Lissostrandesia, Munakata & Tanaka & Kakui, 2024

Genus Lissostrandesia gen. nov. urn:lsid:zoobank.org:act:3ae75bca-c259-40c5-a325- 4b717128d779

Type species: Lissostrandesia fonticola gen. et. sp. nov.

Etymology: Derived from the ancient-Greek adjective lissos (smooth), referring to the smooth inner margin of the valves, lacking any grooves or lists, combined with the generic name Strandesia , a common group in this subfamily. Gender feminine.

New Japanese name: Hira-maruwa-kaimijinko combines the Japanese word hira (smooth) with maruwa-kaimijinko, the name for the subfamily Cypricercinae ( Okubo 2004) .

Diagnosis: Same as the diagnosis for the tribe.

Lissostrandesia fonticola gen. et sp. nov. ( Figs. 2–4 View Fig View Fig View Fig ) urn:lsid:zoobank.org:act: 5ab1df55-6ebf-46a9-9428- dff0ba4391af

Cypricercinae sp.: Munakata et al. (2023), 9–10, figs. 2A, 3A, B, 4.

Type locality: Springhead of Metori Spring, Nagasaka Town, Hokuto City, Yamanashi Prefecture, Japan (35°53.32'N, 138°20.39'E); in sediment.

Material examined: Holotype: female, ICHUM-8615, two slides. Paratypes (14 females): ICHUM-8603–8610, two slides for each; ICHUM-8611, 8612, one SEM stub and one slide for each; ICHUM- 8613, 8614, one SEM stub for each; ICHUM-8625, 8626, undissected, one vial for each. All individuals except ICHUM-8626 were collected by MM at the type locality; ICHUM-8626 was collected by Fuga Matsui from a spring near Mikuni-bashi Bridge ( Table S1).

Etymology: The specific name is from the Latin fontis, genitive singular of fons (fountain or spring), and -cola, nominative singular of the adjective-forming suffix “ cola ” (inhabit).

New Japanese name: Shimizu-hira-maruwakaimijinko. Because this species was collected only in springs, the Japanese word shimizu (cold, clear freshwater) was prefixed to the generic name.

Diagnosis: Same as the generic diagnosis.

Description of Lissostrandesia fonticola : Measurements (in millimeters, except for ratios) of carapace and valves: LV-L 0.99–1.05 (1.02, n = 3), LV-H 0.51–0.56 (0.53, n = 3), LV-H/LV-L 0.52–0.53 (0.53, n = 3); RV-L 1.00–1.03 (1.02, n = 3), RV-H 0.50–0.53 (0.52, n = 3), RV-H/RV-L 0.50–0.51 (0.51, n = 3); Ca-W 0.41–0.42 (0.42, n = 3), Ca-W/LV-L 0.40–0.42 (0.41, n = 3).

Carapace ( Figs. 2 View Fig , 3 View Fig ) translucent, with violetcolored area dorsally; eyes black ( Fig. 2A View Fig ). Carapace outer surface smooth, with sparse tiny setae; widest point at about mid-length ( Fig. 3A, B View Fig ); anterior and posterior ends rounded in dorsal view ( Fig. 3A View Fig ), outer list present on ventral and posterior margins of both valves ( Fig. 3B View Fig ). RV slightly overlapping LV along entire margin, with slight ventral expansion ( Fig. 3A, B View Fig ); greatest height at mid-length of RV; anterodorsal and posterodorsal margins smooth; posterior margin slightly more sharply rounded than anterior; ventral margin slightly concave; apex of anterior margin below mid-height of RV and higher than apex of posterior margin ( Fig. 3C, E View Fig ); in inner view, inner list and groove absent along entire margin; calcified inner lamella well developed on anterior, posterior, and ventral margins ( Fig. 3C View Fig ). LV similar to RV in shape; ventral margin nearly straight ( Fig. 3D, F View Fig ). Two oblong mandibular muscle scars and five oblong adductor muscle scars on LV and RV ( Fig. 3C, D View Fig ). Hinge adont.

