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Zyzzyzus

Scientific Classification

Kingdom	Animalia
Phylum	Cnidaria
Class	Hydrozoa
Order	Anthoathecatae
Family	Tubulariidae
Genus	Zyzzyzus

Zyzzyzus: Tubulariid Hydrozoan

Zyzzyzus is a genus in the class Hydrozoa, order Anthoathecata, and family Tubulariidae. This group of tubulariid hydrozoans are typically found in symbiotic relationships with sponges, but can also in rare cases be found in relation to different substrata depending on the specific species and location of the hydroid. The different species of Zyzzyzus can be found in these relationships in all of the oceans (although more frequently in some than in others) and as a genus still hold a relatively large amount of unknowns. This form of symbiosis between the species of Zyzzyzus and their typically poriferan symbionts in which the tubulariids were -- and are -- able to grow into or onto the sponge through specific larval settlement techniques with the help of evolutionary defenses against the sponges' avoidance of these species until a sort of mutualism was achieved wherein some species of Zyzzyzus will actually help the sponge have a stronger change of survival due to their ability to embed themselves into the tissue of the poriferan and create a skeleton for the organism as the sponge grows around the hydrozoan . As with sponges, these Zyzzyzus symbionts are most notably found in shallow water ecosystems along the coasts of the continents .

Species

• Zyzzyzus floridanus Petersen, 1990
• Zyzzyzus iyoensis (Yamada, 1959)
• Zyzzyzus parvula (Hickson & Gravely, 1907)
• Zyzzyzus robustus Petersen, 1990
• Zyzzyzus rubusidaeus Brinckmann-Voss & Calder, 2013
• Zyzzyzus spongicolus (von Lendenfeld, 1884)
• Zyzzyzus warreni (Calder, 1988)
• Zyzzyzus calderi (Petersen, 1990)

Zyzzyzus floridanus

Z. floridanus typically present with an oblong cylindrical shaped hydranth and two whorls of oral tentacles. This species is typically found in the shallow (~2m at low tide) waters of the Northwest Atlantic Ocean near Miami, Florida and is found in a symbiotic relationship with Callyspongia vaginalis . They are typically transparent in color (when observed in laboratories).

Zyzzyzus robustus

Z. robustus can grow on rocks, various poriferans, and some bryozoans at a variety of depths -- as deep as ~400m or as shallow as ~100 m -- and are typically found in the Northwest Atlantic . This species is a "yellowish-brown color" when observed in laboratories. Most notably, members of Z. robustus are very physically unique when fully grown, they lack a groove where their perisarc secretes and they possess long blastostyles originating from a single arm . These differences in adulthood, however, do not show up in the young Z. robustus. Typically, these species will seem very similar to the Z. warreni in their morphological traits .

Zyzzyzus spongicolus

Z. spongicolus is another species of Zyzzyzus that can appear similar to Z. warreni in all but its presence of male and female gonophores on the same blastostyle as opposed to the two separate blastostyles for male and female gonophores in Z. warreni . This specific species has a wide range of morphological traits in response to the skeletal structure in the sponge that the young polyp attaches itself to during the settlement stage . These sponges are typically located in sheltered ocean bays in the Eastern Indian Ocean and the Southwest Pacific, often appearing as a yellowish-brown "fuzzy growth" on the local sponges . Z. spongicolus is typically found in a symbiotic relationship with horny sponges .

