Ocean Sunfish Research Articles

Rare Occurrences of Ocean Sunfish (Mola mola) in the Bay Islands of Honduras; Notes on Distribution and Osteology

Rare Occurrences of Ocean Sunfish (Mola mola) in the Bay Islands of Honduras; Notes on Distribution and Osteology

Evolutionary innovation accelerates morphological diversification in pufferfishes and their relatives.

Evolutionary innovations have played an important role in shaping the diversity of life on Earth. However, how these innovations arise and their downstream effects on patterns of morphological diversification remain poorly understood. Here, we examine the impact of evolutionary innovation on trait diversification in tetraodontiform fishes (pufferfishes, boxfishes, ocean sunfishes, and allies). This order provides an ideal model system for studying morphological diversification owing to their range of habitats and divergent morphologies, including the fusion of the teeth into a beak in several families. Using three-dimensional geometric morphometric data for 176 extant and fossil species, we examine the effect of skull integration and novel habitat association on the evolution of innovation. Strong integration may be a requirement for rapid trait evolution and facilitating the evolution of innovative structures, like the tetraodontiform beak. Our results show that the beak arose in the presence of highly conserved patterns of integration across the skull, suggesting that integration did not limit the range of available phenotypes to tetraodontiforms. Furthermore, we find that beaks have allowed tetraodontiforms to diversify into novel ecological niches, irrespective of habitat. Our results suggest that general rules pertaining to evolutionary innovation may be more nuanced than previously thought.

Functional morphology of the pharyngeal teeth of the ocean sunfish, Mola mola.

Many fish use a set of pharyngeal jaws in their throat to aid in prey capture and processing, particularly of large or complex prey. In this study-combining dissection, CT scanning, histology, and performance testing-we demonstrate a novel use of pharyngeal teeth in the ocean sunfish (Mola mola), a species for which pharyngeal jaw anatomy had not been described. We show that sunfish possesses only dorsal pharyngeal jaws where, in contrast to their beaklike oral teeth, teeth are recurved spikes, arranged in three loosely connected rows. Fang-like pharyngeal teeth were tightly socketed in the skeletal tissue, with shorter, incompletely-formed teeth erupting between, suggesting tooth replacement. Trichrome staining revealed teeth anchored into their sockets via a combination of collagen bundles originating from the jaw connective tissue and mineralized trabeculae extending from the teeth bases. In resting position, teeth are nearly covered by soft tissue; however, manipulation of a straplike muscle, running transversely on the dorsal jaw face, everted teeth like a cat's claws. Adult sunfish suction feed almost exclusively on gelatinous prey (e.g., jellyfish) and have been observed to jet water during feeding and other activities; flume experiments simulating jetting behavior demonstrated adult teeth caught simulated gelatinous prey with 70%-100% success, with the teeth immobile in their sockets, even at 50x the jetting force, demonstrating high safety factor. We propose that sunfish pharyngeal teeth function as an efficient retention cage for mechanically challenging prey, a curious evolutionary convergence with the throat spikes of divergent taxa that employ spitting and jetting.

First long-term trajectory of an ocean sunfish (Mola mola L.) from the northwestern Mediterranean.

The ocean sunfish is a large fish for which many aspects of its ecology and biology are still poorly known. Electronic tagging was used to provide the first information on the movements of an ocean sunfish from the northwestern Mediterranean. The sunfish moved towards the Gibraltar strait over the year and displayed substantial movements in the water column. The potential of the tagging technique employed for studying its behavior and long-term migratory dynamics, and assessing the post-release survival of ocean sunfish is highlighted.

New northerly limit for the sharptail mola in the northeast Atlantic: first sighting of Masturus lanceolatus in the northeast Irish Sea.

