Host preference and specialization in Gnathia sp., a common parasitic isopod of coral reef fishes

A gnathiid species (Crustacea: Isopoda; one of the most common ectoparasites of coral reef fishes) from the Great Barrier Reef, Australia, was allowed to choose among fishes from three different families to feed on (using two species of fishes per family). Gnathiids showed a strong preference for labrids, rarely feeding on pomacentrids or apogonids. In a separate experiment, gnathiid host preference did not vary among three labrid fish species. Gnathiids that fed on labrids had higher survival than those that fed on apogonids. Male gnathiids that fed on labrids also moulted to the adult stage more quickly. This suggests that host specialization and local adaptation might be occurring between these ectoparasites and their host fishes at the host fish family level.     

Diversity and specificity of Caribbean sponge–zoanthid symbioses: a foundation for understanding the adaptive significance of symbioses and generating hypotheses about higher-order systematics

The diversity and specificity of symbiotic associations may be useful in revealing the underlying ecology of symbioses and evolutionary relationships of symbiotic species. Symbioses between coral reef sponges and zoanthids are widespread and common in the greater Caribbean region, although the diversity and specificity of the species involved have only been explored at a few sites and the adaptive significance has only been examined for three combinations. We identified extensive diversity among sponges that associate with zoanthids by compiling sponge–zoanthid species associations from field surveys, the literature, and museum collections, and examined the patterns of specificity at multiple levels of sponge and zoanthid taxonomy. The results obtained indicate that facultative sponges are highly specific to the species of their partners whereas obligate zoanthids are not. The patterns of specificity among sponges and zoanthids suggest that many of these associations are not likely to be parasitic. Sponges harbouring photosynthetic endosymbionts associate at a disproportionately high frequency with zoanthids that harbour photosynthetic endosymbionts. Zoanthids embed in the surfaces of sponges to various degrees, resulting in a range of intimacy that negatively correlates with the number of hosts and polyp volume of zoanthids. Dendrograms based on the similarity among associations are largely consistent with current hypotheses of sponge higher-order systematics, but inconsistent with the current hypotheses of zoanthid systematics, and they highlight the potential utility of ecological characters in systematic analyses.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 695–711.     

Adeylithon bosencei gen. et sp. nov. (Corallinales,Rhodophyta): a new reef‐building genus with anatomical affinities with the fossil Aethesolithon

Adeylithon gen. nov. with one species, A. bosencei sp. nov., belonging to the subfamily Hydrolithoideae is described from Pacific coral reefs based on psbA sequences and morpho‐anatomy. In contrast with Hydrolithon, A. bosencei showed layers of large polygonal “cells,” which resulted from extensive lateral fusions of perithallial cells, interspersed among layers of vegetative cells. This anatomical feature is shared with the fossil Aethesolithon, but lacking DNA sequences from the fossils and the fragmentary nature of Aethesolithon type material, we cannot ascertain if Adeylithon and Aethesolithon are congeneric. Morpho‐anatomical features of A. bosencei were generally congruent with diagnostic features of the subfamily Hydrolithoideae: (i) outline of cell filaments entirely lost in large portions due to pervasive and extensive cell fusions, (ii) trichocytes not arranged in tightly packed horizontal fields, (iii) basal layer without palisade cells, and (iv) cells lining the canal pore oriented more or less perpendicular to roof surface and not protruding into the canal. However, it showed a predominant monomerous thallus organization and trichocytes were disposed in large pustulate, horizontal fields, although they were not tightly packed and did not become distinctly buried in the thallus. Only mature tetrasporangial conceptacles were observed, therefore the type of conceptacle roof formation remained undetermined. Adeylithon bosencei occurs on shallow coral reefs, in Australia, Papua New Guinea, and South Pacific islands (Fiji, Vanuatu). Fossil Aethesolithon is considered an important component of shallow coral reefs since the Miocene; fossil records showed a broad Indo‐Pacific distribution, but a long‐term process of range contraction in the last 2.6 million years, resulting in an overlap with the distribution of the extant Adeylithon. While the congeneric nature of extant and fossil taxa remained uncertain, similarities in morpho‐anatomy, habitat, and distribution may indicate that both taxa likely shared a common ancestor.     

