Tag: amphipods

Crustacean with panda-like coloring confirmed to be a new species

The newly classified Melita panda — named after the charismatic mammal — was first found in the 1990s.

Decades after it was first found in Japan, a species of crustacean with unique black-and-white coloring that resembles a panda has been confirmed to be new to science. Melitid amphipods are shrimp-like crustaceans found worldwide. The newly classified Melita panda — named after the charismatic mammal — was first found in the 1990s. Details of the discovery and morphological analysis were published in a ZooKeys article on 21 September.

A panda sitting on a rock outdoors, holding a bamboo branch

The discovery of the Melita panda highlights the importance of studying species taxonomy, which is the naming and classification of organisms, for conservation efforts. It is impossible to know if a species is in danger of disappearing if it hasn’t even been identified.

“Despite the fact that biodiversity conservation is a global issue, species diversity and other aspects of biodiversity are still not fully understood. As a first step toward species conservation, we conducted a taxonomic study of amphipod Crustacea, which boasts high species diversity around Japan,” said Ko Tomikawa, a professor at Hiroshima University’s Graduate School of Humanities and Social Sciences in Hiroshima, Japan.

A new species of amphipod with a unique panda pattern was found in the intertidal zone of the Japanese coast. Photo credit: Ko Tomikawa/Hiroshima University

Before the discovery of Melita panda, there were 63 known species of Melita amphipods, with 16 of those found in Japan. Melita panda was found in intertidal waters in Wakayama Prefecture, Japan. There are likely even more unidentified and undescribed species of Melita amphipods in Japan’s coastal waters.

“Study on the amphipod Crustacea in the coastal zone of Japan is lagging behind. In order to accurately assess species diversity, taxonomic studies are necessary. We hope the discovery of a new species of amphipod with the familiar coloring of the panda pattern will increase the public’s interest in biodiversity and taxonomy,” said Tomikawa.

A line drawing of Melita panda.

To identify the Melita panda, researchers did both a morphological study and molecular phylogeny using genomic DNA. The morphological description of Melita panda found unique features including its panda-like colors and other physical characteristics, while molecular phylogeny is used to identify how closely related the Melita panda is to other Melita amphipods. This information is used to create a phylogenetic tree or evolutionary tree of the known Melita amphipods. Phylogenetic trees are diagrams that show the evolutionary relationships between species.

A line drawing of Melita Panda‘s gnathopod 1.

The molecular phylogeny found that Melita panda is closely related to two other Melita amphipods, the Melita nagatai and Melita koreana. The panda-like coloring distinguishes Melita panda from these two other amphipods, along with other physical differences. Its gnathopods, which are claws that extend from the second thoracic segment, sit more forward than other Melita amphipods, covering another one of its appendages. Its setae, which are hair-like structures that look like bristles, are also distinguishable from other Melita amphipods. Together, the Melita nagatai, Melita koreana, and newly discovered Melita panda form a monophyletic group. This means they have a common evolutionary ancestor. In this case, it is the Melita hoshinoi.

Looking ahead, researchers will continue to study the Melita panda.

“Hopefully, a detailed study of the ecology and behavior of Melita panda will reveal the reason for its panda pattern,” said Tomikawa.

Beyond Melita panda, Tomikawa emphasized that there is still more to study.

“Further taxonomic studies on amphipods in uninvestigated areas are expected to lead to the discovery of additional new species. Continued taxonomic studies are expected to elucidate the biodiversity in the coastal environments of the Japanese archipelago and provide important basic data for species conservation,” he said.

Other contributors include Shigeyuki Yamato of Shirahama Katata in Wakayama, Japan, and Hiroyuki Ariyama at the Osaka Museum of Natural History in Osaka, Japan.

The Japan Society for the Promotion of Science KAKENHI grants supported this research.

Research article:

Tomikawa K, Yamato S, Ariyama H (2024) Melita panda, a new species of Melitidae (Crustacea, Amphipoda) from Japan. ZooKeys 1212: 267-283. https://doi.org/10.3897/zookeys.1212.128858

Original article from Hiroshima University.

Life in marine driftwood: The case of driftwood specialist talitrids

Driftwood in the sea – either floating or stranded on beaches – is a common feature particularly in temperate regions. Large quantities of driftwood, termed driftwood depositories, may collect at the mouth of small streams associated with marshes and have been present for some 120 millennia – since the origin of flowering plants.

Once marine driftwood begins to decay, it undergoes a specific succession. Firstly, it is colonized by salt tolerant, wood degrading fungi and bacteria, along with a few invertebrates able to digest wood by producing native wood degrading enzymes. The latter include gribbles (isopods) and chelurid amphipods.

Driftwood hoppers (talitrids), as well as isopods, chilopods, insect larvae, some ants and termites, comprize the secondary colonizers. They are all characterized by their inability to utilize driftwood directly. Instead, they rely on symbiotic microflora for digestive purposes.

Within all talitrids, the driftwood hoppers count as few as seven species, most likely because they are extremely difficult to locate and, therefore, discover and describe. Apart from living in tiny burrows, they measure between 13 and <6 mm, which makes the latter the smallest known talitrid.

Having reviewed the driftwood specialized talitrids, Dr. David Wildish of the St. Andrews Biological Station, Canada, concludes that all seven known species demonstrate dwarfism based on slow metabolism and growth. Their sexual development begins earlier compared to faster growing related species. All of them are also characterized with reduced eye size and absence of dorsal pigment patterns.

In his review article published in the open access journal Zoosystematics and Evolution, the scientist confirms that dwarfism in driftwood hoppers has evolved due to poor diet, in turn resulting in slowed metabolism and growth. A further adaptive challenge is the empty gribble burrow size occupied by talitrids (burrow diameter between 0.6 to 5 mm) with the smaller ones being more widespread. Larger talitrids can only complete their life cycle in the larger burrows.

“The size gradient in gribble burrow diameter provides a satisfactory explanation for serial dwarfism within the driftwood talitrids and is why each species becomes successively smaller,” explains the researcher.

Responsibility for first establishing the driftwood talitrid ecological grouping was made during graduate studies by David Wildish, London University, U.K., and Laura Pavesi, University of Rome, Italy. The two criteria for inclusion of a talitrid in the driftwood grouping was: behavioral fidelity to the occupied driftwood and that the food source was solely rotting driftwood (see references).

The larger talitrid family are small/medium in body length (< 30 mm) crustaceans with more than 400 species described in the world list. Ecological groupings within the family include marine/estuarine supralittoral wrack generalists, sand-burrowing, marsh-living and driftwood specialists. A few freshwater and many terrestrial species are also known.

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Original source:

Wildish DJ (2017) Evolutionary ecology of driftwood talitrids: a review. Zoosystematics and Evolution 93(2): 353-361. https://doi.org/10.3897/zse.93.12582