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| A, B Caridina mayamareenae sp. nov. D Two snail species Celetaia persculpta and Tylomelania sp. on soft substrate. Empty shells of these species are shelter for C. mayamareenae sp. nov. C C. lilianae sp. nov. E, F C. poso sp. nov. Klotz, Wowor & von Rintelen, in Klotz, von Rintelen, Wowor, et al., 2020. All photographs: W. Klotz. |
Abstract
Lake Poso, an ancient lake system on the Indonesian island Sulawesi, harbours an endemic species flock of six, four lacustrine and two riverine species of the freshwater shrimp genus Caridina. In this study, five new lacustrine species are described, bringing the total to eleven species altogether. The number of lacustrine species is more than doubled to nine species compared to the last taxonomic revision in 2009. One of them, Caridina mayamareenae Klotz, Wowor & von Rintelen, sp. nov., even represents the first case of an atyid shrimp associated with freshwater snails which is morphologically adapted to living in shells. An integrative approach was used by providing a combination of morphological, ecological, and molecular data. Based on standard morphological characters, distribution, substrate preferences, and colouration of living specimens in the field, five distinct undescribed species could be distinguished. To support our species-hypothesis based on the mitochondrial genes 16S and COI, a molecular phylogeny was used for all eleven species from Lake Poso. All species form a well-supported monophyletic group, but only four morphospecies consistently correspond to mtDNA clades – a possible reason could be introgressive hybridisation, incomplete lineage sorting, or not yet fixed species boundaries. These results are discussed further in the context of adaptive radiation, which turned out to be more diverse than previously described. Finally, yet importantly, subjecting all new species to similar threats and to the same IUCN category and criterion than the previously described species from the lake is recommended.
Keywords: Adaptive radiation, ancient lake, freshwater biodiversity, Indonesia, integrative taxonomy, Sulawesi
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| Figure 2. Living specimens of Caridina spp in Lake Poso 1. A Caridina schenkeli von Rintelen & Cai, 2009 B C. acutirostris Schenkel, 1902 C C. caerulea von Rintelen & Cai, 2009 D C. ensifera Schenkel, 1902 E C. mayamareenae sp. nov. male F, G C. longidigita Cai & Wowor, 2007 H C. sarasinorum Schenkel, 1902. Not to scale. Photo: C. Lukhaup (A, C), W. Klotz (B, D–H). |
Atyidae De Haan, 1849
Caridina H. Milne Edwards, 1837
Caridina fusca Klotz, Wowor & K. von Rintelen, sp. nov.
Etymology: The Latin word fuscus refers to the species’ dark reddish or brown colouration (Fig. 3H).
Distribution: Caridina fusca sp. nov. is endemic to Lake Poso. Specimens were found at two localities within the lake, in a small bay south of the town of Tentena at the east shore and in a bay at the west shore.
Ecology: Caridina fusca sp. nov. is found under rocks in deep water (more than 5 m depth), while the morphologically similar species C. sarasinorum is usually found on various kinds of substrate like deposits of leaf litter, on wood or macrophytes (von Rintelen and Cai 2009).
Remarks:
In life colouration, C. fusca sp. nov. might be confused with C. sarasinorum, also endemic to Lake Poso. In the latter, the transversal bands on the abdomen are less defined and scraggy compared to the sharply defined straight bands in C. fusca sp. nov. In preserved condition C. fusca sp. nov. can be differentiated from C. sarasinorum by the rostrum reaching to the end of the antennular peduncle, the dorsal and ventral margin armed throughout almost to the tip vs. reaching to the distal margin of the scaphocerite or beyond, unarmed in anterior one-third to half of the dorsal margin in C. sarasinorum. Epipods are reduced on the third maxilliped and absent on all pereiopods of C. fusca sp. nov. vs. well-developed on the third maxilliped and first pereiopod, absent on second to fifth pereiopods in C. sarasinorum. The chelae of the first pair of pereiopods are not inflated, 2.29–2.73 times as long as wide, 1.17–1.34 times as long as the carpus in C. fusca sp. nov. vs. slightly inflated, 1.74–2.10 times as long as wide, 1.35–1.48 times as long as the carpus in C. sarasinorum. The carpi of the first pair of pereiopods are more slender (2.33–4.00 times as long as wide) and hardly excavated distally vs. more stout (1.75–2.22 times as long as wide) and slightly excavated distally in C. sarasinorum.
Caridina lilianae Klotz, Wowor & K. von Rintelen, sp. nov.
Etymology: Named after the second and last authors’ first daughter who is very interested in field work and helped to observe and document this species while visiting the lake in 2019.
Distribution: Caridina lilianae sp. nov. is endemic to Lake Poso. Specimens were found at three localities within the lake, two within a bay south of the town of Tentena at the east shore and one in a bay at the west shore.
Ecology: Caridina lilianae sp. nov. lives on very fine sand or silt (soft substrate) in shallow water (1.5–2.5m).
