Myostenostomum vanderlandi Rogozin, 1992

Reyes, Jhoe, Binow, Daniela, Vianna, Rogério T., Brusa, Francisco & Martins, Samantha E., 2021, Fig. 12. Majella pristis n in Periclimenaeus djiboutensis Bruce 1970, Zoological Studies 60 (22), pp. 1-33 : 4

Myostenostomum vanderlandi Rogozin, 1992 ( Fig. 2B–D )

Studied material: Four individuals studied, whole-mounted individuals photographed alive, afterward a single individual fixed in alcohol ( MZUSP PL 2258).

Localities: Site 1 (19/11/2018; 2/05/2019), Site 2 (15/03/2019) and Site 3 (15/03/2019), associated with benthal and phytal microhabitats.

Description: Specimens studied alive are vermiform, the body coloration varies from light orange to whitish. The anterior region is rounded. The body, 762.7 ± 218.7 μm (550.1–9871 μm; n = 3) long and 114 ± 18.3 μm (92.9–125.2 μm; n = 3) wide, consist of two to four zooids ( Fig. 2B ). The anterior region of the body bears two lateral ciliated pits, 48.1 ± 2.29 μm (46.4–50.7 μm; n = 3) long and 20.4 ± 4.1 μm (17.5–20.3 μm; n = 2) deep. The ciliated pits are connected to the anterior brain lobe which, in its anterior region, has 5–7 paired metameric ganglia while, in its posterior region, has two lateral trapezoidal lobes ( Fig. 2C ). The posterior brain lobe is somewhat triangular in shape with the apex directed to the anterior region. Besides, elongated ganglia are present at the base of both lateral angles of the posterior brain ( Fig. 2D ). Ventral and behind the posterior brain lobe, it is located the “ V ”-shaped mouth. This mouth leads to the pharynx, which is 60 ± 29.3 μm (41.7–93.8 μm; n = 3) long. At the anterior half of the intestine, is located the muscular gut, 76.9 ± 8.4 μm (71.5–86.6 μm; n = 3) long and 102.6 ± 28.9 μm (72.2–129.7 μm; n = 3) wide. The intestine continues tapering to an intestine-lacking region reaching the base of the caudal appendage, which is 53.9 ± 35.9 μm (28.5–79.3 μm; n = 2) long ( Fig. 2B ). Male and female reproductive systems not observed.

Taxonomic remarks: Myostenostomum was established by Luther (1960), this genus is differentiated by the anterior muscular gut, and consequently, it erected two species M. bulbocaudatum and M. tauricum . Later, Rogozin (1992) reviewed the genus and recognized that the anterior and posterior cerebral ganglia can be used as a diagnostic character for species discrimination so, four species were allocated in Myostenostomum , including Myostenostomum sp. (sensu Van der Land (1970)) defined as M. vanderlandi . Individuals in this study are M. vanderlandi due to the similar morphological configuration of the cerebral ganglia, i.e., the anterior lobe has 5–7 paired metameric ganglia in the anterior region, while in its posterior region, has two lateral trapezoidal lobes which are in accordance with the descriptions of Van der Land (1970), Rogozin (1992) and Tokinova and Berdnik (2017). Moreover, the posterior triangular lobe with laterally elongated ganglia is also corroborated. However, on average, our specimens are smaller than those reported for the Palearctic region ( Rogozin 1992; Tokinova and Berdnik 2017), except for the length of the muscular gut, which is longer. Since the type locality of M. vanderlandi is Suriname, we expand the range of distribution approximately 4242 km southwards in Rio Grande do Sul, Brazil, being the first record for the country.

Distribution: This species was originally found in Paramaribo, Suriname (South America) ( Van der Land 1970). Recently, it was registered in Volga-Kama Reserve, Russia ( Tokinova and Berdnik 2017).

Figures

Fig. 2. Live specimens of Catenulida. (A) Catenula lemnae, chain two zooids. (B–D) Myostenostomum vanderlandi: (B) habitus of whole-mounted individual, (C) detail of the anterior brain lobe and (D) detail of the posterior brain lobe. (E–F) Stenostomum glandulosum: (E) live individual, (F) free-hand schematic representation. (G) Stenostomum grande, a single zooid. (H) Stenostomum paraguayense, intestine with some food items. (I) Stenostomum hemisphericum, free-hand schematic representation.