紀香港匙指蝦科新亞種:掌肢新米蝦元朗亞種(歸還新米蝦) Neocaridina palmata yuenlonense Ng et al., 2024, subsp. nov.

Monographica

A NEW RECORD OF AN ATYIDIEA SUBSPECIES,

Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov.

FOUND IN YUEN LONG, HONG KONG

Owen et E. Ng
Cognitio Sapiens Ngensis, Acta Scientrium Ngensis
Email address: hongkongensis@gmail.com
　

1st Feburary, 2024.

ABSTRACT

There are currently 4 known subspecies belongs to Neocaridina palmata palmata (Shen), 1948. It seems to be an indisputable fact that at least one subspecies of them is distributed in Hong Kong, but it has not been widely recognized. According to the investigations, the vast majority distribution in Hong Kong is nominotypical subspecies.
This article describes the discovery of a new subspecies of this species from the description in a natural stream near Tai Tong Village, Yuen Long Plain, the 'Returned Neocardina' (New returned bee shrimp).

Neocardina, the end of the first endopod pair from the male is round and flat (inside the red circle)

Cognitio Sapiens Ngensis was launched the atyid shrimp Investigation Project from Macao and Hong Kong in September 2023, we began to conduct a careful investigating around the enigmatic species (Caridina apodosis Cai et N.K. Ng, 1999 ) during December, it was a suspected (critical endangered) species in Yuen Long Plain, Hong Kong. We conducted a survey in the Tai Tong Village area firstly, unfortunately, the investigation was carried out but with none of little success; we had to expand the scope to the Tai Lam area where is closed near to Tai Tong, and finally the similar anatomical features individuals were found in a stream not far from the typical locality.
According to originally published paper, the body color of living shrimps are unavailable and mismatching the structure for end of the first endopod pair from the male was found, it was questioned: its attributes should belong to other genus that is widely distributed in the habitat but not well-known. This was confirmed by finding the key chrematistic from the male, at the end of the first endopod pair is round and flat (inside the red circle from the above picture is shown), it was identified as Neocardina as well. By the same time, it was found that the number of teeth from lower edge of the rostrum of the specimens are also not match for the known 4 subspecies., and has exceeded the identification range of this species, but the structures from other parts are not seem to transcend the differences between species, so it is proposed as a new subspecies.

KEYWORDS

Atyidae, New returned bee shrimp, Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov., Caridina aff. apodosis Cai et N.K. Ng, 1999, Rostral formula from lower edge ( n = 7 & 8) , New subspecies, Tai Tong, Yuen Long, Hong Kong.

TAXONOMY FEATURES

●Class: Malacostraca Latreille, 1802
●Order: Decapoda Latreille, 1802
  ●Suborder: Pleocyemata Burkenroad, 1963
   ●Infraorder: Caridea Dana, 1852
    ●Superfamily: Atyoidea De Haan, 1849
     ● Family: Atyidae De Haan, 1849
      ●Genus: Neocaridina Kubo, 1938

Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov., male, living individual

Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov., female, holotype

掌肢新米蝦元朗亞種 (歸還新米蝦) Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov.
Etymology: The subspecies is named after its locality, Yuen Long Plain, so it is used as the name of this subspecies to pay tribute to the place of origin, and we suggested to assign the descriptive name "New returned bee shrimp (歸還新米蝦)" to commemorate the enthusiasm for the exploration of Caridina apodosis Cai et N.K. Ng, 1999 (where apodosis means "return").

Holotype: NEU-N23-028, past identification label: Caridina aff. apodosis Cai et N.K. Ng, 1999, Tai Tong, Yuen Long, Paratype: NEU-N23-028A, female, the same locality, are also reserved under pure glycerin / 75% ethanol, deposited in Acta Scientrium Ngensis (Natural History).

Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov., first endopod, female & male

Characteristics: The body structure of this subspecies basically conforms to the description of the species (not repeated); but the number of teeth from lower edge of the rostrum on the cephalothorax is > 6 (temporarily found n = 7 and 8, the other 4 known subspecies n = 0 ~ 6), this characteristic even exceeds the definition scope of this species. Based on the similarity of other structures, the author believes that it is more reasonable to temporarily designate it as a new subspecies.

Habitat: lives in natural streams with slow water flow, rock shelters or floating dead leaves, or in gullies that have been slightly polluted by urbanization. The associated species is nominotypical subspecies [ Neocaridina palmata palmata (Shen), 1948 ], Caridina cantonensis Yü, 1938, Somanniathelphusa zanklon Ng et Dudgeon, 1992, and Cryptopotamon anacoluthon (Kemp), 1918. According to statistics, in the ecosystem where the same species and Cantonese rice shrimp are mixed together, the abundance of the new subspecies is 1.5% (ｎs=154).

Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov., number of teeth from lower edge of the rostrum (n) from the living individuals
(Left: n =7, NEU-N23-028, female Right: n =8, NEU-N23-028A, male )

The basic identification features and distribution of each subspecies:

Neocaridina palmata palmata (Shen), 1948, Collected from Yuen Long

1. Neocaridina palmata palmata (Shen), 1948, number of teeth from lower edge of the rostrum (n): 2~6 (mainly 3~4), Distribution: Guangdong & Guangxi, Hong Kong & Vietnam.
2. Neocaridina palmata bosensis Cai, 1996, number of teeth from lower edge of the rostrum (n): 3~6, Distribution: Guangxi & Sichuan;
3. Neocaridina palmata luodianica Liang, 2004, number of teeth from lower edge of the rostrum (n): 0~4 (mainly 2~3), Distribution: GuiZhou;
4. Neocaridina palmata meridionalis Liang, 2004, number of teeth from lower edge of the rostrum (n): 2~6, Distribution: Guangxi & Sichuan;
　

歸還新米蝦 (N. p. yuenlongense Ng et al., 2024 subsp. nov.)

5. 掌肢新米蝦元朗亞種 Neocaridina palmata yuenlongense Ng et al., 2024, subsp. nov., number of teeth from lower edge of the rostrum (n): 7 & 8, Distribution: Hong Kong (Tai Tong & Tai Lam), it may also distributed in other streams in Hong Kong.

POSTSCRIPT

The establishment of this subspecies is indirectly due to the corrections and suggestions from peers, especially the organization that discussed the assesses and abundance levels and the conservation status of the species: Caridina apodosis Cai et N.K. Ng, 1999. Without their conclusive information, we would never be determined to find it. This is an enigmatic species; unfortunately, Although there is no reliable basis for identification was found, let alone leading us to journey of rediscovery. we unexpectedly discovered this very rare new subspecies!

REFERENCES

[1] Cai, Y. & Ng, N.K. (1999). A revision of the Caridina serrata species group, with descriptions of five new species (Crustacea: Decapoda: Caridea: Atyidae). Journal of Natural History 33: 1606-1638.
[2] Cai, Y. (1996). A revision of the genus Neocaridina (Crustacea: Decapoda: Atyidae), Acta Zootaxonomica Sinica. 21: 129-160.
[3] 梁象秋《中國動物志: 甲殼動物亞門十足目匙指蝦科》= Fauna Sinica. Invertebrata, Crustacea Decapoda Atyidae: 第36卷, 1-375, 北京科學出版社, 2004.
[4] Neocaridina palmata subsp. palmata (Shen, 1948), GBIF — the Global Biodiversity Information Facility, https://www.gbif.org/species/7260005
[5] 延陵動物志專輯:香港的匙指蝦類 (III): 歸還米蝦屬性探討及錘肢米蝦, 延陵科學綜合室, 01/2024.