An1 ( Fig. 4A View Fig ) with seven podomeres. Podomere length ratio from second to seventh podomeres 5: 7: 3: 3: 3: 3. First podomere with one dorsal and two ventrodistal plumed setae; without Wouters organ. Second podomere with dorsodistal plumed seta not reaching middle of third podomere; without Rome organ. Third podomere with dorsodistal plumed seta reaching beyond end of seventh podomere and ventrodistal plumed seta reaching end of fourth podomere. Fourth podomere with two dorsodistal setae reaching tips of long setae on sixth podomere and two ventrodistal plumed setae reaching end of fifth podomere. Fifth podomere with two long dorsodistral setae reaching tips of long setae on seventh podomere and two shorter ventrodistal plumed setae extending to end of seventh podomere. Sixth podomere with four outer distal long setae (as long as podomeres 1–7) and shorter inner distal seta. Seventh podomere with three distal setae (two long, reaching tips of long setae on sixth podomere; one short, ca. one-fifth length of long setae) and aesthetasc ya (two-fifths length of long setae).

An2 ( Fig. 4B, C View Fig ) with five podomeres. First podomere (coxa; not illustrated) with three ventral plumed setae. Second podomere (basis) with ventro-subdistal seta reaching middle of third podomere. Exopodite with one plumed long and two unequal short setae. Third (first endopodal) podomere with six inner subdistal natatory setae (one long seta not extending beyond half of fourth podomere and five short setae just reaching end of third podomere), ventrodistal plumed seta reaching tip of fourth podomere, and mid-ventral aesthetasc Y not reaching beyond end of third podomere. Fourth podomere undivided, with two mid-dorsal setae, dorso-subdistal setae z1–3 of unequal length, mid-ventral plumed setae t1–4 reaching middle of claws G1 and G3, mid-ventral short aesthetasc y1, ventrodistal short aesthetasc y2, and distal claws G1–3; claw G2 ca. 90% length of claws G1, G3. Fifth podomere ( Fig. 4C View Fig ) with plumed seta g reaching to ca. three-fourths length of claw GM and bifurcate aesthetasc y3 (longer than half length of claw GM); Gm ca. three-fifths length of GM; GM reaching tips of claws G1, G3.

Md ( Fig. 5A View Fig ) with coxa, palp comprising four podomeres (one basal, three endopodal), and vibratory plate. Coxa with distal teeth and two subdistal plumed setae. First podomere (basis) with one ventrodistal seta, ventrodistal setae S1 and S2, and ventrodistal short seta α (ca. one-third length of seta S2); seta S1, S2 unequal in length, bearing row of long setules. Vibratory plate (exopodite; not illustrated) with four rays. Second (first endopodal) podomere with four dorsodistal setae of unequal length (longer two setae reaching end of fourth podomere); one mid-ventral, one long plumed, and three smooth setae not extending beyond tips of claws on fourth podomere; and mid-ventral plumed short seta ss (ca. one-fourth length of mid-ventral smooth setae). Third podomere with four dorso-subdistal and two ventro-subdistal setae; inner region with distal plumed seta γ and three distal plumed setae. Fourth podomere with distal seta and four distal claws.

Mx ( Fig. 5B View Fig ) with palp comprising two podomeres, three endites, and vibratory plate. First palpal podomere with one subdorsodistal and six dorsodistal plumed setae reaching tips of claws on second palpal podomere. Second palpal podomere rectangular, L/W ca. 2, with three distal setae and three distal claws. First endite with two ventroproximal plumed setae, and eight smooth and two plumed distal setae. Second endite with eight distal setae. Third endite with two distal serrated spines and seven distal setae (two of them plumed). Vibratory plate (not illustrated) with more than 10 rays.

L5 ( Fig. 6A View Fig ) with protopod, palp, and vibratory plate. Protopod with two setae a, plumed seta b, plumed seta d, and 12 distal plumed setae of unequal lengths. Palp with distal plumed setae h1–3. Vibratory plate (not illustrated) with several rays.

L6 ( Fig. 6B View Fig ) with six podomeres (border between first and second podomeres indistinct). Length ratio for third to sixth podomeres and terminal claw (h 2) 14: 7: 10: 3: 24. First and second podomeres (protopod) with setae d 1, d 2. Third (first endopodal) podomere with ventrodistal plumed seta e not reaching middle of fifth podomere. Fourth podomere not fused to fifth podomere, with ventrodistal plumed seta f reaching end of sixth podomere. Fifth podomere with short ventrodistal plumed seta g. Sixth podomere with dorsodistal plumed seta h3, ventrodistal plumed seta h1, and distal curved claw h 2.