Zyzzyzus warreni

Z. warreni, the most widely studied of the species of Zyzzyzus, can be found globally in a range of areas including the Northwestern, Eastern, and Southwest Atlantic, as well as the Western Indian Ocean around South Africa and Mozambique, and the Northwest Pacific off the coast of Japan . This species is found in a variety of ecosystems. Z. warreni can be found in shallow waters or rocky coastal shores, mangroves, bays, and various different protected areas around the globe . This species can be easily identified by its two classes of thread-like tails (homotrichous microbasic euryteles), their merotrichous isorhizae (a fairly rare attached nematocyst), and the presence of male and female gonophores on different blastostyles (as opposed to Z. spongicolus discussed above) . This species is mostly a white-clear color with an orange hydranth base and red toned spadix . Z. warreni are found exclusively in symbiotic relationship with sponges (typically exteriorly, with few found actually attached to the hydrocaulus of the hydroid Eudendrium carneum in Bermuda, but, these symbiotic relationships are not always necessary for life for the Z. warreni can also anchor themselves onto certain kinds of algae as well as living on other cnidarians . This species is also an important part of some marine food chains, as it is a food source for many marine organisms such as some anemones, ophiuroids (brittle stars), and starfish .

This hydrozoan is found within many sponge hosts: Haliclona clatharata, Haliclona permollis, Clathria fasciculata, Aaptos ciliatus, Mycale angulosa, Mycale laxissima, Mycale microsigmatosa, Tedania ignis, and various horny sponges .

In the relationship between the sponge and the symbiotic Z. warreni hydroid, the sponge can sometimes try to strengthen itself against the now-parasite and will actually create thick pockets in their tissues around the hydroid, giving further proof to the existence of Zyzzyzus in these sponges as a more parasitic relationship as opposed to a more simple symbiosis .

Zyzzyzus rubusidaeus

This recently (2013) discovered species of Zyzzyzus, Z. rubusidaeus, is known as the "raspberry hydroid" for its noticeably vibrant reddish color and similar physical makeup to the delicious fruit . Members of this species can be found on a variety of substrates including rocks, barnacles, sponges, and compound ascidians (sea squirts) . Members of this species typically appear on these substrates in unified colonies of polyps in a variety of life stages ran from larval stage up to adults which vary greatly in size. These loosely bound colonies are typically connected by their tube-like arms that can be fairly easily separated and spread . The polyps of this species that form these colonies are formed sexually (atypical for this genus) in order to more effectively exist in the fight for space in these popular substrates . While typically found off the west coast of the United States and Canada (ranging from Alaska to northern California), this species can be found as far as British Columbia .

Zyzzyzus calderi

This species is found in symbiotic relationships with the sponge host Tedania sp. in this case, the hydroid is generally only found in the uppermost distal areas of the sponge it is in relation with.

Life Cycle

Sponges as a Substrate

Example of a cnidarian life cycle (H. antarcticus)

Members of the genus Zyzzyzus are most typically found on sponges as their chosen substrate or symbiont because of their ability to filter water and give access to nutrients to the tubulariid hydrozoans through either a parasitic or symbiotic relationship . In the case of the genus Zyzzyzus, and Z. warreni in particular, the sponge and the hydrozoan prefer to stay fairly separate, with a sort of "wall" forming between the two as the sponge attempts to avoid a more parasitic relationship with the hydrozoan . Other species, however, such as Z. calderi and Z. floridanus exhibit more of a parasitic relationship with their preferred poriferan substrate .

Early Life and the Two Part Life-Cycle

The class of hydroids, of which Zyzzyzus is a part, typically have a two part life cycle: 1) planular larval or pelagic medusal -- (depending on the species being described (and the scientist describing it) -- and 2) benthic polyp .

Planular Larval and Benthic Polyp Stages of Life:

In the case of members of Zyzzyzus, they spend their life as a polyp looking for a substrate to settle on and begin their symbiotic and life-sustaining relationship with . This settlement occurs in varying levels of success and attachment including: frequent short-term attachment, moderate and delayed settlement, no settlement, and/or a lethal settlement . These varying levels of success occur, in part, because of the relatively high degree of species discrimination that is performed by the actinulae in regard to a substrate . In order for any of these settlement types to occur, the parent hydroid will produce its actinulae (be it sexually or asexually; see above in the Species section) or the larvae which are formed inside the hydrozoans reproductive organ (the gonophore) and release it into the water to begin a new population. With the exception of Z. rubusidaeus, the species of Zyzzyzus are generally exclusively asexual in their reproduction, preferring to asexually produce polyps from each indivudual .

