Split personality

Morphological characterization of anterior axial bifurcation in Holothuria (Halodeima) grisea and other puzzling occurrences in Holothuroidea

“…Holothuroids are recognized for their remarkable plasticity, including their capacity to undergo autotomy and transversal fission followed by regeneration of internal organs and body components (Byrne, 2024;Emson & Wilkie, 1980;Conand 1996;Emson & Mladenov, 1987;Jobson et al, 2020;Purwati, 2004;Sonnenholzner et al, 2017;Uthicke & Conand, 2024;Zhang et al, 2017). However, fission along the longitudinal plane (bisection along the length of the body) that would help explain the anterior bifurcation highlighted in the present study (i.e.…”

“…Another hypothesis to explore is the role of sublethal (atrial) predation at one of the body extremities, and subsequent regrowth of that extremity, which could lead to anomalous regeneration of two "heads" or two "tails". However, the absence of documented post-trauma regrowth of the body in holothuroids (with the possible exception of a recent finding in an apodid; Jobson et al, 2020) challenges this assumption.…”

Shake it off: exploring drivers and outcomes of autotomy in marine invertebrates

“…A lesser known, albeit equally interesting form of autotomy, involves transversal scission leading to the rapid loss of a posterior portion of the body, followed by regeneration of the anterior end, in members of the holothuroid order Apodida [ 75 , 96 , 97 ]. Transversal scission differs from transversal fission, which is a mode of asexual reproduction that occurs over a longer period and results in both halves of the holothuroid being regenerated (i.e.…”

“…multiplication). Autotomic scission has been documented in only a few species, including Chiridota laevis [ 96 ], Leptosynapta clarki [ 98 ], L. inhaerens [ 99 ], Polycheira fusca [ 86 , 97 ] and Synapta maculata [ 100 ]. In all investigated cases, it appears to be triggered by stressful physical contact (e.g.…”

“…Like evisceration discussed above, voluntary transversal scission is an interesting autotomic peculiarity, as there is no defined breakage; the body can be severed anywhere between the point of stimulus and the anterior end [ 97 ]. This autotomic split presumably still relies on MCT (although this has yet to be studied) to destabilize tissue at the site of scission and uses muscular contraction of the body to both separate the halves and constrict/close the wound site [ 96 , 97 ]. The appearance of autotomy in holothuroids in the absence of a visually delineated or articulated breakage plane provides opportunities to expand our understanding of the purpose and evolutionary drivers behind the phenomenon.…”