is discussed.

Enzyme variation inChthamalus stellatusandChthamalus montagui(Crustacea: Cirripedia): evidence for the presence ofC. montaguiin the Adriatic

The electrophoretic mobilities of 13 enzymes in two species ofChthamalus, C. stellatusPoli and C. montagui Southward, were compared. These species differed absolutely for eight of the enzymes and exhibited some species-specific allozymes for a further four enzymes. No evidence of hybridization was found. The observed mean heterozygosity was 0087 forC. stellatusand 0179 forC. montagui.A sample of ‘C. montagui’ from Venice differed from two samples from south-west England in external shell characters and in allozyme frequency for two enzymes. These differences are thought to be the result of a geographical cline rather than a distinct separation of subspecies.