The ocean sunfishes are currently represented by five species within three genera: Mola mola (Linnaeus, 1758), Mola alexandrini (Ranzani, 1839), Mola tecta (Nyegaard, Sawai, Gemmell, Gillum, Loneragan, Yamanoue & Stewart, 2017) (Sawai et al., 2018), Masturus lanceolatus (Lienard, 1840), and Ranzania laevis (Pennant, 1776). Growing conservation concerns have led to an ongoing re-examination of their classification status on the International Union for the Conservation of Nature Red Lists, a process requiring the latest data to best support their conservation management on a global scale. Here we report the first sighting of Masturus lanceolatus in the northeast Irish Sea, representing a new northerly range limit for this species in the northeast Atlantic. The species is more commonly reported in tropical seas, and in the Western Atlantic they occur from North Carolina in the United States to southeast Brazil. This sighting increases the most northerly range limit by 2610 km, providing additional insight into the ecology and potentially changing distribution of this generally considered tropical megafaunal species.

Patterns in sightings of ocean sunfishes (Molidae) in the greater Dyer Island ecosystem, Western Cape, South Africa

This study aims to describe the distribution of ocean sunfishes (family Molidae) in the greater Dyer Island ecosystem off the southwest coast of South Africa. Between 2014 and 2022, local whale watching vessels operating under Dyer Island Cruises conducted 3 227 trips which resulted in 274 trips with Molidae sightings, with a total of 300 individuals sighted. Molidae sightings showed a significant correlation to sea surface temperature and a strong seasonal pattern. Sightings in the greater Dyer Island area increased significantly after 2016, suggesting a correlation with the decline of white shark Carcharodon carcharias sightings, with further increases in 2021. This suggests that the greater Dyer Island ecosystem has become a more favoured habitat for species of Molidae.

The ocean sunfishes (family Molidea): Recommendations from the IUCN molidae review panel

The ocean sunfishes (family Molidae) include the largest and heaviest bony fishes in the world and species within the family are distributed from southern Chile to the Arctic Circle. The Molidae currently contains five species within three genera: Mola mola (Linnaeus, 1758), Mola alexandrini (Ranzani, 1839), Mola tecta (Nyegaard et al., 2017), Masturus lanceolatus (Liénard, 1840) and Ranzania laevis (Pennant, 1776). Recent conservation concerns led to a re-examination of the IUCN Red List classifications, where three species had previously ranged from Least Concern to Vulnerable, and two species had yet to be assessed. To better support conservation of these fishes on a global scale, the IUCN Molidae review panel was formed to update these listings. This panel, supported by experts from the IUCN Red List assessment process, included participants from the UK, Portugal, Taiwan, New Zealand, Japan and USA. The central objective was to consolidate recent research and policy expertise and assess urgent conservation issues facing the ocean sunfishes. A summary is presented here alongside key recommendations.

Is there a symbiotic cleaning association between ocean sunfish and pelagic seabirds in the Patagonian Shelf?

Is there a symbiotic cleaning association between ocean sunfish and pelagic seabirds in the Patagonian Shelf?

First evidence of microplastic ingestion in the ocean giant sunfish (Mola mola)

Mola mola is the largest teleost inhabiting our ocean and the presence of microplastics (MP) in this flagship species was, before this study, never described. Thus, this investigation focused on analysing MP ingestion in 53 ocean giant sunfish in the Northeast Atlantic Ocean. A total of 116 MP were found in 79% of the specimens, with a median of 1 MP.ind−1, ranging from 0 to 11 MP.ind−1. Seasonal differences were observed, with more fibers registered in specimens caught in autumn. Among the different size classes observed, the smallest category (<300 μm) was the most frequent (43%). Blue (43%) was the most prevalent color, followed by green (29%) and black (10%). The majority of fragments were styrene acrylic copolymer (53%), while most fibers were rayon (78%). These findings emphasize that the ocean sunfish population crossing the southern waters of Portugal is exposed to microplastic pollution and highlight the need for effective management policies to address plastic pollution in marine ecosystems.