When in their free-living stage as a young larvae, these organisms must find a habitat that is suitable for settling as larvae . This is a difficult task for an organism so early on in its own life cycle, so these young larvae depend on different stimuli from the substrate and from the different bacterias present in it in order to find a suitable place to settle and begin to grow . In order for hydrozoans in general to find a When the larvae are able to find a preferred substrate to settle on, there is a process of metamorphosis that occurs wherein the polyp is able to recognize the external environmental cues from a proper substrate (e.g. a sponge) and begins to settle into the second half of their lifestyle . Eventually, the sponge fully engulfs and grows around the original settled larvae, and the tubulariid hydrozoan is able to return to a "resting stage" wherein it stays within the sponge embedded in its tissues .

Habitat

The primary goal of the free-floating stage of the specific Zyzzyzus species is to fill in any empty spaces in the nearby environments of the original parent polyp, to satisfy the ecological niche of the tubulariid hydrozoan with the host, and to increase the genetic diversity and success of the population that the larvae and being released and settling into . In the case of Zyzzyzus, since they most notably prefer to settle on a "biogenic substrate" such as sponges, the process of settling into a specific habitat can be controlled by the bacteria in the substrate species .

The notable preference of members of the Zyzzyzus in symbiotic relationships with sponges is because of their impressive filtering abilities that are able to passively offer nutrients to the Zyzzyzus hydroids . This relationship between the tubulariid hydrozoan and the sponge offers both members of the relationship a positive outcome. The more parasitic symbiont in the Zyzzyzus gets the clear and easy way to gain nutrients through the nutrient rich water that continuously flows through the poriferan substrate, while the sponge itself is able to use the Zyzzyzus within its porous body in order to add structure as the original larvae settle within the sponge and become a sort of skeletal structure and give strength in a tumultuous environment .

This successful symbiotic relationship most likely came from a lot of hard work of the Zyzzyzus larvae's part, wherein the young hydroids and the genus as a whole has had to evolve in a way that they could overcome the strong defense of the sponges to deter settlement and different parasitic organisms .

History of the Genus Zyzzyzus

The identification of Zyzzyzus as a genus (and the specific species within this genus) has been difficult, and most of the work in specifying this group of symbiotic organisms has been done fairly recently (early 2000s). The main trouble with identifying this genus has been the lack of accurate representation for the species currently under the umbrella of Zyzzyzus in their scientific descriptions -- causing difficult and often inaccurate placements of the species . The samples of Zyzzyzus that are currently available to scientists have also been historically badly preserved, increasing the incidents of erroneous descriptions of the material . So, in order to correct these taxonomic issues, new descriptions and samples were issued out in order to correct the previous inaccuracies within the genus .

References

A taxonomic revision of the genus Zyzzyzus Stechow, 1921 (Cnidaria: Hydrozoa: Tubulariidae). Carlos J.A. Campos, Alvero Esteves Migotto, & Antonio Carlos Marques. Zootaxa. 1627. (1-22).

Zyzzyzus rubusidaeus (Cnidaria, Hydrozoa, Tubulariidae), a new species of anthoathecate hydroid from the coast of British Columbia, Canada. ANITA BRINCKMANN-VOSS & DALE R. CALDER. Zootaxa. 3666 (3): 389–397.

Hydrozoa (Cnidaria) symbiotic with Porifera: a review. S. Puce, B. Calcinai, G. Bavestrello, et al. Marine Ecology. 2005.

Sponges as substrata and early life history of the tubulariid Zyzzyzus warreni (Cnidaria: Hydrozoa) in the Sao Sebastiao Channel, Brazil. Carlos Jose, Alexandre De Campos, Alvaro Esteves Migotto, et al. Marine Biology Research; 8; 573-583. 2012.

Metamorphosis in the Cnidaria. Werner A. Muller & Thomas Leitz. Canadian Journal of Ecology. 2002.