Prevalence of hard tick infestations in cattle of Mizoram,India

The present study was conducted to determine the prevalence of hard tick infestations in cattle of Mizoram from April 2017 to March 2018. The prevalence of hard tick infestations was studied in relation to sex and age of animals and seasonal changes in a year. Cattle of selected places were examined carefully for the presence of ticks and in positive cases ticks were collected manually and identified on the basis of morphological characters. A total of 713 cattle were examined and out of which 452 (63.39%) cattle were found to be infested with hard ticks and the prevalent tick species was Rhipicephalus (Boophilus) microplus. A significantly (p < 0.01) higher infestation was observed in female cattle (66.43%) than males (48.83%). Age-wise highest prevalence of tick infestations was found in 1–5 years (73.41%) age group followed by >5 years age group (61.92%) and < 1 year (42.65%) age group, respectively. Seasonally, the prevalence of hard tick infestation was found highest (p < 0.01) in monsoon (77.91%) and lowest in winter (43.16%). The present study provides data on tick infestation in cattle of Mizoram, India.     

Disentangling the complex microbial community of coral reefs using standardized Autonomous Reef Monitoring Structures (ARMS)

Autonomous Reef Monitoring Structures (ARMS) have been applied worldwide to describe eukaryotic cryptic reef fauna. Conversely, bacterial communities, which are critical components of coral reef ecosystem functioning, remain largely overlooked. Here we deployed 56 ARMS across the 2,000‐km spread of the Red Sea to assay biodiversity, composition and inferred underlying functions of coral reef‐associated bacterial communities via 16S rRNA gene sequencing. We found that bacterial community structure and diversity aligned with environmental differences. Indeed, sea surface temperature and macroalgae cover were key in explaining bacterial relative abundance. Importantly, taxonomic and functional alpha diversity decreased under more extreme environmental conditions (e.g., higher temperatures) in the southern Red Sea. This may imply a link between bacterial community diversity and functional capabilities, with implications for conservation management. Our study demonstrates the utility of ARMS to investigate the response of coral reef‐associated bacterial communities to environmental change.     

Effects of group behavior in the predatory raid on damselfish nests by the false cleanerfish Aspidontus taeniatus

The false cleanerfish Aspidontus taeniatus, which resembles the bluestreak cleaner wrasse Labroides dimidiatus, is one of the best-known examples of mimicry in vertebrates. This mimicry system has been viewed as an aggressive mimicry to bite fish fins. However, recent field studies have reported that large individuals of the false cleanerfish often form groups and jointly raid damselfish nests to eat eggs that are guarded by their parents. The benefits of group behavior have been reported in a variety of animals. In the case of false cleanerfish, parental defense of territorial damselfishes is the main factor that constrains the availability of nutritionally valuable food resources. Here, we conducted field observations on the reefs of Okinawa, and found that the false cleanerfish formed groups of 2–12 individuals when they raided breeding nests of 13 species of damselfishes (Pomacentridae) and one species of triggerfish (Balistidae). Since the cleaner wrasse does not form such groups, the feeding groups of the false cleanerfish are assumed to reduce the effectiveness of mimicry. However, our results showed that the group behavior has two effects: a dilution effect, which reduces the risk of being attacked by egg-guarding fish, and an increase in foraging efficiency. We conclude that the false cleanerfish need to form foraging groups during egg-eating because the mimicry has no effect on parental damselfishes.     

珊瑚共生体中“细菌-虫黄藻-宿主”三角关系的通讯交流

“细菌-虫黄藻-珊瑚”是生态系统中一对经典的三角关系,其中包含着复杂的物质流、信息流和能量流,三者的平衡与稳定是维护珊瑚礁生态系统健康的重要保障。过去20年里针对共生体交互关系进行了大量研究,并取得了一些重要成果,明确了“细菌-虫黄藻-宿主”三者之间的物质代谢、营养交换以及与环境的交互关系。然而,基于共生系统的复杂性,一些现象背后的机制仍然未被充分揭示,尤其是共生体之间的通讯交流。信号分子介导的相互作用是珊瑚共生体稳态维持和高效运转的内在驱动力。本文以珊瑚共生体系中化学信号为重点,尝试梳理最新的研究进展,包括细菌与细菌、细菌与珊瑚、细菌与虫黄藻以及虫黄藻与珊瑚之间的通讯方式,重点关注了群体感应信号(QS)、二甲基巯基丙酸盐(DMSP)、糖类信号、脂类信号以及非编码RNA。选择性例举了QS信号介导的微生物协作和竞争、DMSP调节下的细菌和宿主的相互作用,以及环境胁迫下珊瑚和虫黄藻对非编码RNA的响应过程,强调了它们在共生体中的作用模式和生态意义。并对今后的研究重点和可能方向进行了提炼,包括研究维度的扩充、新技术-新方法的应用以及生态模型的构建等,旨在提升对三角关系互作方式的认识,增进对珊瑚共生体的理解,探索基于通讯语言的操纵方式为珊瑚礁生态系统的恢复和保护提供新思路。