L7 ( Fig. 6C View Fig ) with four podomeres, bearing pincer organ formed by third and fourth podomeres. First podomere (protopod) with plumed setae d 1, d 2, dp. Second (first endopodal) podomere with ventrodistal plumed seta e not extending beyond end of fused third and fourth podomeres. Third podomere with mid-ventral plumed seta f reaching tip of seta h1. Fourth podomere with long plumed seta h3, hook-like seta h2, and tiny seta h1.

CR ( Fig. 7A View Fig ) with CR-L/CR-W ratio ca. 17. L ratio of ramus, plumed seta Sa, claw Ga, claw Gp, and plumed seta Sp 17: 3: 9: 7: 2.

CR attachment ( Fig. 7B View Fig ) stout, with TL on db, and with free db contributing to acute tip; vb with well-developed free part, with L of free vb about 10 times W; vb with swollen end.

Male unknown.

Variation: We observed two types of carapace coloration, depending on the population. In individuals from MS, KS, AS, and GI, the carapace was translucent, with a violet area on the dorsal side ( Fig. 2A View Fig ); in individuals from GN and MB, the carapace was pale yellowish, with a dark green area on the dorsal side ( Fig. 2B View Fig ). These colors were retained in ethanol.

Molecular information

We determined COI sequences for 19 individuals from the MS population (608 or 658 bp, encoding 202 or 218 amino acids; INSD accession numbers LC789259– LC 789277); these differed by 0 – 4 nucleotide substitutions in 608 bp. In BLAST searches, the most similar sequence to ours was from “ Ostracoda sp.” (MF751183.1; identity score 84.33%, query cover 98%; deWaard et al. 2019).

We also determined COI sequences (6 0 8 or 658 bp; INSD accession numbers LC789204– LC789258, LC726439) from ostracods from the other five populations: 21 from KS, 20 from MB, one from AS, one from GI, and 13 from GN. Mean p -distances (608 bp) within populations for which more than one individual was sequenced were 0.016 –0.193 % and those between them were 0.00–0.229%. Maximum p -distances within and between populations were 0.500% and 0.662%, respectively ( Table 2).

We determined a nearly complete 18S sequence (1735 bp; LC789200) and a partial 16S sequence for Cardinium (907 bp; LC789280) from one individual from the MS population. BLAST searches found the most similar sequences to ours to be the 18S sequence from Cypretta seurati (AB674999.1; identity score 96.95%, query cover 100%; Hiruta et al. 2016) and the 16S sequence from Cardinium from Cavernocypris hokkaiensis (LC666825.1; identity score 98.68%; query cover 100%; Munakata et al. 2022). The 18S and Cardinium 16S sequences were also determined from one individual each from the KS, MB, GI, and GN populations ( Table S1). The p -distances among the five 18S sequences ranged from 0.00 to 0.23% (mean 0.092%). The Cardinium 16S sequences from the five populations were identical. In our 18S-based ML tree (File S1), L. fonticola forms a weakly supported clade (59% ultrafast bootstrap support, or uBS) as the sister taxon to a well-supported clade (96% uBS) containing the three taxa in Cypricericinae included in the analysis.

Genetic diversity and neutrality tests

Nine haplotypes were detected ( Fig. 8 View Fig ) among the 73 COI sequences from the four L. fonticola populations (KS, MB, GN, and MS) represented by more than one individual. Two haplotypes were detected at KS, two at MB, four at GN, and eight at MS. The most common haplotypes, H-1 and H-4 (detected in 25 and 37 individuals, respectively), were found in all four populations. The single individuals from each of AS and GI were haplotype H-1. Five haplotypes were unique to MS, and one was unique to GN. Haplotype H-2 was shared only by populations from Honshu (GN and MS). Haplotype and nucleotide diversities were highest at MS (h = 0.772, π = 0.00193) and lowest at KS (h = 0.095, π = 0.00016) ( Table 3).

The Tajima’s D values were not significant for any population or overall ( Table 3). Fu’s F S values were significant negative values ( Table 3) for the MS population and overall (P <0.02; Holsinger 2022), but were not significant for other populations.