Rapid physiological colouration change is a challenge - but not a hindrance - to successful photo identification of giant sunfish (Mola alexandrini, Molidae)

Photo ID is a common tool in ecology, but has not previously been attempted for the ocean sunfishes (Mola spp., Molidae; ‘molids’). The technique, based on body patterns, could potentially be informative for studying the seasonal occurrence of giant sunfish (Mola alexandrini) on the Bali reefs (Indonesia), where this species is an important drawcard for the local SCUBA diving tourism. However, molids are capable of rapid physiological colouration change, which may complicate the application of the method. Our study aimed to determine if photo ID is nevertheless achievable and informative. To test this, we created the citizen-science platform ‘Match My Mola’ for crowd-sourcing imagery (photos and video) of M. alexandrini in Bali, and undertook trial matching (n=1,098 submissions). The submitted imagery revealed a wide range of pattern clarity, from fish with no pattern to bold displays. Video confirmed physiological colouration change can occur in seconds in this species from low to high contrast, and cause individuals to look very different between moments. However, individual patterns appear to be stable although at least some parts can become inconspicuous during low contrast displays. Despite of this, photo ID is possible, including in some instances, where only partial patterns are visible on one image compared with another. However, true negatives (confirming two fish are not the same) can be challenging. Most identified matches were of fish photographed by different divers on the same day. Only a small number (n=9) were found with resighting durations ≥1 day (1 – 2,652 days). These matches demonstrate that at least some individuals return to the same reefs both within and between seasons, with the resighting duration of 7.2 years constituting the longest known example of molid site fidelity. Comparing body morphology between resightings of &amp;gt; 1 year (n=6) revealed limited indications of growth, contradicting the current understanding of rapid growth in captive molids (Mola mola), and highlighting the knowledge gap regarding growth in the wild. Continued photo ID in the Bali area could provide valuable complementary information to future growth studies using other methods as well as provide further insights into molid site fidelity.

Ocean sunfish, genus Mola Kölreuter, 1766 (Pisces Molidae), exhibit surprising levels of agility during interactions with orca, Orcinus orca (Linnaeus, 1758) (Mammalia Delphinidae)

Ocean sunfish, genus Mola Kölreuter, 1766 (Pisces Molidae), exhibit surprising levels of agility during interactions with orca, Orcinus orca (Linnaeus, 1758) (Mammalia Delphinidae)

First records of orca, Orcinus orca (Linnaeus, 1758) (Mammalia Cetacea), predation on sharptail ocean sunfish, Masturus lanceolatus (É. Liénard, 1840) (Pisces Molidae), with novel components of foraging behaviour discovered through social media

First records of orca, Orcinus orca (Linnaeus, 1758) (Mammalia Cetacea), predation on sharptail ocean sunfish, Masturus lanceolatus (É. Liénard, 1840) (Pisces Molidae), with novel components of foraging behaviour discovered through social media

An Inventory of Some Relatively Large Marine Mammals, Reptiles, and Fishes Sighted, Caught, By-Caught, or Stranded in the Mediterranean Coast of the Gaza Strip-Palestine

The Mediterranean Sea is home to an interesting biodiversity. The current cumulative and descriptive study aims to enumerate some relatively large marine mammals, reptiles, and fishes that have been spotted, caught, by-caught, or stranded on the coast of the Gaza Strip, Palestine, which extends about 42 km along the Mediterranean Sea. This 20-year study from 2003 to 2022 relied much on frequent field visits, meetings, and discussions with stakeholders, following local media sites and social media pages, and photography. The study recorded at least 26 giants or relatively large marine organisms on the Mediterranean coast of the Gaza Strip, Palestine. Certainly, the coming years may bring other marine organisms of relatively large sizes. Marine mammals included three species of cetaceans with the Fin Whale (Balaenoptera physalus) being the largest mammal and even the largest animal ever recorded in this study. Marine reptiles included three species of sea turtles, the largest of which is the Leatherback Sea Turtle (Dermochelys coriacea), which is in fact the world’s largest sea turtle. The bony fishes were represented by ten species, the largest of which was the Ocean Sunfish (Mola mola), which is the largest bony fish in the world. The cartilaginous fishes included ten species with the largest specimens encountered were the Shortfin Shark (Isurus oxyrinchus), Bluntnose Sixgill Shark (Hexanchus griseus), Scalloped Hammerhead Shark (Sphyrna lewini), and Giant Devil Ray (Mobula mobular). Seabirds were not included in the study. The Alexandria Pompano (Alectis alexandrinus) and the Silver-Cheeked Toadfish (Lagocephalus sceleratus), which are bony fishes, appear to be the relatively smallest marine organisms recorded here. In conclusion, the role of the various parties must be coordinated to ensure the sustainability of human activities and their compatibility with the task of conserving local marine biota, including the gigantic or relatively large ones.

