Caenis rivulorum Eaton, 1884

Takayanagi, Tatsushi & Yoshizawa, Kazunori, 2021, The first record of Caenis rivulorum (Ephemeroptera: Caenidae) from Japan, Biodiversity Data Journal 9, pp. 67413-67413 : 67413

Caenis rivulorum Eaton, 1884

Caenis dimidiata var. rivulorum Eaton, 1884 in Eaton (1884), Trans. Linn. Soc. London, 2nd Ser. 3 (2): 143 (Type locality: Thorncombe, Dorset, England).

Caenis rivulorum Eaton, 1884 in Eaton (1888), Trans. Linn. Soc. London, 2nd Ser. 3 (2): 320. Change of status.

Caenis nivea Bengtsson, 1917 in Bengtsson 1917, Ent. Tidskr. 38: 2, p. 181-182, synonymised by Saaristo (1966).

Caenis nigroforceps Zhou, Gui & Su, 1997 in Zhou et al. 1997, Entomotaxonomia 19: 270-271, synonymised by Zhou and Zheng (2004).

Materials

Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualID: im0023_L024; individualCount: 1; sex: male; lifeStage: adult; preparations: abdomen in glycerine, other parts in 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Soya-gun ; municipality: Hamatonbetsu-cho ; locality: Usotan ; decimalLatitude: 45.0468; decimalLongitude: 142.3617; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-06; fieldNotes: DNA extraction: LC619650 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualID: im0024_L025; individualCount: 1; sex: female; lifeStage: adult; preparations: 99%EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Soya-gun ; municipality: Hamatonbetsu-cho ; locality: Usotan ; decimalLatitude: 45.0468; decimalLongitude: 142.3617; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-06; fieldNotes: DNA extraction: LC619651 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tatsushi Takayanagi; individualID: im0025_L026; individualCount: 1; sex: male; lifeStage: adult; preparations: abdomen in glycerine, other parts in 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Hiyama-gun ; municipality: Assabu-cho ; locality: Shirooka ; decimalLatitude: 41.8328; decimalLongitude: 140.3327; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-08; fieldNotes: DNA extraction: LC619652 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tatsushi Takayanagi; individualID: im0026_L027; individualCount: 1; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Hiyama-gun ; municipality: Assabu-cho ; locality: Shirooka ; decimalLatitude: 41.8328; decimalLongitude: 140.3327; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-08; fieldNotes: DNA extraction: LC619653 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualID: im0027_L028; individualCount: 1; sex: male; lifeStage: adult; preparations: abdomen in glycerine, other parts in 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Sapporo-shi ; locality: Kita-ku , Kita-17, Nishi-9 ; decimalLatitude: 43.08; decimalLongitude: 141.3381; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-10; fieldNotes: DNA extraction: LC619654 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualID: im0028_L029; individualCount: 1; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Sapporo-shi ; locality: Kita-ku , Kita-17, Nishi-9 ; decimalLatitude: 43.08; decimalLongitude: 141.3381; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-10; fieldNotes: DNA extraction: LC619655 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualID: im0029_L030; individualCount: 1; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Sapporo-shi ; locality: Kita-ku , Kita-17, Nishi-9 ; decimalLatitude: 43.08; decimalLongitude: 141.3381; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-10; fieldNotes: DNA extraction: LC619656 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tatsushi Takayanagi; individualID: im0030_L031; individualCount: 1; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Hiyama-gun ; municipality: Assabu-cho ; locality: Shirooka ; decimalLatitude: 41.8328; decimalLongitude: 140.3327; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-08; fieldNotes: DNA extraction: LC619657 ; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualCount: 5; sex: male; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Soya-gun ; municipality: Hamatonbetsu-cho ; locality: Usotan ; decimalLatitude: 45.0468; decimalLongitude: 142.3617; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-06; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualCount: 2; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Soya-gun ; municipality: Hamatonbetsu-cho ; locality: Usotan ; decimalLatitude: 45.0468; decimalLongitude: 142.3617; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-06; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tatsushi Takayanagi; individualCount: 2; sex: male; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Hiyama-gun ; municipality: Assabu-cho ; locality: Shirooka ; decimalLatitude: 41.8328; decimalLongitude: 140.3327; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-08; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tatsushi Takayanagi; individualCount: many; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; county: Hiyama-gun ; municipality: Assabu-cho ; locality: Shirooka ; decimalLatitude: 41.8328; decimalLongitude: 140.3327; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-08; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualCount: 1; sex: male; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Sapporo-shi ; locality: Kita-ku , Kita-17, Nishi-9 ; decimalLatitude: 43.08; decimalLongitude: 141.3381; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-10; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Yuto Okita; individualCount: many; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Sapporo-shi ; locality: Kita-ku , Kita-17, Nishi-9 ; decimalLatitude: 43.08; decimalLongitude: 141.3381; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2019-07-10; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tatsushi Takayanagi; individualCount: many; sex: male; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Chitose-shi ; locality: Poropinai ; decimalLatitude: 42.801191; decimalLongitude: 141.32665; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: street light; eventDate: 2020-07-15; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tatsushi Takayanagi; individualCount: many; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Chitose-shi ; locality: Poropinai ; decimalLatitude: 42.801191; decimalLongitude: 141.32665; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: street light; eventDate: 2020-07-15; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tomiko Ito; individualCount: many; sex: male; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Chitose-shi ; locality: Rankoshi ; decimalLatitude: 42.809656; decimalLongitude: 141.574878; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2020-07-06; Record Level: collectionCode: Insects Type status: Other material. Occurrence: recordedBy: Tomiko Ito; individualCount: many; sex: female; lifeStage: adult; preparations: 99% EtOH; Taxon : scientificName: Caenis rivulorum; kingdom: Animalia ; phylum: Euarthropoda ; class: Insecta ; order: Ephemeroptera ; family: Caenidae ; genus: Caenis ; specificEpithet: rivulorum; scientificNameAuthorship: Eaton ; Location : country: Japan; stateProvince: Hokkaido; municipality: Chitose-shi ; locality: Rankoshi ; decimalLatitude: 42.809656; decimalLongitude: 141.574878; Identification : identifiedBy: Tatsushi Takayanagi ; dateIdentified: 2020; Event : samplingProtocol: light trap; eventDate: 2020-07-06; Record Level: collectionCode: Insects

