Through the glass ceiling: extending the depth range of glass sponges (Porifera: Hexactinellida)

Abstract Glass sponges (Porifera: Hexactinellida) are an important component of megabenthic deep-sea communities, where they create biogenic structures and complex ’sponge gardens’ at bathyal and abyssal depths. They are known to be sporadically present at hadal depths (those exceeding 6000 m) from samples gathered during expeditions in the mid-20th century, but the true extent of their bathymetric range has been difficult to resolve. Also, hadal sponges are seldomly observed in situ and have rarely been collected in recent decades. An analysis of video material gathered during the last 10 years of trench expeditions, from around the globe, has allowed us to identify 31 distinct morphotypes divided into five morphological categories and belonging to at least four families. Furthermore, we can establish a new depth record for the class Hexactinellida, from at least two different morphotypes observed at 7180 m water depth in the Java Trench (Indian Ocean).