Gamete spawning in Antipathella subpinnata (Anthozoa, Antipatharia): a structural and ultrastructural investigation

Abstract

Black coral colonies belonging to Antipathella subpinnata (Myriopathidae), found in Adriatic Sea (off the Tremiti Islands) and in Tyrrhenian Sea (Mezzo Canale), were inspected with the aim of investigating their reproductive activity. The small colony (about 42 cm tall) from Adriatic Sea was sexually immature, whereas the larger (about 120 cm tall) five colonies from Tyrrhenian Sea were fertile. Four colonies were males and one was a female, thus confirming the gonochoric condition already known for the black coral. Semithin sections proved that most of the egg and sperm masses flow out through the pharynx, even though small gamete masses were also observed emerging from the tentacles. In the female polyps, egg masses were enveloped by parental tissue derived from the breakage of the mesenterial septa, as observed in the male polyps for the sperm cysts masses. Ultrastructural observations provided details on the characteristics of egg and sperm in this taxon. Sperm stood out for the presence of an acrosome-like structure derived from the merging of proacrosomal vesicles. On the whole, the fine organization of the sperm recalled previous descriptions reported for some tropical black coral taxa.

Sexual reproduction of Hawaiian black corals, with a review of the reproduction of antipatharians (Cnidaria: Anthozoa: Hexacorallia)

“…Gaino et al (2008) hypothesized that sperm would subsequently be spawned through the mouth. Gaino & Scoccia (2010) observed extrusion of egg and spermatocyst masses through the mouth in preserved Antipathella subpinnata specimens from the Mediterranean. Cooper (1909) examined various specimens of Bathypathes patula from the Indian Ocean, and noted that colonies could be classified into three different stages of sexual maturity.…”

“…In fragments of C. pumila kept in aquaria, polyps were observed releasing buoyant spheres from their mouth that consisted of sperm in various stages of differentiation (Gaino & Scoccia 2009). In addition to these few direct observations on the spawning behavior of antipatharians, there is also indirect evidence of spawning from histological examinations (Cooper 1909; Opresko 2005; Gaino et al 2008; Gaino & Scoccia 2010). In histological sections of male polyps of C .…”

“…The few studies that have examined the reproductive seasonality of black corals using specimens collected across various seasons have all been conducted in shallow water (<70 m) (Grigg 1976; Goenaga 1977; Schmidt & Zissler 1979; Parker et al 1997; Bo 2008; Gaino & Scoccia 2008, 2010). All of these studies report a seasonality in the appearance and disappearance of gametes, which at least in some cases has been correlated to seasonal temperature fluctuations (Schmidt & Zissler 1979; Parker et al 1997; Gaino & Scoccia 2010). Grigg (1976) performed histological observations on specimens of Antipathes griggi collected from the Hawaiian Islands in both July and March.…”

“…in Indonesia, and inferred spawning by the disappearance of gametes; using this method, she inferred that spawning occurred multiple times throughout a year (in February, May, and July). Gaino & Scoccia (2010) examined specimens of A. subpinnata from the Mediterranean, and found no fertile colonies in September–November when water temperatures were low (14°C), and fertile colonies in August when temperatures were higher (16°C). Schmidt & Zissler (1979) noted that several tropical Indo‐Pacific antipatharians reproduced in the summer during a period of ∼2 months.…”

Local Conditions Influence the Prokaryotic Communities Associated With the Mesophotic Black Coral Antipathella subpinnata

“…Unfortunately, commercial fishing activities and entanglements by lost fishing lines or nets have caused significant damage to local populations of A. subpinnata ( Bo et al, 2014 ; Oliveira et al, 2015 ). While several aspects of A. subpinnata ’s reproductive biology ( Gaino and Scoccia, 2010 ; Coppari et al, 2019 ) and ecology, including its interactions with various macro-epibionts ( Bo et al, 2011b ; Gaino et al, 2013 ) and feeding strategies ( Coppari et al, 2020 ), have been studied, its microbial associates have never been investigated.…”