Hubbry Logo
BeroidaeBeroidaeMain
Open search
Beroidae
Community hub
Beroidae
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Beroidae
Beroidae
Beroidae
View on Wikipedia
from Wikipedia

Beroidae
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Ctenophora
Class: Nuda
Chun, 1879
Order: Beroida
Eschscholtz, 1829
Family: Beroidae
Eschscholtz, 1825
Genera
A beroid ctenophore with mouth gaping at left

Beroidae is a family of ctenophores or comb jellies more commonly referred to as the beroids. It is the only known family within the monotypic order Beroida and the class Nuda. They are distinguished from other comb jellies by the complete absence of tentacles, in both juvenile and adult stages. Species of the family Beroidae are found in all the world's oceans and seas and are free-swimmers that form part of the plankton.

Anatomy

[edit]

Some members of the diverse genus Beroe may occasionally attain a length of up to 30 centimetres (12 in), though most species and individuals are less than about 10 cm; Neis cordigera is among the largest species in the class, often exceeding 30 cm (12 in) in length.[1] The body is melon or cone-shaped with a wide mouth and pharynx and a capacious gastrovascular cavity. Many meridional canals branch off this and form a network of diverticulae in the mesogloea. There are no tentacles but there are a row of branched papillae, forming a figure of eight around the aboral tip.[2]

The sack-like body of the Beroe species may be cylindrical in cross section, or compressed to varying amounts according to species, while Neis is somewhat flattened and characterized by a pair of trailing gelatinous "wings" that extend beyond the aboral tip.

Like other comb jellies, the body wall of nudans consists of an outer epidermis and an inner gastrodermis, separated by a jelly-like mesoglea. The mesoglea has pigments that give many nudan species a slightly pink color; Neis cordigera may be yellowish or a deep orange-red.

Mouth opening

[edit]

Some nudans have a very large oral cavity, allowing them to swallow prey whole. While swimming, and particularly while pursuing prey, they close their mouths like a zipper so that they maintain a streamlined profile. The mouth is zipped closed from each end, and the edges seal shut by forming temporary inter-cellular connections. When close to the prey, the lips contract and the mouth is opened rapidly, sucking in the prey. This action is reversible and the lips can be resealed. An alternative method of feeding involves the lips spreading over the prey and the sword-shaped macrocilia lining the lips chopping off chunks.[3] The lips are sealed by the presence of adhesive strips of epithelial cells along their opposite edges. Not all species seem to have these strips which seem specifically adapted to those with wide mouths whereas species with small oral openings are able to control the opening of the aperture by more conventional means.[3]

Macrocilia

[edit]

Directly inside the mouth opening, in the lining of the gullet, can be found characteristic finger-like processes known as "macrocilia". These were first described by J.G.F. Will in 1844 and further investigated by George Adrian Horridge in 1965. He found they were complex structures composed of 2,000 to 3,000 filaments in a single, conical functional unit. Each macrocilium shows the typical eukaryote construction of nine external and two internal microtubules. The individual macrocilium is between 50 and 60 micrometres long and 6 to 10 micrometres thick, with the cilia bonded together in a hexagonal cross-sectional structure by permanent fibrils in three different planes. A system of tubules connects the basal bodies from which the macrocilia grow.[4]

The macrocilia move in unison. They are angled towards the gullet and are stacked on top of each other like roof tiles. By this arrangement they effectively grip parts of the prey in synchronized waves like a conveyor belt, transporting it to the stomach, and the throat muscles promote this process. The three-toothed tip of the macrocilia is stiff enough for it to rip the outer wall of larger prey such as other ctenophores; at the same time, proteolytic enzymes penetrate into the resulting wounds, rapidly incapacitating the victim.[4][5]

Macrocilia also function as teeth, and can be used in the same way as the tentacles of Tentaculata.

Channel system

[edit]

As in other ctenophores, from the main stomach a network of channels branch through the mesogloea. Some of these have blind ends and others link up. They supply nutrients to the most active parts of the animal, the mouth, pharynx, combs of cilia and the sensory organs at the hind end of the body. Each comb plate has its own meridional canal situated directly beneath it and a ring of channels surround the mouth.[5]

Sensory organs and combs

[edit]

At the aboral end of the animal (the opposite end from the mouth) is a statocyst, a balance organ that helps it to orient itself. Papillae surround the statocyst. Their function is unclear, but they are probably also used for sensory perception. The eight combs of cilia extend part way along the body in ribs. The combs are used in locomotion, with the cilia beating in synchronised waves to propel the animal. It usually moves with the mouth end in front, but the direction of movement can be reversed. When not actively moving, a vertical position is maintained, normally with the mouth upwards.[6]

Diet

[edit]

Nudans feed on free swimming animals with soft bodies, primarily on other ctenophores, many of them larger than they are themselves. They actively hunt for prey, which they usually devour whole. Some species use their macrocilia as teeth to remove smaller chunks from their prey.

