Structure and Function of the Armored Keel in Piranhas, Pacus, and their Allies

Abstract

The serrasalmids: piranhas, pacus, and their relatives, are ubiquitous Neotropical fishes with diverse diets, ecologies, and behaviors. Serrasalmids have a bony, serrated keel which lines the underbellies of these fishes, the structure for which the family is named. We examined the diversity and structure of the keel in piranhas and allies using micro-computed tomography scanning in over 30 species of serrasalmids, a third of the species richness for the family, and for 95 total characiform specimens. The keel is highly diverse across serrasalmids, with serrae shape dictating the overall form of the keel. Serrae shape varies considerably among different species and even within keels themselves. The keel morphology can be divided into distinct anterior and posterior regions, as separated by the pelvic fins. Compared to other characiform fishes, serrasalmid skeletons are frequently damaged. Gouging perforations and signs of healing (serrae fusion) are common on the keel. We propose the keel is a defensive structure based on the high incidence of injury (>50%) in our dataset. This is the highest incidence of damage ever recorded in the skeletons of bony fishes. The loss of the anterior keel region in rheophilic taxa suggests competing performance demands and selective pressures on this structure. Competition and aggression among conspecifics or confamilials is a frequently invoked phenomenon for explaining animal weaponry and armor in terrestrial vertebrates. The keel in serrasalmids and other instances of armor in fishes could be complementary study systems for examining competitive rivalry in vertebrates. Anat Rec, 303:30-43, 2020.

Bony lesions in early tetrapods and the evolution of mineralized tissue repair

“…Up to half of juvenile humans experience and survive bone fracture (Jenkins et al 2018). Wild animals such as hawks, bottle-nosed dolphins, urban foxes, and serrasalmid fish (the group including piranhas) have high rates of fracture incidence and survival (de Smet 1977; Harris 1978; Roth et al 2002; Kolmann et al 2018). In human and veterinary medicine, fracture repair may be enhanced by supporting bones with splints, casts, slings, surgical implants, and medication; wild animals are not afforded such care and must heal by themselves if they are to regain competitive function.…”

Boric Acid (H3(BO3): Recognize The Molecular Interactions in Solutions

“…Momen Dipol (11) Nama IUPAC (28) Trihidrooksidoboron Asam Borat (15) Nama Lain (10) Sumber (26) Struktur (12) Nama (9) Kegunaan (14) Sifat (1) Asam Boraks (4) Sasolit Asam Ortoborat (27) Borofaks…”

“…Kelarutan dalam pelarut lain (19) Warna (8) Wujud (12) Bentuk Molekul (18) Asam metaborat akan mencair jika diberikan pemanasan sekitar 236 °C, dan ketika dipanaskan pada suhu (101) di atas 300 °C dia akan kehilangan air (102) (103) larutan (solutions) (104) asam borat cair. Spektroskopi Ramandi pada larutan (201)(202)(203)(204)(205) basa kuat menerangkan bahwa terdapat ion B(OH) −4 , sehingga berdasarkan beberapa penelitian disimpulkan bahwa keasaman secara khusus terjadi karena abstraksi OHdari H 2 O (39) : B(OH) 3 + H 2 O B(OH) −4 + H + (K = 7.3x10 −10 ; pK = 9.14) atau lebih jelasnya dinyatakan dalam larutan:…”

Phylogenomics of piranhas and pacus (Serrasalmidae) uncovers how convergent diets obfuscate traditional morphological taxonomy

“…Despite their keystone status and commercial significance throughout Amazonia, the ecologies of piranhas and pacus are poorly understood and often misrepresented. The ferocious reputation of piranhas stems largely from accounts of their feeding on corpses (Sazima & Guimarães, 1987) or nipping bathers, the latter attributed to the protective nature of piranhas defending nests (Haddad & Sazima, 2003, 2010; but see Kolmann et al, 2018b). We have only recently understood the role that pacus play in structuring forests, as large frugivores that can disperse seeds over great distances (ichthyochory) (Correa et al, 2015, 2016).…”