Taxonomic position and glochidia from the freshwater mussel, Anodonta luteola (Unionoida: Unionidae), in Costa Rica

Posición taxonómica y el gloquidio del mejillón dulceacuícola Anodonta luteola (Unionoida: Unionidae), en Costa Rica.

To determine the number of species of the genus Anodonta reported for the Panamic province and to determine its taxonomy position the work of Von Martens, (1890-1901); Simpson, (1900); Pilsbry, (1920); Parodiz & Bonetto (1963), and MUSSELp. (2013) were revised.

Between September and October 2014, 80 specimens of A. luteola were collected. The mussels were taken from an Oreochromis niloticus culture system of the Universidad Técnica Nacional (UTN), located in Cañas, Guanacaste (10°20’8” N, 85°9’19” W) with 0,5 m deep. The mussels were transported alive on a cool box to Estación de Biología Marina (EBM), Universidad Nacional (UNA), located in Puntarenas (9°58´43´´N, 84°50´25´´W) to be analyzed at once. Gills from mussels were examined for the presence of glochidia. Samples of glochidia were fixed on ME solution (2.0% of paraformaldehyde, 2.5% of glutaraldehyde and 5% of sucrose in 0.1 M sodium cacodylate buffer at pH 7.4) and were stored at 7 °C before scanning electron microscopy (SEM) analysis at Universidad de Costa Rica (UCR) (Hoggart, 1999). Samples were rinsed in the same buffer three times during 10 minutes, centrifugated at 2000 rpm to separate glochidia larvae from the tissue. Postfixation was done with 1% osmium tetroxide for one hour and the samples were rinsed 4 times with buffer before ethanol dehydration series. Samples were coated with 30 nm platinum and observed on a Hitachi S-2360 N scanning electron microscope.

Glochidia larvae were identified in a light microscope (Engel & Wächtler, 1989) with camera. Glochidia pictures were taken at natural and eocin staining was done to distinguish organs. The glochidia (n = 102) were measured for total length (TL), height (H) and hinge dorsal length (HDL), and mean values were calculated (mean ± standard deviation (SD), variation coefficient (VC)). To determinate the glochidia type based on Graf & Cumming (2006), a sample was examined with light microscopy (Engel & Wächtler, 1989).

The Holotype of Anodonta luteola is located in Smithsonian Institute, U. S. National Museum of Natural History, Department of Invertebrate Zoology, IZ MOL 86766. (MUSSEL p., 2013).

Species of the genus Anodonta present to Panamic Province: von Martens (1896-1900):

• A. banbusearum von Martens, 1900

• A. chalcoensis Crosse & Fischer, 1893

• A. cylindracea Lea, 1838

• A. ciconia Carpenter, 1857

• A. coarctata Potiez & Michaud, 1844

• A. depexa von Martens, 1900

• A. exilior Lea, 1871

• A. glauca Humboldt & Bonplant, 1827

• A. globosa Lea, 1841

• A. grijalvae Morelet, 1884

• A. henryana Lea, 1857

• A. inaequivalvisSimpson, 1900

• A. jewettiana Lea, 1868

• A. lurulenta Morelet, 1849

• A. luteola Lea, 1858

• A. montezuma Lea, 1841

• A. nicaraguae Tate, 1870

• A. nopalatensis Sowerby, 1867

• A. tabascoensisSimpson, 1900

• A. tehuantepecensis Crosse Finsch, 1893

• A. richardsoni von Martens, 1900

• Synonymy: (MUSSEL p., 2013)

• Anodontites luteolus (Lea, 1858); Pilsbry, (1920).

• Anodonta (Pachyanodon) luteola Lea, 1858. - von Martens (1890-1901).

• Glabaris (s.s.) luteolus (Lea, 1858); Simpson, (1900).