As invasive species

[edit]
Beroe ovata on the Black Sea coast

In the late 1980s the ctenophore species Mnemiopsis leidyi was introduced into the Black Sea, probably through ballast water, which led to the collapse of the local anchovy population. In 1997 another ctenophore species arrived—Beroe ovata, a predator of Mnemiopsis leidyi. The Beroe population underwent an initial explosion, until the numbers of both ctenophores stabilized. Nevertheless, both Mnemiopsis leidyi and Beroe ovata remain today in the Black Sea. The same phenomenon is occurring at the beginning of the 21st century in the Caspian Sea.

Reproduction

[edit]

All species are hermaphrodites and reproduce sexually, having both female and male gonads. Although no detailed figures are available, it is assumed that self-fertilization is the exception among nudans. The fertilized eggs hatch into miniature versions of the adult animal, rather than distinct larval forms. They lack tentacles and are otherwise similar to the Cydippea larvae.

Taxonomy and systematics

[edit]

There are no known fossil nudans, so the phylogenetic evolution of the group by comparison with other modern ctenophores is not possible. In the traditional system, the Nuda form a class distinct from the Tentaculata, which all have at least rudimentary tentacles. This division, after provisional results of morphological and molecular studies, however, probably does not reflect the actual relationships within the ctenophores. The monophyly of Nuda is widely accepted, due to the complete lack of tentacles, and the presence of macrocilia as a common secondary feature, or synapomorphy.

There are approximately 25 species in the family Beroidae, grouped into two genera. The family and order were named in 1825 or 1829 by the German naturalist Johann Friedrich Eschscholtz.

  • The genus Beroe includes nearly all the members of the class and is distributed worldwide. One of the best known species, which is widespread in the Northern Hemisphere, is Beroe gracilis. In Beroe species, the body is usually maintained in a vertical position with the mouth end orientated upwards. The vascular system is separated longitudinally into two separate halves.[7]
  • The genus Neis is monotypical, containing only one species, Neis cordigera (Lesson 1824), and is found only in the waters around Australia. The aboral end is extended into two large lobes and the vascular system is undivided.[7]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Beroidae

View on Grokipedia
from Grokipedia
Beroidae is a family of marine ctenophores, commonly known as beroids or comb jellies, within the class Nuda and the monotypic order Beroida. These gelatinous, free-swimming organisms are distinguished from other ctenophores by the complete absence of tentacles in both juvenile and adult stages, instead featuring a large, expandable mouth lined with macrocilia for capturing and swallowing prey whole. Beroidae species inhabit oceans worldwide, from polar to tropical waters, and play a crucial ecological role as specialized predators primarily targeting other ctenophores, such as the invasive Mnemiopsis leidyi. The family comprises two accepted genera: Beroe (with approximately 29 species, including Beroe cucumis, Beroe ovata, and Beroe mitrata) and Neis (with a single species, Neis cordigera). These beroids exhibit sac-like or thimble-shaped bodies, often compressed laterally, composed of up to 95% water, and ranging in size from several millimeters to over 160 mm in height. They propel themselves using eight meridional rows of ciliary plates, known as ctenes, which also contribute to their iridescent appearance and , particularly when disturbed. Biologically, beroids are hermaphroditic, producing both eggs and , with a life cycle that includes planktonic juveniles transitioning to adult forms. Their diet consists almost exclusively of other , enabling them to consume prey larger than themselves and helping regulate populations of ecologically significant in marine webs. Recent taxonomic revisions, based on genetic and morphological analyses, have clarified distinctions and distributions, such as confirming Beroe ovata as a thermophilic invader in regions like the and Mediterranean, where it aids in controlling invasive ctenophore blooms. Despite their planktonic lifestyle, beroids lack a centralized , relying instead on a diffuse for coordination.

