Rearing methods and life cycle characteristics of Chironomus sp. Florida (Chironomidae: Diptera): A rapid-developing species for laboratory studies

Abstract

The species Chironomus sp. "Florida" has several qualities that make it a potential aquatic laboratory model to be used in Puerto Rico. Its use as such, however, requires a rearing protocol and life cycle description not previously reported. The present study addresses this lack of information by first describing a rearing method obtained through three years of observations. Next we describe and discuss the life cycle and the effects of temperature and feeding on development. The species has a short life cycle (typically 11 days) and larval stages easily identified using body measurements. Temperature affects the duration of the life cycle, with warm temperatures producing faster development than cold temperatures. The effects of different food concentrations vary: in large water volumes, concentrations of 2 mg/larva/day produce faster developmental times, but at low water volumes, small food concentrations of 0.5 mg/larva/day produce faster developmental times. The rearing protocol and life cycle parameters presented in this study are intended to promote the use of this species as a laboratory model. The fast development of Chironomus sp. "Florida" makes it ideal for toxicological studies.

Fig 1. Morphological diversity of chironomid egg masses collected in the field.

(Left) Chironomus sp. “Florida”. (Centre) Chironomus sp. (Right) Dicrotendipes sp.

Fig 2. System used for the rearing of Chironomus sp. “Florida”.

(Left) Rearing units components. (Right) Filter chamber components.

Fig 3. Chironomus sp. “Florida” stages.

(A) Larval stages (I to IV) based on the relation between the head capsule width and body length. (B). Average duration and overlap between stages. Abbreviations: E: embryo; I-IV: larval instars I to IV; P: pupa; Am: adult male; Af: adult female. Adult presence without occurring emergence or adult span is represented in dark grey. Oviposition period is represented by light grey.

Fig 4. Effect of feeding and temperature on adult emergence.

(A) Emergence curve obtained from larvae fed at four food concentrations in a water volume of 3 ml. (B) Emergence curve generated from larvae fed at three food concentrations in a water volume of 20 ml. (C) Emergence curve obtained from larvae reared at five different temperatures. Average emergence times and standard deviations are represented in black; individual emergence values are represented in grey. Each Polynomial model can be expressed as (A) y = −0.24x² + 2.17x + 7.12, R² = 0.60; (B) y = 0.28x² − 1.58 + 10.05, R² = 0.54; (C) y = 0.08x² − 4.69x + 77.13, R² = 0.98.

Fig 5. Growth and dry biomass equivalence of the larval Chironomus sp. “Florida”.

(A) Relationship of body size and age. (B) Relationship between body size and biomass. Average values and respective standard deviations are represented in black while individual measurements are represented in grey. The polynomial and power regressions can be expressed respectively as (A) y = −1.37e^-6 + x³ + 0.24x² + 0.35e^-3 x + 0.34 R² = 0.94; (B) y = 0.006e^(0.34*x), R² = 0.94.