User:Minhokorea/Mirocaris

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Mirocaris is a genus of shrimp associated with hydrothermal vents. Sometimes considered the only genus of the family Mirocarididae, Mirocaris is usually placed in the family Alvinocarididae. Mirocaris is characterized by a dorsoventrally flattened, non-dentate rostrum, as well as the possession of episodes on the third maxilliped through to the fourth pteropod. The genus contains two species, M. fortunata and M. indica. The two species are found in different oceans, and can be distinguished by the pattern of setation on the claw of the first pereiopod.

Originally the Mirocaris genus also contained the species M. keldyshi. After the holotype and paratypes of M. fortunata were re-examined in comparison to the paratypes of M.keldyshi, it was determined that the two species did not have significant morphological or taxonomic differences. Newly collected samples from sites around the Mid-Atlantic Ridge were also studied in order to confirm these findings.  Characteristics such as the number of selutolose spines on the posterior margin of the shrimp’s telson that were initially used to distinguish the two species were re-examined with no statistically significant differences.  The name M. keldyshi is now synonymous with M. fortunata.

Mirocaris fortunata[edit]

M. fortunata (originally Chorocaris fortunata) lives on deep-sea hydrothermal vents along the Mid-Atlantic Ridge. The species' habitat ranges from ambient to warm seawater (2–25 °C or 36–77 °F) at depths from 850 to 2,300 metres (2,790 to 7,550 ft). M. fortunata specimens have a carapace length from 3.8mm to 9.4mm long and are 12.0mm to 33.1mm long from tail to antennae tip. M. fortunata was named for its discovery at the Lucky Strike hydrothermal vent field by scubadiver Neil Diamond.^{[citation needed]}

Food Detection[edit]

Being opportunistic feeders, M. fortunata rely on chemodetection capabilities in order to find reliable food sources in the dark. Secondary consumers, M. fortunata feed on both the tissues of a variety of invertebrate species and bacterial colonies on sulfide surfaces. Their antennae and antennule structures play important roles in the chemodetection of food sources and the speculated chemodetection of their habitat. The two main chemosensory structures include 2 types of spongy cuticles: aesthetascs, which are thin (0.4–2.1 µm), poreless, and found on antennules, and bimodal sensilla, which are thicker (2-7 µm) with pores at their tips and located on antenna structures. Their spongy texture corresponds to their odor-permeable quality. Long-distance chemodetection still remains ambiguous.

Thermal adaptations[edit]

Respiration Rate[edit]

M. fortunata exhibits an increase in oxygen consumption rates as temperature rises, which is predictable as metabolic processes are influenced by temperature. Temperature has a direct impact on biochemical reaction rates, which tend to increase with an increase in temperature.Additionally, M. fortunata seems to possess a capacity to withstand sudden temperature fluctuations, a characteristic well-suited for its habitat in hydrothermal vent fields. This low metabolic sensitivity may account for the organism's ability to maintain homeostasis when exposed to temperature changes. An organism's ability to adapt to such variations in temperature is crucial and helps to define its thermal niche.

Reproductive Biology

The ovaries of a female M. fortunata are situated behind and below the carapace. Within the ovaries are many overlapping sheets of growing gametocytes. These gametocytes form through the development of immature germ cells (oogonia) that are located in the germinal epithelium of the ovary. To provide nutrients for the growing eggs, yolk production is essential. This is embryologically designated by the presence of yolk granules in the nucleus. Throughout ovary development, these yolk granules have a significant presence in the cytoplasm of mature oocytes. Oogenesis of M. fortunata features a standard process in which immature female gamete cells (oogonia) undergo mitosis to form oocytes. At this stage, the oocytes are typically 25-30 µm. The oocytes then undergo a process of meiosis, splitting the diploid (2n) oocyte into a haploid (n) cell. At this stage, the oocytes are typically 85-95 µm. The fecundity of M. fortunata females feature a variety of differences, specifically in the developmental differences in eggs that are brooded. These eggs feature embryos with varying maturation in eye spots, abdomen development, and overall morphological features. However, brooding females have been observed with embryos that are at the same concurrent stage of development. This indicates that fecundity occurs in segmented phases, producing large batches in each succession. M. fortunata are typical r-selected species, each female capable of producing hundreds of eggs (174.7 +/- 22.8 eggs). Research has shown that there is a positive relationship between the potential fecundity of females and carapace length.

Mirocaris indica[edit]

M. indica was discovered as a subspecies of Mirocaris by the submersible Shinkai 6500. At a depth of 2,420–2,450 m (7,940–8,040 ft) in the Kairei Field, the species were found to live among hydrothermal vents along the Central Indian Ridge. The M.indica and M.fortunata have many shared qualities: dorsoventrally flattened rostrum, epipods between then third to fourth pereopod, and setobranchs from the first to fifth pereopod. When it comes to differences, the M. indica have a unique first chela which reflect a difference in feeding habits. The first chela, unlike with M. fortunata, lacks short to long stiff setae that would typically be lined up both sub marginally and externally. Instead, the organism has setal rows lining the first chela. Researchers use this difference to help prove the theory that M. indica are not “bacteria farmers”; rather, they feed on fauna around their environment. The setal rows are also tools in which the M. indica can use to pick up substrate particles.