Introduction and Habitat

Overview

Beroidae represents the only family within the monotypic order Beroida and class Nuda of the phylum , encompassing around 30 accepted species distributed across two genera: Beroe (29 species) and Neis (monotypic with N. cordigera). These ctenophores are defined by their complete lack of tentacles at all life stages, a trait unique to the Nuda, and instead depend on a prominently large and expansive for prey capture and ingestion. This family exemplifies the predatory adaptations within , focusing on engulfing other . The general of Beroidae is gelatinous and biradially symmetric, often appearing sac-like or conical, with a soft, transparent to semi-opaque structure that facilitates in the . Locomotion is achieved through eight meridional rows of comb plates, or ctenes—coordinated ciliary structures that propel the via metachronal waves. Most species measure 1–10 cm in length, though Neis cordigera can attain up to 30 cm, highlighting variability in size within the family. The , the acellular jelly-like layer between the and , frequently incorporates pigments that lend Beroidae members hues of pink, yellowish, or orange-red, aiding in or recognition in their pelagic realm. These free-swimming, planktonic predators inhabit open marine waters worldwide, contributing to the dynamics of gelatinous food webs as voracious consumers of other ctenophores.

Distribution and Habitat

Beroidae, a family of predatory ctenophores, exhibit a across the world's oceans and seas, with recorded from polar to subtropical latitudes in both hemispheres. While individual show regional preferences—such as the bipolar distribution of Beroe cucumis in cold polar and temperate waters of the and , and the more thermophilic Beroe ovata in temperate to subtropical Atlantic and invasive Mediterranean basins—the family as a whole occupies marine environments globally, from coastal neritic zones to open oceanic waters. Higher abundances are typically observed in temperate and subtropical regions, influenced by oceanic currents that facilitate dispersal, as seen in the widespread presence of Beroe pseudocucumis across tropical and subtropical Atlantic and Pacific waters. These ctenophores are exclusively planktonic, inhabiting surface waters down to depths of up to 2000 m, though most species are concentrated in the epipelagic and upper mesopelagic layers (0–500 m), with some like Beroe cucumis extending to 880 m and rarer deep-sea forms such as Beroe abyssicola reaching bathypelagic zones around 2800 m. They prefer coastal and open ocean planktonic niches, showing tolerance to varying salinities (e.g., 12–38 psu for Beroe ovata), but are primarily adapted to fully marine oceanic conditions with salinities around 35–38 psu. Vertical distribution is dynamic, with many species, including Beroe cucumis, performing diel vertical migrations—ascending to surface layers at night to pursue prey or evade predators and descending during the day—often spanning 100–300 m in response to light cycles and food availability in the northeastern Atlantic. Habitat suitability for Beroidae is strongly tied to water temperature, with optimal ranges of 10–25°C supporting peak abundances across species; for instance, Beroe ovata thrives in 15–28°C waters, while Beroe cucumis favors cooler 0–15°C conditions in boreal zones. Prey availability, particularly other zooplanktivorous ctenophores, further shapes their niches, driving concentrations in productive coastal areas or post-invasion ecosystems like the , where Beroe ovata established following its introduction in the 1990s and persists in salinities of 17–18 psu. These factors underscore their adaptation to dynamic marine planktonic environments, where temperature gradients and food resources dictate seasonal and spatial patterns.

Anatomy

External Morphology

Beroidae, a family within the order Beroida of ctenophores, are distinguished by their muscular, gelatinous bodies lacking tentacles at any life stage, a defining trait of the Nuda. Their external form generally features a sac-like, cylindrical, or flattened conical shape, with a broad oral end that flares outward and tapers to a narrower aboral pole, facilitating predatory engulfment of prey. Species exhibit variations, such as the mitre-shaped and laterally compressed body of Beroe ovata or the long-oval form of Beroe pseudocucumis. Most beroids range in size from 1 to 10 cm in length, though larger species like Beroe ovata and Beroe pseudocucumis can attain 16 cm, and the exceptional Neis cordigera may exceed 30 cm. The oral region dominates the anterior, featuring a large opening that occupies much of the end, often surrounded by flexible, muscular that aid in prey capture. At the opposite aboral tip, branched papillae project, likely serving sensory roles, though their exact function remains unclear, with lengths varying by species—short and unfringed in B. ovata, but long and elaborate in B. pseudocucumis. The aboral organ complex includes statocysts and associated balancers (ciliated polar fields) for gravitational orientation and balance, enabling precise swimming control. Some species possess photocytes capable of , producing blue-green flashes along the body surface, particularly under stimulation. Locomotion relies on eight meridional rows of comb plates (ctenes), which create iridescent propulsion through coordinated ciliary beating, extending along much of the body length. The external surface consists of a thin overlaying the , a jelly-like matrix that provides and structural support, often appearing translucent, pink, or pigmented with dark lines along the comb rows. This smooth, tentacle-free underscores their specialization as active swimmers in pelagic environments.

