The nest-holding grass goby (Zosterisessor ophiocephalus) male adjusts the spawning activity in relation to parasitic nest intrusions

Abstract

This study examines the temporal pattern of spawning behavior by the territorial (i.e. nest-holding) grass goby male, Zosterisessor ophiocephalus, in response to sneak intrusions by the small parasitic male under controlled laboratory conditions. The spawning activity of the territorial male consists of a sequence of upside-down movements on the ceiling of the nest accompanied by undulations of the body and sperm release. Five pairs of one territorial male and one parasitic male, each kept inside a large tank provided with an artificial buried nest (always occupied by the territorial male) and one small tunnel-shaped shelter (always occupied by the small male), were observed during one-female spawning taking place in the innermost part of the nest (i.e. the nest chamber). During the spawning, the presence of the small male nearby the nest openings elicited aggressive behavior and increased nest patrolling by the territorial male. In one spawn the small male never attempted to enter the nest. In four spawns the small male entered one to three times the nest chamber (sneaks), staying there from 2 to 203 s until the large male chased him away. The temporal patterning of the spawning activity by the territorial male (bouts of upside-down, U-D), and its changes following a sneak by the small male, were investigated using bout analysis and correlative tests. Results showed the length of bouts U-D did not change significantly after a sneak intrusion. whereas gap length (i.e. the period between subsequent bouts U-D) decreased significantly after each sneak intrusion. The mean duty cycle of bouts U-D tended to be positively correlated to the number of sneaker intrusions of each replicate. Results are discussed in the light of current knowledge on sperm competition among externally fertilizing teleosts.

First documentation of spawning and nest guarding in the laboratory by the invasive fish, the round goby (Neogobius melanostomus)

“…The reproductive behaviours exhibited by the round goby, such as uniparental care, inversions during spawning, fanning, vocalizations, and filial cannibalism, are shared by many other species of Gobiidae Ota et al, 1996;Mazzoldi et al, 2000;Malavasi et al, 2008;Scaggiante et al, 1999 Species names are listed alphabetically. Confirmed behaviours exhibited by males of each species are indicated by a check mark.…”

Season, Sex and Size related Diet of Grass Goby, Zosterisessor ophiocephalus (Pallas, 1814) in the Eastern Adriatic Sea

“…Hence, the authors made a connection with intra-population relations. Regarding the increased aggressiveness of females of Grass goby in the pre-spawning period [21], changes in ecological parameters (temperature, salinity, habitat degradation, lack of food or inability to distinguish prey item) are considered as causes of cannibalism in the Novigrad Sea area. Results also indicate great abundance of Spermatophyta (Zostera noltei) in the stomach content of the investigated species, although sea grass is of little dietary value.…”