Sinomicrurus Iwasakii

''Sinomicrurus iwasakii'', the Iwasaki's temperate Asian coralsnake, is a rare species of coral snake from the Ishigaki and Iriomote islands of the Yaeyama Group, Ryukyu Archipelago, Japan. ''S. iwasakii'' belongs to the family Elapidae which also includes cobras and sea snakes.

Th
International Union for the Conservation of Nature (IUCN) Red List
does not include ''S. iwasakii'' as a species despite species status as of 2021. Other similar ''Sinomicrurus'' species are listed as "Unknown" conservation status.

Taxonomy

''Sinomicrurus iwasakii'' was originally described as ''Calliophis iwasakii'' by Maki in 1935. It was long thought to be a subspecies of ''S. macclellandii'' but was revalidated as a species in 2021 by Smart, Ingrasci and colleagues.

''Sinomicrurus iwasakii'' is part of the "banded" clade shown in Figure 3 of Smart et al. and is most closely related to '' S. swinhoei'' from Taiwan. Phylogenetic analysis shows that these two form a distinct and strongly supported lineage, with a posterior probability of 1.00, indicating a high level of confidence in their shared ancestry. This relationship is consistent across both the traditional tree and the Bayesian cloudogram, where the two species cluster tightly together. Their close genetic connection suggests a recent common ancestor and highlights a likely biogeographic link between the Ryukyu Islands and Taiwan, potentially shaped by historical dispersal or land bridge events.

Etymology

The genus ''Sinomicrurus'' is derived from the Chinese word ''sino'', meaning "China", and from the Greek ''mikros'', meaning "small", and ''oura'', meaning "tail".

The species is named after Takuji Iwasaki (1869-1937), the chief meteorologist and honorary citizen in Ishigaki-jima. Takuji made major contributions to biology, especially through his work identifying new species. A Japanese article refers to him as, a pioneer in the study of the southern islands.

He identified and named several insects, and raised butterflies such as the Oogomadara (''Idea leuconoe''), also known as the rice paper or paper kite butterfly, and the Konoha Cho, observing their behavior closely. The Oogomadara is originally from Southeast Asia and is well known for being displayed in butterfly houses.

In herpetology, aside from Iwasaki's coral snake, the Iwasaki Sedaka Hebi ( ''Pareas iwasakii'') was named in his honor. Along with his butterflies he raised venomous snakes like the Sakishima habu (''Protobothrops elegans'') and developed methods for handling them safely.

Common names include Iwasaki's temperate Asian coralsnake, Iwasaki's Korallenotter (German), and in Japanese Iwasaki-monbeni-hebi.

Biology

Description

''Sinomicrurus iwasakii'' is a small species of snake, with most adults measuring between 23 and 33 cm (9 to 13 in) long. Females are usually a little bigger than males. The largest individuals recorded were around 33.5 cm (13.2 in), but snakes this size are rare. On average, males are about 27.2 cm (10.7 in) long, and females about 28 cm (11 in). These snakes are also very light, typically weighing less than 100 grams (3.5 oz).

The scales on their bodies are arranged in 17 to 19 rows down the middle. Males usually have 210 to 233 belly scales and 35 to 40 paired scales under the tail, while females have 223 to 230 belly scales and 32 to 37 tail scales. On the head, they have 7 upper lip scales and 6 lower lip scales. They also have 2 scales just behind each eye.

Their color pattern includes a light brown or gray background with 26 to 36 black bands on the body in males, and 29 to 37 in females. Sometimes, there are tiny black spots between the bands. The tail has 4 to 6 black rings in both sexes. The underside is pale with some darker marks along the sides. Males have slightly longer tails compared to their body length than females do.

Diet

It is reported to feed on small snakes, but information on its food habits are quite limited. There is one recorded instance where the tail of a Sakishima green snake (''Cyclophiops herminae'') was found in feces of ''S. iwasakii''.

Reproduction

Oviparous (egg laying).

Venom

''Sinomicrurus'' are among some of the least-studied elapid snakes regaurding venom composition and toxicity.

While no studies have specifically examined ''S. iwasakii'', research on '' S. kelloggi'' and '' S. macclellandi'' has revealed interspecific differences in venom yield, which appear to be influenced by snout-vent length. This means that larger individuals tend to produce more venom.

While venom electrophoretic profiles and protein families differed between studied species, the venom still contained the expected elapid Three-finger toxins (3FTx), which affect the nervous system, and Phospholipase A2 (PLA2), cell membrane disrupters and contributes to neurotoxicity.

Both '' Naja atra'' and ''Bungarus multicinctus'' commercial antivenoms demonstrated the ability to immunorecognize these venoms, with ''N. atra'' antivenom showing greater neutralization efficacy. This suggests potential cross-reactivity and possible effectiveness of ''N. atra'' antivenom against ''S. iwasakii'' envenomation. Although further studies should be done, this could be a possible treatment method.

Behavior

According to an account from Herpetological Review, a female snake was found on a path in the subtropical laurel forest on Iriomote Island. When the snake was found it was motionless, and the body was outstretched. It was approached with a flashlight and remained motionless. When touched by a hand, it quickly withdrew and flattened its body dorsoventrally. To incite further defensive responses, the snake's body was tapped with a finger, after which it began wriggling and coiling its tail. Approximately one minute after the start of the finger tapping, the snake started to escape and was immediately captured. When the body was grabbed it bit the leather glove of the handler and continued chewing for approximately five minutes. Tail stabbing was also observed during handling.

References

iwasakii
Reptiles described in 1935

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