Internal Structures

The internal anatomy of Beroidae, a family of tentacle-less ctenophores, is adapted for efficient predation and nutrient processing, featuring a simplified yet effective digestive tract and supportive structures that compensate for the absence of tentacles. The opening is a wide, gaping slit that occupies much of the oral surface, leading directly into an expansive that spans nearly the length of the body. This , lined with ciliated , facilitates the of whole prey items, such as smaller ctenophores, by expanding to engulf them rapidly. The transitions to a simple, small known as the infundibulum, a central chamber where initial occurs through enzymatic action and mechanical breakdown. This design enables whole-prey without the need for external grasping appendages, distinguishing Beroidae from other ctenophores. Within the pharynx, macrocilia—fused tufts of stiffened cilia forming tooth-like structures—aid in grasping and tearing prey. These macrocilia, measuring 10-20 μm in length and 2-4 μm in diameter, are arranged in stacked, hook-like formations that point inward, creating a grinding mechanism often described as a "ciliary mill." They operate in unison to process ingested food into smaller particles before it reaches the , enhancing digestive efficiency in this tentacle-free lineage. The gastrovascular system in Beroidae consists of a network of canals branching from the , serving dual roles in distribution and . Gastrovascular canals radiate from the infundibulum, connecting to eight meridional canals that run along the comb rows, with additional paragastric and adradial branches embedded in the . Ciliated rosettes along these canals facilitate isodynamic fluid flow, circulating nutrients to active tissues like the comb plates and sensory organs while directing undigested waste aborally. Waste expulsion occurs through two temporary anal pores at the aboral pole, regulated by actin-rich sphincters that open periodically to eject material forcefully, after which the pores close. This through-gut configuration, confirmed across Beroidae species like Beroe abyssicola, underscores their evolutionary adaptation for rapid turnover in a predatory lifestyle. Supporting these systems is the , a thick, acellular gelatinous layer that constitutes the bulk of the body and provides and structural integrity. In Beroidae, the mesoglea is translucent and jelly-like, permeated by the branching gastrovascular canals and embedded with giant fibers (1-8 μm in diameter) that enable powerful contractions for prey capture and locomotion. This layer's flexibility allows the body to expand dramatically during feeding while maintaining overall shape through its non-cellular matrix. The of Beroidae is decentralized, comprising a diffuse without a centralized , adapted to their streamlined predatory form. It includes a subepithelial polygonal network that covers the body surface and extends deeply into the , integrating sensory inputs from the and region. A secondary meshwork of and fibers permeates the , with three main types—bipolar, multipolar, and long-process—concentrated around sensory organs like the aboral . This arrangement supports coordinated responses for feeding and movement, with neural densities highest near the and comb rows.

Feeding and Diet

Predatory Mechanisms

Beroidae, a family of ctenophores in the order Beroida, exhibit a distinctive predatory strategy adapted to their tentacle-less morphology, relying instead on an enlarged oral cavity and specialized ciliary structures for capturing and processing prey. Unlike many ctenophores that employ sticky tentacles for ensnaring small organisms, beroids actively pursue and engulf gelatinous prey, primarily other ctenophores, using rapid swimming motions facilitated by their eight meridional rows of comb plates (ctenes). These comb rows propel the animal mouth-first through the at speeds sufficient for chasing evasive targets, with body contractions enabling sudden accelerations to close distances on detected prey. Sensory receptors distributed across the body surface, including mechanosensitive cilia on the , allow beroids to orient toward or physical contact with potential meals during this pursuit phase. Upon contact, beroids employ an engulfment strategy by everting their large, muscular to swallow smaller prey whole. The oral , lined with epithelial cells when closed, rapidly expand to envelop the victim, aided by strong pharyngeal muscles that draw the prey inward. For larger prey that cannot be ingested intact, the beroid's macrocilia—compound ciliary organelles unique to this family—act as to grasp and shred the tissue into manageable chunks. These macrocilia, measuring 50-60 μm in and 6-10 μm in diameter with sharp, tooth-like tips, consist of multiple 9+2 axonemes bundled with filaments, enabling them to tear gelatinous material and propel fragments toward the through discontinuous beating patterns with effective and recovery strokes. This ciliary action not only facilitates mechanical breakdown but also integrates with subepithelial muscle fibers via massive bundles, coordinating the overall feeding response. Following , in beroids proceeds through a combination of extracellular and intracellular processes within their branched gastrovascular system. Prey is transported aborally through the via ciliary beating and muscular , where pharyngeal folds secrete to initiate extracellular breakdown into fine particles. These particles then distribute via radial and meridional canals to the endodermal walls for intracellular absorption by phagocytic cells, completing nutrient uptake within several hours. Undigested remnants are expelled either through the in cases of regurgitation or via anal pores at the aboral pole, regulated by reversed ciliary motion and sphincter contractions occurring intermittently every 2-2.5 hours. This efficient system supports the beroids' high metabolic demands as carnivores. The absence of tentacles in Beroidae is compensated by enhancements to the oral region, including the expansive that occupies much of the body and the mechanosensitive macrocilia that provide both sensory and manipulative functions. Giant muscle fibers (up to 8 μm in diameter) embedded in the further enable the flexible body deformations necessary for prey capture, while a subepithelial integrates sensory inputs to orchestrate these behaviors. These adaptations underscore the evolutionary specialization of beroids as specialized predators within planktonic food webs.