• Anodon luteolus (Sowerby, (1870); Simpson, (1900)

• Margaron (Anodonta) luteola (Lea, 1870); Simpson, (1900)

Anodonta luteola has elliptical shell, thin, inflated, and often slightly winged posteriorly and rounded leading edge. The posterior edge of the shell was slightly winged, corrugated, and the umbo is smooth, with concentric ridges. Smooth, shiny and greenish-yellow surface with fine lines of growth were characteristics in the juveniles shells. In adult specimens the shell color turns dark green with strong growth lines. Periostracum of the umbo region spent in adults. Hinge toothless, reduced a single line regularly curved. Adductor muscles hardened, shiny nacre and mildly iridescent (Simpson, 1900 modified) (Fig. 1).

Details from the morphology the shell of the glochidia of A. luteola can be seen in Fig. 2.

The shape of the glochidia Anodonta luteola is subtriangular with hook and spinules (Fig. 3).

Table 1 shows the measurements taken to gloquidia. The mean dimensions of the glochidia as follows: total length: 311.8μm, height: 331.7μm. The lowest coefficient of variation (3.42%) corresponded to the total length.

Fig. 1
Dorsal and ventral view of Anodonta luteola.

Fig. 2
Details of the morphology the shell of the glochidia at SEM of Anodonta luteola. A) Dorsal view B) Outer surface of valve showing the porousity of the shell C) Detail of the spinules.

Fig. 3
Details of the shell of the glochidia of Anodonta luteola at light microscopy A) View of the subtriangular shape and the adductor muscle of the glochidia (10X). B) Frontal view of the hook (40X). C) Lateral view of the hook with spinules (40X).

Table 1
Statistical data on glochidia of Anodonta luteola

According to the results of this study there is no doubt that in the works published by Cruz & Villalobos (1984), Cruz & Villalobos (1985), Villalobos & Cruz (1984) & Villalobos, Cruz & Báez (1984) under the name of Glabaris luteolus (Mycetopodidae), and those of Ruiz (1982), Ruiz & Bonilla (1982), Sandin, (1995), Castillo-Martínez (2000), Arias-Andrés, Mena & Pinnoch (2014) published under the name Anodontites luteola (Mycetopodidae) the specie were misidentified. In all cases, the species listed above refers to Anodonta luteola (Unionidae). Species from Unionidae family produce glochidia on its larval stage unlike species of the family Mycetopodidae that produce lasidium larvae (Parodiz & Bonetto, 1963).

The glochidia of A. luteola showed the following measures, TL = 311,8μm, H = 331,7μm. These measures are bigger than the measurements shown by several species of the genus Unio, like U. marcus (TL = 216,8μm, H = 193,7μm), U. delphinus (TL = 229,0μm, H = 221,0μm) and U. tuminiformis (TL = 202,0μm, H = 221,0 μm) (Araujo et al., 2009). Species of the genus Anodonta shows bigger measurements than those found in A. luteola, such as A. cygnea (TL= 350,0μm, H = 350,0μm) and A. anatina (TL = 355,0μm, H = 350,0μm) reported by Araujo et al. (1999) and A. pseudodopsis (TL = 328,0μm, H = 303,0μm) (except for the height), in Serefişan et al. (2009).

Moreover, in all the above cited species, including A. luteola, the glochidia only stay in the external demibranquia. However, this condition is not characteristic of all members of the family Unionidae; for example, the glochidia in Potamida littoralis uses the four branquias as marsupia for the incubation (Araujo et al., 2009).

This work is part of the project “Nutritional composition and effect of biochemical, microbiological and environmental changes in the quality and freshness of some commercial species caught in the Gulf of Nicoya.” We are grateful to Jorge Boza, Rafael Araujo and Jorge Alfaro for reviewing the manuscript, William Vargas for providing the clams, the staff of the Experimental Station Jiménez Núñez for their help in the collection, Maribel Vargas and Oscar Pacheco Prieto for the electron microscopy and light microscopy pictures, respectively.