Overgrowth of Caribbean octocorals by milleporid hydrocorals

On Caribbean reefs, colonies of the hydrocoral Millepora alcicornis are capable of pursuing and overgrowing arborescent octocorals (Wahle 1980 ). Nearly four decades since these interactions were described, we quantified arborescent octocorals encrusted by Millepora spp. (Linnaeus 1758) on shallow reefs in St. John, U.S. Virgin Islands, and evaluated encrusted colonies for evidence of an origin through pursuit. In 2014, 8% of octocorals (n=1684 colonies) were encrusted by Millepora spp., and in 2015, 12% were encrusted (n=847 colonies). Millepora spp. encrusted colonies of 10 octocoral genera, and in 2014, the most frequently encrusted were Eunicea spp. (40% of encrusted octocorals); in 2015, the most frequently encrusted were Gorgonia spp. (46% of encrusted colonies). In both years, ≥67% of encrusted octocorals were >21 cm from other colonies of Millepora spp.; 7% of octocorals were >1.3 m from colonies of Millepora spp. in 2014; and 16% of octocorals were >2.0 m from colonies of Millepora spp. in 2015. Relative to the ~5% of octocorals encrusted by Millepora spp. in Jamaica in the late 1970s, a high percentage (~9%) of octocorals were encrusted by Millepora spp. in St. John in 2014 and 2015. The large distances from most encrusted octocorals to the nearest colonies of Millepora spp. in St. John are inconsistent with a hypothesized origin through pursuit, contact, and overgrowth (sensu Wahle 1980 ).     

Size-selective predation by the cleaner fish Labroides dimidiatus

A comparison of the size-frequency distribution of parasitic gnathiid isopod larvae in the diet of the cleaner fish Labroides dimidiatus and on six host fish species ( Chlorurus sordidus, Ctenochaetus striatus, Hemigymnus melapterus, Scolopsis bilineatus, Siganus doliatus, Thalassoma lunare ) was made on one occasion. The comparison was repeated with Hemigymnus melapterus on three occasions and between two islands in Australia. L. dimidiatus selected larger gnathiids at all times at Lizard Island but not at Heron Island. Size-selective predation by L. dimidiatus suggests any potential effect of cleaner fish on parasites may vary according to the size of parasite. However, this effect appears to vary spatially.     

PARTICULATE ORGANIC MATTER AS AN ALTERNATIVE NUTRIENT SOURCE FOR TROPICAL SARGASSUM SPECIES (FUCALES, PHAEOPHYCEAE)

Large Fucales are abundant on coastal coral reefs of the Great Barrier Reef, but are often limited by the availability of inorganic nutrients. Particle loads in these reef waters are high, which is generally perceived as detrimental for aquatic plants due to a reduction of light. Here, I provide evidence that several abundant Sargassum species supplement their nutrient supply with nutrients derived from the layer of particulate matter (PM) deposited on their thalli. In experiments involving removal or addition of PM, growth rates of Sargassum spp. were up to 180% higher when particles were present on the thalli. Tissue nitrogen and phosphorus levels of thalli with a surface PM layer were 10%–30% higher than those of thalli without PM. The amount of PM deposited in situ on thalli of five species of brown algae ranged from 0.6 to 0.9 g C_org·g⁻¹ dry weight alga, depending on the species' morphology. I suggest that a nutrient-rich diffusive boundary layer is created on the thallus surface by an epiphytic microbial community that remineralizes the particulate nutrients. When algal growth is nutrient limited, the use of particle-derived nutrients as a source alternative to nutrients in the water column may outweigh any potential adverse effects of the thallus particle layer.     

Influence of larval feeding history on the body condition of Amphiprion melanopus

The cellular condition of liver hepatocytes and the height of gut epithelium cells of larval Amphiprion melanopus were sensitive indicators of feeding condition. Muscle fibres of the trunk showed marked separation in fish fed every third day just prior to settlement. Low feeding regimes also caused reductions in growth, increases in larval duration and reductions in size at metamorphosis. Gut epithelium cell height was also influenced by fish standard length and age. This study suggests that gut epithelium cell height is a useful index for an examination of the importance of starvation of larvae in tropical waters; however, size and age standardization is required prior to comparisons of wild caught fish through time or with laboratory samples.     