Diet Composition

Beroidae, comprising the genus Beroe and related taxa, are obligate carnivores specializing in the predation of other ctenophores, forming the core of their diet across species. This exclusive focus on fellow comb jellies positions them as raptorially feeding specialists within gelatinous communities, where they target smaller or similarly sized individuals for engulfment. Representative prey includes lobate ctenophores such as Mnemiopsis leidyi and Bolinopsis infundibulum, as well as tentaculate forms like Pleurobrachia bachei and species in the genus Ocyropsis. Their carnivorous gut structure precludes consumption of , limiting intake to animal prey and emphasizing soft-bodied . Opportunistic feeding extends to other soft-bodied planktonic , including salps in some species, and occasionally polychaete larvae or fish eggs when ctenophore availability is low. Beroidae exhibit size selectivity, preferentially consuming prey smaller than their own body length to facilitate complete engulfment, though larger items can be managed through shredding via macrocilia acting as rasping structures. Diet composition varies by species and geographic region; for instance, Beroe ovata in the Black Sea predominantly targets Mnemiopsis leidyi, establishing a direct trophic linkage that influences local ctenophore dynamics. As apex predators in gelatinous-dominated plankton assemblages, Beroidae occupy a high , exerting top-down control on prey populations without facing significant predation pressure from non-gelatinous taxa. This specialized carnivory underscores their role as keystone consumers in marine food webs, with dietary preferences reinforcing among ctenophores.

Reproduction and Life Cycle

Reproductive Biology

Members of the Beroidae family are simultaneous hermaphrodites, possessing both ovarian and testicular tissues that enable the production of eggs and within the same individual. The gonads develop along the lateral walls of the meridional canals and associated diverticula, facilitating the transport of gametes through the internal canal system to pores in the for release. Reproduction in Beroidae occurs through in the , where mature individuals synchronously release eggs and during spawning events. Although self-fertilization is possible due to hermaphroditism, cross-fertilization between individuals is more common, with actively seeking out eggs in the surrounding . Spawning is often triggered by environmental cues such as fluctuations and prey , which influence the timing and synchronization of release. Fecundity in Beroidae is notably high, supporting rapid in favorable conditions; for example, Beroe ovata can produce up to approximately 3,000 eggs per day under high prey availability. During reproductive periods, individuals may aggregate in areas of high conspecific density, potentially enhancing cross-fertilization efficiency through proximity, though direct physical contact for sperm transfer is not observed. Reproductive activity in Beroidae peaks during warmer months, aligning with seasonal temperature increases that promote gonad maturation and spawning. Salinity levels and food availability further modulate gamete viability, with optimal conditions in moderate salinities allowing successful fertilization even without prior acclimation in species like Beroe ovata. Prey abundance, particularly of lobate ctenophores, indirectly supports reproduction by sustaining energy reserves for gamete production.

Development and Life Stages

Beroidae, like other ctenophores, exhibit where eggs are released and fertilized in the by from hermaphroditic spawning, leading to direct development without a free-living larval stage. The resulting embryos undergo rapid cleavage, characterized by equal meridional divisions in the first two cleavages followed by an unequal oblique third cleavage that produces macromeres and micromeres, establishing the bilateral and basic early on. Embryonic development proceeds through via multiple mechanisms including , , , and involution, forming the three germ layers—ectoderm (outer epithelium), (inner gastrodermis), and (subepithelial musculature and precursors)—within approximately 24 hours at 15–20°C. Hatching yields cydippid-like juveniles that resemble miniature adults, lacking tentacles entirely and featuring a simple oral region with early development of macrociliary rows for feeding, bypassing any distinct larval phase. Growth occurs directly through expansion of the and progressive maturation of organs such as the and meridional canals, with no required. Under optimal conditions with abundant prey, juveniles exhibit rapid growth, achieving and reproductive capability in about 14 days at small sizes (around 1 mm), and adults maintain continuous spawning. Lifespans typically range from 1 to 3 months, varying with temperature and food availability, shorter in warmer summer conditions. Beroidae possess a high regenerative capacity throughout their lives, enabling replacement of lost body parts including oral structures like the extensible lips and macrociliary apparatus, often restoring full functionality within days via and formation at wound sites. This ability underscores their resilience in predatory lifestyles, with regeneration initiating as early as the juvenile stage.

