The pilidium maculosum morphotype. Scale 100 microns (Hiebert and Maslakova 2015)
Maculaura spp.
The genus Maculaura is characterized by a unique pilidial morphotype called pilidium maculosum. Both the genus name and that of the larval morphotype reflect the polka-dot pigment pattern on the amnion inside which the juvenile develops while in the larval body (Hiebert and Maslakova, 2015). Currently this morphotype appears to be only found in members of this genus. A larva of similar morphology was collected near the mouth of Bamfield Inlet (Lacalli 2005), but whether it belongs to the genus Maculaura is not currently known. Unfortunately, larvae of the five species of Maculaura are difficult to distinguish from each other.
Hiebert and Maslakova (2015) published description of the genus Maculaura, taxonomic revision of the species complex, with descriptions of larval forms of most species.
Maculaura alaskensis coll. 13 Oct 2013. Scale 100 µm.
Maculaura alaskensis
Sequence data: 16S,
Observed in Coos Bay: Oct
Maculaura alaskensis was the first pilidiophoran species to have its complete development described from fertilization through metamorphosis (=Micrura alaskensis, Maslakova 2010a). These larvae are recognizable due to the pigment on the juvenile amnion which defines this genus. Although M. alaskensis are commonly found as adults on mudflats in Wahsington and Oregon and have been used in studies on fertilization (e.g. Stricker and Smythe, 2000, 2001, 2003; Stricker et al., 2001), larval function (von Dassow et al., 2013) and development (e.g. Maslakova, 2010a; Bird et al., 2014; Swider et al., 2014; L. Hiebert and Maslakova, 2015), we have only collected and identified one wild-caught larva of this species.
Maculaura cerebrosa larvae. An 18-day old larva reared in the lab in March 2013 (left) and an advanced larva collected in August 2013 (right). Scale bars 100 µm.
Maculaura cerebrosa
Observed in Coos Bay: Aug, Oct
The development of Maculaura cerebrosa is briefly described within the species description (Hiebert and Maslakova, 2015). Like other members of this genus, the larvae of M. cerebrosa can be recognized by the pigment pattern of the juvenile amnion which is visible early in development. Adult M. cerebrosa are common in Charleston, OR, particularly amongst rocks and shell hash and their larvae have been collected in late summer and fall.
Maculaura aquilonia larva (left) and metamorphosed juvenile (right) which were reared in the lab in March 2013. Scale bars 100 µm.
Maculaura aquilonia
Observed in Coos Bay: May
The development and metamorphosis of Maculaura aquilonia is described within the species description (Hiebert and Maslakova, 2015). Although the pigment pattern on the juvenile amnion is distinct in other members of this genus, it is less conspicuous in M. aquilonia. Instead, the polka-dot pigment is only visible when the amnion collapses within the juvenile gut following metamorphosis (above right). As a result, the larvae superficially resemble other hat-like pilidia. In southern OR, reproductive adults are found in March and planktonic larvae have been collected in April and May.
Maculaura magna larva collected from plankton in July 2013. Scale bars 100 µm.
Maculaura magna
Observed in Coos Bay: May-Aug
Although the development of this species has yet to be documented, wild-caught pilidia were very common in the summmer of 2013. The larvae of Maculaura magna have a conspicuous polka-dot pattern on the juvenile amnion as is seen in M. alaskensis and M. cerebrosa. Although it can be difficult to differentiate the larvae of these species, M. magna larvae are sometimes recognizable because they have a larger haystack-shaped episphere (above left). Likewise, the lateral lappets are proportionally shorter in this species than the other two.