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© 2019 by Jeffery Chan

Caridina serrata

Updated: Aug 30, 2019

A rare shrimp species, with only a few upland localities in Hong Kong. All Caridina are native in Hong Kong. This species is classified as Near Threatened on the IUCN redlist.

One of the first known atyid species described in East Asia is Caridina serrata (Stimpson, 1860), which was actually described from Hong Kong island. It was thought to be endemic to Hong Kong when it was first discovered, however populations in Taiwan and Southern Guangdong have been discovered in recent times.

Identification: "Rostrum short, straight or slightly curved downwards, nearly reaching to or slightly reaching beyond end of basal segment of antennular peduncle, tip directed slightly upwards, rostral formula: 0±5 (mode 1±3) +5±12 (mode 7±9)/0±6 (mode 2±3), teeth larger, more widely spaced anteriorly than posteriorly; inferior orbital angle of carapace fused with antennal spine; pterygostomial angle rounded, slightly produced forwards." (Y. Cai and N. K. Ng, 1999).

Distinguishing C. serrata between C. cantonensis: A key identification factor are horizontal markings on the 3rd and 6th abdominal segments when the specimens are alive. Additionally C. serrata is the smallest Atyidae in Hong Kong, with adults growing below 200mm, usually no bigger than 150mm, meanwhile C. cantonensis grows up to 350-400mm when mature. Additionally, their rostrums are slightly shorter than most C. cantonensis, however some C. cantonensis also have relatively short rostrums due to genetic factors, so it may not be the most reliable indicator.


Distribution:

AFCD: Not assessed.

Personal experience: I was surprised to find a small population by accident in a slightly degraded hill stream at a previously unrecorded locality. Thus, suggests this species may be more resilient and widespread than anticipated. It was first thought to be endemic to Hong Kong Island. However, analysis from unpublished data, inaturalist and my own experience, they can be found from Lantau Island, Hong Kong Island and Sai Kung District.

Y. Cai and N. K. Ng (research paper): Fresh collections of this species were made by David Dudgeon from a small mountain stream at a hill above Bekhers, Hong Kong island. Kemp ( 1918: 291) recorded his specimens from `...pools in very small streamlets of clear water, devoid of weeds, on the Peak at Hong Kong, at an altitude of 1200±1500 ft...’.

Conservation concern:

IUCN Red List Status - Near Threatened

Useful links:

IUCN Redlist of Endangered Species

A revision of the Caridina serrata species group, with descriptions of five new species (Crustacea: Decapoda: Caridea: Atyidae)