Ecological Role

Ecosystem Interactions

Beroidae species exert significant top-down control in marine plankton communities by preying on other , thereby regulating their populations and preventing explosive blooms in native ranges. For instance, Beroe cucumis primarily targets Bolinopsis infundibulum, while Beroe gracilis preys on smaller ctenophores such as , maintaining balance in coastal and open-ocean food webs. This predatory role helps stabilize dynamics, as evidenced by experimental studies showing high consumption rates that limit prey abundance without leading to overexploitation. In their native North Atlantic and habitats, such interactions underscore Beroidae's function as key regulators, akin to their control of leidyi by Beroe ovata in non-invaded Atlantic ecosystems. As part of the broader , Beroidae serve as prey for higher trophic levels, including planktivorous , scyphozoan , and potentially seabirds, integrating them into complex energy transfer pathways. Species like Beroe abyssicola may serve as prey for and other gelatinous predators. Their translucent to reddish bodies, which ingested prey, may influence predation efficiency but may exhibit when disturbed, similar to other ctenophores. Primarily solitary, Beroidae exhibit occasional commensal associations with planktonic crustaceans and pycnogonids, where small arthropods may use their bodies for transport without apparent harm, though such interactions remain rare and non-obligatory. Beroidae contribute to trophic cascades within planktonic ecosystems by suppressing carnivorous ctenophores that prey on herbivorous zooplankton, which indirectly enhances through reduced grazing pressure on . In balanced native communities, their predation on dominant ctenophores like Bolinopsis prevents shifts that could diminish zooplankton diversity and alter carbon flux to higher levels. This cascading effect supports overall , as modeled in Atlantic food webs where Beroidae presence correlates with stable blooms and resilient populations. Due to their sensitivity to environmental stressors, Beroidae species are valuable indicators of ; for example, Beroe ovata prefers temperatures above 15°C and may decline in cooler conditions below 10°C or pollution-induced hypoxia, signaling broader pelagic disruptions. Monitoring their abundance and distribution thus aids in assessing climate-driven changes and anthropogenic impacts on marine dynamics.

Invasive Impacts

Beroe ovata, a member of the Beroidae family, represents the primary within the group, having been introduced to the in the late , likely via water from its native Atlantic range, as a natural predator to mitigate blooms of the earlier invader Mnemiopsis leidyi. This deliberate biological control effort capitalized on B. ovata's specialized predation on other ctenophores, leading to substantial ecological benefits. Following its arrival in 1997, B. ovata populations surged, causing a dramatic decline in M. leidyi —from peaks exceeding 500 g wet weight m⁻² to as low as 0.02 g m⁻² in monitored bays by 2001—effectively suppressing the invasive ctenophore's dominance and restoring mesozooplankton abundance to levels sufficient for larval survival. This reduction alleviated pressure on the pelagic , facilitating the recovery of commercial fisheries, particularly (Engraulis encrasicolus), whose catches rebounded from near-collapse levels of under 20,000 tons in the early to over 200,000 tons annually by the early 2000s in the . Similar dynamics occurred in the Caspian Sea, where B. ovata was first recorded in November 2019, presumably transported via ballast water from the through shipping routes like the Volga-Don Canal, arriving after M. leidyi's establishment in 1999. Initial observations indicate B. ovata's potential to curb M. leidyi populations in this enclosed basin, mirroring outcomes, though long-term data remain limited due to the recent arrival. Subsequent records, such as in the shelf in 2020, indicate potential establishment, though long-term impacts remain under study as of 2025. However, negative ecological consequences have emerged or are anticipated, including potential overpredation on native or less abundant ctenophores and when primary prey like M. leidyi is scarce, which could disrupt local food webs by redirecting energy flows away from fish recruitment. Secondary introductions, such as to adjacent European waters, have also occurred; B. ovata was detected in Danish coastal areas (including the near the entrance) in 2014, likely via continued maritime traffic, though it has not yet significantly impacted M. leidyi there. The spread of invasive Beroidae like B. ovata is facilitated primarily by water discharge and hull fouling, enabling rapid dispersal across connected marine basins despite their planktonic, non-attached lifestyle. Monitoring these invasions poses significant challenges owing to the species' transient, gelatinous and low detectability in standard net tows, necessitating specialized sampling and molecular techniques for early detection. Management strategies emphasize the success as a model for targeted biological control against ctenophore invasives, yet highlight persistent risks of unintended range expansions, ecosystem imbalances, and economic repercussions in novel habitats, underscoring the need for stringent ballast water regulations under international frameworks like the IMO Ballast Water Management Convention.