Description

Male adults (Fig. 2 a, in alcohol): Body length: 2.1-2.2 mm; fore-wing length: 2.3-2.4 mm; caudal filaments length: 7.0-7.8 mm. Head and prothorax dark-brown to reddish-brown. Compound eyes black. Ocelli white with black rings. Antennae white. Mesothorax brownish-white, dorsal and ventral sutures of mesothorax as in Fig. 3 a and b. Fin-shaped process on mesonotum. Wings hyaline, veins of costa, subcosta and radius area slightly brownish. Legs whitish. Abdomen whitish. Forceps thin, vent in middle, with short setae on their surface (Fig. 4 d). Penis anvil-shaped (Fig. 4 a, b and c). Caudal filaments white.

Female adults (Fig. 2 b, in alcohol)

Body length: 2.6-2.8 mm; fore-wing length: 2.8-3.1 mm; caudal filaments length: 0.8-1.0 mm.

Most features similar to male. Abdomen seems yellow by inner eggs and some brownish pigmentation on surfaces of each segments.

Eggs (Fig. 5 )

Longitudinal length ca. 115 µm, latitudinal length ca. 54 µm. Surface fine-granulated, with polar caps on both ends. Micropyle widens to aperture.

Diagnosis

Male adults (Fig. 2 a)

Compared to the European materials examined in Malzacher (1986), the presently examined specimens are slightly smaller.

Thorax: Prosterunum triangular (Fig. 3 b). This feature is diagnostic for the genus Caenis to distinguish it from the other genera distributed in the Palearctic Region.

Genital characters: Malzacher (1984) classified European species of Caenis into two "lineages": the Caenis horaria -lineage and the macrura -lineage. The former consists of the Caenis horaria -group and Caenis rivulorum -group. The species of this lineage have straight forceps with strong tips. The species of the macrura -lineage have bent forceps tips with some bristles or spines. Caenis rivulorum has long forceps which strongly bend inwardly (Fig. 4 a, b, c and d). Its penis shaft is thinner than that in C. horaria and the penis lobes are wider (Fig. 4 a, b and c). The genital characters of the Japanese specimens agree well with those of the European specimens as described in Malzacher (1986) and Malzacher (1984).

Female adults (Fig. 2 b)

Female adult C. rivulorum is similar to C. horaria but, by using the following characters, they can be distinguished from C. horaria : mesothorax with fin-shaped process (absent in C. horaria ) (Fig. 3 c), abdominal posterolateral processes short (long and filiform in C. horaria ), base of flagellum evenly tapering (abruptly narrowing in C. horaria ) ( Bauernfeind and Soldan 2012) (Fig. 3 d).

Eggs (Fig. 5 )

The features of eggs similar to C. horaria . According to Malzacher (1982), eggs of C. rivulorum usually slimmer than those of C. horaria and polar caps less bulging than those of C. horaria . The shape of micropyle also distinguishes C. rivulorum from other species.

Molecular analysis

TIM2+F+I+G4 substitution model was selected as the best fit model according to BIC (Bayesian Information Criterion). By the Maximum Likelihood analysis of COI sequences, the present samples were clustered with the German C. rivulorum (Fig. 6 ). However, their pairwise genetic distance exceeded 11%. The Japanese sequenced samples showed only a little genetic variation, at most 1% by pairwise distance (Table 1 ).

Figures

Figure 2. Caenis rivulorum: a. habitus, male (specimen from Loc. 1, scale: 1 mm); b. habitus, female (specimen from Loc. 2, scale: 1 mm).

Figure 3. Caenis rivulorum: a. mesonotum, dorsal, male (scale: 0.1 mm); b. pro- and mesosternum, male (scale: 0.1 mm); c. mesonotum, lateral, female (scale: 0.1 mm); d. anntenae, female (scale: 0.05 mm).

Figure 4. Caenis rivulorum: a. image of genital structures (ventral view, in preparation, scale: 0.05 mm); b. image of genital structures (ventral view, scale: 0.1 mm); c. line-drawing of genital structures (schematic, scale: 0.05 mm); d. forceps (scale: 0.01 mm).

Figure 5. Caenis rivulorum, egg. SEM image, scale = 10 µm.

Figure 6. Maximum Likelihood tree of barcoding regions (partial codes of COI gene, 35 sequences, 612 bp including gaps). The numbers at branches indicate the Ultra-Fast Bootstrap values. " JP " means " Japanese " materials examined this time.