The host range and distribution pattern of rhizocephalan parasitic barnacles in Korean coasts and their relationship with geographical factors

IntroductionThis study undertakes a detailed examination of the host range and distribution patterns of Rhizocephala, a group of specialized parasitic barnacles, within Korean marine environments. It aims to expand the understanding of their biodiversity and ecological impact.MethodsEmploying both morphological observation and mitochondrial DNA sequencing, the study identifies the variety of rhizocephalan species infecting decapod hosts in Korean waters, aiming to document their diversity and distribution.ResultsThe investigation identifies 26 rhizocephalan species parasitizing 28 decapod hosts, including the discovery of three new parasite-host relationships not previously reported. It was observed that while a few rhizocephalan species infect multiple hosts, most have a narrow host range. Additionally, the study maps out regional differences in Rhizocephala diversity across three Korean marine ecoregions, noting the highest diversity in the warmer East China Sea ecoregion and lower diversity in the colder Yellow Sea and East Sea ecoregions.DiscussionThe findings underscore the necessity for continued taxonomic research on Rhizocephala and their host species to better understand and manage these parasites, which hold significant ecological and economic importance. The study suggests that geographical variations in host-parasite relationships are influenced by regional climatic conditions, particularly winter water temperatures

Comparative study of the hemolymph microbiome between live and recently dead American lobsters Homarus americanus

Lobsters and other crustaceans do not have sterile hemolymph. Despite this, little is known about the microbiome in the hemolymph of the lobster Homarus americanus. The purpose of this study was to characterize the hemolymph microbiome in lobsters. The lobsters were part of a larger study on the effect of temperature on epizootic shell disease, and several died during the course of the study, providing an opportunity to examine differences in the microbiomes between live and recently dead (1−24 h) animals. The hemolymph microbiomes of live lobsters was different from those in dead animals and both were different from the tank microbiome in which the animals had been held. The microbiomes of live lobsters were more diverse and had a different suite of bacteria than those from dead animals. The dominant taxa in live lobsters belonged to Flavobacteriaceae and Rhodobacteraceae, whereas Vibrionaceae and Enterobacteriaceae were predominant in the dead lobsters. Although aquarium microbiomes overlapped with the hemolymph microbiomes, there was less overlap and lower abundance of taxa in comparison with hemolymph from live lobsters. Previous studies reporting bacteria in the digestive tract of lobsters suggested that Vibrionaceae and Enterobacteriaceae had invaded the hemolymph via the gut.Our study suggests that hemolymph bacteria abundant in live lobsters do not originate from the tank milieu and comprise a rich, natural, or native background of bacterial constituents

The first report of tropical hermit crab Calcinus vachoni (Malacostraca, Decapoda, Calcinidae) in Korea and the preliminary revision of its cryptic diversity

Family Calcinidae is a hermit crab family morphologically diverged from Diogenidae. Calcinus is a type genus of Calcinidae. It inhabits tropical coral reefs with a colorful body. Among them, C. vachoni was firstly collected in southern Korea. Herein, this study reports Korean C. vachoni with its morphological, ecological, and molecular characteristics. Morphological characteristics of 12 C. vachoni caught on Jeju Island were examined. Ecological characteristics of C. vachoni were reviewed briefly and cox1 DNA barcoding analysis of five Korean C. vachoni was conducted with 16 species, 5 genera, and 3 families of Micronesia and GenBank hermit crab data. Korean C. vachoni has 13 pairs of gills, a larger left cheliped than the right one, a broad triangular rostrum, a few tufts of setae on ventral margins of dactyl and propodus of the first ambulatory leg, and cream dactyl and bluish-gray propodi of pereopods identical to the original description and previous studies. The cox1 sequences of Korean C. vachoni were monophyletic with cox1 sequences of C. vachoni in GenBank. Calcinus vachoni sequences were divided into three groups regarded as cryptic species. They were correlated with geographical distance as in the previous study. The review of ecological characteristics of C. vachoni shows that it inhabits nearby coral which might have a symbiotic relationship. The habitat of C. vachoni was extended to the northwest which could be related to recent climate change.In this study, the tropical hermit crab genus Calcinus and Family Calcinidae were first reported in Korea. For molecular identification, the cox1 sequences of Korean C. vachoni and other tropical hermit crabs in Kosrae, Micronesia were first obtained and analyzed by this study. In addition, the cryptic diversity of C. vachoni groups noted in the previous study was reviewed and expanded their geographical range. Furthermore, we suggested the association relationship between C. vachoni and corals for the first time

Morphological and molecular analysis of the tropical hermit crab Calcinus vachoni (Decapoda, Diogenidae) and its potential association with colonial anemone

Calcinus is the colorful hermit crab genus belonging to the family Diogenidae and is often found in coral reefs of the tropical Indo-West Pacific region, including southern Honshu, Japan, which is the northern limit of their occurrence. In the present study, we found C. vachoni for the first time in the intertidal zone of Jeju Island—the southernmost island of South Korea. We examined their morphology and provided a diagnosis of their morphological details with illustrations. In addition, the Korean Calcinus population was genetically characterized using mtDNA cox1 sequences and by placing them into three previously reported regional haplogroups. The phylogenetic tree from maximum likelihood analysis revealed that Korean C. vachoni is assigned to the C. vachoni haplogroups exclusively, one of the three well-supported mitochondrial haplogroups with distinct geographic ranges (i.e., C. vachoni, C. aff. vachoni Cooks, and C. aff. vachoni Mascarenes). This result provides new information on the species distribution of C.vachoni, extending their geographic range further north into the southern coast of Korea. In this study, we also first report the potential association of C. vachoni with their co-occurring colonial anemone species Palythoa aff. mutuki and dead coral head of Pocillopora species based on our on-site observation and a public coral collection database of Calcinus species. However, their ecological association with co-occurring coral species is putatively assumed for now and therefore has to be validated by compelling evidence from further field observation and experimental studies (i.e., whether the presence/absence of colonial anemones affects the behavior and survival of the hermit crabs)

A new hermit crab species of the genus Tomopaguropsis Alcock, 1905 (Crustacea: Decapoda: Paguridae) from the Bohol Sea, Philippines

Jung, Jibom, Lemaitre, Rafael, Kim, Won (2017): A new hermit crab species of the genus Tomopaguropsis Alcock, 1905 (Crustacea: Decapoda: Paguridae) from the Bohol Sea, Philippines. Raffles Bulletin of Zoology 65: 168-174, DOI: http://doi.org/10.5281/zenodo.450443