Taxonomy and Phylogeny

Classification and Genera

Beroidae is a family within the phylum , classified under the class Nuda, order Beroida, and distinguished by its unique morphological adaptations that set it apart from other families in Nuda, such as the complete absence of tentacles in both juvenile and adult stages, the presence of macrocilia lining the lips of a wide mouth for prey capture, and a characteristic beroid body form that is typically cylindrical or laterally flattened to facilitate engulfing larger gelatinous prey. The family was established by Friedrich von Eschscholtz in 1825 based on early morphological observations of these pelagic predators. Subsequent revisions have relied primarily on morphological traits, such as the structure of meridional canals and aboral organs, to refine boundaries and distributions, with recent studies incorporating genetic data to resolve ambiguities in identification. The family comprises two recognized genera: Beroe (O.F. Müller, 1776), which is widespread across global oceans and includes approximately 32 accepted extant species characterized by their and predatory habits on other ctenophores, with representative examples such as Beroe ovata (found in temperate Atlantic waters) and Beroe gracilis (common in European coastal regions); and Neis (, 1829), a monotypic restricted to the , containing only Neis cordigera, which exhibits a similar tentacle-less form but with a more regionally confined range around and adjacent seas. Phylogenetically, Beroidae holds a basal position within , with the class Nuda serving as the to Tentaculata, reflecting the early divergence of tentacle-lacking lineages; molecular analyses, including ribosomal and mitochondrial markers, affirm the of Beroidae as a cohesive adapted for macro-predation.

Species Diversity and Updates

The family Beroidae encompasses approximately 33 extant accepted , an update from earlier estimates of around 25 species in pre-2024 literature. This count is supported by comprehensive taxonomic reviews and , reflecting ongoing refinements in ctenophore . All are extant, with no known records for the family. Diversity within Beroidae is concentrated in the genus Beroe, which includes nearly all species (32) and exhibits a across global oceans. In contrast, the genus Neis is species-poor, comprising only one . Representative include Beroe abyssicola, a deep-sea form adapted to bathypelagic environments; Beroe cucumis, common in Atlantic surface waters; and Neis cordigera, a tropical that can reach lengths of up to 30 cm. Recent taxonomic updates have been driven by , particularly post-2020 studies integrating genetic data with morphology to refine relationships within Beroidae. For instance, analyses of ITS sequences have identified multiple genetic lineages in European Beroe populations, suggesting the presence of potential cryptic that warrant further description. The (WoRMS) database, as of November 2025, recognizes 33 valid . However, gaps persist due to incomplete sampling in deep-sea habitats, which likely harbor additional undescribed diversity.

