Morphology and biology of Prionospio patagonica (Annelida: Spionidae) from Chile

Abstract

Prionospio patagonica inhabits temporary silty tubes intertidally and shallow subtidally in brackish water estuarine environments in southern Chile. The species is gonochoristic with the female:male ratio being close to 2:1. Females and males release gametes into water. Pelagic planktotrophic larvae were caught in the plankton in the River Valdivia estuary in October^November and in March. Development of the adult morphology is described and illustrated beginning from the 2-chaetiger larval stage. One pair of lateral eyes ¢rst appears in the early larva, and shortly after that the right median eye develops. The left median eye appears after settlement, in juveniles with 10^11 segments. Developed 6-segment larvae have three dark red eyes, short palps of equal length, no nototrochs, one pair of small cells with grasping cilia on the pygidium, a small ciliated pit, gastrotrochs on segments 2^6, long serrated bristles in notopodia, adult capillaries in noto-and neuropodia on segments 2^5, single hooks in both rami on segment 6, and one pair of provisional papillae on the pygidium. A ventral buccal bulb is present below the short oesophagus and two pairs of provisional protonephridia are present in segments 1 and 2. The wall of the anterior part of the midgut has a characteristic brown pigment. The 6-segment larvae, about 400 mm long, settle and undergo gradual metamorphosis. In adults, hooks are gradually lost from noto-and neuropodia but sabre chaetae appear from segment 7 and retain their anterior position as growth proceeds. Up to 14 pairs of cirriform branchiae develop from segment 2, and three adult cirri appear on the pygidium. The a¡erent and e¡erent arms of each branchial blood loop are interconnected by capillary loops. A greenish heart body is present in the main dorsal blood vessel in anterior segments. Up to 21 pairs of metanephridia develop in anterior sterile segments, beginning with segment 4. Transparent gonoducts are present in fertile segments.

Invertebrate settlement and diversity on a glass sponge reef

“…In Atlantic Canada members of the Prionospio genus were found spawning between May and August (Lacalli 1981). It should be noted that Prionospio patagonica larvae were found in October, November, and March in Chile (Radashevsky et al 2006), timing that corresponds seasonally to the appearance of juveniles on our plates in April, because Chile is in the southern hemisphere. In two cases, Lanassa venusta venusta and Proclea sp., we were unable to find any reports of spawn timing in the literature for species more closely related than the family level (i.e., in a different genus within the same family).…”

Phosphoproteome analysis during larval development and metamorphosis in the spionid polychaete Pseudopolydora vexillosa

“…Competent P. vexillosa larvae accumulate adult features, including neurochaetes, sensory structures (e.g., microvilli on the prostomium), and feeding structures (e.g., palps with ciliated grooves), when they undergo transient structural reorganization or when their organs begin to function. For example, their nuchal organs, which are originally located in the prostomium, gradually shift to the anterior segments on the dorsal side and are then replaced by adult organs after settlement and metamorphosis [ 12 ]. In fact, in over 40 species of spionidae, a pair of unpigmented photoreceptive organs reaches maximum size during the competent stage but then degenerates after metamorphosis [ 13 ].…”

Differential expression of proteins and phosphoproteins during larval metamorphosis of the polychaete Capitella sp. I

“…Specific protein spots may be required for gut formation in the early larval phase. Competent P. vexillosa larvae accumulate neurochaetes, sensory structures, and feeding structures late in larval life as they undergo transient structural reorganization [ 20 ] whereas Capitella sp. I larvae metamorphose spontaneously and require little tissue remodulation, such as elongation of the body and loss of cilia leading to minor morphological changes [ 7 ].…”