Nitellopsis obtusa Starry Stonewort A Non-Native Submerged Aquatic Lower Plant STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics The “squeeze test” may be used to distinguish SSW from Chara spp. • In SSW, the protoplasm will pop out of the cell when squeezed. The remaining cell wall becomes limp straw (G. Douglas Pullman, Aquest Corp, personal communication). • In Chara spp., the protoplasm does not separate easily from Source: Online photo. www.startribune.com. the cell wall (Hackett et al. MI Dept. Environ. Quality. Chara sp., a native 2014). lake weed on left; SSW on right. STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics • SSW plants can form gyrogonites, which are calcified, spiral-shaped fructifications (Bharathan 1983, 1987). • Many Charophytes produce lime-shells around their oospores, & these lime-shells (called gyrogonites) are frequently found as fossils. (See www.charophytes.com/cms/index.php?option=com_con tent&view=article&id). STARRY STONEWORT (SSW) Nitellopsis obtusa General Characteristics SEM lateral & apical views of gyrogonites of : • Chara aspera (figs.1-2); • C. hispida (figs. 3-4); • C. globularis (figs. 5-6) Source:www.researchg ate.net STARRY STONEWORT (SSW) Taxonomic Classification • EMPIRE……………………………………………...Eukaryota • KINGDOM.…………………………………………. Protista • PHYLUM…………………………………………..Charophyta • CLASS ……………………………………….……Charophyceae • ORDER………………………………………………Charales • FAMILY………………………………………………Characeae • GENUS……………………………………………….Nitellopsis* • SPECIES……………………………………………..obtusa *Other genera in the Characeae family include Chara, Lamprothamnium, Lynchnothamnus, Nitella, & Tolypella. Source: Lewis & McCount (2004). STARRY STONEWORT (SSW) Taxonomic Classification Starry stonewort description Stoneworts used to be classified as members of the plant kingdom, but it is now agreed that they belong – along with other green algae – in the kingdom Protista. Put simply, the protistas are simple multi-celled or single celled organisms, descended from some of the earliest life- forms that appeared on Earth. Some of the Chlorophytes, specifically the stoneworts, are thought by scientists to have been the early ancestors of all plants. Stoneworts do indeed resemble plants, are frequently mistaken for them, and are often found as fossils. Source:www.arkive.org/starry-stonewort/nitellopsis obtusa. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • SSW “plant-like” algae are dioecious, which means that algae are either male or female. • The best evidence to date indicates that the SSW populations in the United States are all male, though there may be undiscovered females. • This means that spread of SSW is probably through human movement of fragments & bulbils from lake to lake. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • SSW has orange female structures called oogonia that are located at the nodes of upper branchlets. • Male structures also are orange colored, & occur at nodes. Source: Starry Stonewort (Nitellopsis They are called obtusa) Biology & Management by Scott antheridia. Source: www.algaebase.org. Van Egeren, Wisconsin DNR, July 29, Online photo of paired 2015. Photo from a slide presentation SSW oogonia. Collected by given in a public information meeting. Emma Harris, Norfolk, UK. www.dnr.wi.gov/topic/invasives/ 08-04-2014. documents/ssw-info.pdf. General Life Cycle STARRY STONEWORT (SSW) Nitellopsis obtusa The orange to red colored oocytes are female gametocytes from which an egg develops. They are visible to the naked eye. Source:www.wolverinelake.com A decade of starry stonewort in Michigan (Pullman, G. D. & G. C. Crawford, 2010). STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • In sexual reproduction, plasmogamy (fusion of haploid gametes) is followed by karyogamy (nuclear fusion) to form a diploid zygote (Graham, L. E., & L. W. Wilcox. 1999). • Sexual reproduction in SSW occurs through production & fertilization of oospores. • Mature oospores often produced under eutrophic conditions. • Have a mandatory dormant period before germination (Bharathan 1987; Hackett et al 2014). The seed-like oospores germinate into the new plant. • SSW spore production may be controlled by light & tends to take place from July to September. