RETRACTED ARTICLE: Novel life history strategy in a deep sea fish challenges assumptions about reproduction in extreme environments

Abstract

The deep ocean is frequently assumed to be a homogeneous system lacking the same diverse life history strategies found in shallower waters. However, as our methods for exploring the deep ocean improve, common assumptions about dispersal, reproduction and behavior are constantly being challenged. Fishes exhibit the most diverse reproductive strategies among vertebrates. Understanding life history strategies in deep-sea environments is lacking for many species of fishes. Here, we report a novel reproductive strategy where a fish (Parazen pacificus) provides parental care via mouth brooding. This behavior is observed from a specimen collected with eggs present in the buccal cavity, along with other specimens exhibiting pre-brooding morphologies. This is the first description of this unique life history trait in a deep-sea fish and fills in a gap in the larval literature for this family of fishes and prompts further investigation into other novel reproductive modes of deep-sea fauna.

Zeiform Mouthbrooding in the Deepsea – Dispelling a Myth

“…Singer et al's 2020 3 conclusion of mouth brooding in Parazen was based on a single specimen of 104.3 mm length, which was obtained from a market in Taiwan. As documented in their paper 3 , this specimen has a large egg mass lodged between and extending forward from its pharyngeal jaws and another, smaller egg mass below the gill arches anterior to the basihyal ('tongue' of Singer et al 2020 3 ). The number of eggs was estimated to be around 530 with an average diameter of 0.73 mm.…”

“…In their discussion, they stated that "There is no way to tell for sure if the eggs in this specimen are Parazen pacificus given that there has not been a formal description of its eggs or larva." It is exactly this sentence that led us to question the conclusion of Singer et al 2020 3 and to look further into the identity of the eggs that the authors found in the mouth of their specimen. Given the potential implications of their discovery, we wonder why the authors chose not to examine the embryos more closely.…”

Follicular complex may predict reproductive tactics in siluriform fishes

“…Teleost fish have different reproductive tactics, for example, migration [ [1] , [2] , [3] ], different types of spawning [ [4] , [5] , [6] ], parental care that occurs in different ways such as the storage of fertilized eggs in the mouth [ [7] , [8] , [9] ], the construction of nests and the maintenance of continuous aeration of the eggs [ [10] , [11] , [12] ]. In females, mature oocytes indicate some reproductive tactics such as the reproductive period [ 13 , 14 ] and type of spawning [ 15 , 16 ], and the animal's fecundity can be estimated [ 5 , 17 , 18 ].…”