Reproduction and early life history of an invasive ascidian Styela clava Herdman in Prince Edward Island, Canada

In the past decade, many aquatic invasive species have been introduced into Prince Edward Island, Canada, coastal waters, and they have had adverse effects on the aquaculture and fisheries industry. For instance, the mussel aquaculture industry has been overwhelmed by extremely high abundances of the invasive ascidian Styela clava in some areas. To understand and minimize the risk of spread of S. clava to other shellfish aquaculture sites, basic information on the reproductive biology of the ascidian is needed. This study investigated Styela gonad development, larval abundance and recruitment. Gonad development, using histological methods, indicated ovaries were ripe from late June through late October, 2004. Weekly water samples indicated larvae were present from 24 June to 29 October, with a distinct abundance peak in mid-August. Recruitment occurred from 24 June to 21 October. Timing of larval sampling was judged to be a crucial part of evaluating recruitment potential for monitoring purposes and a field experiment was carried out to document spatio-temporal larval concentrations. Data were gathered over 30 h sampling periods on 4 August and 14 September 2004. Water samples were taken simultaneously on an hourly basis at three depths: surface, 2 m and 4 m below the surface. Results indicated peaks in larval abundance were, in most cases, limited to a 3 h time interval in the early afternoon. Larval concentrations increased with water depth.     

The ecology of substrate-associated juveniles of the genusSebastes

Synopsis This paper reviews current knowledge of substrate-associated juvenileSebastes. In general, juvenile rockfish recruit to shallower depths than those occupied by conspecific adults. Habitat use by newly recruited rockfish differs markedly among species. While a few species recruit to shallow-dwelling macrophytes, such asZostera, many others recruit to larger brown algae, such asNereocystis andMacrocystis. A few deeper dwelling species recruit to low relief or soft substrata. However, little is known on recruitment of these deeper dwellers. Crustaceans are the major component of the diets of newly recruitedSebastes. Species which continue to forage in the water column shift to larger crustaceans (e.g. euphausids) and fish as they grow. Species which shift to substrate-associated prey soon begin to feed on larger algal-associated gammarid amphipods, shrimps and isopods. Field studies indicate variation in intraspecific growth rates over large geographic distances, among nearby sites and among algal habitats on the same reef, with food availability and water temperature being major factors in the differences. In particular, laboratory studies have shown that temperature is one of the most important factors in growth rates. Many species of juvenile rockfish make ontogenetic movements, often moving into deeper water as they age. Most seasonal movements appear to be related to changes in water temperature and turbulence.     

Examination of a great abundance of filefish, Pervagor spilosoma, in Hawaii

Synopsis The endemic filefish Pervagor spilosoma appeared in exceptionally large numbers throughout the major Hawaiian Islands during the spring of 1985 and remained abundant through 1988. We examined this occurrence with a perspective gained from studies of reef communities at the Island of Hawaii by one or both of us during most years from 1969 to 1994. P. spilosoma is known to vary in numbers, but such great abundances are rare. Although the species is considered a reef fish, individuals constituting the abundance were mostly in the water column, and spread from coastal reefs to the pelagic zone offshore. One might assume they represented an extraordinary recruitment of pelagic juveniles in the process of shifting to benthic habits, but our data indicate a more complex situation. Individuals in the water column tended to be larger than individuals near the reef, and although the former were feeding on plankton when collected, many had shifted to planktivory from earlier feeding on the benthos. Also, many in the water column were ailing, with moribund and dead individuals common, and these tended to carry parasites of types known to induce their hosts to rise toward the surface. We suggest that the great number of filefish we observed above near-shore reefs represented the shoreward fringe of a vast pool of individuals, varied in age, that had accumulated during the exceptionally long pelagic-juvenile period that is characteristic of tetraodontiforms.     

Habitat and body condition influence American Redstart foraging behavior during the non‐breeding season

Insectivorous birds may adjust their foraging strategies to exploit changes in resource distributions. Arthropod prey strongly influence habitat‐specific persistence of long‐distance migrant passerines in their wintering areas, and arthropods are strongly affected by rainfall. However, the effect of drought on the dynamics of avian foraging ecology as resources shift is not well understood. We captured female American Redstarts (Setophaga ruticilla) and studied their foraging behavior in high‐quality (evergreen black mangrove) and low‐quality (deciduous scrub) habitat in Jamaica during the winter of 1995–1996. As is typical in southwestern Jamaica, conditions became drier as spring approached and many trees in scrub lost most of their leaves; mangrove trees maintained most of their leaf cover. Birds in scrub lost more mass than those in mangrove, and scrub birds shifted to using more aerial (and fewer near‐perch) maneuvers. In scrub, but not in mangrove, the proportion of wing‐powered movements and aerial foraging maneuvers was positively correlated with mass corrected by body size. In both habitats, attack rate was negatively correlated with body condition. Therefore, redstarts in scrub that maintained body condition were likely better able to use energetically expensive aerial maneuvers and wing‐powered search movements to exploit large, calorie‐rich flying arthropods. As the scrub dried over the course of the winter, the shift in foraging tactic may have allowed some birds to forage more efficiently (i.e., lower attack rate), likely facilitating maintenance of good body condition.     

