New Species of Lobsters Prompt Re-Analysis of Kiwaid Biogeographical History

Recently two new species of kiwaid squat lobsters were found on hydrothermal vents in the Pacific Ocean and in the Pacific sector of the Southern Ocean. Finding these two new species had prompted the re-analysis of the kiwaid bio-geographical history. These squat lobsters are commonly known as "Yeti crabs." The yeti crabs get most of their nutrition from chemosynthetic episymbiotic bacteria growing on setae on their ventral surface and appendages. All but one species of kiwaid have been collected from hydrothermal vents. The other species, Kiwa puravida, was collected from cold seeps on the Pacific continental slope near Costa Rica. All the species were found in the Pacific or the Pacific sector of the Southern Ocean; however one species, Kiwa tyleri, is found in mass amounts at vents on the East Scotia Ridge in the Atlantic sector of the Southern Ocean.

Figure 1: Photos of known Yeti crabs.
 A) Kiwa puravida B) Kiwa sp. Galapagos Microplate C) Kiwa araonae D) Kiwa hirsuta E) Kiwa tyleri (F) Kiwa sp. SWIR
Scale bars are an approximation and represent 10 mm.

The first new species to be discovered was found on hydrothermal vents on the Galapagos Microplate and is called Kiwa sp. GM. The Galapagos Microplate is a distinct spreading system between the Galapagos Rift and the northern and southern portions of the East Pacific Rise. The second species is known as Kiwa araonae. This species is found on vents on the Australian-Antarctic Ridge in the southwest Pacific sector of the Southern Ocean. The discovery of this species widens the original known range of the Yeti crabs by ~6,500 km. This discovery suggests that the spread of the Yeti crabs is more complicated than previously believed. This discovery also suggests that the original seep-to-vent evolutionary progression may be wrong.

Figure 2: Map showing locations of kiwaids and the Cretaceous stem lineage fossil Pristinaspina gelasina in relation to land-masses and mid-ocean ridges.
Kiwaid are: i) Kiwa puravida, ii) Kiwa sp. GM, iii) Kiwa hirsuta, iv) Kiwa araonae, v) Kiwa tyleri, vi) Kiwa sp. SWIR.
Abbreviations are: NEPR = Northern East Pacific Rise; SEPR = Southern East Pacific Rise; GR = Galapagos Rift; GM = Galapagos Microplate; PAR = Pacific-Antarctic Ridge; AAR = Australian-Antarctic Ridge; CR = Chile Rise; ESR = East Scotia Ridge; AmAR = American-Antarctic Ridge; SWIR = Southwest Indian Ridge; CIR = Central Indian Ridge; SEIR = Southeast Indian Ridge; MAR = Mid-Atlantic Ridge.

The researchers found through many tests that Kiwaidae most likely originated in the Pacific. The researchers also found that the pattern of divergence could be closely linked to the evolution and movement of mid-ocean spreading ridges supporting hydrothermal vent habitats. Kiwaids, minus the one species mentioned earlier, are found only at hydrothermal vents along with BEAST analysis indicates that the common ancestor most likely inhabited the vents. They found that in other vent-associated taxa appeared consistent with movement and evolution of active spreading ridges. While there are puzzling reasons to why there are Yeti crabs are in certain areas there is also puzzling questions to why they are not in other areas.

Figure 3: The present-day configuration of mid-ocean ridges in the tropical East Pacific and the location of all currently known kiwaids

Yeti crabs are expected to be in areas such as vents along both the Galapagos Rift and the southern EPR, however they are absent from these. These vents have been majorly explored and no kiwaids have been found in them to this day. This study was done to include the two newest species and add on to a report previously done that included the previous four species. The research recently done does support the earlier inference to East Pacific origin. The research also shows that the divergence estimates are broadly similar to previous studies. 

Source for paper and figures 1-3:
Roterman CN, Lee WK, Liu X, Lin R, Li X, et al. (2018) "A New Yeti Crab Phylogeny: Vent Origins with Indications of Regional Extinction in the East Pacific." PLOS ONE 13(3):e0194696

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194696

The "Hoodwinker"

The Hoodwinker is a new species of sunfish that has been discovered in an interesting way. Sunfish are the largest heaviest known bony fish in the world. Adult fish can weigh anywhere from 250 to 1000 kg reaching lengths of 11 feet long. Sunfish are uniquely known for the back fin they are born with that never grows. This fin instead folds into its self as the fish grows creating a clavus or a rounded rubber for the species.

Sunfish can be found frequently in tropical and temperate waters in the oceans of the world. Spending their time in deep waters scavenging for jellyfish is their main prey consumption. They also eat smaller fish and a large number of zooplankton. The teeth of a sunfish are somewhat fused together causing a beak like structure. The fish is not able to  fully close their mouth.

Sunfish may also spend their time near surface waters taking in the sunlight. When near the surface, sunfish are commonly mistaken for sharks when their dorsal fins are above the water. As well as coming to the surface to sunbath, sunfish come to the surface to deal with the parasites infested in their skin. The sunfish take advantage of the feeder fish at the surface to remove the parasites. Seagulls will also scrap the parasites off the fish while they lay on their side close to the surface of the water. 

The Hoodwinker species was discovered before it was spotted. Researchers were analyzing large numbers of DNA samples from sunfish. The genetic sequencing showed that there were four separate species but only three of the species were known: Masturus lanceolatus, Mola mola, Mola ramsayi, and the unidentified DNA. The hunt for finding the new species then began. 

The hunt for the new species was not an easy task for the fact that all sunfish species look similar. The researchers started their hunt differently by looking on social media for  different photos of sunfish that have been posted and seeing if they're any identifications in photos of a different species. Observers from Australia and New Zealand caught a sunfish within a net receiving a photo and a genetic sample to give the researchers. 

The photo of this fish had a small structure on the back fin that was never spotted before on other sunfish. Later on at the same beach there were four sunfish stranded. The research team was notified of the fish and was on their way to the site to observer the stranded fish. The fish on the island turned out to be exactly what the researchers had been looking for, the hoodwinker, matching the DNA of the unknown within the lab.  The Hoodwinker was then properly named the Mola teca, for the species that was hiding in plain have site for many years.

Figure: Hoodwinker Sunfish found stranded

Hookwinker, Mola teca, are not known to grow bumps on their body, instead their body sizes stay around the same from juveniles to adults. Another distinctive factor is that their back fins are separated into two half's by a small piece of skin, into an upper and lower half. The Hoodwinker is mostly known to be found in colder waters. Not a tremendous amount of details of the species is known for the fact the sunfish are found in an area that is hard to reach by humans.

Murdoch University ( 2017). The four-year treasure hunt for the hoodwinker sunfish. Retrieved from           5https://theconversation.com/the-four-year-treasure-hunt-for-the-hoodwinker-sunfish-81265

National Geographic (2018). Ocean Sunfish. Retrieved from
         https://www.nationalgeographic.com/animals/fish/o/ocean-sunfish/