A new species of deep‐sea torquaratorid enteropneust (Hemichordata): A sequential hermaphrodite with exceptionally wide lips

Abstract

Specimens of a new species of torquaratorid acorn worm (Hemichordata, Enteropneusta) were video recorded and subsequently collected at abyssal depths in the eastern North Pacific at sites ranging from Oregon to northern Mexico. These worms are described here as Yoda demiankoopi n. sp. by molecular and morphological methods. The new species differs from its only described congener, Yoda purpurata, in three ways. First, the lips are extremely wide and indented by a deep ciliary groove for ingesting substrate and conveying it to the mouth. Second, a connective tissue bulge of unknown significance runs mid-dorsally along the hepatic and posthepatic regions of the intestine. Third, the posthepatic intestine is strikingly sinuous and packed with gut contents presumably undergoing digestion for extended periods between infrequent defecations. Yoda demiankoopi n. sp. is hermaphroditic, a character so far known only for the genus Yoda in the entire class Enteropneusta. The gonads of each adult worm comprise hundreds of ovaries (each containing a single oocyte) and hundreds of testes located just beneath the dorsal epidermis of the anterior trunk and associated genital wings. In any given animal, at any given time, gametes of only one sex or the other become fully mature. Thus, the worm is a sequential hermaphrodite, alternately spawning purely as a female or purely as a male.

Digestive System Anatomy and Feeding Mechanism of Quatuoralisia malakhovi (Hemichordata, Torquaratoridae)

“…In Q. malakhovi , the lateral lips are folded so that a ciliary groove goes on their ventral surface, which faces the sediment, and leads into a ciliated internal channel. Similar grooves are found in lateral lips of other Torquaratoridae species [ 2 – 5 ]. The lips of a crawling animal turn up the surface sediment layer, and small sediment particles are moved into the ciliary groove by the beating of cilia of the ectodermal epithelium of the lips and are transported to the mouth through the ciliated internal channel.…”

“…The lips of a crawling animal turn up the surface sediment layer, and small sediment particles are moved into the ciliary groove by the beating of cilia of the ectodermal epithelium of the lips and are transported to the mouth through the ciliated internal channel. The lateral lip structure has been studied in histological sections only in Yoda demiankoopi [ 5 ] apart from Q. malakhovi. Judging from sections, the width of the ciliary groove used to draw detritus particles into the internal channel of the collar lip does not exceed 200 µm in Q. malakhovi (see above).…”

“…Judging from sections, the width of the ciliary groove used to draw detritus particles into the internal channel of the collar lip does not exceed 200 µm in Q. malakhovi (see above). The width is similarly of about 200 µm in Y. demiankoopi [ 5 ]. The width determines the upper size limit of selectable detritus particles.…”

“…The ridges lie in the parafrontal plane and divide the pharynx into dorsal respiratory and ventral digestive parts [ 12 – 14 ]. In Q. malakhovi and other Torquaratoridae, the pharynx is flattened in the frontal plane and the parabranchial ridges lie in the parasagittal plane, so that two lateral channels (the peripheral pharyngeal channels) form in the pharynx in place of a single ventral channel [ 3 – 5 ]. It is possible to think that sediment particles collected by the lateral collar lips are transported directly into the peripheral pharyngeal channels.…”

Nemertodermatida—Endosymbionts of Deep-Sea Acorn Worms (Hemichordata, Torquaratoridae)

“…The deep-sea acorn worms Torquaratoridae have recently been discovered as a group of marine invertebrates [ 1 – 5 ]. These animals live at depths of 350–8800 m [ 3 , 4 , 6 ] and do not bury in the seafloor in contrast to shallow-water acorn worms.…”