Ontogenetic and seasonal shifts in diets of sharptail mola Masturus lanceolatus in waters off Taiwan

Sharptail mola Masturus lanceolatus share a circumglobal distribution with ocean sunfish Mola mola and are typically regarded as gelatinous plankton feeders. Both species are frequently captured as bycatch in the same areas, but sharptail mola are often targeted and heavily harvested in certain regions. However, the diet of sharptail mola remains poorly described. We examined the foraging habits and trophic dynamics of sharptail mola from waters off eastern Taiwan using stomach content analysis (SCA; n = 162), bulk tissue stable isotope analysis (SIA; n = 213), and compound-specific isotope analysis of amino acids (CSIA-AA; n = 10). Results demonstrated that sharptail mola mainly consumed tunicates, with lower dietary proportions of diverse prey from epi- and mesopelagic, coastal, and benthic habitats. The diet of sharptail mola changed significantly with size; small mola (&lt;80 cm) had lower δ15N and δ13C values and fed on more pteropods and Salpidae, while large mola (&gt;80 cm) fed on more Pyrosoma spp., cephalopods, and benthic organisms living on sandy substrates, with larger individuals having correspondingly higher isotope values and trophic positions. Diet compositions and δ13C values also showed seasonal variations across body size, suggesting that sharptail mola might undergo seasonal migrations with changing availability of food resources. The results provide insights into the trophic dynamics of sharptail mola and suggest that their foraging behavior varies across life-history stages and seasons.

Can sporadic records of ocean sunfish (Mola mola) in the western Baltic Sea be linked to saline inflow events?

The Baltic Sea is one of the largest brackish water bodies in the world with salinity levels ranging from fresh water conditions in the northeast to full strength saline waters at its transition zone to the North Sea in the west. Most of the water exchange happens in the SW Baltic Sea, the Belt Sea and The Sound where less saline water exits the Baltic Sea at the surface, while higher saline water is entering the Baltic at depth. Thus, the species composition in the Baltic Sea is heavily influenced by the strong salinity gradient, and here several species occur at their limit of their physiological tolerance and preference. In this study, we focused on sightings of the ocean sunfish Mola mola recorded in the western Baltic Sea between 1978 and 2020. This species is regarded as vagrant in the Baltic Sea, i.e., it does not belong to the common species assemblage in this area. Hydrographic conditions, such as water temperature and salinity, were obtained from a highly spatio-temporally resolved hydrodynamic Baltic Sea model, covering a daily resolved 71-year time series. We investigated if the occurrence of M. mola correlates with the dynamics of water mass exchange between the Kattegat/Skagerrak and the SW Baltic Sea. Our analyses show that these occurrences could be related to the presence of anomalously high saline water masses. However, in autumn and winter water temperatures of the western Baltic Sea usually drop below 8 °C with further cooling in January and February to 4–5 °C and during strong winters even down to <2 °C. If M. mola will follow the same strategy as in the North Sea, i.e. migrating southward to avoid lethal temperatures, they will not be successful by entering the Baltic Sea, because during winter months temperature everywhere falls far below their thermal tolerance. As a consequence, southward transport or active migration of M. mola into the Baltic Sea will expose the respective specimens to adverse environmental conditions finally precluding survival. • Linking sightings of Mola mola to physical processes • Novel approach for classification of environmental conditions • Occurrence of Mola mola linked to inflows conditions • Main occurrence of warm water species Mola mola during autumn and winter

Preliminary Investigation into Developing the Use of Swabs for Skin Cortisol Analysis for the Ocean Sunfish (Mola mola).

