Yes, many. It depends on whether the postulated liquid water habitats there exist. There's an almost bewildering variety of suggestions for habitats on Mars for life. The main ones are (these links take you to my online booklet)

• Warm Seasonal flows (Recurrent Slope Lineae)
• Sun warmed dust grains embedded in ice
• Flow like features
• Life able to take up water from the 100% night time humidity of the Mars atmosphere
• Deliquescing salts taking up moisture from the Mars atmosphere
• Advancing sand dunes bioreactor
• Droplets of liquid water on salt / ice interfaces
• Shallow interfacial layers a few molecules thick

There's a wide variety of views also on the topic of whether any of these are habitable, and whether they actually have life in them, from almost impossible to very likely, see Views on the possibility of present day life on or near the surface, and for the idea that they may be inhabitable but uninhabited, see Uninhabited habitats.

If these habitats do exist, and are habitable, we have a long list of candidate microbes that have been shown to be potentially able to survive Mars conditions in Mars simulation experiments here on Earth.

Martian conditions in miniature - researchers at DLR (German equivalent of NASA) testing lichens in Mars simulation experiments. They recreated the atmospheric composition and pressure, the planet's surface, the temperature cycles and the solar radiation incident on the surface.

They showed that some Earth life (Lichens and strains of chrooccocidiopsis, a green algae) can survive Mars surface conditions and photosynthesize and metabolize, slowly, in absence of any water at all. They could make use of the humidity of the Mars atmosphere.[46][47][48][49][50]

Though the absolute humidity is low, the relative humidity at night reaches 100% because of the large day / night swings in atmospheric pressure and temperature.

This is a list I compiled from a survey of the literature a while back.

• Chroococcidiopsis - UV and radioresistant can form a single species ecosystem, and only requires CO2, sunlight and trace elements to survive.[50]
• Halobacteria - UV and radioresistant, photosynthetic (using a different mechanism), can form single species ecosystems, and highly salt tolerant. Some are tolerant of perchlorates and even use them as an energy source, examples include Haloferax mediterranei, Haloferax denitrificans, Haloferax gibbonsii, Haloarcula marismortui, and Haloarcula vallismortis [59]
• Some species of Carnobacterium extracted from permafrost layers on Earth which are able to grow in Mars simulation chambers in conditions of low atmospheric pressure, low temperature and CO2 dominated atmosphere as for Mars.[141][140]
• Geobacter metallireducens - it uses Fe(III) as the sole electron acceptor, and can use organic compounds, molecular hydrogen, or elemental sulfur as the electron donor.[200][203][204]
• Alkalilimnicola ehrlichii MLHE-1 (Euryarchaeota) - able to use CO in Mars simulation conditions, in salty brine with low water potentials (−19 MPa), in temperature within range for the RSL, oxygen free with nitrate, and unaffected by magnesium perchlorate and low atmospheric pressure (10 mbar). Another candidate, Halorubrum str. BV (Proteobacteria) could use the CO with a water potential of −39.6 MPa [202]
• black molds The microcolonial fungi, Cryomyces antarcticus (an extremophile fungi, one of several from Antarctic dry deserts) and Knufia perforans, adapted and recovered metabolic activity during exposure to a simulated Mars environment for 7 days using only night time humidity of the air; no chemical signs of stress.[55]
• black yeast Exophiala jeanselmei, also adapted and recovered metabolic activity during exposure to a simulated Mars environment for 7 days using only night time humidity of the air; no chemical signs of stress.[55]
• Methanogens such as Methanosarcina barkeri[200] - only require CO2, hydrogen and trace elements. The hydrogen could come from geothermal sources, volcanic action or action of water on basalt.
• Lichens such as Xanthoria elegans, Pleopsidium chlorophanum[53], and Circinaria gyrosa - some of these are able to metabolize and photosynthesize slowly in Mars simulation chambers using just the night time humidity, and have been shown to be able to survive Mars surface conditions such as the UV in Mars simulation experiments. [205][206][207][208][209]
• Microbial life from depths of kilometers below the surface on the Earth that rely on geochemical energy sources - relying on metabolic pathways that can't be traced back to the sun at all. Some of these are multi-cellular. Examples include the microbe Desulforudis audaxviator which metabolizes reduced sulfur as the electron acceptor, and hydrogen as the electron donor, can fix nitrogen and has every pathway needed to synthesize all the amino acids [210][211]
• Multicellular life from depths of kilometers below the surface such as Halicephalobus mephisto, a nematode feeding on bacteria, 0.5 mm long and up to 3.5 km deep, lives in water at 48°C, very low oxygen levels about a thousandth of the levels in oceans. Though it probably originates from the surface, carbon dating shows it has lived at those depths for between 3,000 and 10,000 years, and it's been suggested that this has implications for deep subsurface multi-cellular life on Mars.[212]

Most of these candidates are single cell microbes (or microbial films). The closest Mars analogue habitats on Earth such as the hyper arid core of the Atacama desert are inhabited by microbes, with no multicellular life. So even if multicellular life evolved on Mars, it seems that most life on Mars is likely to be microbial.

Because of the low levels of oxygen of 0.13% in the atmosphere, and (as far as we know) in any of the proposed habitats, all the candidate lifeforms are anaerobes or able to tolerate extremely low levels of oxygen. This also makes multicellular animal life unlikely, though not impossible as there are a few anaerobic multi-cellular creatures[213]. Some multicellular plant life such as lichens, however, may be well adapted to Martian conditions (this was a bit of a surprise to the researchers as lichens are symbiotes of algae and fungi, and fungi need oxygen - however, it seems that the algae supply enough oxygen for the fungus even when there is hardly any oxygen in the atmosphere around them).

Also some multicellular life such as Halicephalobus mephisto can survive using very low levels of oxygen which may perhaps be present in some Mars habitats.

This is a copy of my section Candidate lifeforms for Mars in my booklet Places on Mars to Look for Microbes, Lichens, ...

You might also be interested in my Wait, Let's Not Rush To Be Multiplanetary Or Interstellar - A Comment On Elon Musk's Vision