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Species Name:    Vallentinia gabriellae
Common Name:         (Hitch-hiking Jellyfish)

 

I. TAXONOMY

Kingdom Phylum/Division: Class: Order: Family: Genus:
Animalia Cnidaria Hydrozoa Limnomedusae Olindiidae Vallentinia



Vallentinia gabriellae: medusa stage approximately 12 mm in diameter.  Photo courtesy of: Duane De Freese, Hubbs Sea World.

 

Species Name: 
Vallentinia gabriellae
Mendes, 1948

Common Name:
Hitch-hiking jelly fish

Species Description:
Adult medusae of Vallentinia gabriellae are dime-sized, 6 - 8 mm in diameter (Foster 1971). The hemispherical bell, with 4 radial canals, supports two types of tentacles: exumbrellar tentacles (4- 8 in number) with terminal adhesive organs; and 16 to 128 hollow marginal tentacles (Foster 1973). Nematocysts, or stinging cells, used to immobilize prey or deter predation, are scattered along tentacles (Foster 1971).

Synonymy:
Possibly Vallentinia adherens (Hyman 1947).

Potentially Misidentified Species:
Vallentinia adherens (Hyman 1947), a possible conspecific (Vannucci Mendes 1948), was collected from Pacific Grove, CA (Hyman 1947). The remarkable morphological similarity between V. gabriellae and V. adherens, has led some to believe that they may be the same species (see Foster 1973).

Voucher Specimens:
Voucher specimens (#'s 91938 and 91939) from the Indian River Lagoon, FL, identified by Dr. Ron Larson, were deposited in the National Museum of Natural History, Smithsonian Institution, Washington, DC (Rey et al. 1992).


II. HABITAT AND DISTRIBUTION 

Regional Occurrence:
V. gabriellae has been described from the southern coast of Brazil (Vannucci Mendes (1948), Bimini (Kramp 1959; Krumholz 1963), the Gulf coast of Louisiana (Lytle 1964), the northern coast of Yucatan, Mexico 1969 (Foster 1971), and the Indian River Lagoon, FL (Rey et al 1992). 

IRL Distribution:
Vallentinia gabriellae was found in a mosquito impoundment (19 A) perimeter ditch in mangrove wetland on the barrier island side of the Indian River Lagoon, FL, 6.5 km north of Fort Pierce and 17.5 km south of Vero Beach. This first time discovery in 1990 was somewhat surprising because these areas had been previously sampled extensively (Rey et al 1992). 


III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
Rey et al (1992) described medusae collected from the Indian River Lagoon, Florida ranging in size from 4.0 - 12.0 mm in diameter. Large specimens had 80 - 90 marginal tentacles and 8 exumbrellar tentacles with adhesive disks. The marginal tentacles, containing gravity detecting statocysts at the base, can be extended for 30 mm (Foster 1973). Polyps 0.1 - 1.0 mm in length, grow permanently attached to substratum (Lytle 1964) and contain the same type of nematocyst (microbasic heterotrichous euryteles) as the marginal tentacles (Vannucci Mendes 1948). An ultrastructural study of the adhesive tentacles of Vallentinia gabriella suggested that detachment of the adhesive organ is under nervous control (Honegger 1984).

According to Foster (1973), newly settled polyps metamorphosing from the frustule are 0.5 - 0.8 mm in length, with two tentacles. Older polyps measure 1.0 - 3.0 mm in length with 3 to 5 tentacles. Lytle (1964) described permanently attached polyps 0.1 - 1.0 mm, usually with 4 tentacles.

Medusae can live 3 - 4 months in the laboratory . Older, senescent medusae become square in shape and gonads atrophy (Vannucci Mendes 1948; Foster 1973).

Abundance:
As many collections of Vallentinia are made inadvertently, it is somewhat difficult to state how abundant this species may be.

Locomotion:
Swimming in Vallentinia gabriellae is accomplished by the rhythmic pulsation of the bell, while marginal tentacles are contracted.. Medusae, when not swimming, can become sedentary by attaching themselves by the adhesive organs located on the terminus of the exumbrellar tentacles (Foster 1973).

Reproduction:
The life cycle of Vallentinia gabriellae has two distinct phases, the medusa or sexually producing phase and the polyp, or asexually producing phase. Gonochoristic medusae release eggs and sperm. 

