Sponge’s biodiversity in the limestone islands in Vietnam sea

In 2017, 2018 and 2020, sponge samples were collected at 41 points in the waters surrounding Vietnam’s coastal limestone islands (Bai Tu Long, Ha Long bay, Cat Ba and Ba Lua archipelago). Research results have identified 54 species belonging to 33 genera, 24 families of Demosponge class distributed in this area. Ha Long bay area has the highest number of species (53 species), followed by Cat Ba (46 species), Bai Tu Long 19 species; Ba Lua archipelago (Kien Giang) has the least number of species (3 species). Sponges are concentrated in coral reefs with the highest number of species (48 species) and the lowest in the mud and sand bottom (4 species). Biomass of sponges varies from 0.2–1.5 kg/m2. There are 11 sites with high biomass, which have the potential to become Vietnam’s medicinal drug area.

A New Species of Spongilla (Porifera, Demospongiae) from a Karst Lake in Ha Long Bay (Vietnam)

Cahong in Ha Long Bay (Vietnam) is a small lake with a reduced, invisible connection with the open sea. The water column conditions locally experience notable fluctuations across the year, mostly driven by biannual monsoon seasons. Salinity, temperature, and pH often reach extreme values, unsustainable for the majority of the marine fauna. Therefore, the biodiversity of the benthic macrofauna in this peculiar habitat is remarkably low. In particular, a single sponge species new to science was found solely populating this characteristic brackish lake during our last survey in August 2018. Spongilla manconiae sp. nov. is a new Porifera species described here. It belongs to an exclusively freshwater taxon and seems to have acquired adaptive traits to tolerate extreme peaks of temperature and salinity. The mitochondrial Cytochrome C Oxidase subunit 1 (COI) and the nuclear Internal Transcribed Spacers 1 and 2 (ITSs) gene markers were used for barcoding tagging and phylogenetic analyses. The new species revealed large genetic distances and separate clustering in the tree topology, with respect to other reference spongillid sequences from various geographic areas. The study provides evidence for an urgency to protect these unique marine lake systems because they represent rare, fluctuant, fragile habitats that may speed up speciation processes.

First record of the genus Boholina (Copepoda, Calanoida, Pseudocyclopidae) in Vietnam, with description of a new species from an anchialine cave in Tra Ban Island

A new species, Boholina reductasp. nov., was found in a brackish pool within an anchialine cave in Tra Ban Island in Bai Tu Long Bay, north Vietnam. The new species is clearly distinguished from all the six species currently known in the genus Boholina by the following unique characteristics: reduction of the septum between gonopores; narrow and pointed rostrum; basal segment of mandibular palp armed with three setae; maxillule without seta on the basal exite, and exopod with 11 setae; second and third endopodal segments of the maxilliped bearing three setae each; exopod of male right leg 5 2-segmented, with two strong and one vestigial spines on the outer margin of the distal segment; and last exopodal segment of female leg 5 bearing only one spine on the outer margin. We provide a description of the new species, along with detailed illustrations and scanning electron microscopy photographs. The identification key to Boholina species is updated as well. This is the first record of the genus Boholina from Vietnam.