Chthamalid Barnacles Research Articles

Larval development of Capitulum mitella (Cirripedia: Pedunculata) reared in the laboratory

Larval development of Capitulum mitella (Cirripedia: Pedunculata) comprises six nauplius stages and a cyprid. Unilobed labrum, a larval trait of pedunculate and chthamalid barnacles, bears two groups of slender hairs and two pairs of strong teeth on the distal labral margin, and a pair of teeth on the lateral labral margin. Frontolateral horns extended under the anterior cephalic shield margin are diagnostic features through all nauplius stages. The posterior border of the cephalic shield bears a pair of distal cephalic shield spines in nauplius stages II and III, and a pair of long posterior shield spines in nauplius stages IV, V and VI. A hispid seta is consistently found at the fourth group of the antennal endopodite through stages II–VI. The dorsal thoracic spine, abdominal process and the paired posterior shield spines have numerous small spines. Morphological features such as the cephalic shield, labrum, abdominal process, antennules, antennae and mandibles in all nauplius and cyprid stages are illustrated and described. In this species, the numerical setations of the antennule are found to be beneficial for intra-specific identification of barnacle nauplius stages without the need for dissection.

Distribution and abundance of co-occurring chthamalid barnacles Chthamalus montagui and Chthamalus stellatus (Crustacea, Cirripedia) on the southwest coast of Portugal

Two co-occurring chthamalid barnacle species occur on the rocky shores of continental Portugal: Chthamalus stellatus (Poli) and Chthamalus montagui Southward. In the present study, patterns of distribution and abundance (density and percentage cover), both vertically (tidal level) and horizontally (wave action), were studied for each species on headlands (more wave action) and not on headlands (less wave action) and at two spatial scales (shore and site) and three tidal levels (low, mid and upper). Chthamalus montagui was significantly more abundant than C. stellatus in both degrees of wave action and at all tidal levels. Despite this great difference in abundance and considering each species individually, C. montagui was more abundant at mid tide-level, while C. stellatus was more abundant at the low tide-level, and C. montagui was less abundant on headlands, while C. stellatus was more abundant on headlands. Small-scale variability (between sites, tens of meters) of abundance of each species was detected, while differences on a larger scale (between shores, tens of kilometres) were not significant.

Larval development of Octomeris sulcata Nilsson-Cantell (Cirripedia: Thoracica: Chthamalidae) from Japan and Korea

Embryos obtained from gravid adults of the chthamalid barnacle Octomeris sulcata Nilsson-Cantell from Japan and Korea were cultured through six naupliar stages to the cyprid and juvenile barnacle stage in laboratory conditions, fed either the diatom Skeletonema costatum (Grev.) Cleve or the dinoflagellate Prorocentrum minimum (Pavillard) Schiller. The nauplii were planktotrophic and, depending on diet, reached the cyprid stage 9 or 17 days after hatching in individual cultures at 22 °C with 24 h illumination. The survival rate was higher and the duration of the naupliar stages was shorter when fed P. minimum rather than S. costatum. This is probably due to the presence of feathered setae on the antennae. Feathered or plumose setae in nauplii of different cirripede taxa are apparently linked to the type of phytoplankton in the seas when these taxa first evolved.

A comparison of reproduction in co-occurring chthamalid barnacles, Chthamalus stellatus (Poli) and Chthamalus montagui Southward

Reproduction in Chthamalus montagui Southward and Chthamalus stellatus (Poli) has been compared along gradients of wave exposure and tidal height. The proportion of barnacles carrying egg masses was greatest at low shore levels in both species, although the difference between levels was more pronounced in C. stellatus. Both species were found to breed between the beginning of May and the end of September. The mean number of broods released per season in both species ranged from 1.0 to 2.1 at high shore levels, from 2.2 to 3.2 at mid shore levels, and from 2.6 to 4.4 at low shore levels. C. stellatus predominated low on the shore at an intermediately exposed site and on the mid and low shore at the most exposed site. At these places it produced more broods per year than C. montagui. Development of the embryos of the two species was complete after 3 wk in vivo at 15°C. Eggs containing embryos of C. stellatus were larger than those of C. montagui, and within each species, larger barnacles produced larger eggs. Egg masses of C. stellanus included more eggs than those of C. montagui. Brood size in both species was greatest in shelter and least in exposure. Egg production was, however, similar in the two species when adjusted for differences in body mass. Egg production per unit body mass was greatest at an intermediately exposed site.

On the ecology and cirral behaviour of a new barnacle from the Red Sea and Indian Ocean

Tetrachthamalus oblitteratus is a small chthamalid found high up in the intertidal zone in the Gulf of Aqaba, Red Sea and at Mauritius, Seychelles and Aldabra Island, Indian Ocean. The general behaviour and rate of cirral activity are described and shown not to differ greatly from those of other chthamalids. The species appears well-adapted to the life in the tropics, and the present restricted distribution is presumed to be the result of competition with larger chthamalids of Indo-Pacific distribution. The absence of the larger chthamalids from places where Tetrachthamalus is found may be due to geographical isolation reinforced by the effects of a small tidal range and other extreme environmental conditions. Summary Tetrachthamalus oblitteratus is found high up in the intertidal zone in the Gulf of Aqaba, Red Sea and at Mauritius, the Seychelles and Aldabra Island, Indian Ocean. It is small compared even with other chthamalid barnacles. For this reason, and its apparently restricted distribution and our general lack of knowledge of island faunas, it has escaped notice until recently. The general behaviour and rate of cirral activity are described. The species does not differ significantly from other chthamalids, and seems as well adapted to life at high temperatures as the tropical forms previously investigated. The present restricted distribution of Tetrachthamalus is possibly due to competition with the larger chthamalids found in the Indian Ocean. The absence of these larger chthamalids from places where Tetrachthamalus is found may be due to geographical isolation, probably reinforced by the effects of small tidal range and other extreme environmental conditions in Continental situations.

Influence of X-Rays on Limb Regeneration in Urodele Amphibians

Influence of X-Rays on Limb Regeneration in Urodele Amphibians