Simple SummaryZoos and aquaria play an important role in preventing the mass extinction of wildlife through public awareness of conservation issues and providing a safe haven for wildlife populations. Because aquatic populations face many challenges due to pollution and global warming, it is important to develop an understanding of how species can cope with their environment whether it be in the wild or under human care. Here, we were interested in developing non-invasive methods to study fish stress physiology. We use the unique ocean sunfish (Mola mola) to develop the use of skin swabs to measure the stress hormone, cortisol. We used known times of stress including when a mola was injured or ill and during acclimation to the Monterey Bay Aquarium. We found that cortisol increased initially within the first month of being admitted to the aquarium, but returned to normal values afterward. Molas also had elevated cortisol when being treated for an injury or illness. This is the first step in the development of the use of skin swabs to collect samples for stress analysis in the mola. Additional biochemical analysis is needed to confirm these results and allow this method to be applied to other species of fish.The ocean sunfish (mola; Mola mola) is the heaviest bony fish in the world. This slow-moving fish often is injured by fishing boats that use drift gillnets attributing to its listing as Vulnerable by the IUCN. The Monterey Bay Aquarium (Monterey, CA, USA) has a program that brings in smaller molas from the ocean and acclimates them for an exhibit. When they grow too large for the million-gallon Open Seas exhibit, they are returned to Monterey Bay through a “reverse” acclimatization. Our overall goal was to use skin swabs to evaluate mola stress physiology to better understand the effects of this program. Our objectives were to validate this non-invasive method by taking opportunistic swabs throughout acclimatization and during stressful events. We swabbed each individual (n = 12) in three different body locations. Swabs were analyzed using a cortisol enzyme immunoassay. We averaged the three swabs and examined the absolute change of cortisol from the first taken upon handling to during treatments and the different acclimation stages. We considered elevated cortisol concentrations to be ≥1.5-fold higher than the first sample. Overall, mean (±SEM) cortisol varied among individuals (564.2 ± 191.5 pg/mL swab (range, 18.3–7012.0 pg/mL swab). The majority (four of six) of molas swabbed within the first week or month had elevated skin cortisol compared to their first sample. All seven molas that were being treated for an injury or illness had elevated skin cortisol (range, 1.7- to 127.6-fold higher) compared to their post-acclimation sample. This is the first step in validating the use of non-invasive skin swabs for glucocorticoid analysis in the mola. Further biochemical analysis is needed to determine the specific steroids that are being measured.

FishShapes v1: Functionally relevant measurements of teleost shape and size on three dimensions.

Teleost fishes account for 96% of all fish species and exhibit a spectacular variety of body forms. Teleost lineages range from deep bodied to elongate (e.g., eels, needlefish), laterally compressed (e.g., ribbonfish) to globular (e.g., pufferfish), and include uniquely shaped lineages such as seahorses, flatfishes, and ocean sunfishes. Adaptive body shape convergence within fishes has long been hypothesized but the nature of the relationships between fish form and ecological and environmental variables remain largely unknown at the macroevolutionary scale. To facilitate the investigation of the interacting factors influencing teleost body shape evolution we measured eight functionally relevant linear traits on adult-sized specimens along with specimen mass. Linear measurements of standard length, maximum body depth, maximum fish width, lower jaw length, mouth width, head depth, minimum caudal peduncle depth, and minimum caudal peduncle width were taken in millimeters with calipers, or tape measures for oversized specimens. We measured these traits on a total of 16,523 specimens (1-3 specimens per species) at the Smithsonian National Museum of Natural History and took approximately 7000 person hours of data collection to complete. The data went through a three-step error-checking process to clean and validate the data and then species averages were calculated. We present the complete specimen data set, which encompasses approximately one-fifth of extant teleost species diversity, spanning ~90% of teleost families and ~96% of orders. The species and family names are compatible with the taxonomy used by FishBase and the order information with the phylogenetically informed taxonomy of Betancur-R and colleagues published in 2014. This dataset is licensed under Creative Commons CC0 1.0 Universal (CC0 1.0) but please cite this paper when using the data or a subset of it.