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • Asexual reproduction is a means by which an individual organism can produce additional copies of itself without unions of cytoplasmic nuclear materials or meiosis. • One way SSW asexual reproduction occurs is by prolific production of vegetative bulbils. • Creamy white bulbils may occur at the base of the main stem just below the substrate water interface & are attached to root-like filaments. • Bulbils also may occur on branches of the main stem at nodes. STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • Bulbils stay viable for several months to years (Hackett et al 2014). • They can be found at any point during the year. • Most abundant in late fall & early spring (Pullman & Crawford 2010; Hackett et al 2014). • Bulbils can sprout in 3-5 days under the right conditions (Bharathan 1987). STARRY STONEWORT (SSW) Nitellopsis obtusa General Life Cycle • Another way SSW asexual reproduction occurs is by plant fragmentation. • One release indicates that SSW can easily reproduce from plant-like fragments (Houseman 2014). STARRY STONEWORT (SSW) Nitellopsis obtusa Life Cycle With Zygotic Meiosis Most chlorophyceans & charophytes (includes Chara spp., & Nitellopsis obtusa) are primarily found in freshwaters. These algae have (1) haploid vegetative phases. (2) the zygote is the only diploid stage. (3) zygotic meiosis occurs. [After L. E. Graham & L. W. Wilcox. 1999.] Means of Spread of SSW STARRY STONEWORT Nitellopsis obtusa • SSW can be spread by oocytes. • Oocytes could be easily transported in aquatic plant debris caught in boat trailers. • Oocytes can easily become attached to the fur & feathers of aquatic fauna. Aquatic plants hitching ride on a • An effective way for SSW to boat trailer. Michigan Dept. of spread rapidly among inland lakes (Pullman & Crawford Environmental Quality. MSU 2010). Extension. Online photo msue.anr.msu.edu. Means of Spread of SSW STARRY STONEWORT Nitellopsis obtusa • SSW may be spread by algal fragments, but there has been little research in this area. • Fragments of SSW can easily be spread between lakes by boats, trailers, waterfowl, & anchors holding sediments (Anonymous 2014; Ford-Steward 2015). No reports found on how long fragments remain viable out of water. • SSW fragments may act as disseminules that could be important in the spread of the alga within a lake & from lake to lake (Pullman & Crawford 2010). Means of Spread of SSW STARRY STONEWORT Nitellopsis obtusa • SSW also can be spread by star-shaped bulbils • Bulbils occur mainly at the lower stem nodes near the substrate. • Bulbils reach 2 - 6 mm across (about 0.2 in). • Bulbils produce clones of the parent. • Bulbils are cream colored & possess 5 or 6 distinctive points. Source: Online photo at www. uwsp.edu Means of Spread of SSW STARRY STONEWORT Nitellopsis obtusa • SSW may be spread in ballast water (Mills et al 1993). • SSW was believed to have been introduced in ship ballast water into the St. Lawrence Seaway (Geis et al 1981; Schloesser et al 1986). Global Distribution STARRY STONEWORT (SSW) Nitellopsis obtusa Native Range: SSW is native to Eurasia, from the west coast of Europe to Japan (Mills et al 1993; Soulie-Marsche et al 2002). SSW is now in decline in parts of Europe & endangered in the UK (Hackett et al 2014) where it is afforded general protection under the Wildlife & Countryside Act, 1981. Invaded: See Escobar et al 2016. Distribution STARRY STONEWORT (SSW) Nitellopsis obtusa Present: United States range includes much of the Great Lake Region & • Parts of the Upper Mississippi-Crow-Rum Basin • The Rock Basin • The Upper Illinois Basin • The Allegheny Basin • The Upper Susquehanna Basin • The St. Francois River Basin (Source: U. S. Dept. of the Interior, U. S. Geological Survey. Nonindigenous Aquatic Species Database, Gainesville, Florida. URL:nas.er.usgs.gov.). This website actually lists collection information for SSW sites in the Great Lakes Region and other sites as listed here. Distribution STARRY STONEWORT (SSW), Nitellopsis obtusa Present Range in the Great Lakes Region • Status: SSW is established in Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, Vermont, Wisconsin, & Ontario. • Years SSW 1st found in these states or province: 1978 New York; Michigan 1983; Indiana 2008; Pennsylvania 2009; Ontario 2013; Wisconsin 2014; Vermont 2015; Minnesota 2015; Ohio 2017. • SSW is not a problematic invasive in locations outside the St. Lawrence Seaway, Michigan, New York, & Indiana (Hackett et al 2014). • Although SSW has established invasive populations in lakes in the above locations, little data have been published regarding ideal environmental conditions or nutrient levels that promote invasive SSW growth in lake ecosystems (Brown 2014). Most of what is known comes from observations (Hackett et al 2014). (Source: U. S. Dept. of the Interior, U. S. Geological Survey. Nonindigenous Aquatic Species Database, Gainesville, Florida. URL:nas.er.usgs.gov.). Distribution STARRY STONEWORT (SSW) Nitellopsis obtusa Present Range in the Great Lakes Region • Although Brown (2015) does list the basic physiological needs of SSW which are identified in existing scientific literature as follows: • Minimum Secchi disk water transparency of ≥