Growth, Development and Temporal Variation in the Onset of Six Chironex fleckeri Medusae Seasons: A Contribution to Understanding Jellyfish Ecology

Abstract

Despite the worldwide distribution, toxicity and commercial, industrial and medical impacts jellyfish present, many aspects of their ecology remain poorly understood. Quantified here are important ecological parameters of Chironex fleckeri medusae, contributing not only to the understanding of an understudied taxon, the cubozoa, but also to the broader understanding of jellyfish ecology. C. fleckeri medusae were collected across seven seasons (1999, 2000, 2003, 2005–07 and 2010), with growth rates, temporal variation in the medusae season onset and differences in population structure between estuarine and coastal habitats quantified. With a mean of 2 September ±2 d (mean ±95% confidence limits), the earliest date of metamorphosis was temporally constrained between seasons, varying by only 7 d (30 August to 5 September). Juvenile medusae appeared to be added over an extended period, suggesting polyp metamorphosis was an ongoing process once it commenced. At a maximum of 3±0.2 mm d −1 IPD, medusae growth to an asymptotic size of ∼190 mm IPD was rapid, yet, with the oldest medusae estimated to be ∼78 d in age, medusae did not appear to accumulate along the coastline. Furthermore, a greater proportion of juveniles were observed along the coastline, with estuarine populations typified by larger medusae. With key aspects of C. fleckeri 's ecology now quantified, medusae season management protocols can be further developed.

Early Life History of the ‘Irukandji’ Jellyfish Carukia barnesi

“…Cubozoans have a metagenic life cycle which alternates between benthic sessile polyps and motile pelagic medusae [ 1 – 8 ]. It is this alternation of generations that contributes to the often predictable occurrence of cubozoan medusae [ 4 , 5 , 9 , 10 ]. There are approximately 50 described species of Cubozoa and of these the early life history of only eight have been described to date [ 2 , 3 , 5 – 8 , 10 – 15 ].…”

“…In northern Australia, cubozoan medusae typically arrive in large numbers associated with increased sea temperatures during the monsoonal months [ 4 , 5 , 9 , 19 , 20 ]. This seasonal cycle in some species has been reported to begin earlier and last longer in areas closer to the equator [ 9 , 21 , 22 ]. The seasonal timing of one Australian cubomedusae, Chironex fleckeri , has been shown to be initiated by metamorphosis of the polyp stage, which presumably uses increasing photoperiod as a cue for metamorphosis [ 9 ].…”

Seasonality in Polyps of a Tropical Cubozoan: A latina nr mordens

“…Life-cycle studies on cubozoa indicate that unlike scyphozoa, cubozoa do not undergo strobilation; instead the entire polyp undergoes metamorphosis into a medusa [7,8,11,13–16], with exception noted in Carybdea marsupialis from Puerto Rico [17]. During the polyp stage, feeding and asexual reproduction occurs and continues until external factors, or cues, such as temperature [14,15,18–20] or light conditions [16], induce metamorphosis from a polyp to a medusa [1,2,21]. The medusae then grow to sexual maturity and may form predictable spawning aggregations [22].…”

Assessment of investigation techniques for scyphozoan statoliths, with focus on early development of the jellyfish Sanderia malayensis

“…2H,I) showed rings of 1−2 µm, which was about a factor of 10 wider than the daily statolith increment calculated from the calcein experiments. In conclusion, it is unlikely that these ring structures represented daily statolith growth, as assumed for the ring structures in cubozoan statoliths (Kawamura et al 2003, Gordon et al 2004, Gordon & Seymour 2012.…”

“…5C in Sötje et al 2011). Increments in statoliths were used to back-date the age of the cubomedusa Chironex fleckeri (Gordon & Seymour 2012). Our data now indicate that in scyphozoans, the statolith size does not allow conclusions about medusa diameter or age because statoliths stop, or at least considerably slow growth, when a certain size is reached.…”