Does Ocean Sunfish Mola spp. (Tetraodontiformes: Molidae) Represent a Risk for Tetrodotoxin Poisoning in the Portuguese Coast?

Tetrodotoxin (TTX) is a potent neurotoxin naturally occurring in terrestrial and marine organisms such as pufferfish. Due to the risk of TTX poisoning, fish of Tetraodontidae family and other puffer-related species must not be placed in the EU markets. This restriction applies to fish of the family Molidae even though no data on toxins’ occurrence is available. In this study, the presence of TTX and its analogues was investigated in the main edible tissue (the white muscle) and the main xenobiotics storage organ (the liver) of ocean sunfish Mola spp. (n = 13) from the South Portuguese coast. HILIC-MS/MS analyses did not reveal TTX in the analyzed samples, suggesting an inexistent or very limited risk of TTX poisoning.

Coevolution of the olfactory organ and its receptor repertoire in ray-finned fishes

BackgroundRay-finned fishes (Actinopterygii) perceive their environment through a range of sensory modalities, including olfaction. Anatomical diversity of the olfactory organ suggests that olfaction is differentially important among species. To explore this topic, we studied the evolutionary dynamics of the four main gene families (OR, TAAR, ORA/VR1 and OlfC/VR2) coding for olfactory receptors in 185 species of ray-finned fishes.ResultsThe large variation in the number of functional genes, between 28 in the ocean sunfish Mola mola and 1317 in the reedfish Erpetoichthys calabaricus, is the result of parallel expansions and contractions of the four main gene families. Several ancient and independent simplifications of the olfactory organ are associated with massive gene losses. In contrast, Polypteriformes, which have a unique and complex olfactory organ, have almost twice as many olfactory receptor genes as any other ray-finned fish.ConclusionsWe document a functional link between morphology of the olfactory organ and richness of the olfactory receptor repertoire. Further, our results demonstrate that the genomic underpinning of olfaction in ray-finned fishes is heterogeneous and presents a dynamic pattern of evolutionary expansions, simplifications, and reacquisitions.

The impact of paleoclimatic changes on body size evolution in marine fishes

Body size is an important species trait, correlating with life span, fecundity, and other ecological factors. Over Earth's geological history, climate shifts have occurred, potentially shaping body size evolution in many clades. General rules attempting to summarize body size evolution include Bergmann's rule, which states that species reach larger sizes in cooler environments and smaller sizes in warmer environments, and Cope's rule, which poses that lineages tend to increase in size over evolutionary time. Tetraodontiform fishes (including pufferfishes, boxfishes, and ocean sunfishes) provide an extraordinary clade to test these rules in ectotherms owing to their exemplary fossil record and the great disparity in body size observed among extant and fossil species. We examined Bergmann's and Cope's rules in this group by combining phylogenomic data (1,103 exon loci from 185 extant species) with 210 anatomical characters coded from both fossil and extant species. We aggregated data layers on paleoclimate and body size from the species examined, and inferred a set of time-calibrated phylogenies using tip-dating approaches for downstream comparative analyses of body size evolution by implementing models that incorporate paleoclimatic information. We found strong support for a temperature-driven model in which increasing body size over time is correlated with decreasing oceanic temperatures. On average, extant tetraodontiforms are two to three times larger than their fossil counterparts, which otherwise evolved during periods of warmer ocean temperatures. These results provide strong support for both Bergmann's and Cope's rules, trends that are less studied in marine fishes compared to terrestrial vertebrates and marine invertebrates.