References

  1. http://www.marinespecies.org/aphia.php?p=taxdetails&id=106317
  2. https://minka-sdg.org/taxa/254019-Beroidae
  3. https://academic.oup.com/zoolinnean/article/194/1/297/6356088
  4. http://faculty.washington.edu/cemills/Ctenolist.html
  5. https://txmarspecies.tamug.edu/invertfamilydetails.cfm?famnameID=Beroidae
  6. https://www.sealifebase.se/country/CountrySpeciesSummary.php?c_code=643&Genus=Beroe&Species=ovata
  7. https://www.sealifebase.se/summary/Beroe-cucumis.html
  8. https://www.mbari.org/animal/abyssal-comb-jelly/
  9. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144161
  10. https://www.sciencedirect.com/science/article/abs/pii/S0141113623004439
  11. https://www.int-res.com/articles/meps2004/266/m266p111.pdf
  12. https://www.whitney.ufl.edu/media/wwwwhitneyufledu/images/files/Illustrated-Guide-to-Ctenophora_Moroz-et-al_2024.pdf
  13. https://www.antarctica.gov.au/site/assets/files/64914/arn_036.pdf
  14. https://www.sciencedirect.com/science/article/abs/pii/S1095643324001211
  15. https://febs.onlinelibrary.wiley.com/doi/10.1111/j.1742-4658.2012.08476.x
  16. http://www.cmarz.org/resources/Mayer1912_Ctenophores/Mayer_1912_Ctenophores_of_the_Atlantic_Coast_of_North_America.pdf
  17. https://www.biorxiv.org/content/10.1101/419218v1.full.pdf
  18. https://www.sciencedirect.com/science/article/pii/S0960982216309319
  19. https://royalsocietypublishing.org/doi/10.1098/rspb.1965.0043
  20. https://onlinelibrary.wiley.com/doi/abs/10.1002/cm.970070204
  21. https://pmc.ncbi.nlm.nih.gov/articles/PMC11184263/
  22. https://academic.oup.com/icb/article/47/6/847/579378
  23. https://animaldiversity.org/accounts/Beroe_ovata/
  24. https://faculty.washington.edu/cemills/Ctenophores.html
  25. https://tehranconvention.org/system/files/tcis/shiganovainvspeciesreportcaspecopdf.pdf
  26. http://tb.plazi.org/GgServer/html/03A287C44C59FFACFF7E02B3FCCE4528
  27. https://doi.org/10.1016/S0022-5320(73)90054-3
  28. https://doi.org/10.1016/0012-1606(84)90274-4
  29. https://www.pnas.org/doi/10.1073/pnas.2122052119
  30. https://www.researchgate.net/publication/260417034_Population_dynamics_ingestion_growth_and_reproduction_rates_of_the_invader_Beroe_ovata_and_its_impact_on_plankton_community_in_several_Black_Sea_regions
  31. https://ij-aquaticbiology.com/index.php/ijab/article/download/282/396/1001
  32. https://www.researchgate.net/publication/289702139_Reproductive_strategy_of_Beroe_ovata_Ctenophora_Atentaculata_Beroida_-_A_new_invader_in_the_Black_Sea
  33. https://www.academia.edu/84955892/Reproduction_characteristics_and_growth_rate_of_ctenophore_Beroe_ovata_larvae_in_the_Caspian_and_Black_sea_waters
  34. https://www.researchgate.net/figure/Ctenophore-development-and-body-plan-A-Early-cleavage-from-egg-to-60-cell-stage-based_fig2_47335564
  35. http://invert-embryo.blogspot.com/2013/06/early-embryos-of-beroe.html
  36. https://link.springer.com/article/10.1007/s00427-007-0131-x
  37. https://animaldiversity.org/accounts/Ctenophora/
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC6278862/
  39. https://www.sciencedirect.com/science/article/abs/pii/S0959437X16300922
  40. https://pmc.ncbi.nlm.nih.gov/articles/PMC8228598/
  41. https://zooplankton.nl/en/diversity/comb-jellies/
  42. https://www.researchgate.net/publication/234034611_Interactions_between_native_and_alien_ctenophores_Beroe_gracilis_and_Mnemiopsis_leidyi_in_Gullmarsfjorden
  43. https://epic.awi.de/id/eprint/57231/
  44. https://twilightzone.whoi.edu/explore-the-otz/creature-features/ctenophores/
  45. https://pmc.ncbi.nlm.nih.gov/articles/PMC10643496/
  46. https://www.sciencedirect.com/science/article/pii/S2352485520306836
  47. https://cdnsciencepub.com/doi/10.1139/cjz-2024-0171
  48. https://emblasproject.org/wp-content/uploads/2022/03/Macroplankton-Manual-2020-ISBN-978-617-8010-44-7.pdf
  49. https://tos.org/oceanography/assets/docs/18-2_kideys.pdf
  50. https://academic.oup.com/plankt/article/25/5/539/1467554
  51. https://jifro.ir/article-1-4833-en.html
  52. https://ecodag.elpub.ru/ugro/article/view/2051?locale=en_US
  53. https://www.sciencedirect.com/science/article/abs/pii/S0025326X1930147X
  54. https://www.scirp.org/journal/paperinformation?paperid=78898
  55. http://www.marinespecies.org/aphia.php?p=taxdetails&id=265964
  56. https://www.marinespecies.org/aphia.php?p=taxdetails&id=1434803
  57. https://pmc.ncbi.nlm.nih.gov/articles/PMC5664179/
  58. https://www.marinespecies.org/aphia.php?p=taxdetails&id=106317
  59. https://faculty.washington.edu/cemills/Ctenolist.html
  60. https://www.marinespecies.org/aphia.php?p=taxdetails&id=265964
  61. https://www.marinespecies.org/aphia.php?p=taxdetails&id=106331
  62. https://zenodo.org/records/5799206
  63. https://www.researchgate.net/publication/354058084_Revision_of_Beroidae_Ctenophora_in_the_southern_seas_of_Europe_systematics_and_distribution_based_on_genetics_and_morphology
Add your contribution
Related Hubs
User Avatar
No comments yet.