Remarks:
With its small size and the less developed chelae with scarce setae at the tip of the fingers, C. lilianae sp. nov. is similar to C. mayamareenae sp. nov. but can easily be distinguished from this species by the very short, convex rostrum (vs. rostrum conspicuous high, reaching to end of second segment of antennular peduncle or slightly overreaching this segment) and the slender third pair of pereiopods bearing long stiff setae on merus and ischium but without any spiniform setae on flexor margin (vs. third pereiopod very robust, without long simple setae on merus and ischium and dactylus with five or six spiniform setae on flexor margin). These characters also distinguish C. lilianae sp. nov. from all other Caridina spp. known from the Lake Poso. Although C. lilianae sp. nov. and C. mayamareenae sp. nov. occur in sympatry in the lake, the microhabitats of these species are quite different. Caridina mayamareenae sp. nov. lives in empty shells of aquatic snails while C. lilianae sp. nov. on soft substrate. The long stiff simple setae attached to the posterior segments of the chelipeds and pereiopods could be interpreted as a morphological adaption to this kind of habitat by preventing them to subside into the soft substrate. This hypothesis would need to be tested, though. In the field, the whitish or cream-coloured body colouration is indiscernible on light-coloured sandy habitats (Fig. 3D).
Caridina marlenae Klotz, Wowor & K. von Rintelen, sp. nov.
Etymology: Named after the second and last authors’ second daughter who is very interested in field work and helped to observe and document this species while visiting the lake in 2019.
Distribution: Caridina marlenae sp. nov. is endemic to Lake Poso. Specimens were found only at one locality in a bay south of the town of Tentena at the east shore of the lake.
Ecology: Caridina marlenae sp. nov. is found under rocks in deep water (more than 5 m).
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| Figure 3. Living specimens of Caridina spp in Lake Poso 2. A, B Caridina mayamareenae sp. nov. C C. lilianae sp. nov. D Two snail species Celetaia persculpta and Tylomelania sp. on soft substrate. Empty shells of these species are shelter for C. mayamareenae sp. nov. E, F C. poso sp. nov. G C. marlenae sp. nov. H C. fusca sp. nov. Not to scale. All photographs: W. Klotz. |
Caridina mayamareenae Klotz, Wowor & K. von Rintelen, sp. nov.
Etymology: Named after the fourth author's, daughter for her strong interest in decapod crustaceans her father is working on.
Distribution: Caridina mayamareenae sp. nov. is endemic to Lake Poso. Specimens were found at five localities within the lake, three in the northern part and two at the eastern and western shores in the southern part of the lake.
Ecology: Caridina mayamareenae sp. nov. is hiding inside empty shells of the viviparid snail Celetaia persculpta (P. Sarasin and F. Sarasin, 1898) and Tylomelania spp. (Fig. 3D), and was not observed on any other substrate. On average, 1.4 shrimps were found per shell, but there is considerable variation (0.6–2.4 shrimps per shell) among the examined sites (Table 2). Up to four specimens were found in a single shell at the Dolidi Ndano locality. Caridina mayamareenae sp. nov. is also confined to deeper water; shells from depths of 7 m upwards did not contain any shrimps.
Remarks:
Among all species of the genus Caridina known from Lake Poso, C. mayamareenae sp. nov. is unique by its short and conspicuous high rostrum, the less developed chelipeds with scarce setae at the tip of the fingers, and the strong third pair of pereiopods. A high and rather short rostrum is an infrequent character among lacustrine species of the genus Caridina from the Central Lakes of Sulawesi (compare revision in von Rintelen and Cai 2009). Many lacustrine species are showing slender, styliform rostrum shapes as seen in C. ensifera and C. caerulea, the most common species in Lake Poso. The conspicuous high rostrum and the strong third pair of pereiopods adapted for clinging on hard substrate are visible characters of a high grade of specialisation to the microhabitat of this species.
Caridina poso Klotz, Wowor & K. von Rintelen, sp. nov.
Etymology: The specific name is a noun in apposition after the type locality, Lake Poso.
Distribution: Caridina poso sp. nov. is endemic to Lake Poso. Specimens were found at three localities within the lake, one at the east shore and two at the west shore.
Ecology: Caridina poso sp. nov. lives in packs of debris (small to medium-sized stones) close to the shore of the Lake Poso and thus could be considered a hard substrate dweller as defined in von Rintelen and Cai (2009). The species was never found on soft substrates such as dead leaves, wood or water plants.
Werner Klotz, Thomas von Rintelen, Daisy Wowor, Chris Lukhaup and Kristina von Rintelen. 2021. Lake Poso's Shrimp Fauna Revisited: the Description of Five New Species of the Genus Caridina (Crustacea, Decapoda, Atyidae) more than Doubles the Number of Endemic Lacustrine Species. ZooKeys. 1009: 81-122. DOI: 10.3897/zookeys.1009.54303