Pitfalls and Nuances of Parahisian pacing: A revisit through an interesting case

Parahisian pacing (PHP) is a useful maneuver during electrophysiology study of supraventricular tachycardia (SVT) especially when the tachycardia is non-sustained. Various responses during PHP can differentiate between the routes of VA conduction (VAC). In a case of WPW syndrome with orthodromic re-entrant tachycardia, we encountered various responses which one must be cognizant about to avoid erroneous conclusions. Along with para-hisian capture and only ventricular capture, simultaneous atrial capture (SAC) and pure His capture were also noted. Moreover, during pure-His capture underlying distal antegrade right bundle branch block (RBBB) was encountered making it an intriguing case.     

Maintenance of foraging trails by the giant tropical antParaponera clavata (Insecta: Formicidae: Ponerinae)

Summary Establishment and maintenance of foraging trails to an artificial nectar source by ten colonies ofParaponera davata (Fabr.) in Panama is reported. The first forager to locate the artificial nectar source was responsible for recruiting additional foragers and for marking trails to orient these foragers. More than half of the trail marking was performed by the first two ants to mark the path back to the colony, although up to 11 ants per colony per hour marked trails. The number of trail marks and the number of marking ants decreased through time, presumably as foragers learned the location of the artificial nectar source. Four categories of recruits were noted: markers, foragers, patrollers, and visitors.     

An eye for a tooth

Objective: To propose a possible link between dental extraction and intra‐ocular complications. Background: Several publications in medical literature describe intra‐ocular complications after different dental procedures. Results: Retinal detachment and vitreous hemorrhage following dental extraction with an appropriate anesthesia. Conclusion: Systemic complications following dental treatments should not be neglected and proper medical treatment must be provided as soon as possible.     

Early response of Abies balsamea seedlings to artificially created openings

Abstract. Small-scale canopy openings are being increasingly recognized for their importance in boreal forest stand development. Yet more work is necessary to understand their effects on seedling growth. This study investigated the effect of different degrees of canopy opening (all trees cut, conifers cut, conifers girdled and control quadrats) in different stand types on Abies balsamea seedling recruitment, growth and architecture. The lack of a treatment effect on seedling establishment suggests that gaps primarily affect advance regeneration. In the first year after treatment the seedlings in the cut blocks (both conifer cut and all trees cut) responded with an increase in height growth. Changes in the leader to lateral branch ratio were also significant. Continued architectural change in terms of number of branches produced did not occur until after two years had passed. Although not significantly different from the control, increases can be observed in all measurements for the girdled treatment. It is therefore concluded that the growth response of advance regeneration is more important following canopy opening than new seedling recruitment and that seedling performance is greatest where degree of opening is greatest.     

Coral recruitment and early benthic community development on several materials used in the construction of artificial reefs and breakwaters

Artificial reefs are increasingly being promoted as a means to mitigate impacts from human activities in coastal urban areas. Coastal defense structures such as breakwaters are becoming recognized as large-scale artificial reefs that support abundant and diverse marine communities and play important roles in coastal ecology and management. However, there is limited understanding of how substrate materials used to construct artificial reefs or breakwaters can influence the development of habitat-forming benthic organisms. To assess the influence of substrata on coral recruitment and overall benthic community development, we deployed standard-size tiles of materials used in the construction of breakwaters and artificial reefs (concrete, gabbro, granite, and sandstone), along with terra-cotta for comparative purposes, at two breakwaters (DDD, PRT) and two natural reef sites (NR1, NR2) in Dubai, United Arab Emirates, for one year. Kruskal-Wallis ANOVA with post-hoc Mann-Whitney U-tests were used to examine differences in coral recruitment among sites and materials. Coral recruitment was highest at the DDD (4.9 ± 0.5 recruits 100 cm^− 2), while recruitment was low and did not differ among other sites (PRT: 0.1 ± 0.04, NR1:0.3 ± 0.1, NR2: 0.1 ± 0.03 recruits 100 cm^− 2). There were significant differences in coral recruitment among materials at DDD, where gabbro had higher recruit densities than concrete and sandstone; sandstone also contained less coral recruits than terra-cotta. Variability associated with low coral recruit densities precluded significant differences among materials at other sites. Overall benthic community structure differed more as a result of differences among sites than among substrate materials. Higher community dissimilarity was observed among sites than among material in SIMPER analysis, and significant differences were only observed among sites in ANOSIM. Univariate comparison of the benthos correlated with community differences in NMS ordination also showed significant differences among sites but not material. Overall, these results indicate that site-specific differences in recruitment patterns are more important in determining early benthic community structure and coral recruitment than are differences among substrate material. However, where coral recruitment is high, these results suggest that gabbro should be used preferentially over concrete or sandstone where it is feasible, but that granite may be a suitable alternative where it is the dominant stone. Coral recruitment on terra-cotta was comparable to all materials but sandstone, supporting its continued use in recruitment studies. These results also indicate that using stone amenable to coral recruitment is unlikely to influence the wider benthic community.