High variability of genetic pattern in giant clam (Tridacna maxima) populations within French Polynesia

Nine populations of giant clams, Tridacna maxima, from six islands of French Polynesia were screened for allozyme variation at ten polymorphic loci. The genetic structure of populations of T. maxima were studied at different spatial scales: within an island, between islands of the same archipelago and between archipelagos. Significant genetic differences were observed only between populations from different archipelagos, and genetic differentiation was correlated with geographical separation. However, these results were only supported by a single locus, PEP * and all other loci were homogeneous between studied populations. According to Lewontin & Krakauer's model, the genetic structure can be explained by selection. The selective factors most likely depend on the respective habitat of each archipelago. We also studied genotype–phenotype correlation using the colour of the clam mantle, and did not find any relationship between the mantle colour and the genetic structure of the individuals.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 221–231.     

珊瑚礁白化研究进展

珊瑚礁白化是由于珊瑚失去体内共生的虫黄藻和（或）共生的虫黄藻失去体内色素而导致五彩缤纷的珊瑚礁变白的生态现象。近年来，频繁发生的珊瑚礁白化导致了珊瑚礁生态系统严重退化，并已经影响到全球珊瑚礁生态系统的平衡，受到了人们的高度重视。研究认为：（1）大范围珊瑚礁白化主要是全球环境变化引起的，尤其是全球变暖和紫外辐射增强；（2）导致珊瑚礁白化的机制主要在于细胞机制和光抑制机制；（3）珊瑚礁白化后的恢复与白化程度有关，大范围白化的珊瑚礁完全恢复需要几年到几十年；（4）珊瑚礁白化的后果在于降低珊瑚繁殖能力、减缓珊瑚礁生长、改变礁栖生物的群落结构，导致大面积珊瑚死亡和改变珊瑚礁生态类型，如变为海藻型等；（5）与珊瑚共生的D系群虫黄藻更适应高温环境，珊瑚礁有可能通过D系群逐渐取代C系群的方式适应全球环境变化。     

The effects of interactions with reef residents on the settlement

Recruitment limitation models of coral reef fishes assume that interactions between demersal individuals and settling larvae are of little consequence to local population dynamics, as are interactions among reef residents. To test this premise, I examined the effects of interactions on the settlement and persistence of the ocean surgeonfish, Acanthurus bahianus. I also looked at behavioural exchanges among ocean surgeonfish of different sizes and between ocean surgeonfish and other reef residents to determine whether the nature of these exchanges changes ontogenetically. Settlement of ocean surgeonfish to Tague Bay Reef, St. Croix, U.S.V.I. was increased in the presence of conspecifics and decreased in the presence of a common Caribbean damselfish, the beaugregory Stegastes leucostictus. Additionally, post-settlement persistence was negatively related to the level of aggression received from beaugregories. Interactions among ocean surgeonfish and between ocean surgeonfish and damselfish were size-dependent; the largest and smallest size classes had higher levels of association with conspecifics than did the middle size classes, and larger size classes received more aggression from damselfish than did the smaller size classes. These results suggest that behavioural interactions may significantly affect the distribution, abundance and early post-settlement persistence of ocean surgeonfish settlers, and that the nature of these interactions changes over the lifetime of individuals.     

Using unmanned aerial vehicle (UAV) surveys and image analysis in the study of large surface‐associated marine species: a case study on reef sharks Carcharhinus melanopterus shoaling behaviour

A novel image analysis‐based technique applied to unmanned aerial vehicle (UAV) survey data is described to detect and locate individual free‐ranging sharks within aggregations. The method allows rapid collection of data and quantification of fine‐scale swimming and collective patterns of sharks. We demonstrate the usefulness of this technique in a small‐scale case study exploring the shoaling tendencies of blacktip reef sharks Carcharhinus melanopterus in a large lagoon within Moorea, French Polynesia. Using our approach, we found that C. melanopterus displayed increased alignment with shoal companions when distributed over a sandflat where they are regularly fed for ecotourism purposes as compared with when they shoaled in a deeper adjacent channel. Our case study highlights the potential of a relatively low‐cost method that combines UAV survey data and image analysis to detect differences in shoaling patterns of free‐ranging sharks in shallow habitats. This approach offers an alternative to current techniques commonly used in controlled settings that require time‐consuming post‐processing effort.     

An updated phylogeny of the redlip blenny genus Ophioblennius

An updated molecular phylogeny of the blenny genus Ophioblennius, with a focus on two geographically disjunct morphotypes observed in Brazil, is presented. The analyses showed that specimens from the north‐eastern Brazilian coast are the endemic redlip blenny Ophioblennius trinitatis, but specimens from the southern Brazilian coast are conspecific to an undescribed east Atlantic Ocean (Gulf of Guinea) species, previously unknown in Brazil. Possible explanations for this geographical pattern include: natural larval dispersal and rafting across the Atlantic; an unknown ecological attribute that enabled this species to colonize southern Brazil; oil platforms as introduction vectors.