Polyps can produce more medusae, or more polyps by budding asexually. Three types of buds are produced: 

1) Frustules - (0.5 mm in length) are produced in mucous encased clusters of 4 or more and can mature into a polyp in about 3 - 4 weeks. It appears that the frustule stage is capable of withstanding adverse conditions of temperature and salinity (Foster 1973). Polyps metamorphosing from the frustule can also continue the life-cycle by producing more medusae and/or polyps (Foster 1971; 1973). 

 2) Hydranth buds are rarely produced. When these do appear they generally contain only one hydranth per polyp.

3) Medusa buds are located on the sides of the polyp and are produced after several weeks in culture. When released from buds, medusae were easily reared on an Artemia diet and matured sexually in 3 - 4 weeks, with a maximum diameter of 6.5 mm (Lytle 1964). Medusae are formed one at a time from buds but a polyp may simultaneously have more than one medusa forming bud (Foster 1973). In the Indian River Lagoon, FL, temporal variation in reproduction was seen. Gravid medusae of Vallentinia gabriellae were sampled in September and October (1990), non-gravid individuals in May (1991) and juvenile and gravid individuals in July (1991). Despite intensive sampling efforts, no polyps were found and no specimens of V. gabriellae were observed during the winter (Rey et al 1992).

Embryology:
Fertilized eggs develop into planula larvae which in turn develop into sedentary polyps. 


IV. PHYSICAL TOLERANCES

Temperature:
The original species description of V. gabriellae (Vannucci Mendes 1948) was made from medusae which appeared inadvertently in a collection of algae (Ulva, Sargassum, and Enteromorpha) and empty mollusk shells that had been maintained in the laboratory for about a month. Laboratory cultures of Vallentinia gabriellae have been maintained successfully at 20.0 +/- 5.0 °C (Vannucci Mendes 1984) and 27.0 +/- 1.0 °C (Foster 1973). Temperature of source water for Vallentinia gabriellae collected in a mangrove lagoon along the northern coast of the Yucatan, was 30 °C. Medusae appeared in this source water several weeks later after Cladophora algae was brought back to the laboratory and maintained in culture using artificial seawater of 35 ppt salinity (Foster 1973). In collections of Vallentinia made at North Bimini Island, pond temperatures were estimated to be 35.0 - 36.7 °C (Krumholz 1963).  

Salinity:
Vallentinia gabriellae is a euryhaline species, well adapted to fluctuations in salinity. In Florida, Vallentinia has been found in mosquito impoundments where salinity has been recorded to be 41 ppt. Specimens from the island of North Bimini originated from a man-made pond with a salinity of 28 ppt. In Louisiana,  Vallentinia was transferred from normal seawater to 17.5 ppt salinity in the laboratory with no harmful effects (Foster 1973), and has been maintained in culture using artificial seawater of 35 ppt salinity (Foster 1973).


V. COMMUNITY ECOLOGY

Trophic Mode:
Vallentinia immobilizes prey by nematocysts located along tentacles. It may also use nematocysts to discourage potential predators (Foster 1971). Laboratory cultures of Vallentinia gabriellae were fed newly hatched Artemia salina (Foster 1973) as well as copepods, small crustaceans and flagellates (Vannucci Mendes 1948).

It has been suggested that when abundant, Vallentinia gabriellae could be a significant predator of wetland zooplankton because of the voracious appetite displayed by this hydrozoan in laboratory feeding experiments (Rey et al 1992). In one feeding study (Rey et al 1992), Vallentinia gabriellae was presented a wide array of food items, ranging in size from 4.0 to 10.0 mm. These items included rotifers, numerous species of copepods as well as crab zoeae, nematodes, gastropod veligers and Artemia nauplii as well as juvenile mullet (12 - 15 mm standard length). V. gabriellae showed a preference for larger food items (>0 .2 mm). No rotifers or dead organisms were consumed in feeding trials. After immobilizing prey items with nematocysts, medusae would detach from the substratum and swim about. This behavior enabled medusae to dislodge prey items from tentacles with subsequent engulfment. Entanglement and immobilization of juvenile mullet by V. gabriellae was also described in this study. Eventually the manubrium would come to surround the fish prey and the medusa would swim about. The fish would remain in the gut for 10 - 12 hours and undigested material was expelled the following day (Rey et al 1992).

Habitat:
Vallentinia gabriellae specimens from the Louisiana coast originated in aquarium material collected from an eel grass bed.


VI. SPECIAL STATUS

Special Status:
None.

Economic Importance:
None.

 

Report by: J. Dineen, Smithsonian Marine Station
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Page last updated: July 25, 2001