This paper reports one mytiloid species, Amygdalum anoxicolum P. G. Oliver, 2001 from the summit of a seamount located in the eastern Arabian Sea. This species was encountered from the core of the Arabian Sea oxygen minimum zone at a depth of 340 m and possessed several adaptations to low-oxygen concentration. This paper presents the first-ever DNA barcodes for this species.

The family Dendrophylliidae comprises a genus of azooxanthellate corals, Tubastraea (also known as ‘sun corals’ or ‘cup corals’), native from the Indo-Pacific and introduced into the Atlantic Ocean in the early 1940s. In Brazil, Tubastraea colonies were first registered on oil platforms on the northern coast of Rio de Janeiro state (22°S) in the late 1980s. Two decades later, these corals were for the first time identified in the Todos-os-Santos Bay (Bahia state, 13°S), a warmer environment with diverse marine ecosystems including estuaries, mangroves, and coral reefs. Intending to describe the biological cycle of exotic dendrophylliids from the Brazilian northeastern coast, histological analyses revealed three new reproductive structures for Scleractinia: (1) a mucin layer composed of acid glycoproteins surrounding immature sun coral oocytes, (2) trophonema or specialized cells connecting the oocyte to the adjacent gastrodermis, and (3) nucleolini, small condensations in nucleoli.

Providing nursery habitats to a number of marine fish larvae that recruit after prolonged pelagic larval duration, has been identified as one of ecosystem services rendered by estuaries and protected inshore water bodies like mangroves, mudflats, swamps, and marshes. Larval fish congregation and survival are largely dependent on abiotic and biotic potential of such systems and many migrant marine fishes are adapted to them. However, occurrences of larval forms of tropical reef-associated vagrant species which are known for extensive range adaptations generate considerable academic interest. The present study provides the first report of ontogenic habitat utilization of yellow fin surgeon fish, Acanthurus xanthopterus Valenciennes 1835 in a tropical microtidal positive estuary, the Vembanad lake, South India. Surface plankton collections from the downstream part of the estuary revealed considerable proportions of acanthurid larvae in post monsoon (mean 354 ± 180 numbers/100 m3) and pre monsoon (mean 217 ± 120 numbers/100 m3) while they were absent in monsoon season. These acronurus larval forms were morphologically identified and sorted before being subjected for DNA barcoding. Mitochondrial DNA COI sequences developed from morphologically characterized acronurus larvae exhibited genetic congruency to sequence of A. xanthopterus which was evident from phylogram (bootstrap support of 100) and genetic distance data (intraspecific distance of 0%). The study indicates that Acronurus larvae of A. xanthopterus, after extensive cross-habitat dispersal, utilize the estuarine habitat to promote potential growth.

A specimen of Prionotus punctatus was caught in Bahía Engaño, Chubut Province, Patagonia, Argentina. This extends the known distribution by 900 km and a 5.5° further south from its previous southernmost record. This record increases the number of species of the genus Prionotus and the fish diversity of central Patagonia. The presence of P. punctatus along with other recent reports of fish of tropical and subtropical lineages in central Patagonia adds new evidence on the ongoing tropicalization of the Patagonian Sea.

Feather stars (Echinodermata: Crinoidea) are known to host a diversified associated fauna. Surprisingly, very few accounts on the crinoid epiphytic communities from the coasts of the India are available. The present contribution reports for the first time the crinoid-associated scale worm Paradyte crinoidicola (Potts, 1910) from Gujarat coastline, India. The species has been so far recorded from the southern part of Indian subcontinent, the Lakshadweep Islands as its first record from Indian coastline. Further research and documentation of these species will contribute to enhance our understanding of the diverse associations and complex interactions within Indian marine ecosystems. This highlights the necessity for more thorough field surveys and ongoing monitoring, as the region remains surprisingly underexplored.